Soy reduces side effects of breast cancer treatment

Consuming soy foods and certain vegetables can reduce the menopausal side effects of breast cancer treatment, research suggests.

These include soy milk, tofu and edamame and cruciferous veggies such as cabbage, kale, brussels sprouts, collard greens, bok choy and broccoli.

Breast cancer survivors often experience side effects from cancer treatments that can persist months or years after completion of treatment. 

But those who had a higher intake of these foods reported fewer problems such as hot flashes and night sweats.

The researchers found that higher soy intake was also associated with less fatigue.  

This was the findings of a team of scientists led by Georgetown Lombardi Comprehensive Cancer Center in Washington, DC.

Earing soy foods and certain vegetables can reduce the menopausal side effects of breast cancer treatment, a study suggests (stock image)


The Georgetown Lombardi researchers warn that women with the disease should not have soy if they’ve not eaten it before.

Results obtained in preclinical studies in animals show that compounds present in both soy and cruciferous vegetables cause breast cancer cells to grow.

But they have opposite effects in animals that consume these compounds well before cancer is diagnosed and continue consuming them during and after cancer treatments.

Breast cancer patients who don’t normally have soy should avoid it, if they have not had it previously – until more research is conducted, according to Dr Leena Hilakivi-Clarke, a professor of oncology and a co-author of the study.

How the research was carried out 

The study, published in the journal Breast Cancer Research and Treatment, looked at 173 non-Hispanic white and 192 Chinese American breast cancer survivors.  

Many treatments designed to prevent breast cancer recurring inhibit the body’s production or use of the hormone estrogen which can fuel the disease’s growth.

They therefore can experience side-effects similar to the menopause, irrespective of their age.

When the study participants were analyzed by ethnicity, the link was strongest among white women.

The researchers believe this is because Chinese women typically report fewer menopausal symptoms and most consume regularly cruciferous vegetables and soy foods – making it difficult to see a significant effect in this subgroup.

Indeed, Chinese breast cancer survivors ate more than twice as much soy and cruciferous vegetables.

The lead author of the research, Dr Sarah Oppeneer Nomura, said that while further research is needed, the results suggest patients may be able to take control of side-effects through their diet.

‘These symptoms can adversely impact survivors’ quality of life and can lead them to stopping ongoing treatments, she said. 

‘Understanding the role of life style factors is important because diet can serve as a modifiable target for possibly reducing symptoms among breast cancer survivors.’ 

Why they are believed to help

The team also found an association between soy and fewer joint problems, hair thinning/loss and memory loss – but this was not ‘statistical significant’.

Soybeans and soy products are the richest sources of isoflavones in the human diet and the researchers believe this compound, along with glucosinolates in cruciferous vegetables, may bring the reported benefits. 

Isoflavones are known to bind to estrogen receptors and produce a weak estrogenic effects.

Glucosinolates may relieve symptoms by affecting levels of metabolizing enzymes that control inflammation and levels of estrogen.


The U.S. Food and Drug Administration in October released a proposal that questions the link between soy protein and a reduced risk of heart disease. 

The agency, which to date has never revoked a health claim, said studies published since it authorized the soy protein claim in 1999 had shown inconsistent results.

‘Our review of that evidence has led us to conclude that the relationship between soy protein and heart disease does not meet the rigorous standard for an FDA-authorized health claim,’ the agency said in a statement.

If the proposal goes through, the statement would be downgraded to a ‘qualified health claim,’ meaning that food companies would need to use language that indicates evidence is limited to support soy’s heart benefits.

The ruling will undergo a 75-day comment period before a final decision is made.