“The paper describes the amount of intake of isoflavones and lignans, which are compounds regularly found in vegetable food products, which in structure are similar to female sex hormones”

Phytoestrogens are plant chemicals that are capable of exhibiting oestrogen-like activity due to their capacity to bind to the oestrogen receptor and they occur in three main classes: isoflavones, coumestans, and lignans. Phytoestrogens are found in various plants—including grains, beans, green vegetables, fruits, nuts, and grasses. Isoflavones are primarily found in soybeans and soy foods. Phytoestrogens are considered to act as selective estrogen receptor modulators (SERMs), with oestrogen agonist as well as antagonist action. Supplementation with isolated soy protein, containing the isoflavones genistein and daidzein, reduces serum total and LDL-cholesterol and triglycerides, in animals as well as in humans. Vascular reactivity might be improved by supplementation with isolated soy protein or isoflavones isolated from red clover. Studies indicate not only a potential for cardiovascular risk reduction, but also potential applications in the field of breast and prostate cancer. Evidence in humans is still scarce.

We still know little of effects of regular dietary phytoestrogen intake. The knowledge we have at this moment stems from studies in which phytoestrogens were supplemented to the usual diet. Most supplementation studies have been conducted with soy isoflavones, whereas the importance of lignans is not yet resolved, although there might be more important phytoestrogen sources than isoflavones in Western populations. Research up till now has been focused on risk factors. Studies into a clinically manifest endpoint are urgently needed. For epidemiologic studies into the relation between phyto-oestrogen intake and disease parameters, phytoestrogen intake can be estimated with several measures, such as biomarkers (concentrations in urine or blood) or with dietary questionnaires. The optimal method for estimating intake is not yet clear. Measuring levels in urine and plasma is difficult, and there are only a few labs able to do so. Furthermore, these assessments are very expensive. We were among the first to describe how isoflavone and lignan intake can be calculated from a food frequency questionnaire (FFQ).

It describes how phytoestrogen intake can be calculated with data gathered from a food frequency questionnaire (FFQ), and presents tables containing the phytoestrogen contents of foods. These tables were derived from the available literature.

The paper describes the amount of intake of isoflavones and lignans, which are compounds regularly found in vegetable food products, which in structure are similar to female sex hormones. For that reason they are believed to be good for female health. The intake of isoflavones and lignans in postmenopausal women participating in the Framingham Heart Study in the USA is low, only one to several milligrams per day. In Asian countries, like Japan, the intake is 40-fold higher, due to the fact that isoflavones occur in large quantities in soy, which is a major food item in Japan but not in Western countries.

My main research interest is in sex hormones and cardiovascular disease. The research has extended over the past years from markers of duration of exposure to endogenous estrogens (age at menopause), to genetics involved in sex hormone metabolism, and exogenous sex hormones. As I was originally trained as a nutritionist, I was happy to find out that our foods contain naturally occurring estrogen-like substances, which I could study in my epidemiological studies.