A study of of nearly 90,000 women has found that when women eat red meat as their primary source of protein from a young age, their risk of breast cancer goes up. Young women who get their protein primarily from legumes, poultry, nuts, and fish may lower their breast cancer risk.

Some studies have suggested red meat consumption in mid- to later life has no effect on breast cancer risk, but few looked at the effect eating red meat had on women prior to menopause.

Maryam Farvid and her colleagues from Harvard and Brown Universities analyzed data from 88,803 women between the ages of 26 and 45 who were enrolled in the Nurses Health Study II. Each of the women had completed a questionnaire on diet in 1991.

A higher intake of red meat was associated with a 22 percent increase in overall breast cancer risk.

Over the 20 years of follow-up, 2,830 cases of breast cancer occurred among study participants.

The investigators organized the women into nine different categories of frequency of red meat consumption, from “never or once per month” to “six or more per day.” They used a statistical model to estimate breast cancer risk based on diet.

Red meat was defined as beef, pork, lamb, and hamburger in the study. Processed red meat included hot dogs, bacon, and sausage. Poultry included chicken and turkey; fish included tuna, salmon, mackerel, and sardines; and legumes included beans, lentils, and peas. Nuts were also considered a source of protein.

“Red meat intake is associated with breast cancer risk in a dose-response manner,” Farvid, a fellow in the Takemi program in international health and an associate professor at the Harvard School of Public Health, said in an email.

The researchers estimated that a higher intake of red meat was associated with a 22 percent increase in overall breast cancer risk, and each additional serving per day of red meat increased overall breast cancer risk by 13 percent (12 percent in premenopausal women and 8 percent in postmenopausal women).

Substituting one serving of poultry per day for one serving of red meat was associated with a 17 percent reduction in breast cancer risk overall and a 24 percent reduction in risk among postmenopausal women according to the same statistical model.

Substituting one serving per day of combined legumes, nuts, poultry, and fish for one serving per day of red meat yielded a 14 percent lower risk of breast cancer overall and in premenopausal women.

Reducing processed meat consumption and limiting one’s intake of red meat, while substituting a combination of poultry, fish, legumes, and nuts as protein sources during early life, appears to help prevent breast cancer, said Farvid.

The study is published in the British Medical Journal.