Isoflavone Research Initiative

Prostate cancer is, just like breast cancer, a hormone-dependent tumour which may react to the presence of estrogen with growth. Estrogen is not only found in the female, but also the male organism. The prostate has receptors (docking places) for estrogens. There are two types which act as counterplayers: the estrogen rexeptor alpha, which is responsible for the typical hormonal effects, and the estrogen receptor beta. The beta-receptor protects from undesired estrogenic effects. The isoflavones convey their effects exactly via this protective receptor. Thus, they do not only protect women from the development of breast cancer, but also men from prostate cancer. Both has been amply demonstrated in many examinations of the benefits of an insoflavone-rich nutrition.  

We recommend that you discuss this subject also with your physician. We will be happy to provide the corresponding scientific evidence.

This topic has been debated since the "Women's Health Initiative" study (WHI) has found an increased breast cancer risk related to hormonal therapy. We now know that the increased cancer risk did not correlate with estrogen as such, but with the combination of estrogen and certain synthetic progesterones.

Regardless of this rather recent clarification, it must be pointed out that phyto-estrogens are not estrogens. The hormonal effects of estrogens including the potential activation of breast cancer cells is related to an effect at the estrogen receptor "alpha", which in the organism has a protective counterplayer, the estrogen receptor "beta". This latter receptor is reponsible for the fact that even the high estrogen levels during the female cycle do not lead to breast cancer.

Plant-derived substances acting at the estrogen receptors are called "phyto-estrogens", or more precisely "selective estrogen receptor modulators". Some of them (e.g. some constituents of hops) may act on the estrogen-receptor alpha, whereas others such as the isoflavones from soy or red clover act on the estrogen-receptor beta. This activation of the protective systems has been related to the cancer-preventive effects of soyfood. Recently the question of safety of application of isoflavones has been addressed in clinical studies. So far, the results do not show any reason for concern: Dietary isoflavones (as soy food or supplements) had no negative impact on the biomarkers of breast safety, e.g. mammographic breast density, even in women with a high risk.

In addition, isoflavones have been shown not to interfere with the typical treatment of breast cancer (such as tamoxifen), and even to improve the efficacy and tolerability of cancer treatments.

According to today's knowledge dietary isoflavones in dose ranges corresponding to those typically consumed with Asian soyfood-based diet (typically 30-80 mg/day)  are not contraindicated in women with breast cancer or a high risk of developing such cancer.

We strongly recommend that you discuss this subject also with your physician. We will be happy to provide the corresponding scientific evidence.

When you know that there is a hereditary risk of breast cancer in the family, you can take preventive counter-measures. Among these preventive measures counts a healthy diet rich in phyto-estrogens such as the isoflavones present in soy. These isoflavones are probably the reason why Japanese women have the lowest mortality rate of breast cancer world-wide. The isoflavones have been shown to activate the estrogen receptor "beta", a protective system countering the hormonal effects of estrogen at the estrogen receptor alpha, such as an increased rate of cell growth in hormone-dependent tissues.

It is now widely accepted that life-long dietary exposure to soyfood and isoflavones reduces the risk of breast cancer in postmenopause. The earlier the contact to soy occurs, the more pronounced the protection.  In adult women who never were exposed to significant quantities of soy food and isoflavones before, the protective effect may not be as pronounced as in women who were already exposed to isoflavones in the youth. However, the protective effect can still be found. The conclusion must therefore be  "better late than never".

When a higher incidence rate of breast cancer in postmenopausal women was observed in the WHI study (women's health initiative), the sexual hormone estrogen was blamed for this observation. In fact, the growth of breast cancer cells can be stimulated in experimental models by the addition of estrogen. When this potential adverse effect became known, the question arised whether socalled "phyto-estrogens", i.e. plant constituents with effects similar to estrogen, might also be able to trigger breast cancer. Quite obviously the isoflavones are not - as shall be explained in the following.

Soy and red clover are the major sources of isoflavones in the diet. As isoflavones act against menopausal disorders such as hot flushes - a condition also treated with estrogen - this class of natural compounds has been called  "phyto-estrogens", plant-derived estrogens. However, the classification as "phyto-estrogens" is misleading inasmuch as the effects of estrogen in the human organism are not based on single mechanism of action: In fact, the processes of fine-tuning the effects of estrogen are rather complex. They basically involve not only the complementary action of male and female sexual hormones, but also basically two different estrogen receptors - one, the estrogen alpha receptor, causes cell division in the breast and uterus, the other, the beta receptor, is the "guardian" preventing overshooting effects at the alpha-receptor. The classification of isoflavones as "phyto-estrogen" seems to imply an activity at the alpha-receptor, which is wrong: Isoflavones act at the beta-receptor, which explains the cancer-protective effects observed with a soy and isoflavone rich diet.

The hypothesis of isoflavones potentially causing breast cancer is further supported by experimental models where isoflavones may trigger the growth of human breast cancer cells transplanted to animals. This model has, however, been criticised as being highly artificial: the animals have no own estrogen production and no immune system, and they receive the isoflavones at incredibly high doses. Even worse: there is no estrogen-beta receptor present in this model. It has been shown that even with a slight variation of the experimental setup towards more natural conditions the isoflavones no longer cause cancer cell growth, but prevent it!

The inadequacy of the animal experiments supposedly confirming a cancer risk is further underlined by the fact that such a hypothesis goes against the observations in meanwhile more than 400,000 women in epidemiological studies, in addition to observations from clinical trials where biomarkers of breast safety have been observed. It has been confirmed in meta-analyses (pooled analyses of several clinical trials which allow for a more reliable statistical evaluation) that isoflavones do not carry a potential to cause breast cancer, not even in women with an individual high risk. Quite the contrary was found: Isoflavones even protect from the formation of breast cancer, and might even be beneficial when used in the treatment of breast cancer - although a definitive answer to this question is not yet possible.

In conclusion, the old tale of isoflavones = phyto-estrogens = risk of breast cancer should no longer be repeated. However, as with the iron contents in spinach we will probably continue encountering this allegation in the future, despite all evidence of the contrary. From the point of view of the women struck by breast cancer this is a sad sítuation: With the known health benefits of an isoflavone-rich diet much suffering could already now be avoided.

On average the quantity of 50 mg soy isoflavones corresponds to the consumption of one slice of tofu (100-150 g) or half a litre or soy milk.

There is, however, a difference between the unprocessed form of isoflavones, the socalled glycosides, and the form present in fermented soy products. The calculation usually refers to the aglycones, which means glycosides minus the attached sugar moiety which is lost not only by fermatation (e.g., in tempeh or some types of tofu), but also upon ingestion in the human intestinal tract. The aglycones are the active form. Still, there are cases where the stated contents refer to the glycosides instead of the aglycones, which may be misleading. The weight of the aglycones is only approximately 60 percent of that of glycosides. I.e., 100 mg of isoflavone glycosides correspond to 60 mg of aglycones.

Typical intakes with a soy based diet are in the range of 30-60 mg of aglycones per day, with values up to 100-120 mg in some regions. The dose of isoflavone supplements is usually oriented at this dietary intake - doses of 50-60 mg cannot be considered concentrates, as is sometimes wrongly stated. 

It is never too late to start taking care of health and well-being. Of course, some of the known effects of isoflavones will no longer reach their full potential when taken in the later stages of life - which does not mean that there is no more benefit.

Anyway, we have to differentiate according to the intended use. If isoflavones are taken as a protective measure against breast cancer after the onset of menopause the effect will be small in comparison with the effect observed in women exposed to isoflavones in young years - small, but still present. In addition, the potential benefits will most likely increase in women combining estrogen and isoflavones for the treatment of menopausal disorders, as recommended by the Austrian and International Menopause society.

Usually, however, the focus of isoflavone intake in menopause is not the protective effects against breast or endometrial cancer, but the effects against hot flushes or other symptoms of menopause such as depressed mood. These symptoms can also be efficiently prevented by an early contact to isoflavones, as can be observed in studies in Asian women. For the treatment of menopausal complaints the efficacy of isoflavones has, however, also been confirmed in Western menopausal women with no significant previous dietary contact to soy.

Finally, women in menopause may also profit from the bone-sparing effects of isoflavones, even without previous exposure. The same goes for the cardiovascular protection and the positive effects on cognitive performance - many reasons to opt for a dietary intake of isoflavone in menopause - despite of those exclusively pointing to the reduction of size of cancer-preventive effects with increasing age.

There are multiple health benefits related to the dietary intake of isoflavones, as in soyfoods. A sufficient dietary supply of isoflavones helps to maintain cardiovasular health, bone strengh and cognitive performance, and has preventive effects on menopausal symptoms and the development of hormonal cancers such as breast or endometrium cancer.

Some of these effects can be used as a dietary measure to counter already manifest health problems, such as the progression of osteoporosis by improving bone mineral density, or menopausal hot flushes. Such benefits can also be reached with supplements containing isoflavones from soy or red clover. Studies have, however, shown that the best effects can be reached with an exposure to isoflavones as early as possible in life-time. E.g., the risk of developing breast cancer is more distinctly reduced with dietary exposure to isoflavones in adolescence than in adult age.

Many of the benefits may not be immediately evident when soyfood is consumed well before menopause. However, in epidemiologic studies a better health status and quality of life in menopause is regularly confirmed for isoflavone consumers in comparisons with population groups not consuming isoflavones in significant quantities (on average 30-60 mg/day).  

Don't be frightened - menopausal complaints may persist for many years. One third of all women suffers from hot flushes up to old age. The application of hormones is usually restricted to relatively short periods. Only few women use hormone preparations for more than 1-2 years, mostly because of second thoughts related to the long-term safety and tolerability. After discontinuation of the hormones the complaints do, however, frequently still persist - thus the high interest in natural remedies such as isoflavones.

The safety of isoflavones has likewise been questioned, as the socalled "phyto-estrogens" have simply been equated with the hormone "estrogen" and its effects. At least in the case of the isoflavones this is, however, clearly wrong. On the contrary such compounds activate the organism's protective systems against overshooting hormonal effects. This also happens in menopause and postmenopause. The safety of isoflavones for postmenopausal women is meanwhile amply documented, and constantly new proofs of benefits and safety are added.

 Even on long-term use no negative consequences are to be expected from the dietary intake of isoflavones. This can be demonstrated by the experience of women from Asian countries such as Japan, who have a life-long exposure to isoflavones. In contrast there are many health benefits associated to long-term ingestion - not only related to the alleviation of hot flushes, but also of bone density, the cognitive and memory functions, and cardiovascular health - above the preventive effects on certain cancer forms.

No restrictions regarding the duration of application may be derived from the known effects of a regular dietary supply of isoflavones - rather the exact opposite.

In clinical examinations with menopausal women it took approximately 4 to 6 weeks to reach a distinct reduction of complaints.  In some cases it may take 2 to 3 months until the women feel a distinct alleviation.
Menopausal complaints are not restricted to hot flushes or profuse sweating. Most women also indicate additional symptoms such as trouble with mood balance, loss of libido, disturbed sleep or dryness of skin and mucosas. Experience from controlled examinations shows that such complaints likewise respond to isoflavones, with different speed of onset of effects. By experience, disturbed sleep and depressed mood respond more quickly to isoflavones than night sweats or dry skin. The total range of positive effects thus appears gradually.