BSc Sports and Exercise Science 

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Should You Be Eating Soy? And How Much Is Safe to Eat? The latest research.

February 6, 2019

(3-minute read) 


Soy has got a name for its-self of being one of the most controversial foods at the moment. 


In this article, I hope to put your mind at rest on whether you should or shouldn’t be eating Soy products, how much you should be eating and what ones you should eat and what you should be avoiding. All this information has come from reliable evidence-based articles from experts in the field. 


A Soybean is about 41% protein and is rich in branch chain amino acids (BCAA’s), making it a complete protein source. The soybean has a good ratio of Omega 3 to Omega 6 dietary fat and contains slow digesting carbohydrates and fibre, excellent for bacteria in the gut. Overall this looks to be quite a sensible food and protein source to be consuming, right?




Does soy have an effect on hormone levels or decrease testosterone?


Research has recently found that soy protein supplements do not seem to decrease testosterone or limit muscle gain. However, there are mixed findings out there, with most having a common theme; suggesting that extremely high levels of soy consumption may have a slightly unfavourable effect on hormone levels. These “extremely” high levels that saw any change in hormone levels where so high that you would physically struggle to eat that much soy in a day, it would be the equivalent to 60 cups of soy milk per day, about 86 servings of tofu, 70 cups of soy (edamame) beans or 15 cups of miso! 


There is so much concern over soy that we forget to look at other dietary factors that may have an impact on hormone levels. 

Large Alcohol consumption has been seen to have an unfavourable effect on testosterone, increasing oestrogen levels and reducing male fertility. 


Dairy products contain large amounts of oestrogen, therefore cause an increase in dietary consumed oestrogen's. Beef (containing hormones - non organic) has been suggested to alter male fertility, so actually if we are looking at foods affecting hormone levels in the body we should be looking at a lot more than just soy as the results from studies would suggest you have to eat an extremely high amount of soy for any effect to be seen on hormone levels. 


Soy and bones?


Studies on soy consumption with menopausal women have been very positive, seeing significantly increased bone formation and bone health, including bone mineral density. 


Is it safe to eat Soy regularly and how much should you eat?


Based on all the evidence, unrefined soy products are safe to eat regularly, I would suggest that if you consume 1-2 servings per day of unrefined soy it is a safe and healthy intake, in addition to a healthy balanced diet. Exceeding 3 portions a day may not be a great idea. 1 serving is 1 cup of soy milk or 115g tofu/temphe or soybeans. I would try and go for organic soy products, e.g organic tofu. 


Unrefined soy foods consist of; Tofu, soybeans (edamame), soy milks, temphe and miso. These products should be eaten within part of a balanced diet. 


I would try to avoid isolated and high refined forms of soy on a regular basis; soy isolates, soy concentrates, textured soy protein and soy lecithin. 


These refined soy foods (soy concentrates, textured soy protein, soy lecithin and many more) find their way into so many food products that you wouldn’t even believe could contain soy. Next time you’re in the supermarket take a look at the bars of chocolate, even the ones you consider “healthier” dark chocolate contain soy as well as hand soap to meat products and soups! 


Consider the amount of each food you’re eating to ensure you are not overloading on any foods, especially dairy, meat products and nuts. 


As always, any questions fire them below or email me,



Kasia :) 


BSc Sports Science, Women’s Fitness Specialist and Personal Trainer 


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