The Critical Link Between Fiber and Breast Cancer: Study

The Critical Link Between Fiber and Breast Cancer: Study

Dietary fiber found in plant foods is probably best known for its ability to prevent or relieve constipation. Foods containing fiber also help maintain a healthy weight and lower the risk for diabetes, heart disease, and some types of cancer. But what about fiber and the risk of breast cancer? First, some background.

What Is Dietary Fiber?

Dietary fiber includes the parts of plant foods that can’t be digested or absorbed. Instead, dietary fiber passes relatively intact through your stomach, small intestine, and colon and out of your body in your bowel movements. There are two classes of dietary fiber:

  • Soluble fiber. This type of fiber dissolves in water to form a gel-like material. It can help lower blood cholesterol and glucose levels. Soluble fiber is found in oats, peas, beans, apples, citrus fruits, carrots, barley, and psyllium.
  • Insoluble fiber. This type of fiber promotes the movement of material through your digestive system and increases stool bulk. Whole-wheat flour, wheat bran, nuts, beans, and vegetables, such as cauliflower, green beans, and potatoes, are good sources of insoluble fiber.

What are the Benefits of a High-Fiber Diet?

  • Fiber normalizes bowel movements.
  • Fiber helps maintain bowel health.
  • Fiber lowers cholesterol levels.
  • Fiber helps control blood sugar levels.
  • Fiber helps with healthy weight.
  • Fiber may help live a longer life.
  • Fiber reduced heart disease risk.

How Much Fiber and What are Good Sources?

Women should try to eat at least 21 to 25 grams of fiber a day, while men should aim for 30 to 38 grams a day. The healthiest diets may have over 50 grams a day of dietary fiber. Some of the highest concentrations of fiber are listed here:

Serving size Total fiber (grams)*
Split peas, boiled 1 cup 16.0
Lentils, boiled 1 cup 15.5
Black beans, boiled 1 cup 15.0
Baked beans, canned 1 cup 10.0
Chia seeds 1 ounce 10.0


New Data on Fiber and Breast Health

Researchers from the Harvard School of Public Health searched for all prior prospective studies assessing fiber intake and breast cancer incidence. They identified 20 nutritional epidemiology studies to combine as a meta-analysis. The main finding was that comparing those with the highest fiber consumption to those with the lowest intake, there was an eight percent lower risk of breast cancer in the fiber champions. The relationship was strongest for soluble fiber but also existed for insoluble fiber sources. The findings were found both for cancers before and after menopause. The authors hypothesized that higher fiber diets helped by decreasing levels of insulin and growth factors, as well as decreasing estrogen levels, all known to be factors in the development of breast cancers.

What Should You Do?

Whether from fruits, beans, grains, or vegetables, dietary fiber appears to lower a woman’s risk for breast cancer. When combined with the other proven benefits for heart health, colon cancer risk, weight, and other proven relationships, it is clear that October and all other months should not be celebrated with pink (unless a grapefruit) but should focus on an unprocessed diet of plant foods rich in fiber and other nutrients.

Dr. Joel Kahn is Professor of Cardiology, Summa cum Laude grad, Kahn Center for Longevity and GreenSpace & Go, author, “The Plant Based Solution.” @drjkahn.