Women who often indulge their cravings for hamburgers, steaks and other red meat may have a slightly higher risk of breast cancer, a new study suggests.

Doctors have long warned that a diet loaded with red meat is linked to cancers including those of the colon and pancreas, but there has been less evidence for its role in breast cancer.

In the new study, researchers at Harvard University analyzed data from more than 88,000 women aged 26 to 45 who had filled in surveys in 1991. Their red meat intake varied from never or less than once a month, to six or more servings a day. Initial results of the study were first published in 2006 and showed a preliminary link between eating red meat and breast cancer after 12 years; the new research confirmed the earlier findings with longer follow-up information, and analyzed other types of breast cancer.

Using a statistical model, scientists estimated that in women who ate the largest amount of red meat, there were an extra 6.8 cases of breast cancer for every 1,000 women over 20 years of follow-up. The researchers couldn't rule out the possibility that other factors might explain the apparent link between red meat and breast cancer.

In developed countries, women have about a 12.5 percent chance of developing breast cancer.

Scientists suspect proteins in red meat speed up cell division and tumor growth; chemicals such as nitrates in processed meats are already classified as probable carcinogens.

The study was carried out mainly among educated, white US women, and researchers said that the results were not necessarily applicable to women of other races. It was paid for by the US National Institutes of Health and published online on Tuesday in the British journal BMJ.