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To Soy or Not To Soy?!: Soy – The Low Down

One of the questions I often get, is whether one should be eating soy products or avoiding it. There is a lot of mixed research around soy products, some studies have demonstrated an inverse relationship between soy consumption and breast cancer risk, while other studies have shown an increased risk or no effect. In fact, soy products have been in the spotlight with regards to their controversial effects on other health conditions too, such as thyroid conditions. I mean, can science make up its mind already?!


What is soy?

Soybeans are legumes that have been a part of the Asian diet for many years and are now infiltrating the Western diet in a big way. An increasing number of food products are now made from soy.

Soybeans can be eaten whole, this is what you are eating when you eat edamame beans. Other well-known food products that contain soy are soya sauce, tofu, veggie burgers (Frys food products) and soy milk. It can also be found in fermented foods such as miso and tempeh. In fact, soybean oil and soy protein are used in the production of many food items, without us even realizing it.


So, is soy healthy or not?

Well, that’s a trick question. Let me explain.

It would be easy to think that soy isn’t healthy as most soy products today are refined and processed and use genetically modified and herbicide roundup sprayed crops. This can be linked to adverse health effects such as obesity, diabetes, cancer, poor cardiac health and gastrointestinal disorders.Further to this, these soy products also contain, what is known as, phytates which result in the decrease of absorption of many nutrients in our gut.


Does this mean we should not be eating soy?

If we look at the research and at the residents of the longevity hotspot, Okinawa, Japan, who eat soy daily, we can see that some forms of soy may not actually be bad. They however, eat soy in its most natural or fermented form. In fact, breast cancer incidences in Asia have been much lower when compared to other countries, because of their high soy intake. However, studies show that when Asian women move into westernized countries and their diet changes, their risk for breast cancer increases.

When contemplating whether to eat a certain food or not, you should always think of whether the food is in its most natural form or not. Whole soybeans, like edamame, contain a good amount of nutrients and they are a good plant-based source of protein.


Ok, so it’s a “no” to processed soy products, a “yes” to whole soybeans, such as edamame beans.


But what about fermented soy products?

Fermented soy products, such as tempeh and miso, help to feed the bacteria in your gut, providing a healthy gut bacteria balance. It also breaks down those phytates which stop us from absorbing all those beneficial nutrients.

So, in actual fact, when we’re looking at the different types of soy on their own, we can now see that the best sources are your less processed edamame beans, tempeh, and miso. Always remember, to check the other ingredients when choosing soy products and go for organic or non-GMO sources where possible.


Now what about all the health claims around soy products?

Soy and breast cancer

Soy products, among other vitamins and minerals, also contain isoflavones – phytoestrogens – which chemically have a very similar structure to the naturally occurring hormone, oestrogen. Studies have shown that this can result in soy  binding to oestrogen receptors , stimulating oestrogen secretion, resulting in the  body’s oestrogen levels to be completely out of whack. We know that an imbalance of oestrogen in the body can result in an increased risk for breast cancer.

So that means we shouldn’t eat soy…Right?

Well, this, again, is not as clear cut as we once thought. Current evidence suggests that a diet containing natural sources of phytoestrogens (like soy and other legume-based foods) are safe, even if you have had breast cancer. In fact, they might be beneficial.

A study  released by the American Cancer Society in 2017, Dr Zhang (a cancer epidemiologist) and Marian Neuhouser (registered dietician and nutritional epidemiologist at the Fred Hutchinson Cancer Research Centre), as well as other recent studies have all shown that soy can either reduce the risk of  breast cancer or its reoccurrence.

What happens if you have an underactive thyroid?

 Many studies show that soy may adversely affect thyroid function. A review, assessing the results of many studies done on thyroid function and soy, showed no effect of soy intake in people that had a normal thyroid function, however it showed that those who had an underactive thyroid may need to take more thyroid hormone replacement therapy than normal. Other studies show no effect of soy on thyroid function but do advise that if you are on thyroid replacement therapy, its best to wait a few hours after taking medication before consuming soy products as it may impair the absorption of your thyroid medication.


 What is the take-home message

 For now, soy is generally better in its raw edamame or fermented forms.

If you’re concerned about its relationship with cancer, there is new evidence emerging about its safety and benefits. As a dietitian, I feel that one must take all the evidence into account as well as work on an individual basis, especially if breast cancer risk is a concern. I do however, feel, that after assessing the new research and having spoken to doctors in the oncology field, I do not see the need to avoid soy, but rather to make sure that it is eaten in its most natural form and in moderation.

Hypothyroidism patients should watch the quantity and timing of soy consumption.

Let’s still keep-one-eye-open for more research on soy’s isoflavone’s effect on our health.

Nourish yourself to the sunrise.

Written with love ,
Sunrise by HM

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