- It is too soon to confirm the link between milk and breast cancer
- Milk is a dietary source of calcium and is important for healthy bones
- Milk consumption is important for healthy growth in kids
Drinking even moderate amounts of dairy milk has been found to increase the risk of breast cancer by up to 80%, depending on the amount of milk consumed. "Fairly strong evidence that either dairy milk or some other factor closely related to drinking dairy milk is a cause of breast cancer in women," said study first author Gary E. Fraser from Loma Linda University in the US, reports IANS. Fraser added that consuming as little as 1/4 to 1/3 cup of dairy milk every day can increase breast cancer risk by 30%. If you drink one cup every day, the risk increases by 50%, and drinking two to three cups of milk can increase the risk by 70 to 80%.
Milk and breast cancer: What the study found
Published in International Journal of Epidemiology, the study was conducted on the basis of dietary intakes of 53,000 North American women. All of these women were followed for eight years, and were initially cancer-free.
Dietary intakes were estimated from food frequency questionnaires (FFQ), also repeated 24 hour recalls, and a baseline questionnaire had questions about demographics, family history of breast cancer, physical activity, alcohol consumption, hormonal and other medication use, breast cancer screening, and reproductive and gynaecological history.
By the end of the study period, there were 1,057 new breast cancer cases during follow-up. No clear associations were found between soy products and breast cancer, independent of dairy.
But, when compared to low or no milk consumption, higher intakes of dairy calories and dairy milk were associated with greater risk of breast cancer, independent of soy intake, the study said.
The researchers noted that the results had minimal variation when comparing intake of full fat versus reduced or non-fat milks; there were no important associations noted with cheese and yogurt.
"However," he said, "dairy foods, especially milk, were associated with increased risk, and the data predicted a marked reduction in risk associated with substituting soymilk for dairy milk."
What is the link between milk intake and breast cancer risk?
Researchers say that the possible reason for association between breast cancer and dairy milk could be the sex hormone content in it. The cows are of course lactating, and about 75% of the dairy herd is pregnant. Breast cancer is known to be a hormone-responsive cancer.
"Dairy milk does have some positive nutritional qualities, but these need to be balanced against other possible, less helpful effects," Fraser concluded.
Is consumption of dairy milk important?
We spoke to clinical nutritionist Rupali Datta about the said the study. "This is an observational study, the researchers now have to take this hypothesis forward with a Randomised Controlled Trial or case controlled study to reach some conclusion," she explains.
On being asked if milk consumption is important for kids and adults, she asserts that it is especially essential for healthy growth of kids. Until the said study is further taken for trials, adults can have half a litre of milk every day, she tells DoctorNDTV.
Nutritionist Nmami Agarwal says that while some studies have raised concerns about dairy milk being linked to breast cancer risk, a conclusive link has not been found. "It is still under research and it is quite early to confirm this claim of the link between dairy milk and breast cancer," she says.
Health benefits of consuming milk
Agarwal goes on to talk about the many health benefits of drinking milk and mentions the following:
1. Low fat calcium-rich dairy is associated with lower blood pressure, prevention of osteoporosis, and muscle growth.
2. Milk and other dairy products are required to build strong bones in childhood
3. Regular milk intake can help in preventing of bone fractures and osteoporosis in adulthood till later years of life.
4. Milk contains protein, calcium, magnesium, manganese, zinc, Vitamin D, and Vitamin K- all of which are necessary for bone health, and to prevent the risk of many chronic diseases.
5. Milk has also been associated with reduced risk of colorectal cancer because calcium from milk can bind to cancer-causing secondary bile acids and ionising fatty acids, reducing their proliferation.
6. Milk obtained from grass-fed cows also contain beneficial fatty acids like omega-3 fatty acids and conjugated linoleic acid.
"But, there is a flip side to milk too, says Agarwal, while adding, "As much as 60% of the world's population suffers from lactose intolerance, which can lead to indigestion, bloating, constipation, diarrhoea or sometimes more serious health concerns on the consumption of milk. Full-fat dairy has also linked with an increase in cholesterol levels," says Agarwal.
At times, cows are injected with bovine growth hormone, insulin-like growth factor-1, and oestrogens. The available evidence shows that the use of BGH (Bovine Growth Hormone) can cause adverse health effects in cows. "The evidence for potential harm to humans is inconclusive," she adds.
According to the Delhi-based nutritionist, adults can have 200-300 ml of dairy products in a day. "This can be consumed in the form of milk, cottage cheese, or yogurt as per your liking."
(Rupali Datta is a Clinical Nutritionist based in Delhi)
(Nmami Agarwal is nutritionist at Nmami Life)
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