Soybean products are more popular than ever because they’re high in protein, iron and can be used to make a wide variety of products. So they definitely have a place in the market for those benefits. (Soy sauce on sushi is amazing.) It’s not perfect, however. The main issue comes from the fact that soybeans contain something called isoflavones. Isoflavones mimic estrogen-like effects which is where we get the classification phytoestrogens.
Because of this men should really reduce soybean consumption in my opinion.
Like soybeans there are a few plants that are phytoestrogens but the primary reason that soybeans are targeted is because they are used in so many products and are the main source of isoflavones in our food supply. Soybeans are used to make vegetable based protein bars, tofu, soy sauce, miso, soy protein, tempeh, infant formulas, soy dogs, soy cheese, soy milk, edamame and tons of baked goods.
So if your vegetarian or vegan… you’ve most likely come across many of these products or even use some of them.
Potential Benefits of Soybean Phytoestrogens
Oregon State University has some interesting studies on soy isoflavones and have great scientific explanations on what estrogen-like effects they have but admit there is more research that needs to be done.
They showed that (in a controlled study) by replacing animal protein with soy protein there was about a 3% reduction in LDL cholesterol (which isn’t much). This is the bad cholesterol. The studies also showed that soy isoflavones may prevent bones loss.
Most of the benefits of phytoestrogens seem to apply to women.
According to The Women’s Sports Center at the Hospital for Special Surgery in New York there are a lot of benefits for soybean consumption in women experiencing menopause. Phytoestrogens in a soy rich diet can help reduce some of the symptoms associated with menopause. The calcium in soybeans may also help with bone health at this stage in life.
Due to the faux estrogen effects it has on the body though, scientists are concerned about pre-menopausal women consuming too much soy since it “may interfere with normal estrogen activities”. So in younger women scientists are concerned about the effects of phytoestrogens but they say more studies still need to be done to determine what these are.
Even Oregon State said many of the observational studies with conclusive results are limited and some of the studies have mixed results. They believe it may have something to do with whether or not a certain metabolite is produced. Long term, high doses of soy supplements also have yet to show what the effects are.
There seems to be a potential link that (scientists are studying) between the decreased amounts of certain diseases in Asian countries and higher instances of these specific diseases in western countries. Since soy intake is much higher in Asian countries compared to western ones… they think there is a link between soy and lower rates of specific disease.
Potential Negative Effects of Phytoestrogens
SUNY Downstate Medical Center in Brooklyn New York showed in 2008 that by reducing or eliminating soy intake they could reduce abnormal uterine bleeding and painful menstruation. This study demonstrated that high amounts isoflavones from can affect female reproductive health because they have endocrine disrupting properties.
Another article published by Heather Patisaul and Wendy Jefferson at the Department of Biology at NC State University titled The Pros and Cons of Phytoestrogens says that isoflavone phytoestrogens are the subject of debate for evidence of endocrine disruption in both the United States and many other countries.
At the Centre for Neuroscience at King’s College London, male rats who were fed phytoestrogens had a major increase in stress-induced anxiety and stress hormone levels.
Soy Products Decrease Testosterone in Men
Another study at the Centre for Reproductive Biology in the UK was done on marmoset monkeys and published in the Oxford Journals. It showed that male infants who were fed soy milk formulas had considerably lower levels of testosterone (some levels were half) compared to infants who were fed cow’s milk as a control.
They also stated there were no consistent links between soy milk formulas and testosterone levels. In the end, they suggested that similar if not greater results may happen in human male infants who are fed soy milk formulas. This was back in 2002.
Human studies were done on this in 2005 and the results were not good.
At the Department of Human Biology and Nutritional Sciences at the University of Guelph in Ontario Canada the study showed soy protein significantly decreased the levels of testosterone in human men compared to milk protein.
In 2011, Harvard Medical School had a case that linked soy consumption with erectile dysfunction and decrease in DHEA levels.
If your into the science of how certain foods affect the body, these articles make for really good reading material because they go into so much depth.
Nearly every study on soy and the effects of phytoestrogens I have come across has said “more research is needed” where other studies find some very compelling evidence of soy’s negative effects on men.
If there is something that can affect sex hormones (especially female hormones) as a man I would be concerned about using them too much. Not cutting them out completely, just reducing there use. If your using them on a daily basis in large quantities and your a man, there is probably room for concern. Like getting your testosterone levels checked.
Same goes for women. If the opposite was true and there was a food source that affected testosterone and you used it on a daily basis in decent sized quantities… it would probably be something to look into.
There is still a lot of research that needs to be done but from what we see in these research articles is that there are both positive and negative effects of soy.
As a healthy male with no disease issues, with the basic knowledge of soy phytoestrogens and knowing it decreases testosterone (as shown in that study)… I would certainly reduce intake of soy products if not remove them for that reason alone.