What foods are high in estrogen

Phytoestrogens - plant substances with hormonal effects

Dr. oec. troph. Antonie Danz

The search for alternatives to hormone therapy for menopause has made phytoestrogens popular. With a targeted selection of plant-based foods, the intake can of course be increased. It is not advisable to use supplements.

© photodee / 123RF.com

Menopausal hot flashes, cardiovascular disease, osteoporosis and estrogen-dependent cancers are less common in Asian countries such as Japan and China compared to western industrialized countries. This phenomenon is associated with the high proportion of Phytoestrogens in a traditional (South) East Asian diet. The greater amount of phytoestrogens in the diet in these countries is due in particular to the copious consumption of soy. Based on these observations, numerous studies on the effects of soy and its concentrates and of isolated phytoestrogens have been carried out.

Phytoestrogens are secondary plant substances that largely belong to three structural classes: isoflavones, lignans and coumestans. These substance groups are similar in structure and function to 17-ß-estradiol, one of the most effective natural forms of estrogen. Because they can both activate and block the estrogen receptors, they have an estrogenic and anti-estrogenic effect at the same time. They also have antioxidant and cell growth inhibiting properties. The estrogenic effect of phytoestrogens is less than that of 17-ß-estradiol by a factor of 100 to 10,000. However, depending on food intake and metabolism, their concentration in the body can exceed the endogenous estrogen concentration by 100 to 10,000 times.

Natural sources

Lignans and isoflavones are the phytoestrogens with the greatest importance for the human metabolism according to the current state of knowledge. Coumestans are only found to a small extent in the human diet. These diphenolic substances only become available to humans when they are metabolized by intestinal germs. The conversion of these plant phytoestrogens into biologically effective ones therefore depends on an intact intestinal flora. The administration of antibiotics to test subjects, for example, worsened the enzymatic digestion in the intestine. Depending on the structure of the phytoestrogens, absorption through passive diffusion is also discussed. The microbial degradation of dietary phytoestrogens in the large intestine, which is subject to strong inter-individual differences, also influences the concentration of biologically active phytoestrogens.

Soybeans and their products are particularly rich in the precursors of the isoflavones active in the human organism. Lignans are found primarily in flaxseed and, to a lesser extent, in other seeds such as sunflower seeds and pumpkin seeds. In addition, phytoestrogens are found in legumes, grain bran, whole grains, hops, sage and some alcoholic beverages such as beer and wine, and in lower concentrations in many types of vegetables and fruits (see table).

Phytoestrogens in foods

FoodIsoflavones mg / 100g (fresh weight)
Soybeans160 -145
tofu113,5 - 33,2
soy milk14,7 - 9,7
Miso160,4
Beans (various types)2    0 - 6,3
Peas (various types)20 - 7,3
Lignans µg / 100 g (dry weight)
linseed3371100
Pumpkin seeds21400
rye1112,1
barley158
Nuts (various types)396-257
broccoli1437
Olives11254
Strawberries11578,1
cranberry11054

1 Jackson / Gilani 2002, 2 USDA Database 2008, 3 Adlerkreutz / Mazur 1997

Fermentation processes, such as those that take place in the traditional production of miso or tempeh from soy, can increase the concentration of phytoestrogens in foods and improve bioavailability. In addition, the phytoestrogen content of foods is determined by the variety, climate, harvest time and fruit ripeness. It is therefore difficult to give standardized values ​​for food.

Help with Menopause?

Isoflavones have been discussed as an alternative to hormone therapy for a number of years. Corresponding preparations can be found in pharmacies and drug stores. The scientific studies carried out for this purpose examined either the effects of soy as a food, soy protein isolates or soy extracts. In some cases, the researchers also used red clover preparations. The investigation period was usually between two and six months. Far fewer studies and primarily only case-control studies are available on the influence of lignans.

The majority of the randomized clinical studies published to date on the effect of isoflavones on hot flashes and sweating during menopause do not show a significantly better effect compared to dummy preparations (placebo). Some studies have seen a decrease in the number and / or severity of hot flashes, but this was shown in both groups. On the basis of the current state of knowledge, the intake of preparations based on soy or red clover or the daily intake of soy products have no comparable potency to classic hormone therapy.

Protection against osteoporosis?

The currently available studies on the influence of isoflavones in the form of food, soy protein or preparations on bone metabolism are inconsistent. Some studies show a positive effect on bone density or bone metabolism markers, while others do not. It should be noted critically with all studies that they were only carried out over a short period of a maximum of one year. The inconsistent menopausal status and the different ages of the test subjects from the various examinations as well as the sometimes only relatively minor effects do not allow a generally valid statement. It would therefore be premature to attribute soy and isoflavones to the current state of knowledge as having a protective effect against osteoporosis.

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The data situation is hardly better for possible protective effects on the development of cancer. Phytoestrogens can intervene in the complex mechanisms behind the development of breast, uterine and prostate cancer in a number of ways. These effects are based on the slightly oestrogenic and anti-oestrogenic properties as well as other hormone-independent effects, such as oxidative effects. However, the exact mechanism of action is not yet known. Case-control studies show a reduced breast cancer rate with high concentrations of phytoestrogens in plasma and urine. However, the protective effect of phytoestrogens against breast cancer has not yet been clearly proven in intervention studies on humans. This also applies to uterine and prostate cancer. In addition, a negative effect of high phytoestrogen doses on breast tissue cannot be ruled out.

Positive for blood lipids

Several studies have shown that a daily intake of at least 20 grams of soy protein lowers serum levels of LDL cholesterol, total cholesterol and triglycerides. In some cases, an increase in the favorable HDL cholesterol and a decrease in systolic and diastolic blood pressure could also be observed. In most studies, however, the administration of isoflavone preparations did not lead to improved blood lipid values. Such preparations may improve the elasticity of the blood vessels, but this can still be clearly proven in further studies. The observed positive effects on the risk profile of cardiovascular diseases seem to be primarily due to soy protein and not to isoflavones.

The whole is decisive

The effects of a phytoestrogen-rich diet on the diseases mentioned in Southeast Asia cannot be explained solely by the high consumption of soy products there. Compared to Europe, the population in the Far East traditionally eats less meat, less dairy products - and thus less animal fats -, more vegetables, algae and fish. The differences observed in epidemiological comparative studies with European consumption habits can therefore be related to various nutritional factors. In addition, some studies, for example in the field of cancer research, indicate that diet-related preventive and therapeutic effects are due to the effect of the nutrient compound in complex foods and less to isolated nutrients.

The recommendation to focus the food selection on a plant-rich and wholesome diet, which can also contain soy products if well tolerated, not only has the advantage of increased phytoestrogen intake. In this way, many other health-promoting nutritional ingredients such as other secondary plant substances, fiber, vitamins and minerals are absorbed. Possible side effects from taking phytoestrogen preparations are also avoided. According to a statement by the Federal Institute for Risk Assessment (BfR), long-term use of phytoestrogen preparations or foods fortified with them is not without risk. For advice, it is also advisable to always take into account the individual tolerance of soy products such as soybeans, soy milk and tofu. Because the contained soy lectins can be difficult to digest in large quantities. In addition, the BfR assumes that 0.3 to 0.4 percent of the population is allergic to soy protein.

Source: Danz, A .: UGBforum special. Getting through menopause, 2015, pp. 20-22

This article is taken from the UGB archive.

We would like to point out that the content may have to be re-evaluated due to new scientific findings.