Certain breast cancer risk factors are related to personal behaviors, such as diet and exercise.
Other lifestyle-related risk factors include decisions about having children and taking birth control.
Drinking alcohol is clearly linked to an increased risk of developing breast cancer. The risk increases with the amount of alcohol consumed. Compared with non-drinkers, women who have 1 alcoholic drink a day have a very small increase in risk.
Those who have 2 to 5 drinks daily have about 1½ times the risk of women who don’t drink alcohol. Excessive alcohol consumption is known to increase the risk of other cancers, too.
The American Cancer Society recommends that women have no more than 1 alcoholic drink a day. A drink is 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of 80-proof distilled spirits.
Being overweight or obese after menopause increases breast cancer risk. Before menopause your ovaries make most of your estrogen, and fat tissue makes only a small amount.
After menopause (when the ovaries stop making estrogen), most of a woman’s estrogen comes from fat tissue. Having more fat tissue after menopause can raise estrogen levels and increase your chance of getting breast cancer.
Also, women who are overweight tend to have higher blood insulin levels. Higher insulin levels have been linked to some cancers, including breast cancer.
Evidence is growing that physical activity reduces breast cancer risk.
The main question is how much exercise is needed. In one study from the Women’s Health Initiative, as little as 1¼ to 2½ hours per week of brisk walking reduced a woman’s risk by 18%. Walking 10 hours a week reduced the risk a little more.
To reduce your risk of breast cancer, the American Cancer Society recommends that adults get at least 150 minutes of moderate intensity or 75 minutes of vigorous intensity activity each week (or a combination of these), preferably spread throughout the week.
Having children. Women who have not had children or who had their first child after age 30 have a slightly higher breast cancer risk overall. Having many pregnancies and becoming pregnant at an early age reduces breast cancer risk overall.
Still, the effect of pregnancy is different for different types of breast cancer. For a certain type of breast cancer known as triple-negative, pregnancy seems to increase risk.
Birth control. Oral contraceptives: Studies have found that women using oral contraceptives (birth control pills) have a slightly higher risk of breast cancer than women who have never used them.
Once the pills are stopped, this risk seems to go back to normal over time. Women who stopped using oral contraceptives more than 10 years ago do not appear to have any increased breast cancer risk.
Birth control shot: Depo-Provera is an injectable form of progesterone that’s given once every 3 months as birth control. A few studies have looked at the effect of birth control shots on breast cancer risk.
Women currently using birth-control shots seem to have an increase in breast cancer risk, but it appears that there is no increased risk in women 5 years after they stop getting the shots.
Birth control implant, IUD, skin patch, vaginal ring: These forms of birth control also use hormones that could fuel breast cancer growth.
Some studies have shown a link between use of hormone-releasing IUD and breast cancer risk, but few studies have looked into the use of birth control implants, patch, and ring and breast cancer risk.
When thinking about using hormonal birth control, women should discuss their other risk factors for breast cancer with their health care provider.
Hormone therapy with estrogen (often combined with progesterone) has been used for many years to help relieve symptoms of menopause and help prevent osteoporosis (thinning of the bones).
This treatment goes by many names, such as post-menopausal hormone therapy (PHT), hormone replacement therapy (HRT), and menopausal hormone therapy (MHT).
There are 2 main types of hormone therapy. For women who still have a uterus (womb), doctors generally prescribe estrogen and progesterone (known as combined hormone therapy or HT).
Progesterone is needed because estrogen alone can increase the risk of cancer of the uterus. For women who’ve had a hysterectomy (those who no longer have a uterus), estrogen alone can be used. This is known as estrogen replacement therapy (ERT) or just estrogen therapy (ET).
Some studies suggest that breastfeeding may slightly lower breast cancer risk, especially if it’s continued for 1½ to 2 years. But this has been hard to study, especially in countries like the United States, where breastfeeding for this long is uncommon.
The explanation for this possible effect may be that breastfeeding reduces a woman’s total number of lifetime menstrual cycles (the same as starting menstrual periods at a later age or going through early menopause).