Will drinking alcohol and eating tofu increase the risk of getting breast cancer?
It’s Breast Cancer Awareness Month, and CNA Lifestyle asked medical experts to weigh in on whether our lifestyle habits have an impact on getting the disease.
When it comes to breast cancer, there are a few risk factors that can’t be helped, such as genetics, age, and yes, the fact that you’re a woman. But there are also some everyday choices that could contribute to the risk of developing it.
Having said that, it is also important to know that there is no magic bullet to dodge; for instance, avoiding alcohol doesn't mean you'll be free of breast cancer.
“Cancer causes are multifactorial, so no one single cause alone is responsible,” said Dr Raymond Ng Chee Hui, senior consultant with National Cancer Centre Singapore’s Division of Medical Oncology.
As Breast Cancer Awareness Month (BCAM) rolls in this October, CNA Lifestyle asked some breast cancer experts about whether or not some lifestyle habits do have an effect or not – from work-related stress to what you consume.
You might want to put down that drink, ladies. With every 10g increase in alcohol consumed per day, the risk of breast cancer is increased by 5 per cent in women who have not reached menopause, and by 9 per cent in those who are menopausal, said Dr Samuel Ow, vice chairperson of the organising committee of BCAM-related events in Singapore this year.
A standard drink refers to about 14g of pure alcohol, which can be found in a 355ml or a small can of regular beer; a 145ml or a small glass of wine; and 45ml or a shot of distilled spirit.
“Alcohol can change the way a woman’s body metabolises oestrogen, leading to an increased level of oestrogen and other hormones associated with hormone-receptor-positive breast cancer,” said Dr Esther Chuwa, consultant breast and general surgeon at Gleneagles Hospital.
“Alcohol may also increase breast cancer risk by damaging DNA in cells.”
And if you think drinking red wine is fine because of its purported health benefits, the alcohol in it just doesn’t work in your favour.
“The association between alcohol consumption and breast cancer does not differ between the type of alcoholic beverages,” added Dr Ow.
PUTTING ON WEIGHT
The possibility of breast cancer is a more important reason to watch your weight than fitting into clothes and looking good – especially as you grow older.
Women’s oestrogen levels drop substantially after menopause when the ovaries cease to produce the hormone, said Dr Chuwa. But in overweight or obese post-menopausal women, oestrogen continues to be made by the fatty tissues.
Body fat also produces insulin, which, along with oestrogen, are risk factors for breast cancer, said Dr Ow, who is also consultant with the Department of Haematology-Oncology at National University Cancer Institute, Singapore.
And for the record, obesity can also increase the risk of other tumours such as in the colon, uterus and pancreas, added Dr Ng.
“Regular exercise can lower one’s breast cancer risk by 10 per cent to 20 per cent,” said Dr Chuwa. If you’re already exercising, that’s great – but consider cranking up the intensity.
To reap those protective benefits, you’ll need to exercise for at least 150 minutes a week at a moderate intensity, such as brisk walking or cycling.
If you don’t have the time, aim for 75 minutes a week but amp up the intensity when you’re jogging or swimming, she said.
If you’re wondering which is better – jogging, weight training or yoga – cardio exercises that increase your heart rate, and make you pant and perspire are the best.
“Exercises that help with weight loss are probably preferred,” said Dr Ng.
EATING TOFU, SOYBEAN MILK AND EDAMAME
You might have read that soy, soybean milk and other foods rich in isoflavones are contenders for raising the risk of breast cancer.
Isoflavones are phytoestrogens (the plant version of oestrogen), which have been linked to increased risks in high concentrations.
But according to Dr Chuwa, it depends. Whole food sources of soy do not contain enough levels of isoflavones to be dangerous enough, but some soy supplements do contain higher levels, she said.
“Some studies have suggested a link between soy or isoflavone supplements and an increased risk of breast cancer in women who have a family or personal history of breast cancer or thyroid problems.”
But overall, Dr Ow agreed that phytoestrogens from foods do not increase the risk of breast cancer. “In fact, there is a suggestion that phytoestrogens may protect Asian women from breast cancer,” he said.
Citing a Singapore study done on more than 35,000 women, Dr Chuwa said that approximately 10mg of isoflavones (that’s one standard serving of tofu) a day reduces breast cancer risk by 18 per cent.
“But, as with any food, eating in moderation is recommended,” she said, explaining that a moderate amount of whole soy foods is one to two daily servings.
If you’re wondering how much soy-based foods that is, a single serving can be a cup of soy milk, half a cup of cooked soy beans or edamame, an ounce of soy nuts or one-third cup of tofu.
STRESSING OUT AT WORK
There’s no clear-cut evidence to point at stress as a culprit, but Dr Ng did warn that it can lead to bad habits such as smoking, excessive alcohol intake and poor diet – all of which are associated with an increased risk of cancer.
However, Dr Chuwa believed that “stress is an imminent risk factor”. “Long-term or chronic stress has been associated with a weakened immune system that, in turn, leads to a lowered defence against cancer,” she said.
USING BIRTH CONTROL PILLS
A 2017 study published in The New England Journal of Medicine found that women who used hormonal contraception had a slight risk increase of breast cancer compared with women who had never used them.
It was a massive study of nearly 1.8 million women over 11 years, but according to the experts, the 11,517 breast cancer cases that turned up is a very small number.
“The increased relative risk observed in the study translates into one new case of invasive breast cancer for every 7,690 women using hormonal contraception every year,” said Dr Chuwa. “The overall risk of breast cancer among hormonal contraceptive users is low.”
Dr Ow agreed that birth control pills, a commonly used form of hormonal contraception in Singapore, has “little or no increased risk of breast cancer”.
In addition, Dr Chuwa said that hormonal contraception has “other significant health benefits”.
“The small increased risk of breast cancer identified in this study needs to be interpreted in the context of the benefits of hormonal contraceptive use, including the decreased risk of ovarian, endometrial, and colon cancer,” she said.
If you need to speak confidentially to someone about breast cancer, call 6225 5655, a free helpline by the National Cancer Centre Singapore. It is the first cancer helpline in Singapore and is manned by trained nurse counsellors, who can also arrange complimentary wig fittings for patients.