Soy Milk and Breast Cancer - The Study

"...dairy-alternate milks may be an optimal choice." — Dr. Gary Fraser

A recent large study titled 'Dairy, soy, and risk of breast cancer: those confounded milks' followed 50,000 women for nearly 8 years to finally get to the truth about dairy milk, soya milk, and breast cancer risk. No, I'm not making it up. That's the actual name of the study, published in the International Journal of Epidemiology.

Consuming what is considered 'normal' amount of dairy milk regularly could increase risk of breast cancer in women by a whopping 80%! The study also found that replacing dairy milk with soya milk could significantly reduce breast cancer risk.

"Can you give me food without soya?"

At SampoornaAhara.com, a lot of people ask us if we can serve food without soya in it, saying they have heard soya is unhealthy, it causes hormone fluctuations, and increases risk of cancers like breast cancer, uterine cancer and ovarian cancer. Once we show them the evidence, they are convinced.

If you have tried reading about this online, you may have found different websites saying different things. Associations between soy, dairy intakes and breast cancer risk are inconsistent. No studies have been conducted with large numbers of dairy consumers and soy consumers to assess mutual confounding, until now!

Does Soya Milk Cause Breast Cancer?

This huge study published in February 2020 "found no convincing evidence that soy foods were associated with risk of breast cancer. However dairy foods, especially milk, were associated with increased risk, and there was a marked reduction in risk when substituting soy milk for an approximately equivalent quantity (medians of users) of dairy milk" 

How Much Milk Causes Breast Cancer?

The first author of the paper, Dr. Gary E. Fraser, MBChB, PhD, said "Consuming as little as 1/4 to 1/3 cup of dairy milk per day was associated with an increased risk of breast cancer of 30%. By drinking up to one cup per day, the associated risk went up to 50%, and for those drinking two to three cups per day, the risk increased further to 70% to 80%."

The Discovery

How did Dr. Fraser and his team discover this? They analysed the diets of 50,000+ women from North America who were all cancer-free when the study started. They followed these women for almost 8 years. At the end, they found 1,057 new breast cancer cases. Who developed these cancers? The women who drank soya milk or consumed soya products did not show an increased risk of developing breast cancer, independent of dairy. However, the women who consumed even small quantities of dairy milk showed increased risk of developing breast cancer, independent of soya. 

What about skimmed milk?

Reduced or nonfat dairy milks carried similar risk as full fat dairy milk, the study found.

The study did not find an association with cheese and yogurt, but Dr. Fraser said, "dairy foods, especially milk, were associated with increased risk, and the data predicted a marked reduction in risk associated with substituting soy milk for dairy milk. This raises the possibility that dairy-alternate milks may be an optimal choice.”

Current Recommendations - Safe or Risky?

The National Institute of Nutrition, India, recommends three 100-gram servings of milk and milk products for women everyday. This level of milk consumption may result in the highest risk found in this study - 80% increased risk of breast cancer. The current US dietary guidelines also recommend 3 glasses of milk everyday. Dr. Fraser's study concluded, "Higher intakes of dairy milk were associated with greater risk of breast cancer, when adjusted for soy intake. Current guidelines for dairy milk consumption could be viewed with some caution"

Why Does Milk Increase Breast Cancer Risk?

Bovine sex hormones and dairy hormones are associated with increased levels of IGF-1 and increased breast cancer risk. Breast cancer is a hormone-related cancer. Most of the cows in the dairy industry are pregnant while being milked. This increases the levels of both estrogen and progesterone in cow's milk. One study concluded that for breast cancer, "among dietary risk factors, we are most concerned with milk and dairy products, because the milk we drink today is produced from pregnant cows, in which estrogen and progesterone levels are markedly elevated." 

The high hormone levels in skimmed milk may even delay natural menopause delay natural menopause, apart from elevating breast cancer risk.

Why Replace Milk with Soya Milk?

Soya is rich in natural plant-based isoflavones, which may block the effect of our body's own estrogen where it matters, reducing risk of breast and ovarian cancer. At the same time, they may enhance the effect of estrogen in our skeletal system, strengthening our bones. This is especially important during and post menopause. Isoflavones may also have antiproliferative effects and antioxidant activity,  and enhance DNA repair systems. Dr. Fraser's team found that substituting dairy milk with soya milk is associated with a 40% reduced risk of breast cancer!

How to Make Soya Milk at Home?

Making soya milk is deceptively simple. Here's a detailed recipe with instructions to make your own soya milk at home:

1. Soak one cup of raw, dried soya beans overnight.
2. Grind to a smooth paste with 2 cups of water and strain through a cheesecloth or muslin cloth.
3. Mix 2 more cups of water and bring to a boil on the stove. Boil for 20 minutes to fully cook it. That's it!

Enjoy your soya milk with some date syrup, use it to make herbal and spice teas, use it in creamy gravies, or even to make your own dairy-free ice cream!