Phytoestrogen impact on health?

The UK's independent scientific Committee on Toxicity (COT) is urging the government's health department, which has responsibility for infant health and feeding practices, to review its advice on the use of soya-based infant formulas.

The recommendations are based on a new report on the impact of phytoestrogens in health, to be presented to the Food Standards Agency at its open meeting on 8 May.

It is possible that phytoestrogens could adversely affect people with hypothyroidism, concluded the group, who found that despite many claims that phytoestrogens have a beneficial impact on health, the evidence does not convincingly support this view.

Phytoestrogens are compounds produced naturally by some edible plants, most notably soya. In the body, they mimic or block the action of the human hormone oestrogen, although they are much less potent.

Extensive research worldwide on phytoestrogens has led to many conflicting reports on the risks and benefits of consuming phytoestrogen-rich foods. A recent study on rats found that exposure to large quantities of phytoestrogens damaged fertility, leading to concerns that similar effects could occur in humans, particularly babies fed soya-based infant formulas.

But other studies on populations that traditionally consume diets rich in phytoestrogens, such as the Japanese and Chinese, suggest that they may have a beneficial effect on osteoporosis, cardiovascular disease and some cancers.

The COT working group claims to have examined all the available information on the possible health effects of phytoestrogens. Further research to address specific knowledge gaps is needed, the scientists say.

Such gaps include the potential for drug-phytoestrogen interactions, important for individuals consuming phytoestrogen dietary supplements while taking prescribed drugs with hormonal effects, and potential differences in the metabolism of phytoestrogens between Western and Easternpopulations, not yet determined. Such knowledge could aid assessmentof epidemiological studies.

The team says that future research should be conducted in humans where possible. A study of populations in the UK who ingest relatively large amounts ofphytoestrogens, such as infants, vegetarians/vegans and users of phytoestrogen-rich foods andsupplements, would allow a more informed view of the health implications of phytoestrogens.

It also said "there is a need for further research on the potential effects of phytoestrogens in infants fed soy-based infant formulae. It may be possible to use established cohortsof infants fed soy-based formula to investigate the possible long-term health effects of exposure tophytoestrogens during infancy."​The full report is available from the FSA​.