Is Soy good or bad for you?

By Hannah Buckland, Healthy Hearts Care Planner

Soy has always been a controversial topic in the nutrition world. On the one hand, it is extremely nutrient dense, a great source of protein, polyunsaturated fats, fibre and vitamins. On the other hand, it has been linked to breast cancer, reduced thyroid function and reduced testosterone levels in men. Understandably, this can leave people confused as to whether or not they should include soy in their diet. We’ve taken a look at the latest evidence to better understand the impact of soy on your health.

Soy is a type of legume that can be found in a variety of forms, including soy milk, tofu, yoghurt, soybeans and meat substitutes. It was traditionally eaten mostly in Eastern Asia but has recently become more common in Western countries; particularly for those following a plant-based diet. This is because soybeans are one of only a few plant-based complete proteins, meaning that they contain all of the essential amino acids we need from food. In fact, a cup of cooked soybeans contains almost as much protein as a serving of steak!

The reason why soy is so controversial is that it contains phytoestrogens – plant hormones that have a chemical structure similar to the human hormone oestrogen. Since some cancers grow in the presence of oestrogen, concerns have been raised that soy foods could increase cancer risk. However, research shows that phytoestrogens do not behave the same way in the human body as oestrogen. Furthermore, fears that soy disrupts sexual development or reduces men’s testosterone levels stem from studies conducted on animals, which provides very weak evidence. Finally, studies have confirmed that soy foods do not interfere with thyroid function.* Therefore, the latest evidence does not suggest that there are any risks to consuming soy.

In contrast, research conducted on humans has shown that soy may be beneficial for menopause, cholesterol and fertility, and reduce the risk of prostate cancer. Likewise, studies investigating the consumption of whole soy foods such as tofu, soy milk and soybeans suggest a protective effect against breast cancer rather than an increased risk.

Indeed, comprehensive reviews by the World Health Organisation, World Cancer Research Fund and European Food Safety Authority all conclude that soy foods are safe to consume as part of a healthy, balanced diet. In addition, soy products are typically affordable, nutritious, and can be a tasty alternative to meat; providing a more sustainable option that can benefit the environment. Remember, when it comes to diet, variety and diversity are key. Trying new foods can encourage us to consume a diverse and well-balanced diet. So, if you’ve not tried any soy foods before – why not experiment this week? Perhaps swap mince meat for soy mince, or switch to soy milk in your tea or coffee.

Feel free to get in touch and let us know how you get on – we’d love to hear from you!

* Note: soy can interfere with the absorption of thyroid medication levothyroxine, so it is advised to take thyroxine medication on an empty stomach.


British Dietetic Association (2020). Soya Foods: Food Fact Sheet. British Dietetic Association. Available from [Accessed 26th August 2020].

British Nutrition Foundation (2002). Soya and health. British Nutrition Foundation. Available from [Accessed 26th August 2020].

Rhitrition (2020). Is soya good or bad for your health? Rhitrition. Available from [Accessed 20th August 2020].

The Food Medic (2018). Soy and breast cancer. The Food Medic. Available from [Accessed 24th August 2020].

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