Miraculous plant or endocrine disruptor? The question divides researchers. In her book 'Soy Planet ', investigative journalist Julie Lotz warns of its dangerousness. Explanations.
After having advised us to abandon meat for our well-being and that of the planet, are we now heading towards a new slogan 'bye bye also tofu and soy drinks?'. A hell of a dilemma since soy and its derivatives (in steaks, patties, etc.), rich in protein and fiber, are supposed to be alternatives to meat! Result: we do not know what to put on our plate as studies on this legume diverge. Indeed, some believe that soy has a protective effect against cancer, others advise against it because of its isoflavones (or phytoestrogens) whose chemical structure is close to that of estrogens (female sex hormones) and which can mimic Their mechanism of action in the body. This is a potential risk, especially in the case of treatment for breast or ovarian cancer.
Soy: it disrupts the menstrual cycle
To understand, Julie Lotz's book "Planète Soy" (edition of the Rock) is particularly enlightening... And creepy! As a preamble, the journalist quotes the words of Catherine Bennetau-Pelissero, the main whistleblower on the deleterious effects of the plant: "If you drink a liter of soy juice in two hours, you will trigger your period in the night". As a result, the journalist who only ate soy occasionally in the form of soy sauce, vanilla dessert, or vegetarian steak, decides to experiment with it. "When suddenly, three days after taking the soybeans, four days before the normal arrival of my period, the English arrives... She says. And with them, unusual menstrual pains (...). What happened? Are soybeans responsible? " Researcher Catherine Bennetau-Pelissero's response, "Drinking soy juice in less than two hours created a spike in estrogen similar to that which occurs naturally in women's bodies before menstruation arrives. " Moreover, several studies cited in the book indicate that these soy isoflavones can have an impact on the female cycle (and even on male fertility!). In one of them, it is even stated that "45 mg of isoflavones (i.e. A soy steak) have an impact on the menstrual cycle". For its part, in 2005, the French National Agency for Health Security (ANSES) advised against their consumption to pregnant women because, "consumed during pregnancy, they can increase the risk of testicular and breast cancers in the child to come".
Phytoestrogens: what impacts on breast cancer or thyroid?
According to ANSES experts, the consumption of soya and isoflavone-based food supplements can also accelerate the development of hormone-dependent cancer cells, especially in women who have or have had breast cancer and those who have a family history. At the same time, they believe that in some cases, especially in Asian women who do not carry hormone-dependent cancers, the consumption of soy-derived products and isoflavones can reduce the risk of breast cancer. Go figure... In addition, these experts also advise against ingesting it to people who suffer from hypothyroidism because isoflavones can act in interaction with the synthesis of thyroid hormones and can also prevent the effectiveness of treatment. They, therefore, recommend that people with hypothyroidism do not consume it, in any form whatsoever.
Health Effects of Soy: Conflicting Opinions
But not everyone agrees! In 2005, the year of the publication of ANSES's divisive report, Michel Roussel, a phytotherapist, stated in a book that the said legume was good for health. Thus, in "The Miracles of Soy" (Alpen edition), the doctor wrote that its consumption "could prevent cancers and cardiovascular diseases", "decrease menopausal disorders, or "lower cholesterol levels by 20%". Today, Julie Lotz's book throws a new stone into the pool of pro-soybeans. According to Sojaxa, a collective of companies offering soy products from French crops, without GMOs, this book "lacks objectivity and does not take into account all the scientific data available to date (...). On the contrary, many studies, including some recent ones, are very reassuring. " For example, quotes the collective: "The review of the literature published in the Bulletin of Cancer last January, as well as the large American cohort study whose results were published in the International Journal of Epidemiology on February 25, both highlight the lack of a link between soy foods and breast cancer."
Tofu, tempeh, soy steak...: do we eat it or not?
The products are multiplying: dumplings or steaks of vegetable proteins, vanilla or chocolate soy desserts, or tofu, tempeh, miso... But what about their isoflavones content? These are very variable, and this is where the problem lies, says Julie Lotz. The highest levels are found in toasted soybeans for an aperitif (247.74 mg of isoflavones per 100 g!), soy flour and soy flakes, infant formula based on soy protein. And for a simple "vegetable steak tomato/onion"? That's 55.51 mg per 100 g. Another problem: nothing is indicated on the labels! In its famous report in 2005, ANSES recommended that manufacturers mention the level of phytoestrogens as well as warning messages. " Out of more than thirty stores visited, says the journalist, I found only one product with a warning." Indeed, only a soy juice of the Monoprix brand indicates "Not recommended for children under 3 years and pregnant women. This beverage may not be used as a single food for an infant under 12 months of age."
Soy isoflavones: we consume them without knowing it!
But there are also some meats, fish, ready-made dishes, baked goods... In the form of flour, concentrate, or protein isolates. It is also found in chocolate, noodles, aperitif cookies, cereals or snacks for children, and even in some chewing gum. In this case, it is rather present in the form of soy lecithin, a food additive authorized in Europe under the code E322. There, manufacturers are required to indicate this. And Julie Lotz reassures "Lecithin concentrates very few isoflavones and it is present in such small quantities in foods that we ingest very little". However, given the fact that we consume more and more soy products, the cumulative effect raises questions, especially since the levels ingested would be underestimated...
Soy: the dose that would not be dangerous
Also in 2005, ANSES recommended not to exceed 1mg per kilo of body weight per day. Thus, a woman of 60 kilos should limit herself to 60 mg of phytoestrogens per day: a steak and a glass of soy juice. Faced with so many uncertainties, some nutritionists go further by invoking the precautionary principle. Thus Véronique Beck, author of "Reduce meat" (Jouvence edition) proposes to vary the sources of vegetable proteins by alternating tofu, tempeh or miso, etc...; and pulses, cereals, oilseeds, seeds, while not consuming soy foods more than once a week, and without exceeding 80mg of isoflavones, or two servings. For example 100g of tofu plus 1 soy dessert.
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