Surveys suggest that many consumers neither recognize nor understand the term functional food, and even within the food industry, no standardized definition yet exists. But research also indicates that consumers are increasingly interested in foods that can claim to promote general health, reduce risk of specific diseases, boost energy and improve immune system function. Growing consumer understanding of the connection between diet and health has encouraged the development of some interesting products, from ?designer? eggs and meats to fortified milk, fruit juices and baked goods specifically formulated for health effects. Based on strong scientific support for their health benefits, phytosterols, omega-3 fatty acids, and probiotics, prebiotics and synbiotics are three ingredient categories that have enjoyed particularly widespread acceptance and incorporation into mainstream food products in Europe and the United States.
Cardiovascular disease remains the leading cause of mortality in the United States, and food products designed to promote cardiovascular health are proliferating. In the United States, Europe, Japan and Australia, foods and drinks that carry specific heart-health claims represented a combined $3.6 billion market in 2004, according to a report released in April by the United Kingdom-based market research firm Leatherhead Food International.
The cholesterol-lowering properties of phytosterolsâa component of plant fats found in varying concentrations in virtually all plantsâhave been solidly established through clinical studies.1,2 Significant lipid-lowering effects are associated with a daily intake of at least 2 g of phytosterols.2 Eating a diet low in saturated fats and cholesterol and high in plant sterols or stanol esters can reduce ?bad? low-density-lipoprotein cholesterol by as much as 20 percent.1 The first sterol-fortified products to hit American grocery shelves were heart-healthy margarines in 1999, and in 2002 the U. S. Food and Drug Administration decided to allow additional sterol-containing foods to carry cholesterol-lowering claims. Since then, numerous sterol-fortified foods have been developed, tested and introduced to the European and North American markets.
The best naturally occurring dietary sources of phytosterols are high-quality vegetable oils, nuts, legumes and whole grains. Unrefined, cold-pressed vegetable oils such as flaxseed, olive, sesame, rice bran, wheat germ, walnut and hazelnut are all rich in phytosterols. Soybeans and various vegetable oils are important commercial sources of phytosterols for enhancing the sterol content of prepared foods.
Among sterol-fortified foods, orange juice has garnered more widespread attention than most. A clinical study published in 2004 in the journal Arteriosclerosis, Thrombosis and Vascular Biology demonstrated significant reductions in total cholesterol and LDL among people who drank phytosterol-fortified orange juice providing 2 g of phytosterols per day. For the study, 72 people with mildly elevated cholesterol were randomly assigned to drink either phytosterol-fortified orange juice or ordinary orange juice for eight weeks. By the end of the study, participants who drank the phytosterol-fortified orange juice demonstrated a 7 percent reduction in total cholesterol and a 12 percent reduction in LDL. There was no change in cholesterol levels in the control group.3
Beyond orange juice, sterol-enhanced chocolate, low-fat milk, yogurt, cereal, bread and other bakery products, as well as frankfurters and cold cuts, have all significantly reduced cholesterol levels in clinical studies.4,5,6,7,8,9,10,11,12 In one study that compared the cholesterol-lowering effects of various foods fortified with 1.6 g per day of sterols, all tested foods significantly lowered total cholesterol and LDL, but sterol-fortified low-fat milk was significantly more effective than fortified low-fat yogurt, bread or cereal.12 There remains some concern that phytosterol-enriched products can interfere with absorption of fat-soluble vitamins such as E and A, but more study is needed before a conclusion can be drawn.13
Omega-3 fatty acids
For decades, evidence has been accumulating to support the multiple health benefits of omega-3 essential fatty acids. Clinical trials have shown that omega-3 EFAs significantly reduce risks of cardiovascular disease, including heart attacks, strokes and sudden cardiac death.14,15,16,17,18 A variety of mechanisms appear to contribute to this protective effect. Omega-3s lower blood levels of serum triglycerides, improve the ratio of beneficial high-density lipoprotein to LDL cholesterol, prevent clumping of blood platelets and have anti-arrhythmic effects.14,15,16,17,18
Of particular interest are the EFA compounds known as eicosapentaenoic acid and docosahexaenoic acid. In September 2003, the FDA approved a qualified health claim for foods and supplements containing both these omega-3s. Based on ?supportive but not conclusive research,? the agency now allows labeling for such products to state that ?consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease.? The FDA specifies no amount, but research shows daily intake of 200 mg DHA is associated with a 50 percent reduction in risk of sudden cardiac death.19
Compelling evidence also suggests that the benefits of omega-3s extend far beyond heart health. Omega-3s have anti-inflammatory effects that could have important implications for the treatment of arthritis, allergies, asthma, inflammatory bowel disease and skin conditions such as eczema and psoriasis.20,21 Adequate DHA intake is essential for optimal brain and eye function and has been shown to enhance brain and nerve development and visual acuity in infants.14,19,22,23,24,25
In the elderly, decreasing levels of DHA in the brain are associated with declining cognitive function and onset of Alzheimer?s disease.19 A recent controlled study showed that a diet high in DHA markedly slowed the development of experimentally induced Alzheimer?s disease in mice, a finding with important implications for future Alzheimer?s research.26
The best naturally occurring sources of omega-3 EFAs are oils from fatty, cold-water fish (such as mackerel, sardines and salmon) and certain nut and seed oils (predominantly flaxseed but also soy, walnut, hemp and canola). Fish oil is naturally rich in EPA and DHA, and plant sources like flaxseed contain alpha linolenic acid, which the body generally can convert into EPA and DHA.
Now, food technologists have developed livestock feeding protocols that boost levels of DHA in eggs and meat. Enhancing cholesterol-rich eggs with omega-3s as a means of improving cardiovascular health may seem counterintuitive, but research suggests otherwise. When laying hens eat a diet rich in omega-3 fatty acids (feed containing a high percentage of flaxseed, for example) they produce eggs that are higher in DHA and ALA but no different in cholesterol content than ordinary eggs.27 Studies show that people who consume such eggs experience increases in levels of total omega-3s and DHA without significant changes in blood cholesterol levels.27,28 In one study, participants who ate four omega-3-enriched eggs a day for four weeks had no significant increase in total cholesterol or LDL, but did show a reduction in triglycerides. The researchers concluded that eating three omega-3-enriched eggs provided approximately the same amount of omega-3 as one serving of fish.28
DHA offers additional benefits for pregnant women, developing fetuses and infants, and DHA-rich eggs have proven to be an effective vehicle for increasing DHA intake by expectant mothers.22 In one important trial, women who ate DHA-enriched eggs during the last trimester of pregnancy had an increased length of gestation compared with controls.23 In another study, visual acuity matured significantly faster in 6-month-old breast-fed babies who ate baby food containing DHA-enriched egg yolk, compared with babies who were not fed DHA-enriched food.25
Probiotics, prebiotics and synbiotics
Probiotics, prebiotics and synbiotics represent another category of ingredients receiving increased attention from the mainstream medical community, based on a growing body of scientific evidence supporting their health benefits. Probiotics are commonly understood to be ?friendly? bacteria that improve the balance of the intestinal flora to promote health.
A paper published in the American Journal of Clinical Nutrition offers a more technical and inclusive definition for probiotics: ?a preparation of or a product containing viable, defined microorganisms in sufficient numbers, which alter the microflora (by implantation or colonization) in a compartment of the host and by that exert beneficial health effects in that host.?29 By using the term ?compartment,? this definition encompasses not just the intestines, but also the mouth, vagina and skin.29
The most widely employed probiotic organisms are lactic-acid producing bacteria, most of which are members of two particular genera, Lactobacillus and Bifidobacterium. Probiotics occur naturally in fermented foods, including yogurt, miso, tempeh, buttermilk, kefir and sauerkraut.
Prebiotics are indigestible carbohydrate substances that selectively stimulate the growth of lactobacilli and bifidobacterium in the gut. Some common prebiotics substances are oligosaccharides, fructans and inulinâfound in a variety of vegetables, fruits, grains and other plants.
Synbiotics are foods that contain a combination of prebiotics and probiotic organisms, such as some cheeses and yogurts.
More than 200 published studies have documented a wide range of health benefits for probiotics, all stemming from their positive effects in the gastrointestinal tract.30 Probiotics have proven effective in preventing and treating rotavirus-associated children?s diarrhea and improving lactose intolerance, and can reduce the frequency and duration of diarrhea induced by chemotherapy or antibiotic treatment.29,30,31,32 Increasing evidence suggests that prebiotics may have similar effects, and consumption of cheese (a synbiotic) has been reported to reduce the risk of gastroenteris caused by Campylobacter infection.31,32,33 Probiotics can help prevent vaginitis, travelers? diarrhea and infant colic, and there is some evidence that they are helpful in treating Helicobacter pylori infection.29,30,34 Compelling evidence also indicates that probiotics stimulate immune system function.29
Probiotic metabolites reduce mutagenicity in the gut, and researchers believe probiotics have a role to play in reducing risks of colon cancer.29,35,36 Other preliminary studies suggest that probiotics have potential for preventing urinary tract infections; treating inflammatory bowel disease, autoimmune disorders and allergies; and improving dental health.37,38,39,40,41 Probiotics and prebiotics hold important promise for improving children?s health worldwide, especially because of their ability to boost immune system function and improve outcomes in cases of childhood diarrhea. Researchers continue to investigate various applications for pro- and prebiotic infant formulas.
Enhanced foods and everyday diets
Experts caution that foods formulated to improve specific health parameters cannot replace more traditional recommendations to lower saturated-fat intake and eat a wide variety of nutrient-dense foods, and questions remain as to how to best incorporate fortified foods into the diet for optimal results. But such foods appear to be here to stay. Vitamin-fortified cereals, breads and milk probably seemed strange to consumers when they were first introduced decades ago, but they soon became commonplace. In the future, we will likely see a wider range of enhanced and fortified foods on grocery shelves, from prebiotic baby foods to heart-healthy baked goods and candy.
Evelyn Leigh is a freelance writer and natural products industry consultant in Boulder, Colo.
Natural Foods Merchandiser volume XXVI/number 7/p. 44, 46, 48
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