SUMMARY

Soybeans contain plant compounds that may help prevent breast and prostate cancer. What’s more, these legumes may relieve menopause symptoms and cut the risk of osteoporosis in postmenopausal women.

Even though soybeans have a number of health benefits, some individuals need to limit their consumption of soy products — or avoid them altogether.

Suppression of thyroid function

High intake of soy products may suppress thyroid function in some people and contribute to hypothyroidism — a condition characterized by low production of thyroid hormones (53Trusted Source).

The thyroid is a large gland that regulates growth and controls the rate at which your body expends energy.

Animal and human studies indicate that the isoflavones found in soybeans may suppress the formation of thyroid hormones (54Trusted Source, 55Trusted Source).

One study in 37 Japanese adults showed that eating 1 ounce (30 grams) of soybeans every day for 3 months caused symptoms related to suppressed thyroid function.

The symptoms included discomfort, sleepiness, constipation, and thyroid enlargement — all of which disappeared after the study ended (56Trusted Source).

Another study in adults with mild hypothyroidism found that taking 16 mg of isoflavones every day for 2 months suppressed thyroid function in 10% of the participants (55Trusted Source).

The amount of isoflavones consumed was rather small — equivalent to eating 0.3 ounces (8 grams) of soybeans per day (57Trusted Source).

However, most studies in healthy adults have not found any significant links between soy consumption and changes in thyroid function (58Trusted Source, 59Trusted Source, 60Trusted Source).

An analysis of 14 studies noted no significant adverse effects of soybean consumption on thyroid function in healthy adults, whereas infants born with thyroid hormone deficiency were considered at risk (58Trusted Source).

In short, regular consumption of soy products or isoflavone supplements may lead to hypothyroidism in sensitive individuals, especially those who have an underactive thyroid gland.

Flatulence and diarrhea

Like most other beans, soybeans contain insoluble fibers, which may cause flatulence and diarrhea in sensitive individuals (13Trusted Source, 14Trusted Source).

Although not unhealthy, these side effects can be unpleasant.

Belonging to a class of fibers called FODMAPs, the fibers raffinose and stachyose may worsen symptoms of IBS, a common digestive disorder (15Trusted Source).

If you have IBS, avoiding or limiting the consumption of soybeans may be a good idea.

Soy allergy

Food allergy is a common condition caused by a harmful immune reaction to certain components in foods.

Soy allergy is triggered by soy proteins — glycinin and conglycinin — found in most soy products (7Trusted Source).

Even though soybeans are one of the most common allergenic foods, soy allergy is relatively uncommon in both children and adults (61Trusted Source, 62Trusted Source).

SUMMARY

In some people, soy products may suppress thyroid function, cause flatulence and diarrhea, and lead to allergic reactions.

Soybeans are high in protein and a decent source of both carbs and fat.

They are a rich source of various vitamins, minerals, and beneficial plant compounds, such as isoflavones.

For this reason, regular soybean intake may alleviate the symptoms of menopause and reduce your risk of prostate and breast cancer.

However, they can cause digestive problems and suppress thyroid function in predisposed individuals.

Reference:  Healthline.com