High intakes of fibre and plant foods may lower testosterone levels when compared to high intakes of fat and energy.
The hormone diet association is a well known phenomenon. Dietary changes can influence the prevailing milieu of hormones and this in turn can have a profound influence on health. As well as being reported in the academic literature, the hormone diet association has been written about in the mainstream nutritional press by such authors as Michael Colgan in his book Hormonal Health. Hormones are known to affect the aetiology of a number of diseases including cancer. Hormone related cancers such as those of the prostate, testis, breast, uterus and ovary have been investigated with respect to the hormone diet association. Diets high in fat and calories are known to stimulate production of testosterone, at least in the short-term. Whereas diets high in fruits, vegetables, vegetable protein and fibre are known to lower testosterone levels. As testosterone can be converted to both oestrogen and other androgens particularly dihydrotestosterone, such changes may have a profound influence of disease risk.
The hormone diet association have been investigated in a number of research studies. In one such study1, the authors investigated the hormone diet association by assessing the diet and hormonal levels of 12 Seventh-Day Adventist vegetarians, 10 Seventh-Day Adventist non-vegetarians and 8 non-Seventh-Day Adventist non-vegetarian men. Seventh Day Adventists were included in the study to control for possible lifestyle factors that may affect the comparison of vegetarian and non-vegetarian diets. The results showed that the Seventh Day Adventists vegetarians consumed significantly more dietary fibre than the non-vegetarian groups (because of higher plant food intakes). In the Seventh Day Adventist vegetarians, the plasma levels of testosterone and 17-β estradiol were significantly lower compared to non-vegetarian groups. Combining all the groups showed a significant hormone diet association. In particular, testosterone and 17-β estradiol plasma levels were significantly associated with dietary fibre intakes.
Because both the Seventh Day Adventist omnivores and the non-Seventh Day Adventist omnivous had significantly different hormonal levels compared to the Seventh Day Adventist vegetarians, the difference was likely not due to lifestyle factors. No difference in the obesity levels between the groups was detected suggesting that the hormonal difference did not affect body fat. The hormone diet association has been investigated in other studies, and generally it is known that high fat high calorie diets increase level of testosterone. Because testosterone can be converted to oestrogen through the aromatase enzyme, the higher levels of oestrogen in this study could have been a result of the raised levels of testosterone. High intakes of dietary fibre can increase the excretion of cholesterol and lower plasma levels of cholesterol. As cholesterol is a precursor to all steroid synthesis, this may affect the production of other steroid hormones. However, plant foods are also good sources of phytoestrogens and these too may influence the hormone diet association.
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