Soy protein powder side effects

Possible Negative Effects on Health

While soy has several health benefits, its effects on other conditions are unclear.

Effect on Breast Cancer Is Unknown

Soy contains isoflavones, which act like estrogen in the body. Since many breast cancers need estrogen to grow, it would stand to reason that soy could increase breast cancer risk. However, this isn’t the case in most studies.

In a review of 35 studies on soy isoflavone intake and breast cancer incidence, higher soy intake reduced breast cancer risk in both pre- and postmenopausal Asian women.

For women in Western countries, one study showed soy intake had no effect on the risk of developing breast cancer .

This difference may be due to the different types of soy eaten in the Asian compared to the Western diet. Soy is typically consumed whole or fermented in Asian diets, whereas in Western countries, soy is mostly processed or in supplement form.

In an animal study, rats fed fermented soy milk were 20% less likely to develop breast cancer than rats not receiving this type of food. Rats fed soy isoflavones were 10–13% less likely to develop breast cancer .

Therefore, fermented soy may have a more protective effect against breast cancer compared to soy supplements.

Additionally, soy has been linked to a longer lifespan after breast cancer diagnosis.

In a review of five long-term studies, women who ate soy after diagnosis were 21% less likely to have a recurrence of cancer and 15% less likely to die than women who avoided soy.

Impact on Thyroid Function

Soy contains goitrogens, substances that may negatively impact the thyroid by blocking iodine absorption.

Test-tube and animal studies have shown that soy isoflavones block the production of thyroid hormones .

Studies on the impact of soy on thyroid function in humans suggest it may not have a significant impact.

In a review of 14 studies, soy had little to no effect on thyroid function, and the authors concluded that people with hypothyroid disease do not need to avoid soy as long as their iodine intake is adequate .

Plus, two randomized trials in postmenopausal women found that up to 120 mg a day of soy isoflavones had no significant effect on thyroid hormone production .

Effect on Male Sex Hormones

Because soy contains phytoestrogens, men may worry about including it in their diet.

However, studies do not indicate that soy negatively impacts the production of testosterone in men.

In a review of 15 studies in men, intake of soy foods, protein powders or isoflavone supplements up to 70 grams of soy protein and 240 mg of soy isoflavones per day did not affect free testosterone or total testosterone levels.

What’s more, soy may reduce the risk of prostate cancer in men.

In a review of 30 studies, high soy consumption was linked to a significantly lower risk of developing the disease .

Most Soy Contains GMOs

More than 90% of the soy produced in the US is genetically modified .

There’s much debate over the safety of genetically modified organisms (GMOs). More long-term scientific studies are necessary to determine their effects in humans and in what quantity they’re safe.

Additionally, most genetically modified soy products withstand the pesticide glyphosate which is controversial.

Certain GMO soy products have been found to contain glyphosate residues and have a poorer nutritional profile compared to organic soybeans.

Therefore, to avoid GMOs and exposure to glyphosate, stick with organic soy.

Soy Protein Powder Side Effects

Soy protein powder is a popular plant-based protein supplement derived from soybeans. While it can be a nutritious addition to your diet, some people may experience side effects. It’s essential to note that individual reactions can vary, and not everyone will experience these side effects. Here are some potential side effects of soy protein powder:

1. Allergic reactions: Some individuals may be allergic to soy, experiencing symptoms such as itching, swelling, hives, or difficulty breathing. If you have a known soy allergy, it’s crucial to avoid soy protein powder.
2. Digestive issues: Soy contains certain compounds, like oligosaccharides, that can be challenging for some people to digest. This may lead to gas, bloating, or digestive discomfort. Choosing a soy protein isolate or hydrolyzed soy protein may reduce these issues, as they contain fewer of these compounds.
3. Hormonal effects: Soy contains compounds called phytoestrogens, which are plant-based compounds that can mimic the effects of estrogen in the body. Some people are concerned that consuming too much soy may affect hormone levels, particularly in men. However, current research suggests that moderate soy consumption is generally safe and might even have health benefits.
4. Thyroid function: There is a concern that soy may interfere with thyroid function due to its goitrogenic properties. Goitrogens can affect the thyroid gland’s ability to produce hormones. However, the evidence on this is mixed, and moderate soy consumption is generally considered safe for most people. If you have thyroid concerns, it’s advisable to consult with a healthcare professional.
5. Anti-nutrients: Soy contains anti-nutrients like phytates, which can bind to minerals and reduce their absorption. While this is a concern for some, a balanced diet that includes a variety of nutrient-dense foods can mitigate any potential negative effects.