Consumers are showing a growing interest in the relationship between diet and health. With this growing interest is a growing demand for information about the benefits and the risks of food choices. Greater than 95 percent of the population believes that food possesses the potential to improve health and that food, quality of life and disease risk management are associated intimately. Greater interest in preventive health, health education, rising healthcare costs, the aging of the population and frequently changing labeling regulations contribute to the interest and demand, fueling a growing industry: functional foods.
As defined by the Institute of Food Technologists, functional foods are those which are understood to be foods common to the human diet that provide essential nutrients beyond what is necessary for normal maintenance, growth and development. In addition, functional foods are shown to benefit overall health and well-being beyond basic nutritional functions. They may help prevent or treat a disease or pathologic condition.
A functional food component is an ingredient that, when added to food, improves physical or mental performance or, like functional foods, helps prevent or treat a disease or unfavorable condition. As the functional components of foods are identified and appreciated, they are added to conventional foods to form new foods that enhance overall health.
The United States Food and Drug Administration (FDA) regulates the claims that manufacturers can make about nutrient content and the effects on disease, health or body functions, under the United States Dietary Supplement Health Education Act (DSHEA) of 1994. The DSHEA recognizes the growing importance of nutrition and dietary supplements and the benefits of health promotion and disease prevention. These include chronic diseases, such as cancer, heart disease and osteoporosis. The language defined supplements like vitamins, minerals, herbs, amino acids and others.
The DSHEA 1994 stated that the dietary supplement manufacturer is responsible for ensuring that a dietary supplement is safe before it is marketed. The U.S. Food and Drug Administration (FDA) was responsible for taking action against any unsafe dietary supplement product after it reached the market. Generally, manufacturers did not need to register their products with the FDA nor get FDA approval before producing or selling dietary supplements. Manufacturers were required to make sure that product label information was truthful and not misleading.
The Dietary Supplement Safety Act of 2010 amended the Federal Food, Drug, and Cosmetic Act to regulate dietary supplements that may pose safety risks unknown to consumers more effectively. It requires manufacturers to submit research, including evidence of safety, for approval before a new substance or formulation is marketed to the public.
More information about the regulation of functional foods is available on the FDA’s site.
Different dietary fibers are classified as soluble (can be dissolved in liquid) or insoluble (cannot be dissolved in liquid). Fiber is resistant to digestion by human gastrointestinal (GI) enzymes. Some types of fiber are cellulose, pectin and lignin. Some foods with soluble fiber include:
Oat bran, a soluble fiber, was the first functional component of food approved to claim a health-enhancing effect ― cardiovascular risk management. The claim, authorized to appear on packaging, encouraged consuming 25 grams of fiber per day from oat-containing foods to reduce the risk of heart disease. Numerous studies show that an intake of dietary fiber of greater than 25 grams per day is associated with a significant reduction in the risk of cardiovascular disease. The fiber lowers total cholesterol and low-density lipoproteins (LDLs), so-called “bad cholesterol.” The National Health and Nutrition Examination Survey showed that men who consumed greater than 27 grams of fiber per day or 10 grams of fiber per day greater than the general population of men, had a relative risk of dying from coronary artery disease of 0.83, a statistically significant decrease. Soluble fiber also lowers LDL cholesterol by altering glucose and cholesterol metabolism, reducing the absorption of fat and cholesterol in the GI tract.
Organisms that are colonized in the colon cause fermentation of undigested fiber, providing fuel for the GI mucosa. The effect is associated with lowering serum cholesterol and decreasing the risk of colon and breast cancer. Undigested fiber also increases both dry fecal weight and water absorption, speeding up the passage of stool (transit time). There is less exposure to the GI mucosa to both nutrient absorption and potentially carcinogenic compounds.
Probiotics and Prebiotics
The GI tract is colonized with an enormous number of different types of microorganisms that are somewhat affected by the food consumed.
Probiotics are living organisms, which in sufficient numbers, have beneficial effects on the population of bacteria in the GI tract. They may be used to lower cholesterol, protect against gastrointestinal diseases and enhance immune function. Some examples of probiotics are yogurt, kefir, fermented vegetables and buttermilk.
Prebiotics are indigestible food ingredients that stimulate growth or activity of one or more types of bacteria in the colon. Soy oligosaccharides (polymers of sugar molecules) are one type of prebiotic.
Fermented milk, as a probiotic, increases the bacterial count in the colon. It decreases circulating cholesterol by inhibiting the production of cholesterol in the liver or redistributing cholesterol from blood to the liver.
Lactobacillus and bifidobacteria, probiotic microorganisms found in yogurt, are used to treat gastrointestinal disease. They prevent disease-causing microorganisms from populating the colon. Probiotics also strengthen the immune barrier, and some may protect the colon from carcinogens. Some compounds produced during fermentation may enhance the reproduction of normal mucosal cells and inhibit the proliferation of abnormal mucosal cells.
It was previously thought that it was the bacteria generating the probiotic effects, but it has also been demonstrated that products produced by the bacteria may be the active agents.
Plant Sterols and Stanols
Plant sterols and stanols are functional food components found in yogurt or spreads used as substitutes for butter. They are chemically similar to cholesterol. These compounds act in the small bowel, lowering cholesterol by competitively inhibiting its receptors. Sterols and stanols may also inhibit some precursors of colon cancer cells. In addition, they may improve urinary symptoms and flow in patients with benign prostatic hypertrophy.
Fish Oil & Fatty Acids
The benefits of fatty acids found in fish are receiving a lot of attention for their role in the risk and management of cardiovascular disease. They are showing benefits to health in several common diseases.
Omega-3 fatty acids have been known for two decades to be important in the health of the nervous system, especially during development. A 6-year-old girl was maintained on total parenteral nutrition (TPN) for five months. The parenteral solution contained an abundance of linoleic acid, an omega-6 fatty acid, but low in linolenic acid, an omega-3 fatty acid. She developed migrating numbness and paresthesias in her extremities, weakness, inability to walk, pain in her legs and blurred vision. When linolenic acid was restored in her diet, her symptoms disappeared.
Omega-3 rich foods are salmon, herring, anchovies, sablefish, whitefish, tuna and others. Some eggs are enriched with omega-3 fatty acids.
Common vegetable oils have a higher concentration of omega-6 fatty acids than omega-3 fatty acids, although flaxseed, canola, mustard, walnut and soybean oils are rich in omega-3 fatty acids. The lowering of serum cholesterol is attributed to lowered triglycerides levels, antithrombotic, anti-inflammatory and antihypertensive effects of the omega-3 fatty acids.
Several clinical studies have shown that intake of fish oil reduces serum triglyceride levels in both normal individuals and people with hypertriglyceridemia, lowers the frequency of arrhythmia and the progress of atherosclerosis. In a study of postmenopausal women, the incidence of coronary artery disease was reduced along a continuum with the intake of fish, from once monthly, up to three times monthly, once a week, two to four times per week and five times per week. The incidence of ischemic stroke also decreased in a continuum with increased fish intake.
According to a recent meta-analysis of 20 randomized clinical trials (RCTs) performed on about 68,000 subjects, omega-3 supplements did not reduce overall mortality rate or mortality rate caused by cardiovascular disease, the risk of myocardial infarction or stroke. However, several limitations have been pointed out in the results of those studies.
It’s become apparent that omega-3 fatty acids are important in modulating the risk of several common diseases. In the U.S., the FDA has concluded that, although omega-3 fatty acids have been shown effective in reducing the risk of coronary heart disease, the evidence is not conclusive.
Health claims are allowed on the packaging of soy protein products, under the DSHEA. The FDA concluded that soy protein, consumed with a diet low in saturated fats and cholesterol, may reduce the risk of coronary heart disease. It’s believed that part of the amino acid profile differs from that of the amino acid profile in animal protein. The soy protein amino acids lead to the lowering of circulating LDL cholesterol.
Glucosamine is an amino monosaccharide synthesized from glucose in the body and is a precursor for the synthesis of glycosaminoglycans and glycoproteins. Glucosamine is naturally found in all human tissues but is found at higher concentrations in connective tissues and the highest concentration in joint cartilage. Glucosamine is made using adenosine triphosphate (ATP) and the amine from glutamine. However, most glucosamine supplements are made from crustacean sources containing sulfate. After oral administration of glucosamine sulfate, 90% is absorbed and helps to build articular cartilage.
Glucosamine supplements exist in several different forms including sulfate, hydrochloride, N-acetyl-glucosamine and chloral hydrate salt. It remains controversial which form is most effective. Glucosamine sulfate has shown effective clinical results to date, but many clinical studies have reported the ineffectiveness of glucosamine sold in other forms. Even though the potential mechanisms of glucosamine synthesis are known to be a direct stimulation of chondrocytes, incorporation of sulfur into cartilage and protection against degradative processes, but the exact mechanism is unclear. In addition, the effect of glucosamine in the treatment of osteoarthritis remains controversial.
Everything you eat over time matters. The right variety of foods can make you healthier now and long-term. The future roles of functional foods depend on public acceptance. The public must be convinced clearly and unequivocally that the health benefits are authentic. Therefore, the industry must be rigorously honest in their health claims, without exaggerating the truth. While these foods, especially those modified with the addition of functional food components, are often more expensive than foods that have not been enhanced, it appears the public is willing to pay for the health benefits.
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(All indexed by the National Library of Medicine, the National Institutes of Medicine)
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Dietary Supplement Health and Education Act of 1994; Public Law 103-417; 103rd Congress https://ods.od.nih.gov/About/DHEA_wording.aspx