Harmful effects of soya and soya milk consumption

For years we have been sold through different advertising campaigns that both soy and popular derived products such as soy milk, are healthy products and suitable from a nutritional point of view for the different benefits and properties they provide. But the reality according to existing scientific studies is quite different.

Although it is true, as we mentioned in a previous article, that soya milk provides omega-3 fatty acids, isoflavones rich in vegetable oestrogens, lecithin, B-complex vitamins, essential amino acids and minerals such as calcium and phosphorus, various scientific studies have shown that, despite its nutritional value, it is a drink whose consumption is not really recommended.

Therefore, before consuming the popular soya drink we want to analyze what its harmful effects are, since both in the short and long term they would be really dangerous for our organism and for our own health.

The main negative effects of the consumption of soya and its derivatives

Endocrine Disruption

Soy is rich in genistein, a protein that causes pancreatic and thyroid disorders. Several scientific studies have described an increase in thyrotropin hormone (pituitary TSH) in response to its antithyroid action, causing hypothyroidism, diffuse goiter and subacute autoimmune thyroiditis (1).

Because genistein inhibits thyroid peroxidase, it causes irreversible damage to the enzymes that synthesize thyroid hormones. To give just one example, in 1988 Dr. Theodore Kay (Kyoto University Medical School) found that people fed soybeans – especially children and women – suffer from an enlarged thyroid.

In addition, long-term consumption is known to increase the risk of thyroid cancer, while children fed soy formulas have twice the risk of diabetes.

Alterations in fertility

Although this section is within the different endocrine alterations produced by the consumption of soya, we want to make a separate section to be able to analyze it in depth.

We must not forget that soya contains phytoestrogens, whose action combines with other endocrine disruptors and xenoestrogens, responsible for alterations in sexual behaviour, sexual hormones, reduced fertility and androgens.

In the case of men, not only are androgens and fertility itself diminished, but the genistein and daidzein found in soya are genotoxic compounds for sperm. In turn, phytoestrogens cause swelling, fluid retention and breast development (gynecomastia).

If soy consumption occurs from childhood, early puberty and congenital abnormalities of the male genital tract may occur. In fact, the highest incidence of these types of defects has been found in male babies born to vegetarian mothers who are heavy consumers of soya (2).

Effects of Soya

Alterations in the immune system

Soy is rich in genistein, a protein that exerts an immunosuppressive effect, producing atrophic alterations of the thymus. In fact, even normal consumption of soy products during pregnancy and breastfeeding has been linked to the development of autoimmune diseases in children.

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Allergic alterations

It is known that soya protein produces different allergic alterations, generating almost 30% of severe reactions, in addition to being a cause of alopecia.

Alterations in DNA, and malformations at birth

Different scientific studies have described alterations in the natural repair mechanisms of chromosomal alterations, as well as negative DNA alterations (3).

In case of pregnancy, different researches carried out by the John Hopkins University have concluded that there is a potential connection between the consumption of isoflavones during pregnancy, birth defects (such as hypospadias, cryptorchids, spina bifida, absence of some organ, miscarriages and deformed legs) and thyroid alterations.

Alterations of the nervous system

A scientific study conducted by the Hawaiian Epidemiology Center for more than 3 decades on 7,000 men found that the more soybeans they consumed, the worse their mental abilities were.

Experts also indicate that drinking approximately 25 grams of soybeans per day can lead to cognitive problems. In this regard, the National Institute on Aging reported findings that revealed that consuming soy in two or more servings a week resulted in poor cognitive performance and low brain weight.

Soya beans

Behavioural alterations

Long-term consumption of soya products is known to cause increased stress and anxiety, aggressive behaviour and in turn a decrease in social behaviour.

Not only does it not prevent cancer, but it increases the risk of cancer

For years, the soybean and soy products industry has been advertising that it is a cancer-preventing food. However, in the scientific literature we can find cases that show that, in reality, not only does it not prevent it, but it can promote gynecological and thyroid cancers, pancreatic and breast cancer and childhood leukemia.

In the industrial processing of soya, a carcinogenic substance known as lisinealine is produced, while the solvents used leave other residues such as hexane, which is also carcinogenic (4).

Encourages the development of breast cancer

Although we have already dealt with this issue in the previous section, we wanted to open a special space dedicated to this topic, mainly because one of the supposed advantages or benefits of soy consumption for women is the alleged prevention of breast cancer.

However, we must bear in mind that soya is rich in phytoestrogens, so it could be linked to an increased risk of breast cancer. This was found by Cornell University, which showed that high levels of estrogen in the long term are linked to an increased risk of breast cancer. It appears that these carcinogenic effects are even greater in pre-menopausal women (5).

Appearance of uterine fibroids and menarche

A 4-year study conducted by the Environmental Health Perspective involving 50,000 women found that women who were fed soy milk as children had a 25% higher incidence of uterine fibroids by age 35.

In 2011, the results of a scientific study found that girls who were fed soy in childhood have a 25% higher risk of early menarche (i.e., early adolescence) (6).

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Does not prevent osteoporosis

It seems that the claim that soya prevents osteoporosis is also completely false, since it is actually a plant product that not only blocks the absorption of calcium, but also causes a deficit of vitamin D.

Why is Asia one of the continents with the lowest levels of osteoporosis? Not precisely because of the consumption of soya, but because its diet is richer in vitamin D, which comes from other foods such as shellfish, bacon, and broths made with bones (very rich in calcium).

Appearance of kidney stones

Soya is rich in oxalates, which cannot be metabolized by our body and are eliminated by the urine. A recent study conducted by Washington State University (in Spokane), has shown that oxalates bind with calcium in the kidneys, which can lead to the formation of kidney stones. Therefore, soy consumption is not recommended for people at risk for stones.

So, it’s not safe to consume soy?

We must bear in mind that there are no foods that are one hundred percent beneficial or harmful. Furthermore, in most cases, the problem with soya comes from consuming soya beans and derivatives obtained from transgenic crops.

Fortunately, according to European regulations in Genetically Modified OrganismsAs with any other food, if the soya is transgenic it must be indicated on the product packaging, so every time we are going to buy a soya product or derivative, the most appropriate thing to do is to look at its labelling. You will probably find a notice such as “produced from non-GM soy”, or perhaps “contains GM soy”.

However, the best way to ensure that you consume 100% safe soya is to opt for products from organic farming.

On the other hand, we must also pay special attention to the daily quantities of soya we consume, since even though it is not transgenic and even comes from organic farming, if we go overboard with its consumption we will notice its negative effects, and it will not be as beneficial to health. Studies indicate that we should not exceed 3 daily rations of soy or soy derivatives per day, while to notice the effects of isoflavones (especially in men), we should exceed 12 daily rations.


(1) Endocrine disruption:

(2) Alterations in fertility:

(3) DNA alterations and malformations at birth:

(4) It increases the risk of some types of cancer:

(5) It promotes the development of breast cancer:

(6) It promotes the development of uterine fibroids and menarche:

This article is published for information purposes only. It cannot and should not substitute for consultation with a Nutritionist. We advise you to consult your trusted Nutritionist.

This article is published for information purposes only. It cannot and should not substitute for consultation with a Nutritionist. We advise you to consult your trusted Nutritionist.