What are Functional Foods?

Colin Berry

Reproduced from Quarterly Journal of Medicine (2002). Vol 95, 639-640
(Permission for reproduction pending)

The idea of a “functional” food came from Japan in the 1980s, apparently developing as the Ministry of Health and Welfare became concerned about the costs of caring for an ageing population, and sought to encourage any methodology that might improve long-term health prospects. The inverted commas indicate the author’s wonder at the term, and his concern about the development of dysfunctional food analysis as a speciality.

What does the word mean? The American Dietetic Association describes functional foods as “any potential health food or food ingredient that may provide a health benefit beyond the traditional nutrients it contains”, which is broad enough to satisfy anyone. Perhaps more satisfactory to the critically-minded, and less all-enveloping, is the International Life Sciences Institute restriction of the term to food that may provide a benefit because of the presence of a physiologically active component. The Food & Drugs Administration (FDA) have taken an apparently robust line on such foods, with “significant scientific agreement” that a health claim is valid being necessary for approval of the use of “functional” in the description of the product.

What constitutes acceptable wording for this description is remarkable. If we consider as an example the relationship of dietary calcium intake to osteoporosis, the American Council on Science and Health (ACSH) suggests: “Regular exercise and a healthy diet with enough calcium help teens and young adult white and Asian women maintain good bone health and may reduce their risk of osteoporosis”. It’s hardly a ringing endorsement of calcium-containing products.

Similarly, for fibre-containing grain products and cancer, we have: “Low fat diets rich in fibre-containing grain products, fruits and vegetables may reduce the risks of some types of cancer, a disease associated with many factors”.

That these are cautions as much as endorsements is clear, although it is not difficult to see how wording on packets may include these implied reservations without affecting the capacity of the advertisers to make hay. But if you examine some of the statements that have real (if moderate) scientific support, things become even more difficult.

Consider soy protein and coronary heart disease. The ACSH suggest: “Diets low in saturated fats and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease”. These words are carefully chosen. There are 40 human volunteer studies, and amounts <25 g/day have not been shown to have a cholesterol-lowering effect. In practice, 250 g of firm tofu contains about 25 g of soy protein; a soy burger contains 10-12 g (so you need two a day). No-one emphasizes that a little of what you fancy may not do you any good. Importantly, the FDA have approved only claims made about whole soy foods. There is no evidence to suggest that the so-called active components, the phytoestrogens genestein and diadzein, are beneficial. Indeed, there is some evidence of adverse effects from these compounds as supplements. Soybean oil contains no soy protein.

The caution, the use of “may” or “could”, the need for combination with other advice about diet, risk factors and medication, are seldom major factors in modifying people’s enthusiasm for particular foodstuffs. Yet the ACSH (a sensible body-although I must declare an interest here, as I have just joined its Advisory Board, and I got many of these data from them) gives a list of functional foods currently on the market for which the evidence of activity is considered strong. These include whole oat products in lowering cholesterol levels (via beta-glucan), Psyllium (a soluble fibre) doing the same, soy proteins as we have seen, plant stanol- or sterol- fortified margarines or salad dressings improving lipid profiles, and sugarless chewing gums preventing dental caries (if you brush your teeth). You may not be surprised to know that the evidence for cranberry juice (proanthocanidins), garlic (organo-sulphur compounds), green tea (catechins), tomatoes (lycopene) and cruciferous vegetables (isothiocyanates and indoles) is not strong.

Most of us are keen on the advice to drink some red wine every day. The polyphenolics in wine from red grape skins are anticoagulant and antioxidant, and these activities may help to protect against heart disease, but the alcohol may be more important. This is the problem: putting the marginal gain in perspective. There is little evidence that an increasingly obese and indolent population bothers about the “mays”; “coulds” or additional activities (exercise) or restraints (stopping smoking, dieting) that should be in the equation, other than in the short term. All of the good animal data, and there is a vast amount, referred to elsewhere in this series of articles, show that it is “hypercalorism” that is the most important dietary risk factor for neoplasia.

Some of these foods have not been without risk. There is evidence of over-consumption by some food faddists, and the addition of St John’s Wort, echinacea; ginseng, ginko biloba and other ingredients to food has produced allergic reactions, coagulation disorders and interfered with the actions of immunosuppressants. If a compound is listed as a dietary supplement rather than a functional food, the rules are different and, effectively, far less restrictive - there has been more evidence of harm from this route, with L-tryptophan and germanium as well-documented examples.

The Californian dream, that a good diet and exercise programme may allow you to live forever, contains a valid health message. The addition of a particular food on an irregular basis to a normal pattern of intermittent overindulgence is unlikely to confer benefit.

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What are Functional Foods?

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