Calcium and Vitamin Supplements Reduce Breast Cancer Risk

"It is not an immediate effect. You don't take a vitamin today and your breast cancer risk is reduced tomorrow," researcher Jaime Matta said. "However, we did see a long-term effect in terms of breast cancer reduction."

The researchers conducted the study on 457 healthy women and 268 with breast cancer, all of whom had been taking vitamin and mineral supplements for the past five years. The women filled out a questionnaire about which vitamins and minerals they were taking, how regularly they took them, and if they were still taking them.

They then took samples of each woman's blood and measured her DNA's ability to repair itself of damage.

"This process involves at least five separate pathways and is critical for maintaining genomic stability," Matta said. "When the DNA is not repaired, it leads to mutation that leads to cancer."

The researchers found that calcium supplements significantly increased a woman's DNA repair capacity. Taking calcium supplements also decreased a woman's risk of breast cancer by 40 percent, while vitamin supplements decreased it by 40 percent.

Women who had a low DNA repair capacity, a family history of breast cancer, and no history of breast feeding were all more likely to suffer from breast cancer. When the researchers adjusted for calcium's effect on DNA repair capacity, they found little remaining effect on breast cancer risk.

This suggests that calcium helps prevent cancers by boosting DNA's ability to regenerate from damage. The mechanisms by which vitamin supplements protect the body from cancer were not determined.