In the last two decades, soy has become a mainstream alternative to animal-based protein products. With popularity comes scrutiny, let’s examine some of the common fears incited by critics.
Soy is a legume cultivated and consumed for centuries as a staple in many Asian cultures. Its popularity continues to grow because of its excellent protein profile, palatability, and protective health properties demonstrated by soy-consuming populations. However, concerns raise possible negative effects of consuming too much.
What is the root of the soy fear?
Much of the controversy and confusion is around soy isoflavones and their action in the body. Some isoflavones, also called phytoestrogens or “plant estrogens”, have a similar chemical structure to estrogen (note the key word similar – not identical), which may have estrogen-promoting effects. Interestingly, these same compounds don’t always mimic estrogen. In certain tissues, they may actually block the action of estrogen. This is done by disrupting more potent natural estrogens from binding to the estrogen receptor.
Because estrogen plays such a wide role in our biology, researchers have studied whether soy’s phytoestrogen compounds have similar effects. Despite numerous published studies, conclusions vary. Many studies that throw fuel to the fire used either extremely high doses of isolated soy compounds, while others bypass normal consumption routes through injection of animal models that don’t necessarily translate well as actual human physiology.
Let’s dive in further and see what’s proven, what’s hype, and what health experts really think.
While human estrogen links to breast cancer-promoting effects, there is no evidence suggesting phytoestrogens cause the onset of breast cancer. A review of research literature summed up the evidence:
Women consuming moderate amounts of soy throughout their life actually have lower breast cancer risk than women who do not consume any.
Other large studies on ethnic populations who consume one to two servings per day, including the Singapore Chinese Health Study, the Shanghai Women’s Study, and the Japan Public Health Center study, all found higher intakes of soy were actually associated with a reduced risk of cancer.
Since estrogen is a hormone replacement therapy (HRT) for menopausal women, popular belief is soy can be a natural alternative. In fact, the Women’s Health Initiative has reported a decline in estrogen therapy usage in recent years, while seeing an increase of menopausal women consuming soy products.
However, limited studies using soy as an estrogen replacement make it difficult to conclude if there is an effect.
Considering the conflicting results from a small number of studies, soy’s efficacy in improving menopausal symptoms remains unclear.
‘MOOBS’ (OR MAN BOOBS)
Contrary to popular belief, the vast majority of men who consume soy will not likely develop feminine features. In a 2010 review, researchers indicate there is no evidence that soy isoflavone exposure impacts circulating estrogen in men. At moderate amounts, soy has not shown to cause feminine characteristics in men. However, some studies show some men with increased sensitivity when consuming soy at extremely high amounts (more than twelve servings a day) and go on to develop tender, enlarged breast tissue.
Overall, these studies show that it’s extremely rare for a typical male to suffer from ‘feminization’ effects.
In fact, it is difficult for any typical person to consume close to enough soy for any negative effect.
So what are the health benefits of eating soy and how much is recommended?
Even with mixed evidence, we still know many misconceptions remain exaggerated myths. Most studies point to soy’s positive benefits, whereas its negative effects are speculative at best.
In fact, eating moderate amounts, such as one serving a day (equivalent to 1 cup of soy milk or ½ cup of tofu) make it an excellent part of a balanced diet and a wonderful protein alternative. It can help us decrease saturated fat and meat consumption that often links to heart disease.
This is undisputedly beneficial to our health, and the majority of Americans can benefit tremendously by making this simple swap.
Mascha Davis, MPH, RDN is a Los Angeles-based private practice dietitian who shares her love of health and wellness through a unique global perspective. From world-class U.S. medical centers to rural villages in Africa, Mascha has dedicated herself to traveling the world, spreading her love of healthy living through both her humanitarian work and private practice. Learn more about Mascha at Nomadista Nutrition.