Fruit and vegetable consumption is recommended to be increased for most of the population. This is based on the simple fact that most people do not consume much, if any plant based food regularly. Plant foods, particularly fruits and vegetables are a rich source of phytochemicals, many of which have been shown to possess possible health effects. The polyphenols are perhaps the most studied in this regard. Polyphenols are a group of chemicals made up of a number of phenolic rings, and this confers on them antioxidant potential. Of the polyphenols, the flavonoids are perhaps the most well known and studied. Fruits and vegetables are a rich source of flavonoids and, along with tea and wine, are perhaps the most important source of polyphenols in the human diet. The flavonoids are likely a major reason why those who consume high amounts of plant foods show a lower risk of many diseases, particularly the diseases of the West such as cancer, cardiovascular disease and obesity.
Most of the useful data concerning the benefits of flavonoids have come from three types of studies. Human clinical trials and animal experiments have shown the effects of flavonoids on markers of disease and on physiological changes. These studies are useful because they show direct mechanisms or measurable changes that can be tested against a placebo or baseline conditions, and in this way guide the researcher to possible beneficial disease outcomes derived from flavonoids. Another type of useful study is the epidemiological study. Although lacking the ability to ascribe cause and effects, epidemiology is a useful measure of the ability of flavonoids to be associated with particular diseases. A number of large scale epidemiological studies for example have investigated the association between flavonoids and cancer and cardiovascular disease. The data from epidemiological studies has generally been consistent, although it must be taken in its context to be useful.
A recent study published in the American Journal of Clinical Nutrition used epidemiological data to investigate the association between flavonoids and all cause mortality1. Food compositional data bases were used to assess the flavonoid intake of 1063 randomly selected individuals, and a 5 year follow up was performed to assess the mortality in the subjects. The results of the study showed that those with the highest intake of flavonoids were at significantly less risk of total mortality compared to those with the lowest intake. When further analysis was performed a similar pattern of association was observed for cardiovascular mortality and cancer mortality. While this study was not as large as many that have previously been performed, it was consistent with the protective effects of flavonoids seen in such studies. The recommendation to eat more fruits and vegetables may therefore have significant health effects and may decrease the risk of both cardiovascular disease and cancer.
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