High Fiber Diet Blocks Calcium Absorption in Diabetics

Kathleen Blanchard's picture

A new study warns that diabetics who eat a beneficial high fiber diet may need to boost calcium intake. Dr. Abhimanyu Garg, professor of internal medicine and an investigator in the Center for Human Nutrition at UT Southwestern Medical Center explains, "We already know that fiber helps improve your cholesterol and glucose control and improves your bowel regularity. Our new findings suggest that dietary fiber reduces the body's capacity to absorb calcium. Because more calcium equals better bone health, we recommend that people on high-fiber diets talk to their physician about increasing their dietary calcium as well, in order to get the most benefit from both."

Calcium is plentiful in the body. Eating fiber or foods high in roughage can “push” calcium through the body before it can be absorbed. In essence, the amount of calcium absorbed by the body for strong bones may depend on how much fiber you eat, making a personalized approach to osteoporosis prevention necessary.

Dr. Garg suggests nutritional counselling, or discussion with your physician to determine how much calcium is right for you. A dietary analysis is the safest way to ensure you get the right amount of calcium if you eat a high fiber diet – too much calcium can cause kidney stones.


For optimal health, the American Diabetes Association recommends 25 Gms of fiber daily. Diabetics who eat more than 25 Gms of fiber daily are especially at risk for low calcium. The researchers discovered that type 2 diabetics who ate 50 Gms of fiber daily excreted less calcium in their urine, indicating less calcium is absorbed. According to Dr. Garg, “In other words, the participants excreted less calcium on the high-fiber diet because the additional fiber caused their bodies to absorb less calcium.”

Getting fiber from fruits and vegetables lowers the risk of type 2 diabetes, and helps keep glucose levels normal. The current study looked at 13 patients given 50 Gms of fiber daily, or 24 Gms, recommended by the ADA. After six weeks, the groups switched diets, finding that high fiber diet decreased absorption of calcium, though calories from carbs, protein and fats, as well as mineral content was equal in both diets.

Dr. Garg says he is uncertain whether soluble or insoluble fiber affects calcium absorption. “Generally, more fiber of either type is beneficial. We should encourage people to try food sources rich in fiber and calcium such as spinach, broccoli, figs, papaya, artichoke, okra, beans, mustard and turnip greens, and cactus pads.”

The study shows that fiber is beneficial, and should be consumed by everyone on a daily basis. However, a high fiber diet from fruits and vegetables might signal a need for more calcium in the diet. Individual needs should be discussed with a nutritionist before increasing dietary calcium. The study is especially important for those with type 2 diabetes who eat a high fiber diet, blocking calcium absorption.