Emerging science...isn’t
With growing numbers of people attributing near magical abilities of “healthy” foods to keep them youthful, prevent cancer and other diseases of aging, and ensure a longer life, scientists in the United States and Europe are starting to clamp down on claims about healthful properties in foods that don’t have credible evidence to support them.
The Journal of the National Cancer Institute has just published the results of a nearly two-year review by the U.S. Food and Drug Administration (FDA) Center for Food Safety and Applied Nutrition on the scientific evidence behind claims surrounding lycopene — an antioxidant in red tomatoes — as reducing risks for various cancers. Their analysis found no credible evidence that lycopene, either in food or in a dietary supplement, was associated with reduced risk of any of the cancers evaluated. Just how flimsy the evidence behind such claims is would surprise most consumers.
We’ve often reviewed the inferior evidence surrounding fruits and vegetables and their abilities to prevent major chronic diseases, including the 2004 comprehensive examination of the scientific literature done for the Produce for Better Health Foundation campaign, 5-A-Day, under the National Cancer Institute. That year, a study led by Walter Willet, M.D., DrPH, professor of epidemiology and nutrition at Harvard School of Public Health in Boston, MA, was also published. It had followed 71,910 women and 37,725 men for 15 years and found no relationship between fruits and vegetables and cancer, or any statistically significant associations with major chronic disease or cardiovascular disease. But, time and again, the media makes little more than a whisper when studies are published questioning claims surrounding the “emerging” science of functional foods and supplements. For instance, how many heard about the May study in the journal Cancer Epidemiology, Biomarkers & Prevention on lycopene and prostate cancer? Researchers based at the National Cancer Institute and Fred Hutchinson Cancer Research Center had examined 692 cases of prostate cancer diagnosed among 28,000 men enrolled in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, an ongoing, randomized National Cancer Institute trial to evaluate cancer screening methods and to investigate early markers of cancer. They found no association between serum lycopene and total prostate cancers or aggressive prostate cancers. The FDA’s findings are not surprising to those who’ve following the science for years, but few consumers ever hear of the evidence. According to a Florida Department of Citrus consumer survey a few months ago, nearly half of all babyboomers worry about getting old and look for foods rich in lycopene, for instance, believing it will help them prevent cancer. Looking closely at the FDA’s findings provides valuable insights into how easily suggestions based on correlations observed among large groups of people are being misinterpreted into causations and used to suggest treatments and preventive interventions. Correlations typically lead us astray. Time and again, clinical trials have disproven beliefs about a food, supplement or ingredient that had been based upon observational studies. As the FDA recognized, actual intervention trials on humans are the only types of studies that can credibly begin to offer conclusions about the possible benefits or risks of a food, drug or other treatment. But among all of the studies on lycopene and cancer risk reduction, not a single one was an interventional study. They all merely looked for relationships among large groups of people, and reported results in term of relative risks. And none of the relative risks would have even be considered tenable for these types of studies, even by the National Cancer Institute itself. However, observational studies that use dietary recall data have a limited ability to ascertain the actual intake of a food or nutrient... Second, the lycopene content of foods can vary substantially depending on the type of food, its stage of ripening, the procedures used to process or cook it, and the duration and temperature of storage... Third, lycopene-containing foods contain other nutrients that may be associated with the metabolism of lycopene or the etiology of certain cancers, making it difficult to study lycopene in isolation... Furthermore, the observational studies that calculated lycopene intake from estimated dietary intake did not specify whether the reported intakes of tomatoes and tomato-based foods were derived from red tomatoes.... only red tomatoes contain lycopene. Another 23 studies used a single measure of blood levels of lycopene in healthy people to predict their cancer risk. But “dietary lycopene intake is poorly correlated with serum lycopene levels (correlation coefficients range from 0.11 to 0.45). Second, many factors can affect the serum lycopene levels, including age, basal metabolic index, smoking status, serum cholesterol levels, and time of the year. Therefore, a single measure of serum lycopene may not accurately reflect a subject's usual lycopene intake over time.” And other studies used patients with cancer, yet health claims for healthy people can’t be extrapolated from cancer patients, said the FDA. Despite all of this, the FDA found the observational studies evaluated still offered “no credible evidence supporting a relationship between lycopene consumption, either as a food ingredient, a component of food, or as a dietary supplement, and any of the cancers evaluated in the studies.” While the FDA clamps down on health claims here, the European Union began a new crackdown last month on false or unsubstantiated claims about the health benefits of foods. As the Times reported: 'Healthy food' firms told to put up or shut up The products – ranging from baby foods said to bolster a child’s immune system to a tea claimed to boost memory – will be allowed to carry the claims only if they can show they are based on scientific research. Known as “functional foods,” the market is now worth £1 billion a year, but critics say many of the health claims have not been thoroughly vetted.... One of the biggest growth markets has been in products containing probiotics, which are said to help maintain the levels of beneficial bacteria in the gut and to aid digestion. A study last year [found no reliable evidence to show they improved general wellbeing. Activia, the probiotic yoghurt made by Danone, suggests that it can “beat that bloated feeling.” As the Food Commission, the lobby organisation, has pointed out, this appears to be based on just one study involving 292 women eating Activia. Probiotics, which are said to promote the growth of beneficial bacteria, are also a popular additive in foods. Cow & Gate, the baby food company, says this additive helps to “support” a baby’s natural immune system. The company says this is backed by research, but it has withdrawn the claim from its labelling after a ruling against it by the Advertising Standards Authority. The health benefits of Flora’s margarine with omega 3, which is said to maintain heart health, and its spread with plant sterols to reduce cholesterol are supported by several studies. But a review of research published in the British Medical Journal last year raised doubts about the benefits of omega 3, concluding there was no clear evidence that these fatty acids protected people from heart disease. As we know, looking for a strong correlation is the first step towards tracking down a cause. But if scientists are unable to even find a link, then they move on and look elsewhere for a cause that might lead them to an effective preventative or treatment. After examining 145 studies, the FDA could find no credible evidence for a link between lycopene and cancers — and without even a link, then the possibility of it leading to a credible cure defies logic. Yet, that hasn’t stopped some from denying the significance of the FDA findings and asserting that lycopene remains a promising area of research. But you know the real scoop.
About half (43 of 81) of the studies had used food frequency questionnaires and then estimated lycopene intakes. The FDA scientists found considerable problems with this technique to begin with:
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