There is a widespread belief that the consumption of soy, and in particular, its isoflavones, is one of the most effective strategies to alleviate the symptoms of menopause. It is also believed that these phytochemicals are a great ally for bone and cardiovascular health during menopause. However, there are many experts who, like Carmen Cuadrado, honorary member of the Spanish Academy of Nutrition and Dietetics, assure that scientific evidence is still lacking solvent that supports claims as broken as that soy isoflavones protect women from osteoporosis, or that their intake promotes weight gain.
What are isoflavones?
Isoflavones are a subclass of flavonoids, a group of phytochemicals (plant chemicals) present in many fruits, vegetables and spices and are responsible for their intense colors. «They are a group of bioactive, non-nutritive compounds, of a phenolic, non-steroidal nature, with a chemical structure similar to that of estradiol (female sex hormone) and a weak estrogenic activity,» explains the expert, doctor in Pharmacy and Professor of Nutrition and Dietetics at the Complutense University. This is what she explains is that soy isoflavones are considered phytoestrogens.
Not all isoflavones are the same. There are the majority ones (genistein, daidzein and glycitein), and two other minor ones (formononetin and biochanin A). They are distinguished by their chemical composition, but these differences have no nutritional effects.
Possible benefits of soy isoflavones.
Although current research has not yet reached a consensus on the effects of soy isoflavones in humans, there are some certainties in this regard. In this sense, «among its mechanisms of action, the ability to bind to estrogen receptors, acting as estrogen and alleviating the deficiency of this hormone that is typical of menopause. They will also have other effects, such as enzyme inhibition or antioxidant activity”, summarizes the expert.
Furthermore, “it seems that the estrogenic activity of isoflavones depends on the amount of endogenous estrogens, so that when the concentration of estrogens is low, they would act by enhancing their effect. This could contribute to Reduce menopause symptoms in some women.”.
Do they alleviate the effects of menopause?
The most important source of isoflavones is soybeans. Now, «its quantity may vary depending on various factors, such as variety, harvest and geographical location. In addition, preparation processes (cleaning, drying, crushing and hulling) and extraction of soybeans are carried out to produce oil refined soy, soy lecithin, free fatty acids, glycerol and soy flour,” says Cuadrado.
With all this, «it is not clear that isoflavones have beneficial effects on the symptoms of menopause. Nor on certain chronic diseases, since there are clinical trials that indicate positive effects, while others do not find differences.»
Regarding its participation in bone and cardiovascular health, aspects that are especially relevant in menopause and premenopause, the expert emphasizes that «the mechanism of action of soy isoflavones in the bone could be considered beneficial, since they seem to act stimulating the activity of osteoblasts to form bone matrix, the basic structure of bones. At the same time, they induce a decrease in the survival and activity of osteoclasts, which are the cells that degrade this matrix.”
While these mechanisms of action of soy isoflavones are well established, others remain less clear. «It has been postulated that the main effect would be genomic through estrogen receptors, but other non-genomic effects have also been proven. There is epidemiological evidence of a lower incidence of cardiovascular diseases in Asian countries associated with soy consumption, however , the results do not seem to be conclusive.»
Do isoflavones make you fat?
Another of the most deeply rooted myths is that they favor weight gain. Cuadrado insists that there is not enough evidence to corroborate it either.
Something similar happens in relation to cholesterol. «The evidence to date is insufficient to be able to recommend its intake to lower cholesterol. A clear conclusion cannot be obtained because there are many variables involved. For example, in subjects who initially had hypercholesterolemia, a greater cholesterol reduction was detected than in those with normal cholesterol levels,” he explains.
The expert believes that in these cases it would be necessary to clarify whether the presence of other concomitant cardiovascular risk factors (diabetes, menopause…) could translate into a greater benefit with the consumption of isoflavones. «In addition, the number of clinical trials with men must be increased, since the vast majority of studies are done with postmenopausal women,» she adds.
Foods that provide isoflavones
The foods that contain the most isoflavones are legumes.
soy
Soybeans and their derivatives are those with the highest concentrations.
According to the results of cohort studies, in people who regularly consume soy products, the daily intake of isoflavones can be between 30 and 90 mg of isoflavones.
Soy sauce or miso soup contain a very low amount of isoflavones. Soybean oil does not contain isoflavones.
Other legumes
In the case of lentils, peas, white beans and chickpeas, the amount of isoflavones is much lower than soy (0.1-0.7 milligrams per 100 grams).
Cruciferous
Cruciferous vegetables (cabbage and cauliflower) contain very little isoflavones (5-10 micrograms per 100 grams of dry weight).
barley
It contains a small amount (10-15 micrograms per 100 grams).
Is it good to take soy supplements?
Both natural soy and supplements are not recommended for women who are experiencing hormone-dependent cancer. “Some studies have suggested that there is a relationship between soy or isoflavone supplements and an increased risk of breast cancer in women who have a family or personal history of breast cancer or also thyroid problems,” since there are some indications that Soy products may inhibit the absorption of the drug levothyroxine used in hypothyroidism if taken at the same time
In this sense, the expert warns that «soy or isoflavone supplements generally contain higher levels of isoflavones, their bioavailability is greater and they do not share the nutritional properties of the natural source in the form of legumes, vegetables or cereals (proteins, vitamins, minerals…etc)”.
Risks and side effects of consuming isoflavones
Cuadro strongly states that “the safety of isoflavones is not clear. In fact, toxicological information is considered insufficient. Reviewing the literature associated with the safety of these flavonoids, it appears that the isoflavone consumption is safe if it is in the form of soy products in the quantities mentioned above within the framework of a varied diet. «It is almost impossible to achieve the amounts of isoflavones in supplements through food.»
Regarding possible side effects, “isoflavones taken in larger quantities can interfere with metabolism and act as endocrine disruptors. It could also cause interference in the action of some medications,» he warns.
How to incorporate soy and its derivatives into the diet during menopause
Knowing the properties and limitations that, with the studies in hand, can be attributed to isoflavones, the expert recalls that «No food acts alone or in isolation, but in the context of a dietary and lifestyle pattern.«. From there, if we want to introduce soy and its derivatives into our daily diet, the expert suggests doing so «in the form of edamame (they are sold frozen or raw), cooked like other legumes or in derivatives such as vegetable drinks, fermented . or not, or in others like miso, tempeh or tofu.
The entry Isoflavones: what they are, what foods they are in and what they have to do with menopause was first published in Nutriiendo.
