Medical Matters:Hippocrates reportedly said, "let food be thy medicine". Modern food manufacturers have certainly responded to his advice, with the global market for so-called functional foods estimated at $60 billion. So how practical is it to eat your medicine instead of taking drugs?, asks Muiris Houston.
Functional foods, also called nutraceuticals, are essentially hybrids of food laced with other agents associated with health benefits. They include products such as cholesterol-lowering margarines, probiotic yoghurts and vitamin-enhanced cereals.
But there are concerns about their long-term safety and effectiveness.
Earlier this year, experts from the Dutch National Institute for Public Health and the Environment warned there is "little understanding of the circumstances under which the foods are eaten and whether target groups are reached".
They said that while EU regulations focus primarily on evaluating the safety of functional foods before they reach the supermarket, there are no regulations to assess their effects after the products have been launched.
Nutrition guidelines published by the Irish Heart Foundation in May state that functional foods, marketed as having an added health benefit, are not an essential part of a "heart healthy" diet for the general population.
So where does this leave the consumer? Should you eat yoghurt that promises to boost your immune system? And will those margarines laced with cholesterol-lowering additives actually benefit the average person?
One of the most popular nutraceuticals is omega-3 fatty acid. Whether marketed as enhanced soya milk or as capsules, a good dietary supply of long-chain omega-3 fatty acids has been linked to a lower risk of coronary heart disease.
The first evidence of their benefits emerged in the early 1970s when Danish doctors noted that Eskimos living in Greenland had a markedly lower incidence of heart disease even though they consumed a high-fat diet. Further research established that it was a diet rich in oily fish that was responsible.
We now know that Inuit Eskimos eat large amounts of oily fat in the form of the long-chain omega-3 fatty acids EPA and DHA and that these substances reduce blood levels of bad cholesterol and triglycerides.
The scientific evidence for the cardiac benefits of omega-3 is robust. A trial of 19,000 patients with high cholesterol, published this year, found that the risk of a major coronary event in those who received long-chain omega-3s was lowered by 18 per cent. And for people who have already suffered a heart attack, a study of 11,000 patients treated with omega-3s found a 44 per cent reduction in the risk of cardiac death within three months of commencing supplementation with long-chain fatty acids.
Earlier this year, the Drugs and Therapeutics Bulletin published a review of the effects of omega-3 fatty acids in depression. Although it reported some "soft" evidence that EPA and DHA benefited people with both depression and bipolar illnesses, the review stopped short of recommending omega-3s as a sole treatment for depression.
It concluded that "there is limited evidence suggesting that long-chain omega-3 fatty acid supplements might help to relieve depression when given in addition to existing antidepressant medication".
Some evidence has emerged of the benefits of omega-3 fatty acids in patients with arthritis and other joint diseases.
A study presented at this month's annual meeting of the Irish Society for Rheumatology by researchers from Musgrave Park Hospital Belfast showed that low doses of fish oils significantly reduced disease activity in the connective tissue disorder, Systemic Lupus Erythematosis.
Dr Steven Wright and his colleagues also demonstrated how omega-3 supplements improve the function of the lining of arteries, a likely mechanism for the cardiovascular benefits shown by separate research.
So much for the science of omega-3 fish oils. What about the practicalities of taking the right dose? Two servings of oily fish such as salmon, mackerel or fresh tuna should supply the right amount. But for people with existing heart disease, the suggested intake of 1,000mg a day is almost impossible to achieve without taking fish oil supplements.
Although up to three-quarters of adults do not consume oily fish, it is the best way to ensure a therapeutic dose of omega-3 fatty acids.
However, if you do take supplements, be aware that high doses pose a small risk of bleeding. If you are taking blood-thinning drugs such as aspirin, warfarin or clopidrogel, then it is best to check with your doctor before taking omega-3 supplements.
And it is also worth noting that some four out of five consumers are unaware of how much omega-3 they need to benefit health. So read the functional food labels carefully. Aim to have the equivalent of 450mg a day for adults and 200mg a day for children. If you have had a heart attack in the past, then 1g each day of omega-3 is appropriate.
And do try, where possible, to meet your omega-3 requirements naturally by having two portions of oily fish every week.
After all, Hippocrates advised us to let real food, not functional food, be our medicine.
Dr Houston is pleased to hear from readers at mhouston@irish-times.ie but regrets he is unable to reply to individual medical queries.
