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Chromium Critical for Glucose Tolerance

By Judy McBride
September 15, 1999

Rats raised on a chromium-deficient diet showed the earliest stage of diabetes--high blood insulin levels. That was the outcome of an Agricultural Research Service study published in the August issue of Metabolism.

The finding underscores that chromium is necessary for maintaining normal glucose tolerance, the researchers concluded. And it suggests that low-chromium intakes--very common in industrialized nations--may contribute to onset of Type 2 diabetes mellitus, or middle-age diabetes, over the long term. Fortified cereals and whole grain products are good sources of chromium.

The study was done at ARS' Nutrient Requirements and Functions Laboratory in Beltsville, Md., by John Striffler, now at the City of Hope National Medical Center, Duarte, Calif., and by ARS chemists Richard Anderson and Marilyn Polansky. ARS is USDA's chief scientific agency.

The hormone insulin escorts blood glucose into body cells and enables the cells to use that glucose for fuel. Diabetes begins when the cells become less sensitive to insulin. To use a metaphor, the cell's biochemical door doesn't open when insulin comes knocking. Or, if it gets in that first door, a second door stays locked. Chromium is one of the keys to keeping both doors unlocked.

As the cells become insensitive to insulin, the body produces more of it. So high blood insulin is an early indicator of potential diabetes. By the time blood glucose is elevated, a person already has the disease.

During a glucose tolerance test, rats that got virtually no chromium in their food or water for three months had insulin levels twice as high as a group that got chromium-fortified water or a control group fed a standard chow that contains chromium.

Anderson noted that, in animal studies, the effects of chromium deficiency are seldom obvious until the animal is stressed. The glucose tolerance test with its sugar load was the stressor in this study.