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Introductıon to Bioactives in Fruits and Cereals

Introductıon to Bioactives in Fruits and Cereals

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Fruit and Cereal Bioactives: Sources, Chemistry, and Applications

corresponding antioxidant capacities (Gharras, 2009). Recent evidences show that there is a great

interest to anticarcinogenic effects of polyphenolic compounds, as well as the potential to prevent

cardiovascular and cerebrovascular diseases (Cheynier 2005).

Polyphenols divide into several subgroups including flavonoids, hydroxybenzoic and hydroxycinnamic

acids, lignans, stilbens, tannins, and coumarins that have specific physiological and biogical effects

(Andersen and Markham 2006; Meskin et al. 2003; Tokuşoğlu 2001; Figure 1.1).

Flavonoids are a chemically defined family of polyphenols that includes several thousand compounds. The flavonoids have a basic structure (Figure 1.2), and several subclasses of flavonoids are

characterized by a substitution pattern in the B- and C-rings. The main subclasses of flavonoids include

flavan-3-ols, flavonols, flavones, flavanones, isoflavones, anthocyanidins, anthocyanins, flavononols,

and chalcons (Figure 1.3) that are distributed in plants and food of plant origin (Crozier, Jaganath, and

Clifford 2006).

Flavonoids in the circulation may protect against cardiovascular disease through their interaction with

low-density lipoprotein (LDL). Biochemical and clinical studies in both humans and experimental animals have suggested that oxidized low-density lipoprotein (oLDL) has its atherogenic action through the

formation of lipid hydroperoxides and the products derived therefrom. The in vivo antioxidant status of

the LDL particles and the plasma are thus important determinants of the susceptibility of LDL to lipid

peroxidation (Hertog et al. 1993).

Many of the phytochemicals and some vitamins (vitamin E, tocopherol) have antioxidant activity in

vitro, which has led to the use of the general term “antioxidants.”

Phenolic compounds




Phenolic acids


Hydroxybenzoic acids


Hydroxycinnamiz acids
























Figure 1.1  Family of phenolic compounds. (From Andersen, Q. M., and Markham, K. R., Flavonoids. Chemistry,

Biochemistry, and Applications, CRC Press, Taylor & Francis, Boca Raton, FL, 2006; Meskin, M. S., Bidlack W. R.,

Davies, A. J., Lewis, D. S., and R. K. Randolph, Phytochemicals: Mechanisms of Action. CRC Press, Boca Raton, FL,

2003; Tokuşoğlu, Ö., The Determination of the Major Phenolic Compounds (Flavanols, Flavonols, Tannins and Aroma

Properties of Black Teas, PhD Thesis, Department of Food Engineering, Bornova, Izmir, Turkey: Ege University, 2001).)
















Figure 1.2  Chemical structure of flavonoids.


Introduction to Bioactives in Fruits and Cereals
















Biokenin A






6 -O-Asetildaidzin

6 -O-Asetilgenistin

6 -O-Asetilglisitin

6 -OMalonildaidzin

6 -OMalonilgenistin

6 -OMalonilglisitin












































Grape extract

Figure 1.3  Flavonoid family in food plants. (Adopted from Tokuşoğlu, Ö., The Determination of the Major Phenolic

Compounds (Flavanols, Flavonols, Tannins and Aroma Properties of Black Teas, PhD Thesis, Department of Food

Engineering, Bornova, Izmir, Turkey: Ege University, 2001; Merken, H. M., and Beecher, G. R., J. Agric. Food Chem.,

48(3), 579–95, 2000; Beecher, G. R., Antioxidant Food Supplements in Human Health, Academic Press, New York, 1999;

Fennema, O. R., Food Chemistry, Marcel Dekker, New York, 681–96, 1996; Vinson, J. A., Dabbagh, Y. A., Serry, M. M.,

and Jang, J., J. Agric. Food Chem., 43, 2800–2802, 1995.)

Carotenoids in Fruit and Cereals

Carotenoids (Figure 1.4), a group of lipid-soluble compounds responsible for yellow, orange, red, and

violet colors of various fruits and cereals products, are one of the most important groups of natural pigments, owing to their wide distribution, structural diversity, and numerous biological functions (Astorg

1997; Fraser and Bramley 2004).

The provitamin A activity of some carotenoid bioactives, recently, have demonstrated to be effective

in preventing chronic diseases such as cardiovascular disease and skin cancer. Carotenoid bioactives

are classified into four groups: carotenoid hydrocarbons, carotenoid alcohols (xanthophylls), carotenoid

ketons, carotenoid acids.

Hydrocarbon carotenoids are known as carotenes, and the oxygenated derivatives are termed xanthophylls (Astorg 1997; Fraser and Bramley 2004; Lee and Schwartz 2005)

Functional Lipids and Lipid Soluble Constituents

There has been a great interest concerning functional lipids in cereals due to their promotion for health

and preventing diseases. Fatty acids play a central role in growth and development through their roles

in membrane lipids, as ligands for receptors and transcription factors that regulate gene expression, as a

precursor for eicosanoids, in cellular communication, and through direct interactions with proteins.

The main fatty acids in cereals are the saturated fatty acids, palmitic (16:0) and stearic (18:0), the

monounsaturated fatty acid oleic acid (18:1), and the diunsaturated fatty acid inoleic acid (18:2) existing

with smaller amounts of other fatty acids. These fatty acids are mainly assembled in glycerolipids; that

is, triacylglycerols (TAG) and variable amounts of phospholipids (PL), glycolipids (GL), in sterol esters

(SE), and waxes (or policosanols) in the different cereal grains.

Lipid soluble vitamins tocopherols and amphiphilic lipids alkylresorcinols, and terpen alcohol compounds are also important bioactive constituents in cereal grains (Figure 1.5). Cereal lipids have high

levels of tocotrienols that coexist with tocopherols, which are the biologically most active antioxidants


Fruit and Cereal Bioactives: Sources, Chemistry, and Applications















H 3C




H 3C








Figure 1.4  Major carotenoids. (Ross, C. A. and Harrison, E. H., Handbook of Vitamins, Taylor & Francis Group, Boca

Raton, FL, 1–39, 2007.)














































Triterpen alcohols

-Amyrin R1= methyl, R2 = hydrogen

-Amyrin R1= hydrogen, R2 = methyl

Figure 1.5  Some lipid soluble constituents and cereal grains.

Introduction to Bioactives in Fruits and Cereals


(Peterson 2004). Alkylresorcinols have been shown to have bioactivities in vitro and in vivo experiments.

They increase the γ-tocopherol level in rat liver and lung by possibly inhibiting γ-tocopherol metabolism

(Ross, Kamal-Eldin, and Aman 2004). Sterols and sterol-based constituents, terpenoids play a role in traditional herbal remedies and it is reported they show antibacterial, cholesterol-lowering, antiatherogenic,

and anticarcinogenic effects. Phytosterols appear not only to play an important role in the regulation of

cardiovascular disease but also to exhibit anticancer properties (Jones & AbuMweis, 2009).

Those beneficial bioactives of many fruits and cereals have been declared to possess anticarcinogenic

and antimutagenic effects in test animals. Recently, it has also been detected in the strong antioxidant

capacities of many edible fruits and cereals.

Mycotoxic Bioactives in Fruits and Cereals

Mycotoxigenic bioactives are toxic substances that are produced by the secondary metabolism of various

fungal species (Ho, Rafi and Ghai, 2007). Various studies have been reported about their high toxicity

and the possible risk for consumer health. Fungal spoilage of cereals and mycotoxic bioactive production

is most important.

It has been shown that the presence of fungi on fruits is not necessarily associated with mycotoxin

(aflatoxins, ochratoxin A, patulin, citrinin, T2, etc.) contamination. The mycotoxin formation depends

more on endogenous and environmental factors than fungal growth does (Andersen and Thrane 2006).

The studies indicated that Alternaria, and Fusarium in fruit and cereals may pose a mycotoxin

risk. During spoilage of cherries and apples, Penicillum expansum is known to produce patulin. Both

Alternaria and Fusarium are able to produce additional mycotoxic bioactives in moldy fruit samples:

alternariols and aurofusarin.

Penicillum verrucosum is known to produce Ochratoxin A in many cereals. Fusarium is able to produce zearalenone in addition to Ochratoxin A from P.verrucosum in moldy cereals. Aspergillus ochraceus, A.niger, and A.carbonarious produce Ochratoxin A in dried fruits such as raisins and currants

(Iamanaka et al. 2006).

Concluding Remarks

Fruit and Cereal Bioactives are comprised of the specific focus on the chemistry of beneficial and

nutritional bioactives (phytochemicals such as phenolics, flavonoids, tocols, carotenoids, phytosterols,

avenanthramides, alkylresorcinols, and some essential fatty acids) and toxicant biactives (mycotoxins; aflatoxins, ocratoxin A, patulin, citrinin, cyclopiazonic acid, T-2, fumonisin, deoksinivalenol, and

zearalenon) from the sources of selected fleshy fruits including temperate fruits (pome, stone, and berry

fruits), citrus and tropical fruits, nuts, and from various cereals (and pseudocereals), pulses (e.g., legumes

and edible beans).

Each chapter reviews dietary sources, occurrences, chemical properties, desirable and undesirable

health effects, antioxidant activity, evidentiary findings, applications as well as toxicity of the abovementioned bioactives and have been individually highlighted based on the fruit and cereal type. Fruit

and Cereal Bioactives present a unique and unified data to the fruit and cereal chemistry from a biochemical standpoint.


Andersen, B., and Thrane, U. 2006. Food-borne fungi in fruit and cereals and their production of mycotoxins.

In Advances in Food Mycology. Vol. 571, 137–52. Berlin: Springer-Verlag.

Andersen, Q. M., and Markham, K. R. 2006. Flavonoids. Chemistry, Biochemistry, and Applications. Boca

Raton, FL: CRC Press, Taylor & Francis.

Astorg, P. 1997. Food carotenoids and cancer prevention: An overview of current research. Trends Food Sci

Tech 8:406–13.


Fruit and Cereal Bioactives: Sources, Chemistry, and Applications

Beecher, G. R. 1999. Flavonoids in foods. In Antioxidant Food Supplements in Human Health, eds. L. Packer,

M. Hiramatsu, and T. Yoshikawa. New York: Academic Press.

Cheynier, V. 2005. Polyphenols in foods are more complex than often thought. Am. J. Clin. Nutr. 81 (Suppl):


Crozier, A., Jaganath, I. B., and Clifford, M. N. 2006. Phenols, polyphenols and tannins: An overview. In

Plant Secondary Metabolites, eds. A. Crozier, M. N. Clifford, and H. Ashihara, 1–24. Oxford: Blackwell

Publishing, Ltd.

Fennema, O. R. 1996. Flavonoids. In Food Chemistry. 3rd ed., 681–96. New York: Marcel Dekker.

Fraser, P. D., and Bramley, P. M. 2004. The biosynthesis and nutritional uses of carotenoids. Progress in Lipid

Research 43: 228–65.

Gharras, H. E. 2009. Polyphenols: Food sources, properties and applications—A review. Int J Food Sci and

Technol. 44: 2512–8.

Hertog, M. G. L., Feskens, E. J. M., Hollma, P. C. H., Katan, M. B., and Kromhout, D. 1993. Dietary antioxidant flavonoids and risk of coronary heart disease. The Zutphen Elderly Study. Lancet 342:1007–11.

Ho, C. T., Rafi, M. M., and Ghai, G. 2007. Bioactive Substances: Nutraceuticals and Toxicants. In Fennema's

Food Chemistry, 4th, eds. Srinivasan Damodaran, Kirk L. Parkin, Owen R. Fennema, CRC Press, Taylor

& Francis, Boca Raton, FL, USA ISBN: 9780824723453, ISBN 10: 0824723457. 1160.

Iamanaka, B. T., Taniwaki, M. H., Vicente, E., and Menezes, H. C. 2006. Fungi producing ochratoxin in dried

fruits. In Advances in Food Mycology. Vol. 571, 181–88. Berlin: Springer-Verlag.

Jones, P. J., and AbuMweis, S. S. 2009. Phytosterols as functional food ingredients: Linkages to cardiovascular

disease and cancer. Curr Opin Clin Nutr Metab Care 12 (2): 147–51.

Lee, J. H., and Schwartz, S. J. 2005. Analysis of carotenoids and chlorophylls in foods. In Methods of Analysis

of Food Components and Additives, 179–98. New York: Taylor & Francis Group.

Merken, H. M., and Beecher, G. R. 2000. Measurement of food flavonoids by high performance liquid chromatography: A review. J Agric Food Chem 48 (3): 579–95.

Meskin, M. S., Bidlack W. R., Davies, A. J., Lewis, D. S., and R. K. Randolph. 2003. Phytochemicals:

Mechanisms of Action. Boca Raton, FL: CRC Press.

Omaye, S. T., Bidlack, W. R., Meskin, M. S., and D. K. W. Topham. 2000. Phytochemicals as Bioactive Agents.

Lancaster, PA: Technomic Pub.

Peterson, D. M. 2004. Barley tocols—Effects of milling, malting, and mashing. Cereal Chem 71 (1): 42–4.

Ross, C. A., and Harrison, E. H. 2007. Vitamin A: Nutritional aspects of retinoids and carotenoids. In Handbook

of Vitamins. 4th ed., eds. J. Zempleni, R. B. Rucker, D. B. McCormick, and J. W. Suttie, 1–39. Boca

Raton, FL: Taylor & Francis Group.

Ross, A. B., Kamal-Eldin, A., and Aman, P. 2004. Dietary alkylresorcinols: Absorption, bioactivities, and possible use as biomarkers of whole-grain wheat- and rye-rich foods. Nutr Rev 62 (3): 81–95.

Tokuşoğlu, Ö. 2001. The Determination of the Major Phenolic Compounds (Flavanols, Flavonols, Tannins and

Aroma Properties of Black Teas. PhD Thesis. Department of Food Engineering, Bornova, Izmir, Turkey:

Ege University.

Vinson, J. A., Dabbagh, Y. A., Serry, M. M., and Jang, J. 1995. Plant flavonoids, especially tea flavonols,

are powerful antioxidants using an in vitro oxidation model for heart disease. J Agric Food Chem 43:



Health Promoting Effects of Cereal

and Cereal Products

Joseph M. Awika


Introduction................................................................................................................................................. 9

Cereal Consumption and Cancer.............................................................................................................. 10

Possible Mechanisms of Cereal Grains in Chemoprevention...............................................................11

Dietary Fiber Related Mechanisms..................................................................................................11

Antioxidant Related Mechanisms....................................................................................................11

Phytoestrogen Related Mechanisms............................................................................................... 12

Mediation of Glucose Response..................................................................................................... 12

Cereal Grain Consumption and Cardiovascular Disease.......................................................................... 12

Cereal Grain Consumption in Obesity and Diabetes................................................................................ 13




Cereal grains are consumed as the primary source of energy by most humans. Consumption of whole/

unrefined cereal products is known to contribute significantly to health and chronic disease prevention.

Whole cereal grains contain nutritionally significant quantities of dietary fiber, as well as various minerals and vitamins that are important for health. More recent evidence also indicates that cereals contain

significant quantities of phytochemicals, like antioxidants and phytoestrogens, which may significantly

contribute to reported health benefits of whole grain consumption. In most cases, these beneficial compounds are concentrated in outer layers (bran) of the grain (Table 2.1). Unfortunately, modern grain milling methods remove most of these compounds with the bran to produce refined endosperm fractions that

are more appealing to consumers in most food applications.

The refined grain products generally lack the health benefits that whole grains provide. At the moment,

the vast majority of cereal products consumed around the world are made from refined grain. For example, in the United States, the Harris Interactive survey commissioned by the Grain Foods Foundation estimated that whole grain products constituted about 11% of total grain consumption in 2008. Additionally,

only 10% of the U.S. population consumes the daily recommended whole grain intake of at least three

servings per day. On the positive side, emerging strong links between unrefined grain-based diets and

population health, coupled with public education, are renewing consumer interest in whole grain products. For example, various market trend data indicate that whole grain popularity is on the rise with consumers; between 2003 and 2008, the whole grain segment was among the fastest growing food product

categories in the United States. The level of whole grain consumption in the United States in 2008 was

20% higher than it was in 2005.

Efforts to promote whole grain consumption were until relatively recently not based on any strong epidemiological evidence of disease prevention (Slavin 1994), but mostly on recognized need for increased



Fruit and Cereal Bioactives: Sources, Chemistry, and Applications

Table 2.1

Antioxidant Activity and Dietary Fiber Content of Sorghum and

Wheat Grain and Brana

Antioxidant Activityb

Bran Dietary Fiber (% db)






Red wheat

White sorghum

Red sorghum

Black sorghum

Tannin sorghum

CV %

























Adapted from Awika, J. M., McDonough, C. M., and Rooney, L. W., Journal

of Agricultural and Food Chemistry, 53(16), 6230–34, 2005; Awika, J. M.,

Rooney, L. W., Wu, X. L., Prior, R. L., and Cisneros-Zevallos, L., Journal of

Agricultural and Food Chemistry, 51(23), 6657–62, 2003.

µmol TE/g, measured by the ABTS method.

fiber intake that was known to improve fecal bulk and intestinal transit time, and thus believed to improve

gut health. However, in the recent past, numerous epidemiological and intervention studies from around

the world have demonstrated significant health benefits directly linked to whole grain consumption

(Jacobs et al. 2000). Cereal grain-based products have been linked to reduced incidences of some types

of cancer (Bidoli et al. 1992; Slattery et al. 1997), cardiovascular disease (CVD; Liu et al. 1999; Nettleton

et al. 2009; Tighe et al. 2007), diabetes and obesity (Fung et al. 2001).

Cereal Consumption and Cancer

Evidence linking grain consumption with cancer risk has been reported for some time, even though plausible mechanisms have been mostly speculative. Whole grain consumption is widely believed to help reduce

cancer risk, whereas refined grain products have no beneficial effect. In fact, a few reports have linked

increased consumption of some grains with an elevated risk of certain gastrointestinal cancers (Chen et al.

1993), even though such evidence could be attributed to other factors like aflatoxin (Isaacson 2005) that can

be found in some grains, like corn, when grown in hot environments or handled improperly post harvest.

Sorghum consumption has been particularly linked to reduced incidences of esophageal cancer in

various parts of the world where this type of cancer was endemic, including parts of Africa, Iran, and

China (Vanrensburg 1981). These findings were supported by epidemiological evidence linking sorghum

and millet consumption with 1.4–3.2 times lower mortality from cancer of the esophagus in Sachxi

Province of China (Chen et al. 1993). Interestingly, both authors reported no benefit or elevated risk of

cancer of the esophagus with increased consumption of corn and wheat flour in these studies. The forms

in which these grains were consumed in these regions were not reported. However, dietary patterns in

these areas indicate that wheat, for example, is mostly consumed in a highly refined form in these areas.

A case in point is China, where steamed bread, a major form in which wheat is consumed, is usually

prized for whiteness and smooth texture, properties only possible with highly refined wheat flour. Such

refined products have not been shown to contribute to chemoprevention. On the other hand the beneficial

effects reported for sorghum consumption may be related to the fact that sorghum is mostly consumed

with limited to no refining. Additional evidence also indicates that sorghum contains high levels of phytochemicals relative to other cereals (Awika et al. 2003). The sorghum phytochemicals may also have

higher bioactivity than those found in other grains. For example, recent evidence demonstrates that some

unique compounds in sorghum (e.g., 3-deoxyanthocyanins) may have stronger chemoprotective properties than their analogs from other plant sources (Yang, Browning, and Awika 2009).

In the recent past, a flood of evidence (based on epidemiological and intervention studies) linking

cereal grain consumption with reduced incidences of, especially, gastrointestinal cancer have emerged

Health Promoting Effects of Cereal and Cereal Products


(Jacobs et al. 1998a; Kasum et al. 2001; Larsson et al. 2005; Levi et al. 2000; Schatzkin et al. 2008).

In almost all cases, the positive benefits are only realized when grain is consumed in an unrefined

form, or when cereal bran components are included in a diet. Thus it is safe to assume that the refined

cereal endosperm products will not provide any meaningful health benefits beyond basic nutrition. For

example, Larsson et al. (2005) reported a risk of 0.65 for colon cancer among those who consumed

at least 4.5 servings of whole grain per day compared to those who consumed less than 1.5 servings.

Levi et al. (2000) reported a significant reduction in the risk of oral, esophageal, and laryngeal cancer

with increased consumption of whole grain as opposed to refined grain products. Numerous bodies of

evidence that corroborate the link between whole grain consumption and gastrointestinal cancer are

available in literature. Most of these investigations have, however, been conducted in developed countries. It is still not known how these data would translate to developing countries where malnutrition

and presence of other confounding factors, like aflatoxin in grain, can be significant. This should be

investigated since the developing countries consume a lot more cereal grain as a proportion of diet than

the developed countries.

Less clear is the link between whole grain consumption and some hormonally dependent cancers, such

as breast cancer (La Vecchia and Chatenoud 1998). For example, a recent cohort study by Egeberg et

al. (2009) failed to find a link between whole grain consumption and breast cancer risk among Danish

postmenopausal women, similar to previous findings (Fung et al. 2005; Nicodemus, Jacobs, and Folsom

2001). On the other hand Kasum et al. (2001) reported that even though there was no statistical association between whole grain intake and endometrial cancer among postmenopausal women in general, a

significant reduction in risk was observed when women who never used hormone replacement ­therapy

were considered independently. In general, however, the link between breast and other hormonally

dependent cancers and cereal grain consumption is weak. This may be due partly to the generally low

levels and wide variation in phytoestrogens (usually lignans) in cereal grains. Additional evidence is

needed in this regard.

Possible Mechanisms of Cereal Grains in Chemoprevention

Various mechanisms have been proposed for the effects of whole grain on cancer risk based on animal

and in vitro model studies. Since the strongest evidence of whole grain consumption and cancer risk are

for gastrointestinal cancer, it is believed cereal components may exert their effects via direct interaction

with gastrointestinal epithelial cells. The mechanisms can be summarized into four broad and generally

inclusive categories: dietary fiber related mechanisms, antioxidant related mechanisms, phytoestrogen

related mechanisms, and mediation of glucose response (Slavin 2000).

Dietary Fiber Related Mechanisms

Dietary fiber is believed to impart its beneficial effect by two mechanisms: (1) increasing fecal bulk and

reducing intestinal transit time, thus limiting interaction of potential fecal mutagens with intestinal epithelium, and (2) fermentation of soluble fiber by colon microflora to produce short chain fatty acids like

butyrate, propionate, and acetate, which lower intestinal pH and promote gut health by diminishing bile

acid solubility and cocarcionogenicity, and also possibly via direct suppression of tumor formation by

butyrate (McIntyre, Gibson, and Young 1993). Thus, different cereal products may impact chemoprotection via different mechanisms depending on their dietary fiber composition.

Antioxidant Related Mechanisms

Oxidative damage can lead to chronic cell injury, which is one of the mechanisms that may lead to cancer (Klaunig et al. 1998). Whole grains are rich in antioxidant phenolics (e.g., ferulates and flavonoids),

­vitamins (e.g., vitamin E), minerals (e.g., selenium), and other components mostly concentrated in their

bran and germ. These dietary antioxidants directly suppress oxidative damage by quenching potentially

damaging free radicals generated by various metabolic processes. They are also known to suppress the


Fruit and Cereal Bioactives: Sources, Chemistry, and Applications

growth of preformed cancer cells, which may contribute to elimination of cancer in early stages. Some

of the antioxidants (e.g., selenium) are also cofactors of antioxidant enzymes, while others may enhance

activity of protective phase II enzymes (Yang, Browning, and Awika 2009). For example, sorghum is an

especially rich source of antioxidants (Table 2.1); this may partly explain the distinct chemoprotective

properties against esophageal cancer reported for sorghum relative to corn or wheat.

Phytoestrogen Related Mechanisms

Estrogenic effects of cereals may be produced by lignans that are found in low quantities in cereal brans.

These plant lignans (e.g., secoisolariciresinol) can be metabolized by intestinal microflora into mammalian lignans like enterodiol, which are estrogenic. Other authors have suggested that dietary fiber may

also interrupt enterohepatic circulation of estrogen, leading to increased fecal estrogen secretion (Goldin

et al. 1982).

Mediation of Glucose Response

Since a link between the cause of obesity and cancer has been suggested, it is believed that whole grains,

through their effect of slowing glycemic response and thus insulin secretion, may contribute to chemoprevention (Schoen et al. 1999). See the section near the end of this chapter about cereal grain consumption in obesity and diabetes for more detail.

Cereal Grain Consumption and Cardiovascular Disease

Cardiovascular disease (CVD) remains the leading cause of deaths in much of the developed world,

and a major contributor to morbidity and health care costs. It has been long recognized that diets rich

in unrefined grain or grain components, as well as dietary fiber can help significantly lower the risk for

CVD (Trowell 1972), even though systemic evidence began emerging only in the latter part of the 1990s.

A recent meta-analysis of several cohort studies estimated that an average of 2.5 servings of whole grain

per day reduced the risk of CVD events by 21% compared to 0.2 servings/day of whole grain (Mellen,

Walsh, and Herrington 2008). Evidence indicates that the beneficial effect of cereal grains on cardiovascular health may be related to bran components. For example, Jensen et al. (2004) reported that adding

bran to a whole grain diet reduced coronary heart disease (CHD) risk by 30% compared to whole grain

alone, which reduced the risk by 18% among male professionals aged 40–75 years. The authors found

that the added germ had no effect on CHD risk. Similar findings have been documented in various other

studies. This type of evidence initially led to the assumption that the dietary fiber in the bran part of

whole grain was primarily responsible for the beneficial effect. However, other studies have found that

the benefit of whole grain consumption cannot be fully explained by their dietary fiber content alone

(Liu et al. 1999).

Other than soluble and insoluble dietary fiber, cereal bran contains a complex mixture of antioxidant

molecules, phytoseterols, policosanols, phytoestrogens, trace minerals, vitamins, and other compounds

that have been associated with positive cardiovascular outcomes in controlled studies. Effects of cereal

dietary fiber components on cardiovascular health are well documented. However, the exact mechanisms

involved are not very clear. Some studies have reported a higher effect of insoluble cereal fiber on cardiovascular health than soluble fibers (Lairon et al. 2005), while others have reported the opposite effect.

However, such inconsistencies may be due to the simple fact that it is often difficult, if not impossible, to

isolate the effect of various forms of dietary fiber in cereals on cardiovascular health. In general, there is

an agreement that soluble dietary fiber increases viscosity of gastric content, reducing the rate of absorption of nutrients. This may improve glycemic response and consequently reduce insulin demand and

improve the blood lipid profile. The soluble fibers may also exert their effect via partial fermentation into

short chain fatty acids by colon microflora; reducing colon pH and thus reducing bile acid solubility and

sterol reabsorption. Some short chain fatty acids, especially butyric and propionic acid, may also directly

inhibit cholesterol biosynthesis.

Health Promoting Effects of Cereal and Cereal Products


Cereal bran wax components, specifically phytosterols and policosanols have been reported in various studies to reduce cholesterol absorption and biosynthesis. For example, sorghum dry distiller grain

hexane extracts were shown to significantly reduce cholesterol absorption by up to 17% and non-HDL

plasma cholesterol by up to 70% in animal models (Carr et al. 2005). The authors attributed the unusually potent effect of sorghum lipid extracts to the relatively high policosanol content of sorghum bran.

Phenolics and other antioxidants found in cereal bran are also believed to contribute to cardiovascular

health by reducing inflammation and LDL oxidation, as well as improving endothelial function, and

inhibiting platelet aggregation. Some studies have also implicated phenolic compounds in cholesterol

reduction (Fki, Sahnoun, and Sayadi 2007; Parker et al. 1996). Phytoestrogens found in cereal bran

(mostly lignans) are hypothesized to promote favorable vascular responses to stress as well as endothelium-modulated dilation by inhibiting platelet aggregation or platelet release of vasoconstrictors (Anderson

et al. 2000; Slavin, Jacobs, and Marquart 1997).

It seems that the net effect of whole grain diets on cardiovascular health is a result of synergistic

and complex interactions of dietary fiber with various minor components in ways that are not yet fully

understood. This may also explain why isolated cellulose fiber does not produce similar cardiovascular

benefits as whole grain or cereal bran (Kahlon, Chow, and Wood 1999).

Cereal Grain Consumption in Obesity and Diabetes

Appetite suppression and control is the single most important mechanism to regulate calorie intake and

thus affect weight gain. Satiety (longer duration between meals) and satiation (lower meal energy intake)

play key roles in appetite control and energy intake. Whole grain products are believed to influence

satiety and satiation due, at least partly, to their effect on glycemic response. Unrefined grain products

are digested and absorbed more slowly, resulting in smaller postprandial glucose responses and insulin

demand on the pancreatic β cells (Slavin, Jacobs, and Marquart 1997). By regulating insulin response,

whole grain products may prevent problems associated with elevated blood insulin, including altered adipose tissue physiology and increased lipogenesis and appetite. Ludwig et al. (1999) reported that the high

glycemic index (GI) foods may actually promote overeating in obese children. The authors reported that

voluntary energy intake after a high GI meal was 53% higher than after a medium GI meal among obese

teenage boys. On the other hand, Burton-Freeman and Keim (2008) reported that high GI meals resulted

in greater satiety and suppression of hunger than low GI meals in obese women. The authors concluded

that low GI diets may not be suitable for optimal appetite and satiety among overweight women.

Such controversy is understandable given that satiety and GI are not by themselves precise measures of

anything meaningful. Satiety is highly subjective and related to behavioral factors not fully understood.

Additionally, GI in itself is highly variable depending on measuring conditions, among other factors, and

its use as a predictor on the health impact of carbohydrate consumption remains very much questionable.

Such variability have led some authors to propose doing away with the GI as such and evaluating meal

quality based on individual and demonstrated merits like whole grain content (Sloth and Astrup 2006).

All the same, glycemic response as a mechanism is useful in explaining some observations related

to whole grain and dietary fiber intake. The reduced glycemic response of whole grain foods is partly

attributed to the dietary fiber. Both soluble and insoluble dietary fiber found in whole grain products

can provide a physical barrier to digestive enzymes, thus resulting in slow and sometimes incomplete

digestion of starch. Indeed, it is known that whole grain products have higher type 1 resistant starch

(physically inaccessible starch) than refined grain counterparts. The soluble part of dietary fiber may

additionally increase gastric lumen viscosity that further slows digestion and macronutrient absorption.

Another factor that may contribute to reduced insulin response is the reduced energy intake due to the

bulking effect of dietary fiber that reduces energy density of a meal and increases satiation.

However, dietary fiber alone does not explain the insulin response modulating properties of whole

grain products. For example, long-term wheat bran consumption was shown to improve glucose tolerance better than pectin (Brodribb and Humphreys 1976). Other components concentrated in the bran and

possibly germ, like antioxidants, vitamin E, and Mg, may also contribute to insulin sensitivity. Oxidative

stress has been associated with reduced insulin-dependent glucose disposal and diabetic complications


Fruit and Cereal Bioactives: Sources, Chemistry, and Applications

(Oberley 1988), whereas vitamin E and Mg may be involved in glucose metabolism (Slavin, Jacobs, and

Marquart 1997).

Whole grain may also affect satiation by insulin-independent mechanisms. For example, it has been

shown that ingestion of whole grain products and cereal fiber may increase a secretion of the hormone,

cholecystokinin, in the small intestine (Bourdon et al. 1999). This hormone is known to contribute to

appetite suppression, as well as slowed gastric emptying and the inducement of satiety.

Both clinical and observational studies show that an intake of whole grain is inversely associated

with plasma biomarkers for metabolic syndrome and obesity, like C-peptide and leptin ­concentrations

(Koh-Banerjee and Rimm 2003). Whole grain and fiber enhanced cereal products are reported to

reduce overall calorie intake, and thus obesity, by suppressing appetite and via other mechanisms proposed above. For example, Hamedani et al. (2009) reported that breakfast cereal high in insoluble fiber

significantly reduced short-term calorie intake in healthy individuals. Relatively recent epidemiological

and some intervention studies seem to support the overall notion that whole grain consumption reduces

obesity and metabolic syndrome. The Iowa Women’s Health Study found that whole grain intake was

inversely correlated with body weight and fat distribution (Jacobs et al. 1998b). Pereira et al. (1998)

also reported that the whole grain intake was inversely related to BMI at a 7-year follow-up of the

participants of the study. Another large study of health men and women, the Multi-Ethnic Study of

Atherosclerosis (MESA), reported an inverse association between whole grain intake and obesity, along

with insulin resistance, inflammation, and elevated fasting glucose or newly diagnosed diabetes (Lutsey

et al. 2007).


Even though some controversies still remain, many studies support the link between whole grain consumption and overall health. However, most of these studies do not provide information on causality

of the associations. Just like with other dietary components, it is very difficult to accurately pinpoint

how and what components of a complex matrix like whole grain may impact specific health outcomes.

However, given many of the rigorous studies show obvious benefits linked to whole cereal product consumption, even after correcting for various confounding variables, it is safe to conclude that whole grains

should be actively promoted as a part of a healthy diet. Meanwhile more rigorous studies are needed

to unravel the mechanisms by which whole grains impact health. This way, food product development

efforts can be directed toward optimizing ingredient functionality to deliver health-promoting products

that consumers can buy into en masse. This is especially important because no amount of preaching of

health benefits will make consumers flock to a product consistently if the sensory appeal is substandard.

Whole grain products, unfortunately, still largely suffer from the inferior sensory quality perception

among the majority of consumers. Given that most human beings consume cereal grain-based products

on a daily basis for primary nourishment, and will continue to do so into the foreseeable future, there

is a tremendous opportunity to improve human health with a combination of innovative whole grain

based products, public education, and cutting-edge research exposing the link between grain components and health.


Anderson, J. W., T. J. Hanna, X. J. Peng, and R. J. Kryscio. 2000. Whole grain foods and heart disease risk.

Journal of the American College of Nutrition 19 (3): 291S–9S.

Awika, J. M., C. M. McDonough, and L. W. Rooney. 2005. Decorticating sorghum to concentrate healthy

­phytochemicals. Journal of Agricultural and Food Chemistry 53 (16): 6230–4.

Awika, J. M., L. W. Rooney, X. L. Wu, R. L. Prior, and L. Cisneros-Zevallos. 2003. Screening methods to measure antioxidant activity of sorghum (Sorghum bicolor) and sorghum products. Journal of Agricultural

and Food Chemistry 51 (23): 6657–62.

Bidoli, E., S. Franceschi, R. Talamini, S. Barra, and C. Lavecchia. 1992. Food-consumption and cancer of the

colon and rectum in North-Eastern Italy. International Journal of Cancer 50 (2): 223–9.

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Introductıon to Bioactives in Fruits and Cereals

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