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By: Abigail Larson, MS, CSCS
Nutrition is of great importance to many athletes. It can mean the difference between getting sick and staying healthy or recovering from a workout or not. Some athletes choose to use supplements, others focus on diet, and some on both. I prefer to use diet as my primary means of obtaining all the nutrients I require for life and training. Food is less expensive and more readily absorbed by the body than many supplements. In addition, science is discovering that a variety of foods provide additional health benefits than their basic vitamin and mineral content would suggest. These foods are called “functional foods”.
A functional food provides an additional physiological benefit beyond that of meeting basic nutritional needs. It is a new catch term on the nutrition front with several definitions depending on the source. The ADA states a “functional food can be any healthful food or food ingredient that may provide a health benefit beyond the traditional nutrients it contains”. It can also refer to a food that has some identified value leading to health benefits, such as reduced risk for a certain disease. There are many “functional foods” on the market today. Some of them are whole foods that have been available for hundreds of years (fruits and vegetables) and some are new to the food system, such as margarine's made from flaxseed oil. The following is a list of some of the most common functional foods with the highest efficacy for promoting a given health benefit.
Functional Foods from Plant Sources
Overwhelming evidence indicates that a plant-based diet can reduce the risk of chronic disease, especially cancer. There are components in a plant-based diet other than traditional nutrients that can reduce cancer risk; these biologically active plant chemicals are "phytochemicals."
Oats: Oat products are a widely studied dietary source of the cholesterol-lowering soluble fiber b-glucan. There is now significant scientific agreement that consumption of this particular plant food can reduce total and low density lipoprotein (LDL) cholesterol, thereby reducing the risk of coronary heart disease (CHD). The amount of oat bran or oatmeal needed daily to have a therapeutic effect is about 60 grams (3/4 cup dry) of oatmeal or 40 grams of oat bran (for a 5% reduction in cholesterol).
Soy: Soy is a complete protein, thought to play preventive and therapeutic roles in cardiovascular disease (CVD), cancer, osteoporosis, and the alleviation of menopausal symptoms.
The cholesterol-lowering effect of soy has been proven in numerous studies. A decrease in blood lipids is thought to be due to isoflavones but the exact mechanism is yet to be determined. A soy protein intake of 25 g a day elicits a reduction in cholesterol.
Soy may also prevent cancer as a result of anti carcinogens (phytic acid and isoflavones) that have been identified in soybeans. The epidemiological data on soy intake and cancer risk are inconsistent but future research may shed a more conclusive light on soy’s cancer prevention role.
Bone health appears to be positively affected by consuming soy. A recent clinical study found increased bone mineral content and density after 6 months of 25g/day soy intake in postmenopausal women. Soy may also alleviate menopausal symptoms. This theory was prompted by the observation that Asian women report significantly lower levels of hot flushes and night sweats compared to Western women.
Flaxseed: Flaxseed oil is a rich source of omega-3 fatty acid (a-linolenic acid) an essential fatty acid that has been shown to reduce total and LDL cholesterol and platelet aggregation. It is also the richest source of lignan precursors, which could decrease size of cancerous tumors as well as prevent cancer (intakes of 10g/day).
Tomatoes: Tomatoes have received significant attention within the last three years because of its high lycopene content, (a carotenoid) and its role in cancer risk reduction. Decreased risk of prostate cancer and myocardial infarction were found in men who consumed tomato products at least 10 times a week; possibly due to lycopene’s powerful antioxidant qualities.
Garlic: Garlic is a member of the allium family and is widely known for its medicinal properties. The purported health benefits of garlic are numerous, including cancer prevention, antibacterial, anti-hypertensive, and cholesterol reduction.
The characteristic flavor and pungency of garlic are due to sulfur-containing elements, which are also likely responsible for the various medicinal effects ascribed to this plant. These elements have been investigated for their chemopreventive activity. Several studies have correlated high garlic intake with decreased incidence of stomach and colon cancer. Some data suggests that all allium vegetables, including onions, may have a protective effect on cancers of the gastrointestinal tract.
Garlic has also been touted for the prevention of CVD. Cardio-protective effects are likely due to its cholesterol-lowering effect but possibly through decreasing blood pressure. 900 mg garlic/day (as little as one half to one clove of garlic) could decrease total serum cholesterol levels by approximately 9% - 12%. It is currently unclear which component in garlic is responsible for its cholesterol-lowering effect.
Broccoli and other Cruciferous Vegetables: Frequent consumption of cruciferous vegetables (broccoli, cabbage, Brussels sprouts and cauliflower) has been associated with decreased cancer risk. The anticarcinogenic property of cruciferous vegetables is due to their relatively high content of glucosinolates (these induce detoxification enzymes in the cells). Broccoli sprouts are also a good source of many of these compounds.
Citrus Fruits: Although oranges, lemons, limes, and grapefruits are an excellent source of vitamin C, folate, and fiber, it appears that another component is responsible for their anticancer activity. Citrus fruits are particularly high in a class of phytochemicals known as the limonoids and over the last decade, evidence has been accumulating in support of the cancer preventative effect of limonene.
Cranberry: High in benzoic acid, cranberry causes acidification of the urine and is often used in the treatment of urinary tract infections. Studies have confirmed cranberry juice’s ability to prevent and treat urinary tract infections and additional investigations have focused on the ability of cranberry juice to inhibit Escherichia coli reproduction in the intestine.
Tea: Tea is widely consumed and a great deal of attention has been directed to its possible pharmacological effects. Most research pertaining to tea has focused on its anticarcinogenic properties. Green tea is particularly rich in polyphenols, an antioxidant. Epidemiological studies concerning tea’s anticancer effect is inconclusive but research findings in laboratory animals clearly support a cancer chemopreventive effect.
There is some evidence that tea consumption may also reduce the risk of CVD. Tea is a source of flavonoids and intake of the five flavonoids is inversely associated with CHD.
Wine and Grapes: There is growing evidence that wine, particularly red wine, can reduce the risk of CVD. Research suggests a strong negative correlation between wine intake and death from heart disease in both men and women. France in particular has a relatively low rate of CVD despite diets high in dairy fat. Although this "French Paradox" can be partly explained by the ability of alcohol to increase HDL cholesterol, more recent investigations have focused on the non-alcohol components of wine, in particular, the flavonoids.
The high antioxidant content of red wine, which is about 20-50 times higher than white wine, is due to the incorporation of the grape skins into the fermenting grape juice during production. These phenolic substances seem to prevent the oxidation of LDL in the body, a critical event in the process of atherogenesis (hardening of the arteries).
A note of caution is in order; alcoholic beverages of all kinds have been linked to increased risk of several types of cancer. Those who desire health benefits of wine without potential risk may wish to consider alcohol-free wine or commercial grape juice, which is also effective in inhibiting the oxidation of LDL.
Functional Foods from Animal Sources
Although most of the naturally occurring health-enhancing substances are of plant origin, there are a number of components in animal products that may have a potential role in optimal health.
Fish: Omega-3 fatty acids are an essential class of polyunsaturated fatty acids (PUFAs) derived primarily from fish oil. It has been suggested that the Western diet is currently deficient in n-3 fatty acids and increased consumption may play an important role in CVD prevention (by reducing triglycerides). The cardioprotective effect of fish consumption has been observed in some investigations but eating large amounts of fish has not unequivocally been shown to reduce CVD risk.
Dairy Products: One of the best sources of calcium, an essential nutrient which can prevent osteoporosis and possibly colon cancer. In addition to calcium, fermented dairy products such as yogurt and keifer contain health-promoting components known as probiotics. Probiotics are potentially beneficial bacteria or yeast. In the human GI there are many kinds of bacteria, some are helpful and some are harmful. Probiotics (notably lactobacillus) found in dairy may be useful in preventing cancer (especially colon), reducing cholesterol, and improving immune function.
Always remember, sound nutrition remains an absolute prerequisite for optimal performance in sports and life.
References:
- www.americandieteticsassociation.org, Function Foods Position Statement, 2005
- Functional Foods: Their Role in Disease Prevention and Health Promotion, Clare M Hasler, PhD, Institute of Food Technologies, www.nutriwatch.org.
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