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Cereal Foods World, Vol. 64, No. 5
DOI: https://doi.org/10.1094/CFW-64-5-0050
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A Shifting Climate for Grains and Flour
Andrew S. Ross1

Department of Crop and Soil Science, Oregon State University, Corvallis, OR, U.S.A.

1 E-mail: andrew.ross@oregonstate.edu

© 2019 AACC International, Inc.


Refined flour is ubiquitous in the food industry and is associated with certain nutritional issues in both developed and developing countries. Although flour refinement has been practiced for millennia, it became most effective with the advent of roller mills and air purifiers. Widespread access to this very refined flour led to diseases of deficiency that are often addressed by fortification of refined flour with a limited number of micronutrients. Fortification does not completely replace what is lost during the refinement process, however. Phytochemicals that act synergistically with fiber, and which are not replaced in mandated fortification programs, are arguably the foundation of the well-documented health benefits associated with whole grain consumption. New information also is highlighting an expanded role for insoluble fibers as microbiota-accessible carbohydrates, further solidifying our understanding of the fundamental benefits of a fiber-rich diet. These benefits cannot be realized, however, unless people eat whole grains and whole grain products. There is a broad movement aimed at making whole grains more attractive and compelling as food ingredients. Farmers, millers, bakers, and breeders, at scales from community to global, are revisiting a diverse array of grains and forms in which they can be consumed. Superimposed in these trends is the threat to the global food supply and the negative effects of rising atmospheric CO2 levels and global heating on the nutrient composition of grains. Potential responses to these threats involve breeding, crop management, and crop selection.

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Refinement and Fortification

Nothing seems more ubiquitous in modern cereal processing than refined wheat flour. I wrote previously (68) that, “The proliferation of cheap refined flour has had immense, and not always positive, impacts.” This article was suggested by the Cereal Foods World (CFW) guest editors as an expansion of that thought. I contend that the diminution of the amount of fiber in the typical Western diet is the biggest “not always positive” impact in the developed world. The effects of flour refinement on vitamin and mineral nutrition in communities without access to diversified diets and the use of biofortification to address these insufficiencies was addressed in the May-June 2019 issue of CFW (52,80). It is estimated that in North America more than 90% of all flour sold is refined flour; however, this may be changing in a positive direction. The National Health and Nutrition Examination Survey (NHANES) indicates a small but significant 9 g/day increase in whole grain consumption by U.S. residents between 2003–2004 and 2013–2014. This increase was accompanied by a 17 g/day decrease in refined grain consumption. With this increase, the ratio of refined to whole grains consumed in 2014 was 84:16 (15). Sixteen percent is an improvement over 1939, when it was estimated that only 3% of all U.S. bread sales were whole wheat breads (82). Less encouraging is the estimate that overall global whole grain consumption decreased by about 9 g/day between 1990 and 2010 (59).

Taking a historical perspective, by 1916 the market dominance of roller-milled refined flour was well established following the initial deployment of roller mills in North America during the late 1870s. It is instructive to read The American Miller and Processor trade journal from that era (60). There was much disparagement of whole wheat flours with respect to nutrition in the service of promoting refined flour. One letter to the editor is illustrative: “One of the best samples of Graham…was made on a burrstone mill, the stones being set very close…. This was a real Graham and a real whole wheat flour. If there is any virtue in such flours, which we doubt [emphasis added], this miller’s flour had it.” Other comments on bran include a statement from the 1916 Fraternity of Operative Millers of America Convention (6): “The public does not want and will not have a bran containing flour…[and] will not be coerced or cajoled in the matter.” In a Farmer’s Bulletin published in 1910, the U.S. Department of Agriculture stated, “…the outer hull of the wheat grain contains woody substances which pass through the alimentary canal of man undigested…,” with the inference that these “woody substances” conferred no nutritional value whatsoever when consumed (9). In general, the arguments that refined flour is nutritionally superior were based around the concepts of calorie density and its dilution by the bran and germ. However, even in 1916 the laxative effect of bran, which is a key weapon in fighting constipation (14,27), was recognized, even if it was thought at times that these “irritants in the alimentary canal…sometimes increase peristalsis, thus hastening the contents along too rapidly to permit complete absorption” (6).

That refined flour was an incomplete nutritional resource became clear very early in its newfound dominance in the early 20th century, with a concomitant increase in the incidence of diseases of deficiency. Fortifying refined flour to replace some of the assimilable micronutrients lost by removing the bran and germ was, and remains, the most widespread response. Wilder (82) wrote that the whiter roller-milled flour was nutritionally poorer than the “gray coarse stone-ground flour.” The roller-milled version contained “less of the coatings of the wheat grain and thus less vitamins and minerals.” Thiamine deficiency was an advance warning of the danger: the average American diet of the 1930s provided only about one-third of the thiamine requirement, and something needed to be done to correct the deficiency. In January 1943 the U.S. War Food Administration required that white bread be fortified. Around 1948–1949, by the time fortification was well established, studies in Chicago showed a nearly complete absence of the diseases associated with thiamine and niacin deficiency (82). Another public health achievement was the fortification of refined flour with folate. From January 1998 going forward, the U.S. Food and Drug Administration (77) mandated folic acid fortification of refined flours at a level of 140 µg/100 g of product to provide women with a 400 µg/day dose of folic acid. Fortification at this level was accompanied by a reduction in neural tube birth defects in the United States of 36% between 1996 and 2006 (17), and in Canada of 50% between 1997 and 2002 (26).

One might argue that fortification would not have been necessary if everyone simply ate whole wheat and grain products instead of products made with refined flour. But, do whole grains, in particular whole wheat, contain sufficient folate on their own? Koehler et al. (47) estimated the folate content of whole wheat grain to be in the order of 50 µg/100 g (dry mass), about one-third the amount found in fortified flour. Schoenlechner et al. (71) gave a much lower value of 13.5 µg/100 g for the single wheat variety tested in their study. These findings indicate that, in particular, women around the time of conception may want to “consume some folate-fortified flour” in order to confidently meet their folate intake target.

There may be other ways to introduce folate into unfortified whole wheat-based foods that would be compatible with the popularity of “clean-label” foods, for example, and would meet the target of 400 µg/day. In their study, Koehler et al. (47) showed an increase in folate concentration to around 200 µg/100 g of seed (dry weight) in wheat germinated at 20°C for 102 hr. Clearly, wheat germinated for such a long time could present technical challenges as a result of its increased enzyme level, but careful germination and kilning have been shown to enable the use of 100% sprouted wheat in whole wheat breads (67), so it could be argued that germination or sprouting is a feasible strategy. Another approach would be to supplement bread formulations with alternative grain sources that are rich in folate, such as quinoa, which contains between 80 and 130 µg/100 g of seed (dry weight) (69,72). This would achieve folate enrichment, as well as other nutritional goals, such as increasing the variety of grains consumed beyond wheat, to diversify fiber and phytochemical consumption (73). Consuming biological sources of folate raises the question of bioavailability, which is suggested to be 50% lower from biological sources compared with pteroylmonoglutamic acid, which is used in fortification (70). However, this is not a settled argument and has recently been contested (61). Additionally, fortification is not without controversy (43). For example, the indication of a tolerable upper intake level for folate consumption has recently been challenged by Wald et al. (78) and Iacobucci (38).

Iron is also in the fortification spotlight. Oversupply of iron through fortification might be considered a public health risk in some developed countries. Whittaker et al. (81) showed that iron in breakfast cereals is present at between 120 and 150% of the mandated level. Excess fortification can be compounded by the consumption of more than the recommended number of servings, rapidly leading to iron oversufficiency, approaching or exceeding the tolerable upper intake level of 45 mg/day (39), and as was reported in the science magazine Nautilus, “that’s just breakfast” (22). The issue with potential oversupply of iron is its reactivity. Bechaux et al. (12) comprehensively reviewed iron-catalyzed chemistry in the gastrointestinal tract and concluded that although iron is an essential nutrient for humans, its excessive consumption can lead to the production of free radicals and nitrite reactive species in the digestive tract, with potentially negative health consequences. Bechaux et al. (12) also noted that dietary chelating agents (e.g., phytate and polyphenols) and dietary antioxidants (e.g., tocopherols, carotenoids, and polyphenols) were effective in ameliorating the potentially harmful outcomes of excess iron.

The Whole Grain

In this discussion, I am asserting that increased whole grain consumption is desirable. I am basing the assertion on evidence, such as that reported in the systematic examination of dietary risks in 195 countries in the Global Burden of Disease Study (3). The study indicates that, across the globe, low intake of whole grains is one of the three largest dietary risk factors for noncommunicable diseases and, from 1990 to 2017, was associated with 2–4 million deaths and 59–109 million years of lost healthy life (83). Excess sodium intake and low intake of fruits are the other two major dietary risk factors according to the study (3). Other recent meta-analyses (10,24,66) support my assertion that whole grain consumption is desirable. For example, based on systematic meta-analyses covering “135 million person-years of data from 185 prospective studies and 58 clinical trials with 4635 adult participants,” Reynolds et al. (66) concluded that higher consumption of whole grains is associated with reduced risk of mortality and a range of noncommunicable diseases. This view is not without its critics, however. In a review of 9 randomized controlled trials with around 1,400 subjects, Kelly et al. (45) found insufficient evidence to recommend whole grain diets for amelioration of cardiovascular disease or elevated blood pressure or cholesterol. Kristensen et al. (49) lamented the low rate of compliance in intervention trials and recommended the use of biomarkers as objective measures of compliance and impact.

Fortification has been defended routinely as a means of replacing nutrients lost with bran and germ removal during refined flour milling (2). Although there are well-documented public health successes, such as those noted earlier, what is not addressed is a component that current fortification programs do not replace: the “woody substances” or the fiber. The “fiber gap” has been cited as a serious health deficit in Western diets, specifically with respect to the gut microbiome (23). Also, dietary fiber brings with it many phytochemicals, such as tocopherols, phenolics, phytates (for better and worse), and omega-3 unsaturated fatty acids, among others (42,50), that are not replaced as part of mandated nutrient fortification (e.g., iron and folate). Bach Knudsen et al. (11) suggested “the biochemical mechanisms behind the health benefits of [whole grain] still remain speculative, but can most likely be ascribed to a concerted action of [dietary fiber] and a wide variety of phytochemicals, phenolic compounds, carotenoids, vitamin E, sterols, and phytates.” The effects of these components were reviewed by Fardet (28), and Alexander et al. (5) stated in an article on the importance of short-chain fatty acid (SCFA) production from fiber that, “it has become increasingly obvious that dietary fiber or nondigestible carbohydrate consumption is critical for maintaining optimal health and managing symptoms of metabolic disease.”

One of the recent shifts in view that is exciting, to me, is the recognition that insoluble fiber, a major component of cereal bran layers, is also metabolically active (microbiota accessible) in the colon and is not just an inert water absorber and bulking agent. The concept of microbiota-accessible carbohydrates (MACs) was proposed by Sonnenburg and Sonnenburg (75) as a legitimate way of getting around the complexities of differentiation of fiber types (e.g., soluble versus insoluble and fermentable versus nonfermentable) and the differential abilities of each individual’s unique gut microbiota to access these carbohydrates. In general, it has been considered that soluble fibers are MACs but that insoluble fibers are largely not. This was despite the recognition by Sonnenburg and Sonnenburg (75) that the gut microbiomes of some individuals could metabolize cellulose (18). In parallel, and with more specificity to cereals, a number of studies have begun to reveal the role and fate of cereal bran in the colon. Observations that adsorption to a solid-state support structure could increase microbial fermentation efficiency has led to another way of thinking about bran and cell wall fragments in the colon. Macfarlane et al. (56) described the aggregation of bacteria on plant cell structures (by inference, insoluble) and how the adherent bacteria were more efficient at breaking down insoluble polymers. Gong et al. (33), in an in vitro study using fecal microbiota from one human donor, showed that whole wheat flours stimulated growth of beneficial bacteria compared with refined wheat flours from the same cultivars. These studies highlight the roles of insoluble fibers and cereal grain cell wall fragments beyond the role of inert filler. Comino et al. (21) based their approach on the well-established knowledge that soluble and insoluble cereal fibers are commonly similar in composition. Rather than compare soluble and insoluble fibers with different compositions (e.g., cellulose versus soluble arabinoxylan), they compared fibers with similar compositions from three cereal types. Using monogastric (porcine) fecal microbiota in vitro, they showed comparable fermentation rates and extents with similar levels of SCFA production for soluble and insoluble fibers from wheat, rye, and hull-less (naked) barley. Tuncil et al. (76) also showed, using in vitro fermentation with human fecal microbes, that the bran fraction was microbiota accessible and that the outcomes were modulated by the particle size of the bran fractions used as substrates. Particle size modified microbial taxonomic composition but also was associated with differences in the monosaccharide compositions of the bran fractions, which could be a confounding factor. Bran was butyrogenic, with the finer particle size producing relatively more butyrate early in fermentation and the largest particle size producing relatively more butyrate after 48 hr of fermentation. Clearly there were interactions, but the bran was a fermentable substrate regardless of particle size. The fact that bran can selectively enrich species was supported by the work of De Paepe et al. (25). In this in vitro study using fecal bacteria from six human donors, the researchers showed an increased abundance of species that were “not thriving in the luminal environment” when fed insoluble wheat bran residue. In accord with Tuncil et al. (76), they also showed that wheat bran stimulated butyrate production. Of the SCFAs, butyrate is considered to be of value in gut health due to its “beneficial effects on intestinal homeostasis and energy metabolism. With anti-inflammatory properties, butyrate [also] enhances intestinal barrier function and mucosal immunity” (53). One might argue that reliance on these in vitro studies is artificial and may not reflect what is occurring in an individual’s gut. However, research needs to start somewhere to support the observations of the benefits of whole grain consumption in epidemiological studies and intervention trials. Even the arguable gold standard, randomized blinded trials, has shortcomings (49).

Shifting the Landscape: Millers and Bakers

The question remains, how do we get people to eat a majority of their grains, cereals, and breads at 100% extraction (as whole grains)? In 1958 Kent-Jones (46) recalled “the strong preference of the public for white bread as against even the slightly darker bread made from [only] 80% extraction flour.” There are many nongovernmental organizations, nonprofit organizations, and institutions doing great work in promoting whole grain consumption: for example, the successful public–private Danish Whole Grain Partnership in Denmark (55), the Oldways Whole Grains Council in the United States, and the HealthGrain Initiative in the European Union. It is encouraging that over the last decade a new wave of milling operations, at all scales, has begun providing bakers and consumers with a cornucopia of diverse whole grains and flours milled from them. In the United States companies with national reach are now including whole grain flours from hexaploid wheat varieties of diverse heritage, emmer and other tetraploids, einkorn, naked barley, amaranth, quinoa, and sprouted grains, among others, in their portfolios. Across the Western world there are also many small- to medium-scale regional and community-based millers and bakeries with in-house mills that are promoting whole grains as the focus of their production rather than as an afterthought.

Whole wheat and other whole grain products need to be appealing in their own right for consumers to purchase them. If nutritional justifications were enough, everyone would already be eating whole grain versions of grain-based foods—we need other incentives. Simple improvements in presentation are helpful (Fig. 1), as are imaginative ways of using whole grains in products that, for example, require little leavening (Fig. 2). Partnering with chefs can also be a winning strategy (Fig. 3). Some of the bakers I work with are pioneers in making grains “sexy” again and are the champions for wheat and other whole grains that the enterprise needs to be successful. Chefs and bakers also are exploiting the growing diversity in readily available grains to expand the palette of choices with respect to flavor, aroma, color, and texture (Fig. 4). This is where the trend toward heritage and ancient wheats and other grains is a positive development: it makes grains more compelling and gives consumers a new experience of whole grains that arguably will keep them coming back for more. I have also been confronted with the argument that deployment of specialty grains cannot be done at scale. I have two responses to this argument: the brewing industry misjudged the market penetration of craft breweries, and clever people will make it work if the demand and economic return is there. As I wrote previously (68), modern artisan bakers are reinvigorating the use of einkorn, emmer, and spelt in the United States, partly from a desire to exploit their unique flavor and aroma characteristics. These bakers are adapting their methods to work with the generally weak doughs of flours milled from hulled wheats (36) through processing or blending with higher strength hexaploid wheats. In my experience as a baker, it is possible to make good breads from these grains, which from a conventional view of breadmaking quality might hardly be considered bread wheats at all.

The economic arguments are different for growers, processors, and consumers. For growers and processors, differentiation drives value and potentially allows these operations to charge prices that can keep their businesses viable. Conversely, for consumers affordability is the key economic driver. A negative economic argument suggests that craft bakeries in North America are producing a premium product that not everyone can afford unless they are affluent and live in an affluent region. As a result, the expensive, carefully crafted artisan whole grain loaf produced by new-wave millers and bakers is arguably inaccessible to a large portion of the population. Obviously, as large-scale operators continue to embrace whole grains, economies of scale can help keep consumer costs manageable while allowing for sufficient revenue to keep bakeries viable. But, what about smaller scale operations? I am a founding member of The Bread Lab Collective (http://thebreadlab.wsu.edu/the-bread-lab-collective), a group of North American bakers, millers, and researchers dedicated to the creation and deployment of simple, nutritious whole wheat bread that is affordable for small- to medium-scale processors to make and sell at a price that is affordable for consumers. The collective’s members include a representative sample of the small- to medium-scale millers and bakers mentioned earlier. Although large processors may see this as too small an initiative, I contend that every beachhead we can establish that increases the visibility, availability, and affordability of straightforward, nutritious whole grains is of value.

A Shifting Climate: Environmental Threats

There is another important factor related to the nutritional value of whole grains and access to them. As a cereals research community, we are faced with the task of ensuring basic crop health and survival in the shadow of a world that is growing hotter with increasing atmospheric CO2 levels. For temperate cereal crops, there is also the specter of the possible drying out of the midlatitude regions where wheat, for example, grows best (65). The regions at risk of becoming more arid include the U.S. Great Plains, the grain belts north of the Black and Caspian Seas and east into Kazakhstan, and the eastern wheat belt of Australia. Substantial aridification and resultant crop stress and increased risk of failure may occur at a net heating of as little as 1.5–2.0 degrees Celsius (65), let alone even hotter. The potential for widespread crop failures increases under this scenario, limiting access to cereal foods if the potential is realized. Even under less somber scenarios, we are still faced with climate instability (35,40), and the search for traits leading to climate resilience is urgent. What role does quality and nutrition play here? Should we focus only on reducing production risks, minimizing the footprint of grain cultivation, and reducing the production of greenhouse gases (13)? We find ourselves in new territory. Atmospheric CO2 exceeded 415 ppm just prior to the writing of this article (72), and although increasing temperatures and aridification are grim prospects, there is also an immediate threat to the nutritional and functional value of the grains we grow and use from increased atmospheric CO2.

Higher atmospheric CO2 concentrations have been associated with increased wheat yields (4,16), while heat waves have been reported to decrease yields (64). Despite an increase in protein content under acute heat stress (64), increased atmospheric CO2 levels have regularly been associated with decreased protein and mineral contents in plants generally (54,85), and decreases in nitrogen-containing vitamins in rice specifically (84). In cereal grains, with a general focus on wheat, the trend has been repeated in free atmosphere CO2-enrichment (FACE) studies. Fernando et al. (30) showed a 12.7% decrease in protein in the wheat variety Yipti at 550 ppm CO2 and decreases in sulfur, calcium, iron, and zinc, although there was an interaction with time of sowing for the decrease in mineral content. Mineral decreases were partly offset by water stress with later sowing. Another study by the same group (31) confirmed their earlier study and concluded that the reductions in nitrogen and minerals were not fully explained by biomass dilution. In a subsequent paper (29), they also reported decreased loaf volume and dough strength, increased mixing time, and a decrease in relative abundance of three high molecular weight glutenin subunits. Decreased protein concentration (a 1.1% decline in absolute protein concentration) was further confirmed by Asseng et al. (7) in a study that combined crop modeling with FACE experiments. The effects of rising atmospheric CO2 on cereal crops are profound and associated with lower bread quality and nutritional value, which may not be solved by the deployment of adaptive traits such as Gpc-B1, and with increased water and nitrogen use efficiency (79). Medek et al. (57), in a meta-analysis that confirmed decreases in protein in wheat, rice, and barley, concluded that, “Anthropogenic CO2 emissions threaten the adequacy of protein intake worldwide.” One could add to this the threat to adequate mineral nutrition. I contend that the predicted negative outcomes from increased atmospheric CO2 with respect to plant micronutrients and protein content are existential threats and that every step we take from here on needs to be informed by that knowledge.

Some of these threats have begun to be addressed through the biofortification of grains (e.g., with zinc), which has been reported by Walton (80) and Listman et al. (52). Henry et al. (37) expanded the thinking to include accelerated domestication of new species to deal with both sustainability and nutrition threats in, as they termed it, “new and variable climates.” Interestingly, eating whole grains, adequately processed to release the minerals in the outer layers of the seeds, is one small, low-tech, step that may be taken to ensure continuing micronutrient sufficiency for humanity.

Shifting the Landscape: Breeding and Research

It seems to me that there are currently four core components to the breeding enterprise for cereals:

  1. The essential task of “just” breeding for yield and tolerance to abiotic and biotic stresses (e.g., drought and plant diseases, respectively).
  2. Breeding for resilience to the triple threat of global heating, climate instability, and increased atmospheric CO2 concentrations.
  3. Breeding for processing functionality.
  4. Breeding for enhanced nutritional value, which interacts with the negative effects of increased atmospheric CO2 concentrations.

There are entire literature fields devoted to these core areas, which are far too expansive too cite here. Simple database search strings such as “breeding cereals for climate resilience” or “breeding cereals for nutritional enhancement” are useful starting points for those who are interested in exploring further.

For some traits, there are strong genetic components to the differences observed in nutritional composition (e.g., the higher levels of carotenoid pigments in einkorn, emmer, durum, and Khorasan) (74). However, the effects of environment and genetic × environment interactions need to be taken into account. For minerals, using ash level as a proxy for overall mineral content, Morris et al. (62) showed that within a group of around 2,000 soft and hard hexaploid semidwarf wheats the dominant effects on total wheat ash were crop year and location, with effects one to two orders of magnitude larger than the effect for genotype. In general, the total ash in these samples grown in the U.S. Pacific Northwest was lower than in samples grown in the North American Great Plains, showing a broadscale effect of environment. However, there was a consistent effect of genotype, indicating that there was sufficient genetic variability to manipulate mineral content. It is this type of genetic variability that can be exploited to increase the mineral content of wheat, even using conventional plant breeding methods (32,62). One issue with increasing the uptake of iron and zinc, for example, is the challenge of doing this while also minimizing uptake of toxic metals and metalloids (e.g., cadmium, lead, and arsenic) (32). Strategies to achieve this are being investigated: for example, genetic markers that show that zinc and cadmium uptake are independent (34).

Despite the primacy of breeding in the core areas, there is also an opportunity to breed for more flavorful grains with the goal of making whole grain foods more appealing to a wider audience. Flavor is a specifically targeted trait in the wheat breeding program headed by Stephen Jones (44), and it is also a targeted trait in the naked-barley breeding program at Oregon State University (OSU) (58). In addition, the OSU wheat breeding program, among others, has colored wheat varieties in their breeding pipelines with a view to improving both flavor and nutritional components (1). Brett Carver has been hailed by the Bellegarde Bakery in New Orleans, LA, for the “rich auburn color and fragrant nuttiness” of his modern wheat variety ‘Ruby Lee’ (48). Likewise, Anna McClung at the National Rice Research Center has been leading a group that is breeding purple rice for high levels of phenolics (20) and increased bran weight (19) as nutritional improvements. Their purple rice has also been touted for its “perfect balance of health and taste” (41). These are just a few examples of a shift in emphasis in cereal breeding that could be more widely addressed to make whole grains more exciting and appealing as foods.

Changes in flavor and aroma are important, but I would argue that texture characteristics need to fit within customary and traditional eating habits and practices if people are going to eat whole grain foods. For example, it seems clear that high-amylose starches, with their enhancement of fiber content via RS3 resistant starch (51,63), are going to provide a textural experience that may not be acceptable in certain markets or cultures. Li et al. (51) specifically addressed this issue with respect to pasta and noodles, for which there are divergent texture preferences depending on product and country of consumption. This is just one example, but it speaks to the broader issue that food is more than calories, protein, phytochemicals, or fiber. Altering arabinoxylans in wheat may generate not only textural changes in foods derived from the wheat, but also initiate processing challenges (79). Food is woven into the fabric of our existence and has personal, social, community, cultural, and traditional aspects that need to be accounted for when, for example, we are trying to increase the perilously low intake of whole grains worldwide (3). Atalan-Helicke (8) discusses local tastes and global markets with regard to siyez, a variety of einkorn grown in Turkey, which for human consumption is prepared primarily as bulgur. Once known as a peasant food, it is making inroads into urban areas. In its traditional cultural range, the grain is desired for its nutty flavor, but it also takes longer to cook. So, although these traits fit well in the traditional home of siyez, an adjustment to its flavor and adaptation for quicker cooking time is required for it to be acceptable in more modern, fast-paced environments. The culinary barriers to widespread adoption of siyez are arguably emblematic, in general, of barriers to getting a population that is adapted to refined grains to not only accept but to desire and seek out whole grain versions in the service of improved nutrition at a population level.


People have sought refined flour for millennia, but highly refined flour without fortification is nutritionally incomplete. Even mandatory fortification only replaces some of what is lost in milling grain to refined flour. Whole grains arguably provide great nutritional benefits and offer synergy between fiber and phytochemicals. In addition, bran, once thought to be at best a bulking agent in the gut, is proving to be much more dynamic in that system. However, there are barriers to access to and acceptability of whole grains that need to be addressed at a culinary level. Layered among these challenges are threats to the production and nutrient value of grains imposed by global heating and increased atmospheric CO2 levels. There are vigorous efforts underway in breeding that address both climate resilience and threats to the nutritional value of cereal grains, while respecting the need for humans to eat with dignity.


  1. Abdel-Aal, E. S. M., Young, J. C., and Rabalski, I. Anthocyanin composition in black, blue, pink, purple, and red cereal grains. J. Agric. Food Chem. 54:4696, 2006.
  2. Adams, J. The state of science regarding consumption of refined and enriched grains. Cereal Foods World 58:264, 2013.
  3. Afshin, A., Sur, P. J., Fay, K. A., Cornaby, L., Ferrara, G., et al. Health effects of dietary risks in 195 countries, 1990–2017: A systematic analysis for the Global Burden of Disease Study 2017. Lancet 393:1958, 2019.
  4. Ainsworth, E. A., Lemonnier, P., and Wedow, J. M. The influence of rising tropospheric carbon dioxide and ozone on plant productivity. Plant Biol. (Stuttg.). DOI: https://doi.org/10.1111/plb.12973. 2019.
  5. Alexander, C., Swanson, K. S., Fahey, G. C., and Garleb, K. A. Perspective: Physiologic importance of short-chain fatty acids from nondigestible carbohydrate fermentation. Adv. Nutr. 10:576, 2019.
  6. Anonymous. The F. O. M. A. Convention at St. Louis. Page 579 in: The American Miller and Processor. Vol. 44, No. 7. Mitchell Brothers Publishing Co., Chicago, IL, 1916.
  7. Asseng, S., Martre, P., Maiorano, A., Rötter, R. P., O’Leary, G. J., et al. Climate change impact and adaptation for wheat protein. Global Change Biol. 25:155, 2019.
  8. Atalan-Helicke, N. “You can never give up siyez if you taste it once”: Local taste, global markets, and the conservation of einkorn, an ancient wheat. Gastronomica 18:33, 2018.
  9. Atwater, W. O. Principles of Nutrition and Nutritive Value of Foods. U.S. Department of Agriculture, Farmers’ Bulletin No. 142. Government Printing Office, Washington, DC, 1910.
  10. Aune, D., Keum, N., Giovannucci, E., Fadnes, L. T., Boffetta, P., Greenwood, D. C., Tonstad, S., Vatten, L. J., Riboli, E., and Norat, T. Whole grain consumption and risk of cardiovascular disease, cancer, and all cause and cause specific mortality: Systematic review and dose-response meta-analysis of prospective studies. BMJ 353. DOI: https://doi.org/10.1136/bmj.i2716. 2016.
  11. Bach Knudsen, K. E., Nørskov, N. P., Bolvig, A. K., Hedemann, M. S., and Lærke, H. N. Dietary fibers and associated phytochemicals in cereals. Mol. Nutr. Food Res. 61(7). DOI: https://doi.org/10.1002/mnfr.201600518. 2017.
  12. Bechaux, J., de La Pomelie, D., Théron, L., Santé-Lhoutellier, V., and Gatellier, P. Iron-catalysed chemistry in the gastrointestinal tract: Mechanisms, kinetics and consequences. A review. Food Chem. 268:27, 2018.
  13. Berry, P. M., Kindred, D. R., and Paveley, N. D. Quantifying the effects of fungicides and disease resistance on greenhouse gas emissions associated with wheat production. Plant Pathol. 57:1000, 2008.
  14. Black, C. J., and Ford, A. C. Chronic idiopathic constipation in adults: Epidemiology, pathophysiology, diagnosis and clinical management. Med. J. Aust. 209:86, 2018.
  15. Bowman, S., Clemens, J. C., Friday, J. E., Lynch, K. L., LaComb, R. P., and Moshfegh, A. J. Food patterns equivalents intakes by Americans: What we eat in America, NHANES 2003–2004 and 2013–2014. Food Surveys Research Group Dietary Data Brief No. 17. Published online at www.ars.usda.gov/ARSUserFiles/80400530/pdf/DBrief/17_Food_Patterns_Equivalents_0304_1314.pdf. U.S. Department of Agriculture, Agricultural Research Service, Beltsville, MD, 2017.
  16. Cai, C., Yin, X., He, S., Jiang, W., Si, C., Struik, P. C., Luo, W., Xie, Y., Xiong, Y., and Pan, G. Responses of wheat and rice to factorial combinations of ambient and elevated CO2 and temperature in FACE experiments. Global Change Biol. 22:856, 2016.
  17. Centers for Disease Control and Prevention. CDC grand rounds: Additional opportunities to prevent neural tube defects with folic acid fortification. Morb. Mortal. Wkly. Rep. 59:980, 2010.
  18. Chassard, C., Delmas, E., Robert, C., and Bernalier-Donadille, A. The cellulose-degrading microbial community of the human gut varies according to the presence or absence of methanogens. FEMS Microbiol. Ecol. 74:205, 2010.
  19. Chen, M. H., and McClung, A. M. Genotypic diversity of bran weight of whole grain rice and its relationship with grain physical traits. Cereal Chem. 96:252, 2019.
  20. Chen, M. H., McClung, A. M., and Bergman, C. J. Phenolic content, anthocyanins and antiradical capacity of diverse purple bran rice genotypes as compared to other bran colors. J. Cereal Sci. 77:110, 2017.
  21. Comino, P., Williams, B. A., and Gidley, M. J. In vitro fermentation gas kinetics and end-products of soluble and insoluble cereal flour dietary fibres are similar. Food Funct. 9:898, 2018.
  22. Dalton, C. Iron is the new cholesterol. Published online at http://nautil.us/issue/67/reboot/iron-is-the-new-cholesterol. Nautilus 67, 2018.
  23. Deehan, E. C., and Walter, J. The fiber gap and the disappearing gut microbiome: Implications for human nutrition. Trends Endocrinol. Metab. 27:239, 2016.
  24. Delzenne, N. M., Olivares, M., Neyrinck, A. M., Beaumont, M., Kjølbæk, L., et al. Nutritional interest of dietary fiber and prebiotics in obesity: Lessons from the MyNewGut consortium. Clinical Nutr. DOI: https://doi.org/10.1016/j.clnu.2019.03.002. 2019.
  25. De Paepe, K., Verspreet, J., Verbeke, K., Raes, J., Courtin, C. M., and Van de Wiele, T. Introducing insoluble wheat bran as a gut microbiota niche in an in vitro dynamic gut model stimulates propionate and butyrate production and induces colon region specific shifts in the luminal and mucosal microbial community. Environ. Microbiol. 20:3406, 2018.
  26. De Wals, P., Tairou, F., Van Allen, M. I., Uh, S. H., Lowry, R. B., et al. Reduction in neural-tube defects after folic acid fortification in Canada. N. Engl. J. Med. 357:135, 2007.
  27. Dreher, M. L. Fiber in laxation and constipation. Page 95 in: Dietary Fiber in Health and Disease, Nutrition and Health. Springer International Publishing AG, Basel, Switzerland, 2018.
  28. Fardet, A. New hypotheses for the health-protective mechanisms of whole-grain cereals: What is beyond fibre? Nutr. Res. Rev. 23:65, 2010.
  29. Fernando, N., Panozzo, J., Tausz, M., Norton, R., Fitzgerald, G., Khan, A., and Seneweera, S. Rising CO2 concentration altered wheat grain proteome and flour rheological characteristics. Food Chem. 170:448, 2015.
  30. Fernando, N., Panozzo, J., Tausz, M., Norton, R., Fitzgerald, G., and Seneweera, S. Rising atmospheric CO2 concentration affects mineral nutrient and protein concentration of wheat grain. Food Chem. 133:1307, 2012.
  31. Fernando, N., Panozzo, J., Tausz, M., Norton, R. M., Neumann, N., Fitzgerald, G. J., and Seneweera, S. Elevated CO2 alters grain quality of two bread wheat cultivars grown under different environmental conditions. Agric. Ecosyst. Environ. 185:24, 2014.
  32. Garcia-Oliveira, A. L., Chander, S., Ortiz, R., Menkir, A., and Gedil, M. Genetic basis and breeding perspectives of grain iron and zinc enrichment in cereals. Front. Plant Sci. 9:937, 2018.
  33. Gong, L., Chi, H., Wang, J., Zhang, H., and Sun, B. In vitro fermentabilities of whole wheat as compared with refined wheat in different cultivars. J. Funct. Foods 52:505, 2019.
  34. Guttieri, M. J., Baenziger, P. S., Frels, K., Carver, B., Arnall, B., Wang, S., Akhunov, E., and Waters, B. M. Prospects for selecting wheat with increased zinc and decreased cadmium concentration in grain. Crop Sci. 55:1712, 2015.
  35. Halford, N. G., Curtis, T. Y., Chen, Z., and Huang, J. Effects of abiotic stress and crop management on cereal grain composition: Implications for food quality and safety. J. Exp. Bot. 66:1145, 2015.
  36. Hammed, A. M., and Simsek, S. Hulled wheats: A review of nutritional properties and processing methods. Cereal Chem. 91:97, 2014.
  37. Henry, R. J., Rangan, P., and Furtado, A. Functional cereals for production in new and variable climates. Curr. Opin. Plant Biol. 30:11, 2016.
  38. Iacobucci, G. Experts urge addition of folic acid to flour to halt “avoidable tragedy” of birth defects. BMJ 360. DOI: https://doi.org/10.1136/bmj.k477. 2018.
  39. Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. The National Academies Press, Washington, DC, 2001.
  40. Intergovernmental Panel on Climate Change. Climate Change 2014—Impacts, Adaptation, and Vulnerability: Part A: Global and Sectoral Aspects. Working Group II Contribution to the Fifth IPCC Assessment Report. Cambridge University Press, Cambridge, U.K., 2014.
  41. Izlar, R. Purple bran rice defies convention. Published online at www.crops.org/science-news/purple-bran-rice-defies-convention. Crop Science Society of America, Madison, WI, 2015.
  42. Jones, J. M. Grain-based foods and health. Cereal Foods World 51:108, 2006.
  43. Jones, J. M. Folic acid fortification and the controversy. Cereal Foods World 55:113, 2010.
  44. Jones, S. S., and Econopouly, B. F. Breeding away from all purpose. Agroecol. Sustain. Food Syst. 42:712, 2018.
  45. Kelly, S. A., Hartley, L., Loveman, E., Colquitt, J. L., Jones, H. M., et al. Whole grain cereals for the primary or secondary prevention of cardiovascular disease. Cochrane Database Syst. Rev. DOI: https://doi.org/10.1002/14651858.CD005051.pub3. 2017.
  46. Kent-Jones, D. W. The case for fortified flour. Proc. Nutr. Soc. 17:38, 1958.
  47. Koehler, P., Hartmann, G., Wieser, H., and Rychlik, M. Changes of folates, dietary fiber, and proteins in wheat as affected by germination. J. Agric. Food Chem. 55:4678, 2007.
  48. Krebs, C. Wheat conference to focus on end use. Published online at www.agjournalonline.com/news/20190509/wheat-conference-to-focus-on-end-use. Ag J., 2019.
  49. Kristensen, M., Pelletier, X., Ross, A., and Thielecke, F. A high rate of non-compliance confounds the study of whole grains and weight maintenance in a randomised intervention trial—The case for greater use of dietary biomarkers in nutrition intervention studies. Nutrients 9:55, 2017.
  50. Lærke, H. N., and Knudsen, K. B. Copassengers of dietary fiber in whole grain rye and oats compared with wheat and other cereals. Cereal Foods World 56:65, 2011.
  51. Li, H., Gidley, M. J., and Dhital, S. High-amylose starches to bridge the “fiber gap”: Development, structure, and nutritional functionality. Compre. Rev. Food Sci. Food Saf. 18:362, 2019.
  52. Listman, G. M., Guzmán, C., Palacios-Rojas, N., Pfeiffer, W. H., San Vicente, F., and Govindan, V. Improving nutrition through biofortification: Preharvest and postharvest technologies. Cereal Foods World 64(3). DOI: https://doi.org/10.1094/CFW-64-3-0025. 2019.
  53. Liu, H., Wang, J., He, T., Becker, S., Zhang, G., Li, D., and Ma, X. Butyrate: A double-edged sword for health? Adv. Nutr. 9:21, 2018.
  54. Loladze, I. Hidden shift of the ionome of plants exposed to elevated CO2 depletes minerals at the base of human nutrition. eLife 3. DOI: https://doi.org/10.7554/eLife.02245. 2014.
  55. Lourenço, S., Hansen, G. L., Stærk, B., Frank, P., and Petersen, C. T. The Whole Grain Partnership—How a public–private partnership helped increase whole grain intake in Denmark. Cereal Foods World 64(3). DOI: https://doi.org/10.1094/CFW-64-3-0027. 2019.
  56. Macfarlane, M. J., Hopkins, G. T., and Macfarlane, S. Bacterial growth and metabolism on surfaces in the large intestine. Microb. Ecol. Health Dis. 12:64, 2000.
  57. Medek, D. E., Schwartz, J., and Myers, S. S. Estimated effects of future atmospheric CO2 concentrations on protein intake and the risk of protein deficiency by country and region. Environ. Health Perspect. 125(8). DOI: https://doi.org/10.1289/EHP41. 2017.
  58. Meints, B., Cuesta-Marcos, A., Fisk, S., Ross, A., and Hayes, P. Food barley quality and germplasm utilization. Page 41 in: Exploration, Identification, and Utilization of Barley Germplasm. G. Zhang and C. Li, eds. Academic Press, London, U.K., 2016.
  59. Micha, R., Khatibzadeh, S., Shi, P., Andrews, K. G., Engell, R. E., and Mozaffarian, D. Global, regional and national consumption of major food groups in 1990 and 2010: A systematic analysis including 266 country-specific nutrition surveys worldwide. BMJ Open 5(9). DOI: http://dx.doi.org/10.1136/bmjopen-2015-008705. 2015.
  60. Mitchell Brothers Publishing Co. The American Miller and Processor. Vol 44, No. 6. Mitchell Brothers Publishing Co., Chicago, IL, 1916.
  61. Mönch, S., Netzel, M., Netzel, G., Ott, U., Frank, T., and Rychlik, M. Folate bioavailability from foods rich in folates assessed in a short term human study using stable isotope dilution assays. Food Funct. 6:241, 2015.
  62. Morris, C. F., Li, S., King, G. E., Engle, D. A., Burns, J. W., and Ross, A. S. A comprehensive genotype and environment assessment of wheat grain ash content in Oregon and Washington: Analysis of variation. Cereal Chem. 86:307, 2009.
  63. Newberry, M., Berbezy, P., Belobrajdic, D., Chapron, S., Tabouillot, P., Regina, A., and Bird, A. High-amylose wheat foods: A new opportunity to meet dietary fiber targets for health. Cereal Foods World 63:188, 2018.
  64. Nuttall, J. G., Barlow, K. M., Delahunty, A. J., Christy, B. P., and O’Leary, G. J. Acute high temperature response in wheat. Agron. J. 110:1296, 2018.
  65. Park, C. E., Jeong, S. J., Joshi, M., Osborn, T. J., Ho, C. H., et al. Keeping global warming within 1.5°C constrains emergence of aridification. Nat. Clim. Change 8:70, 2018.
  66. Reynolds, A., Mann, J., Cummings, J., Winter, N., Mete, E., and Te Morenga, L. Carbohydrate quality and human health: A series of systematic reviews and meta-analyses. Lancet 393:434, 2019.
  67. Richter, K., Christiansen, K., and Guo, G. Wheat sprouting enhances bread baking performance. Cereal Foods World 59:231, 2014.
  68. Ross, A. S. Flour quality and artisan bread. Cereal Foods World 63:56, 2018.
  69. Ruales, J., and Nair, B. M. Content of fat, vitamins and minerals in quinoa (Chenopodium quinoa, Willd) seeds. Food Chem. 48:131, 1993.
  70. Sauberlich, H. E., Kretsch, M. J., Skala, J. H., Johnson, H. L., and Taylor, P. C. Folate requirement and metabolism in nonpregnant women. Am. J. Clin. Nutr. 46:1016, 1987.
  71. Schoenlechner, R., Wendner, M., Siebenhandl-Ehn, S., and Berghofer, E. Pseudocereals as alternative sources for high folate content in staple foods. J. Cereal Sci. 52:475, 2010.
  72. Scripps Institution of Oceanography. The Keeling Curve. Published online at https://scripps.ucsd.edu/programs/keelingcurve. Scripps Institution of Oceanography, University of California San Diego, San Diego, CA, 2019.
  73. Seal, C. The importance of whole grains in improving diet quality: Is it a valid public health policy goal? Cereal Foods World 64(3). DOI: https://doi.org/10.1094/CFW-64-3-0030. 2019.
  74. Shewry, P. R. Do ancient types of wheat have health benefits compared with modern bread wheat? J. Cereal Sci. 79:469, 2018.
  75. Sonnenburg, E. D., and Sonnenburg, J. L. Starving our microbial self: The deleterious consequences of a diet deficient in microbiota-accessible carbohydrates. Cell Metab. 20:779, 2014.
  76. Tuncil, Y. E., Thakkar, R. D., Marcia, A. D. R., Hamaker, B. R., and Lindemann, S. R. Divergent short-chain fatty acid production and succession of colonic microbiota arise in fermentation of variously-sized wheat bran fractions. Sci. Rep. 8. DOI: https://doi.org/10.1038/s41598-018-34912-8. 2018.
  77. U.S. Food and Drug Administration. Food standards: Amendment of standards of identity for enriched grain products to require addition of folic acid. Fed. Reg. 61:8781,1996.
  78. Wald, N. J., Morris, J. K., and Blakemore, C. Public health failure in the prevention of neural tube defects: Time to abandon the tolerable upper intake level of folate. Public Health Rev. 39:2, 2018.
  79. Walker, C. K., Panozzo, J. F., Békés, F., Fitzgerald, G., Tömösközi, S., and Török, K. Adaptive traits do not mitigate the decline in bread wheat quality under elevated CO2. J. Cereal Sci. 88:24, 2019.
  80. Walton, J. Improving nutrition through biofortification: From strategy to implementation. Cereal Foods World 64(3). DOI: https://doi.org/10.1094/CFW-64-3-0026. 2019.
  81. Whittaker, P., Tufaro, P. R., and Rader, J. I. Iron and folate in fortified cereals. J. Am. Coll. Nutr. 20:247, 2001.
  82. Wilder, R. M. A brief history of the enrichment of flour and bread. J. Am. Med. Assoc. 162:1539, 1956.
  83. World Health Organization. Metrics: Disability-adjusted life year (DALY): Quantifying the burden of disease from mortality and morbidity. Published online at www.who.int/healthinfo/global_burden_disease/metrics_daly/en. WHO, Geneva, Switzerland, 2019.
  84. Zhu, C., Kobayashi, K., Loladze, I., Zhu, J., Jiang, Q., et al. Carbon dioxide (CO2) levels this century will alter the protein, micronutrients, and vitamin content of rice grains with potential health consequences for the poorest rice-dependent countries. Sci. Adv. 4(5). DOI: 10.1126/sciadv.aaq1012. 2018.
  85. Ziska, L. H., Pettis, J. S., Edwards, J., Hancock, J. E., Tomecek, M. B., Clark, A., Dukes, J. S., Loladze, I., and Polley, H. W. Rising atmospheric CO2 is reducing the protein concentration of a floral pollen source essential for North American bees. Proc. R. Soc. Biol. Sci. Ser. B 283(1828). DOI: https://doi.org/10.1098/rspb.2016.0414. 2016.