Health Matters: Whole Grains

Grains have been the “staff of life” for thousands of years, serving as a vital food source for humans. Until the last century grains were commonly eaten as whole grains. Grains are an important source of carbohydrates. Carbohydrates supply energy to the body in the form of glucose, whichy is the only energy source for red blood cells and the preferred energy source for the brain and central nervous system. Grains contain carbohydrate primarily in the form of starches and some fibre. Dietary guidelines recommend 130 grams of carbohydrates a day, based on the minimum amount required to provide the brain with an adequate supply of glucose.

Advances in the milling processing of grains allowed large scale separation and removal of parts of the grain. This was known as refined flour, which became popular because it produced baked goods with a softer texture and extended freshness. This refining process removed a large amount of the nutrients that were present in the whole grain.

Grains are the seeds of plants belonging to the grass family. All grains start life as whole grains. In their natural state growing in the fields, whole grains are the entire seed of a plant. This seed is made up of three key parts: the bran, the germ, and the endosperm.

The bran is the multi-layered outer skin of the kernel, and is tough enough to protect the other two parts of the kernel from assaults by sunlight, pests, water, and disease. It contains important antioxidants, B vitamins, and fibre.

The germ is the embryo, which, if fertilized by pollen, will sprout into a new plant. It contains many B vitamins, some protein, minerals, and healthy fats.

The endosperm is the germ’s food supply, which provides essential energy to the young plant so it can send roots down for water and nutrients, and send sprouts up for sunlight’s photosynthesizing power. The endosperm is by far the largest portion of the kernel. It contains starchy carbohydrates, proteins, and small amounts of vitamins and minerals.

Whole grains or foods that are made from them contain all three parts of the kernel. Most of the health-promoting substances are found in the germ and bran of a grain kernel and include resistant starch, oligosaccharides, lignans, phytosterols, phytic acid, tannins, lipids, and antioxidants. Refining normally removes the bran and the germ, leaving only the endosperm. Without the bran and the germ, about 25% of a grain’s protein is lost, along with at least seventeen key nutrients, including fibre, B vitamins, vitamin E, trace minerals, unsaturated fat, and about 75% of the phytochemicals. Phytochemicals are substances in plant-based foods with physiologically active components that have functional health benefits.

Today, foods made with whole grains are recognized as important sources of nutrients. Compared with refined grains, whole grains are healthier, provide more protein, more fibre, and many important vitamins and minerals. If the grain has been processed, i.e. cracked, crushed, rolled, and/or cooked, for a food product to be called a whole grain, it should deliver the same rich balance of nutrients that are found in the original grain seed.

The following foods, when consumed in a form which includes the bran, germ, and endosperm, are considered whole grains: amaranth, barley, buckwheat, corn, millet, oats, quinoa, brown rice, rye, sorghum, teff, triticale, wheat (including varieties such as spelt, emmer, farro, einkorn, Kamut, durum, bulgur, cracked wheat, and wheatberries), and wild rice. This list does not include all whole grains, but are the most common ones.

Whole grains have come into prominence with people wanting to adapt healthier lifestyles. In 2005, the US government”s Dietary Guidelines advised Americans to “make half your grains whole,” which is 3-5 servings of whole grain a day. A serving should contain at least 16 grams of whole grain ingredients. Canada”s Food Guide is not as specific, but whole grains are thought of as healthier than products made from refined grains. The average North American eats less than one serving of whole grains a day, even though common knowledge is that we should be eating more whole grains.

When buying whole grain products, it is important to read the product label. The label should list the amount of grams of whole grains, or make a comment such as “100% whole wheat.” Be sceptical if you see words such as, “whole grain,” without more details. The product may contain only miniscule amounts of whole grains. The amount of fibre in a whole grain food varies depending on the type of grain, amount of bran, density of the product and moisture content. Some grains may not be an excellent source of fibre.

What can whole grains do for you” What are their health benefits” Researchers have found that whole grains can lower your risk of heart disease, stroke, diabetes, cancer, obesity and constipation. Research also shows that refined grains have none of these health benefits. Although much of the research has focused on individual components of whole grains, such as fibre and antioxidants, evidence suggests that the whole grain food offers protection against a wide range of diseases that is greater than what is seen with any individual component. The array of nutrients and other components in whole grains are believed to have an additive and synergistic effect on health. Whole grains also have some valuable antioxidants not found in fruits and vegetables, as well as B vitamins, vitamin E, magnesium, iron and fibre.

Heart Disease

The strongest health benefit of whole grains is in preventing cardiovascular disease. Several studies have proved this. In one study, 34,000 women, who reported eating at least one serving of whole grains a day had a 30 to 36 per cent lower risk of heart disease than those who reported eating no whole grains. Another study of 75,000 women, who said that they ate roughly three servings of whole grain a day had a 25 per cent lower risk of heart disease and a 36 per cent lower risk of stroke than those who said they ate no whole grains. In a study of 44,000 men, those who reported eating at least three servings a day of whole grains (42 grams) had an 18 per cent lower risk of heart attack than those who reported eating less than 4 grams a day.

Even though researchers found this obvious health benefit in the studies that they did, they were not convinced that it was only whole grains that made the difference. People who eat whole grains tend to do a lot of other healthy things as well, like exercising and not smoking. They also ate less saturated fat and more vitamins. Therefore they looked further to find an explanation as to why whole grains might protect the heart. Some of the possibilities include:

Cholesterol. Whole grains that are rich in water-soluble fibre”like oats and barley”lower LDL (“bad”) cholesterol and increase HDL (“good”) cholesterol. They also lower blood pressure and triglyceride levels. But most people eat far less barley and oats than whole wheat, which is high in insoluble fibre. And, wheat bran, one of the richest sources of insoluble fibre, doesn”t lower cholesterol. Yet men who eat the most bran have the lowest risk of heart disease.

If you consider the fibre data, it is clear that grains rich in insoluble fibre are heart protective. Research must look beyond cholesterol for a full explanation of the benefit of whole grains, which include insoluble fibres such as wheat.

Insulin. In a small study, researchers fed 11 overweight adults with high insulin levels 6 to 10 servings a day of either whole or refined grains. Fasting insulin levels were lower after six weeks on the whole grains than after six weeks on the refined grains.

Whole grains seem to improve insulin metabolism. High insulin levels can raise the risk of both heart disease and diabetes. And a new study found a lower risk of the metabolic syndrome”which is linked to high insulin levels”in older people who ate whole grains.

Antioxidants. Whole grains are rich in antioxidants that may protect against tissue damage by scavenging marauding free radicals.

Research has shown that high doses of antioxidants, such as Vitamin E, do not prevent heart attacks. It is possible, they theorize, that when you isolate antioxidants and take them in high doses, they don”t work. They work the best when they are taken in foods which are rich in antioxidants.

Whole grains are also rich in a number of other possibly protective substances, including plant sterols, lignans, phytates, vitamins, and minerals.

Magnesium, folate and potassium are abundant in whole grains, three minerals which are heart-protective. These minerals are lacking in refined grains.

Diabetes

Do whole grains prevent diabetes? In a study done in the US, people who consumed at least three servings a day of whole grains had a 20 to 30 per cent lower risk of diabetes over the next decade or so than people who ate roughly one serving a week.

But again, people who eat whole grains have healthier behaviour overall. But researchers are encouraged by evidence for mechanisms that could explain why whole grains may prevent diabetes. Lower insulin levels is one possibility. Among the other are:

Fibre. The soluble fibre in whole grains like oats and barley can keep carbohydrates from entering the bloodstream too quickly. If the absorption of carbohydrates were slowed, you would have less stress on the pancreas, and insulin levels would not shoot up. Immediately after a meal, carbohydrate from refined grains causes a higher and more rapid elevation in blood glucose levels as well as a greater demand for insulin. Therefore, whole grains lower fasting insulin levels and decrease insulin resistance. Insulin resistance is a condition of decreased insulin sensitivity that increases the risk of developing Type 2 diabetes.

But, many whole grains, including wheat bran, are rich in insoluble fibre, which doesn’t slow absorption. Therefore, the health benefits of whole grains on insulin levels include those grains which contain soluble fibres. In studies that examined fibre sources, researchers found that fibre from whole grains, but not from fruit and vegetable sources appear to exert the protective effect in reducing risk for developing Type 2 diabetes.

Glycemic index. Many people assume that whole grains raise blood sugar levels less than refined grains (they have a lower glycemic index). However, what matters isn’t whether the grain is whole or refined, but whether it is finely ground (like flour) or intact (like bulgur or brown rice).

Whole-grain flour has nearly the same glycemic index as refined flour. Intact whole grains have a low glycemic index. Therefore, we need to eat more foods that contain intact whole grains, as opposed to grains that have been finely ground.

Bowel Function

Whole grains may have their biggest impact on the bowel, where fibre helps keep things moving.

For example, Australian researchers gave 28 overweight middle-aged men enough whole-grain wheat or rye to bring their fibre to 32 grams a day. This amount is what experts now recommend, and is about twice as much as the average man consumes. Stool weights were higher than when the men ate low-fibre versions of the same foods (only 19 grams of fibre a day). The large intestine responds to the larger and softer mass of residue produced by contracting, which speeds the movement of the bowel towards excretion. The effect of promoting intestinal regularity makes whole grain products integral components of diet plans to help alleviate constipation and decrease the risk of developing diverticulosis and diverticulitis.

Obesity

In a 12-year study, women who consumed more whole grains consistently weighed less than women who consumed fewer whole grains and those with the highest fibre intake had a lower risk of major weight gain. The reasons by which whole grains may support weight management include a feeling of fullness with less calories taken in, prolonged emptying of the stomach to delay the return of hunger, and increased insulin sensitivity to lower insulin demand.

Cancer

If there is one benefit people expect from whole grains, it is a lower risk of colon cancer. Whole grains appear to be associated with a reduced number of gastrointestinal cancers, as well as several hormone-dependent cancers. A review of 40 studies on gastrointestinal cancers found a 21 to 43 per cent lower cancer risk with high intake of whole grains. Whole grain foods may reduce the risk of cancer by a variety of mechanisms. Fibre and certain starches found in whole grains ferment in the colon to help reduce transit time and improve gastrointestinal health. Whole grains also contain antioxidants that may help against oxidation damage, which may play a role in cancer development.

The Bottom Line

Whole grains contain many healthful components, including dietary fibre, starch, essential fatty acids, antioxidants, vitamins, minerals, lignans and phenolic compounds that have been linked to reduced risk of heart disease, cancer, diabetes, obesity, and other chronic diseases. Since most of the health-promoting components are found in the germ and bran, foods made with whole grains can play an important role in maintaining good health.

Some strategies to use when shopping: Look for products that list whole grains as the first ingredient; look for whole grain products that contain at least 2 grams of fibre per serving; and, look for products that display the health claim of reducing the risk of heart disease and certain cancers.

To increase your whole grain intake: Eat whole grain breakfast cereals; substitute whole grain breads and pastas for those made from refined flours; substitute brown rice for white rice; add barley to soups and stews; and, when baking, use whole grain flour.