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Ideal Grain Ingredients: BREEDING WHEAT FOR HEALTH

Nancy Ames1* | Dylan S. MacKay2

Reviews-IdealGrainWheat is the predominant cereal crop grown and exported in Canada. Wheat products are among the most widely consumed food products in the world, making them an excellent vehicle for providing nutrients to the population. Although wheat already offers many health benefits, in North America there is a lack of consumer awareness or misinformation about the healthfulness of wheat. Recent consumer trends towards gluten-free and wheat free diets may not be based on medical need or scientific validation indicating more effort is needed to highlight substantiated scientific information in the media. For example, there are many bioactive compounds in wheat that have potential health benefits that have been documented in scientific journals but are not necessarily known to the general public. Examples include betaine1, lutein2,3, phenolic acids4,5, phytosterols6 and arabinoxylan7 and other fibres.

Many of these beneficial bioactive components are concentrated in the outer layers of the wheat kernel, reinforcing the importance of whole wheat intake. Wheat is a good source of the compound betaine which is concentrated in the aleurone layer, one of the outer layers in wheat bran. A four week human feeding study showed that including wheat aleurone in the diet increased betaine plasma levels and were accompanied by a decrease in LDL cholesterol1. Arabinoxylan is a soluble fibre component present in wheat aleurone that has been shown to reduce glycaemic response7. Consumption of arabinoxylan enriched muffins and bread for 5 weeks lowered fasting glucose values in type 2 diabetics8. Other studies found that wheat germ consumption was able to reduce cholesterol absorption9, which may be due to its phytosterol content. Ferulic acid, the most abundant phenolic acid found in wheat, has been shown to have anti-inflammatory and anti-oxidant properties in animal and in-vitro models. In healthy men, consumption of a wheat bran bread processed to make phenolic acids more bioavailable, increased blood ferulic acid concentrations and may have positive effects on the immune system10. Furthermore, there are several recent epidemiological11 and review12,13,14 papers that discuss the evidence for beneficial health effects of whole grain consumption, including wheat. For example, increasing whole-grain intake is associated with lower visceral adipose tissue (VAT) in adults, whereas higher intakes of refined grains are associated with higher VAT15. Bodinham et al.16 found that consumption of 48g of whole wheat fed for 3 weeks produced a significant reduction in systolic blood pressure compared to refined grain. In another study, a significant reduction in both total and LDL cholesterol was found with the consumption of a whole wheat diet17. These examples of documented nutritional benefits associated with specific wheat bioactives provide an opportunity for plant breeders to further enhance the healthfulness of wheat and satisfy consumer demand for ideal grain ingredients.

Currently, wheat breeding in Canada focusses on reducing plant disease and increasing yield while maintaining the high milling and baking quality that defines Canadian wheat18. Modern wheat cultivars have been bred to meet the demands of the milling industry. Wheat quality testing is performed on the straight grade flour, and although over 50 quality traits are tested, none of them focus on nutrition. High yield and milling quality are undoubtedly important traits for wheat to possess, but it is also possible to focus breeding criteria on nutrition. For example, barley is primarily bred for the malting and feed industries but more recently breeding programs are focusing on nutritional traits and food quality. This is especially apparent with the development of a new food barley class of grain in western Canada and the recent approval of a health claim for cholesterol lowering by Health Canada19. The barley health claim is based on scientific data showing that consumption of at least three grams of barley beta-glucan a day can help reduce cholesterol. Beta-glucan is a type of soluble fibre that is found in both barley and oats.
The Canadian oat breeding program is also a good example of where yield, milling quality and nutrition have been considered collectively when developing new varieties. Oats have historically been bred for health traits such as high soluble and total dietary fibre with a focus on retention of the nutrient rich bran layers during milling. Industry and consumers recognise the nutritional value of oats, which is aided by well-established health and nutrient content claims20. The context of the oat and barley breeding programs may serve as a guide for the wheat breeding program.

In order to add nutrition-based quality criteria into the wheat breeding program, support will be required from the research community and industry partners. Research can serve many roles: substantiating health benefits and claims, developing and implementing the new rapid screening tests, identifying sources of superior germplasm and working with industry on utilization opportunities. Methodology for measuring these traits must be established with the breeding system in mind; rapid testing and high repeatability are crucial to handle the large sample quantities. In addition, knowledge of the genetic control over a particular trait can aid in breeding progress and is useful in overcoming technical challenges such as genotype by environment interactions. For many traits, much of this information as well as data showing evaluation of diverse germplasm already exist. For example, lutein shows wide genetic variation and has been found in particularly high amounts among certain durum and hard red spring wheat germplasm. Industry already plays an important role in creating market opportunities for wheat as a healthy food ingredient. The industry’s close relationship with consumers puts them in a unique position to increase consumer knowledge of the health benefits of wheat. Consumers who become aware of the health benefits of wheat will then in turn create end-user demand for nutritionally superior varieties.

Wheat is the major cereal grain grown and exported from Canada. This means that wheat has the largest platform on which improvements to its nutritional traits can impact consumer health. Wheat is already nutritious, but the potential exists to make wheat even better through a wheat breeding program that focuses on nutrition, as well as yield and milling quality.

References
[1] Price, R. et al. (2010). J. Nutr., 140, 2153.
[2] Ma, L. et al. (2012). Brit. J. Nutr., 10, 350.
[3] Seddon, J, et al. (1994). J. Am. Med. Assoc., 272, 1413.
[4] Adom, K. et al. (2005). J. Agric. Food Chem., 53, 2297.
[5] Mateo Anson, N. et al. (2010). J. Cereal Sci., 51, 110.
[6] Ostlund Jr, R. et al. (2003). Am. J. Clinical Nutr., 77, 1385.
[7] European Food Safety Authority. (2011). EFSA Journal 9, 2205.
[8] Lu, Z.X. et al. (2004). Eur. J. Clinical Nutr., 58, 621.
[9] Borel, P. et al. (1990). J. Nutr. Biochem., 1, 28.
[10] Mateo Anson, N. et al. (2010). J. Nutr., 141, 137.
[11] Lutsey, P. et al. (2007). Brit. J. Nutr., 98, 397.
[12] Fardet, A. (2010). Nutr. Res. Rev., 23, 65.
[13] Harris, K & Kris-Etherton, P. (2010). Cur. Atherosclerosis Reports, 12, 368.
[14] Jacobs Jr, D. & Gallaher, D. (2004). Cur. Atherosclerosis Reports, 6, 415.
[15] McKeown, N. et al. (2010). Am. J. Clinical Nutr., 92, 1165.
[16] Bodinham, C.L. et al. (2011). Brit. J. Nutr.., 106, 327.
[17] Giacco, R. et al. (2010). Nutrition, Metabolism and Cardiovascular Diseases, 20, 186.
[18] McCallum, B.D. & DePauw, R.M. (2008). Can. J. Plant Sci., 88, 649.
[19] Health Canada, Bureau of Nutritional Sciences, Food Directorate, Health Products and Food Branch. 2012. Summary of Assessment of a Health Claim about Barley Products and Bloods Cholesterol Lowering. http://www.hc-sc.gc.ca/fn-an/label-etiquet/claims-reclam/assess-evalu/barley-orge-eng.php
[20] Health Canada, Bureau of Nutritional Sciences, Food Directorate, Health Products and Food Branch. (2010). Summary of Assessment of a Health Claim about Oat Products and Bloods Cholesterol Lowering. http://www.hc-sc.gc.ca/fn-an/label-etiquet/claims-reclam/assess-evalu/oat-avoine-eng.php

1Agriculture and Agri-food Canada, Winnipeg, Manitoba, R3T 2N2
2Richardson Centre for Functional Foods and Nutraceuticals, Winnipeg, Manitoba, R3T 6C5
(*Corresponding author: E-mail: nancy.ames@agr.gc.ca)

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