Table of Contents
- Chromium: What is it?
What foods provide chromium?
What are recommended intakes of chromium?
What affects chromium levels in the body?
When can a chromium deficiency occur?
Who may need extra chromium?
What are some current issues and controversies about chromium?
What are the health risks of too much chromium?
Chromium and medication interactions
Supplemental sources of chromium
Chromium intakes and healthful diets
Chromium is known to enhance the action of insulin [1-3], a hormone critical to the metabolism and storage of carbohydrate, fat, and protein in the body . In 1957, a compound in brewers' yeast was found to prevent an age-related decline in the ability of rats to maintain normal levels of sugar (glucose) in their blood . Chromium was identified as the active ingredient in this so-called "glucose tolerance factor" in 1959 .
Chromium also appears to be directly involved in carbohydrate, fat, and protein metabolism [1-2,6-11], but more research is needed to determine the full range of its roles in the body. The challenges to meeting this goal include:
- Defining the types of individuals who respond to chromium supplementation;
- Evaluating the chromium content of foods and its bioavailability;
- Determining if a clinically relevant chromium-deficiency state exists in humans due to inadequate dietary intakes; and
- Developing valid and reliable measures of chromium status .
Dietary intakes of chromium cannot be reliably determined because the content of the mineral in foods is substantially affected by agricultural and manufacturing processes and perhaps by contamination with chromium when the foods are analyzed [10,12,14]. Therefore, Table 1, and food-composition databases generally, provide approximate values of chromium in foods that should only serve as a guide.
Table 1: Selected food sources of chromium [12,15-16] Food Chromium (mcg) Broccoli, ½ cup 11 Grape juice, 1 cup 8 English muffin, whole wheat, 1 4 Potatoes, mashed, 1 cup 3 Garlic, dried, 1 teaspoon 3 Basil, dried, 1 tablespoon 2 Beef cubes, 3 ounces 2 Orange juice, 1 cup 2 Turkey breast, 3 ounces 2 Whole wheat bread, 2 slices 2 Red wine, 5 ounces 1-13 Apple, unpeeled, 1 medium 1 Banana, 1 medium 1 Green beans, ½ cup 1
What are recommended intakes of chromium? Recommended chromium intakes are provided in the Dietary Reference Intakes (DRIs) developed by the Institute of Medicine of the National Academy of Sciences . Dietary Reference Intakes is the general term for a set of reference values to plan and assess the nutrient intakes of healthy people. These values include the Recommended Dietary Allowance (RDA) and the Adequate Intake (AI). The RDA is the average daily intake that meets a nutrient requirement of nearly all (97 to 98%) healthy individuals . An AI is established when there is insufficient research to establish an RDA; it is generally set at a level that healthy people typically consume.
In 1989, the National Academy of Sciences established an "estimated safe and adequate daily dietary intake" range for chromium. For adults and adolescents that range was 50 to 200 mcg . In 2001, DRIs for chromium were established. The research base was insufficient to establish RDAs, so AIs were developed based on average intakes of chromium from food as found in several studies . Chromium AIs are provided in Table 2.
Table 2: Adequate Intakes (AIs) for chromium  Age Infants and children (mcg/day) Males
(mcg/day) 0 to 6 months 0.2 7 to 12 months 5.5 1 to 3 years 11 4 to 8 years 15 9 to 13 years 25 21 14 to 18 years 35 24 29 44 19 to 50 years 35 25 30 45 >50 years 30 20 mcg = micrograms
Adult women in the United States consume about 23 to 29 mcg of chromium per day from food, which meets their AIs unless they're pregnant or lactating. In contrast, adult men average 39 to 54 mcg per day, which exceeds their AIs .
The average amount of chromium in the breast milk of healthy, well-nourished mothers is 0.24 mcg per quart, so infants exclusively fed breast milk obtain about 0.2 mcg (based on an estimated consumption of 0.82 quarts per day) . Infant formula provides about 0.5 mcg of chromium per quart . No studies have compared how well infants absorb and utilize chromium from human milk and formula [10,14].
What affects chromium levels in the body? Absorption of chromium from the intestinal tract is low, ranging from less than 0.4% to 2.5% of the amount consumed [19-25], and the remainder is excreted in the feces [1,23]. Enhancing the mineral's absorption are vitamin C (found in fruits and vegetables and their juices) and the B vitamin niacin (found in meats, poultry, fish, and grain products) . Absorbed chromium is stored in the liver, spleen, soft tissue, and bone .
The body's chromium content may be reduced under several conditions. Diets high in simple sugars (comprising more than 35% of calories) can increase chromium excretion in the urine . Infection, acute exercise, pregnancy and lactation, and stressful states (such as physical trauma) increase chromium losses and can lead to deficiency, especially if chromium intakes are already low [28-29].
When can a chromium deficiency occur? In the 1960s, chromium was found to correct glucose intolerance and insulin resistance in deficient animals, two indicators that the body is failing to properly control blood-sugar levels and which are precursors of type 2 diabetes . However, reports of actual chromium deficiency in humans are rare. Three hospitalized patients who were fed intravenously showed signs of diabetes (including weight loss, neuropathy, and impaired glucose tolerance) until chromium was added to their feeding solution. The chromium, added at doses of 150 to 250 mcg/day for up to two weeks, corrected their diabetes symptoms [7,30-31]. Chromium is now routinely added to intravenous solutions.
Who may need extra chromium? There are reports of significant age-related decreases in the chromium concentrations of hair, sweat and blood , which might suggest that older people are more vulnerable to chromium depletion than younger adults . One cannot be sure, however, as chromium status is difficult to determine . That's because blood, urine, and hair levels do not necessarily reflect body stores [9,14]. Furthermore, no chromium-specific enzyme or other biochemical marker has been found to reliably assess a person's chromium status [9,34].
There is considerable interest in the possibility that supplemental chromium may help to treat impaired glucose tolerance and type 2 diabetes, but the research to date is inconclusive. No large, randomized, controlled clinical trials testing this hypothesis have been reported in the United States . Nevertheless, this is an active area of research.
What are some current issues and controversies about chromium? Chromium has long been of interest for its possible connection to various health conditions. Among the most active areas of chromium research are its use in supplement form to treat diabetes, lower blood lipid levels, promote weight loss, and improve body composition.
- Type 2 diabetes and glucose intolerance
In type 2 diabetes, the pancreas is usually producing enough insulin but, for unknown reasons, the body cannot use the insulin effectively. The disease typically occurs, in part, because the cells comprising muscle and other tissues become resistant to insulin's action, especially among the obese. Insulin permits the entry of glucose into most cells, where this sugar is used for energy, stored in the liver and muscles (as glycogen), and converted to fat when present in excess. Insulin resistance leads to higher than normal levels of glucose in the blood (hyperglycemia).
Chromium deficiency impairs the body's ability to use glucose to meet its energy needs and raises insulin requirements. It has therefore been suggested that chromium supplements might help to control type 2 diabetes or the glucose and insulin responses in persons at high risk of developing the disease. A review of randomized controlled clinical trials evaluated this hypothesis . This meta-analysis assessed the effects of chromium supplements on three markers of diabetes in the blood: glucose, insulin, and glycated hemoglobin (which provides a measure of long-term glucose levels; also known as hemoglobin A1C). It summarized data from 15 trials on 618 participants, of which 425 were in good health or had impaired glucose tolerance and 193 had type 2 diabetes. Chromium supplementation had no effect on glucose or insulin concentrations in the non-diabetic subjects nor did it reduce these levels in subjects with diabetes, except in one study. However, that study, conducted in China (in which 155 diabetics were given either 200 or 1,000 mcg/day of chromium or a placebo) might simply show the benefits of supplementation in a chromium-deficient population.
Overall, the value of chromium supplements for diabetics is inconclusive and controversial . Randomized controlled clinical trials in well-defined, at-risk populations where dietary intakes are known are necessary to determine the effects of chromium on markers of diabetes .
The effects of chromium supplementation on blood lipid levels in humans are also inconclusive [1,8,37]. In some studies, 150 to 1,000 mcg/day has decreased total and low-density-lipoprotein (LDL or "bad") cholesterol and triglyceride levels and increased concentrations of apolipoprotein A (a component of high-density-lipoprotein cholesterol known as HDL or "good" cholesterol) in subjects with atherosclerosis or elevated cholesterol or among those taking a beta-blocker drug [38-40]. These findings are consistent with the results of earlier studies [41-44].
However, chromium supplements have shown no favorable effects on blood lipids in other studies [45-50]. The mixed research findings may be due to difficulties in determining the chromium status of subjects at the start of the trials and the researchers' failure to control for dietary factors that influence blood lipid levels [9-10].
Body weight and composition
Chromium supplements are sometimes claimed to reduce body fat and increase lean (muscle) mass. Yet a recent review of 24 studies that examined the effects of 200 to 1,000 mcg/day of chromium (in the form of chromium picolinate) on body mass or composition found no significant benefits . Another recent review of randomized, controlled clinical trials did find supplements of chromium picolinate to help with weight loss when compared to placebos, but the differences were small and of debatable clinical relevance . In several studies, chromium's effects on body weight and composition may be called into question because the researchers failed to adequately control for the participants' food intakes. Furthermore, most studies included only a small number of subjects and were of short duration .
Chromium and medication interactions Certain medications may interact with chromium, especially when taken on a regular basis (see Table 3). Before taking dietary supplements, check with your doctor or other qualified healthcare provider, especially if you take prescription or over-the-counter medications.
Table 3: Interactions between chromium and medications [14,52-54] Medications Nature of interaction
Supplemental sources of chromium Chromium is a widely used supplement. Estimated sales to consumers were $85 million in 2002, representing 5.6% of the total mineral-supplement market . Chromium is sold as a single-ingredient supplement as well as in combination formulas, particularly those marketed for weight loss and performance enhancement. Supplement doses typically range from 50 to 200 mcg.
The safety and efficacy of chromium supplements need more investigation. Please consult with a doctor or other trained healthcare professional before taking any dietary supplements.
Chromium supplements are available as chromium chloride, chromium nicotinate, chromium picolinate, high-chromium yeast, and chromium citrate. Chromium chloride in particular appears to have poor bioavailability . However, given the limited data on chromium absorption in humans, it is not clear which forms are best to take.
Chromium intakes and healthful diets Eating a variety of whole grains, fruits, vegetables, meats, and milk and milk products should provide sufficient chromium. According to the 2005 Dietary Guidelines for Americans, "Nutrient needs should be met primarily through consuming foods. Foods provide an array of nutrients and other compounds that may have beneficial effects on health. In certain cases, fortified foods and dietary supplements may be useful sources of one or more nutrients that otherwise might be consumed in less than recommended amounts. However, dietary supplements, while recommended in some cases, cannot replace a healthful diet."
The Dietary Guidelines for Americans describes a healthy diet as one that:
- emphasizes a variety of fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products;
- includes lean meats, poultry, fish, beans, eggs, and nuts;
- is low in saturated fats, trans fats, cholesterol, salt (sodium), and added sugars; and
- stays within your daily calorie needs.
For more information about building a healthful diet, refer to the Dietary Guidelines for Americans (http://www.healthierus.gov/dietaryguidelines/index.html) and the U.S. Department of Agriculture's food guidance system (My Pyramid; http://www.mypyramid.gov).
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Reasonable care has been taken in preparing this document, and the information provided herein is believed to be accurate. However, this information is not intended to constitute an "authoritative statement" under Food and Drug Administration rules and regulations.
General Safety Advisory
Health professionals and consumers need credible information to make thoughtful decisions about eating a healthful diet and using vitamin and mineral supplements. To help guide those decisions, registered dietitians at the NIH Clinical Center developed a series of Fact Sheets in conjunction with ODS. These Fact Sheets provide responsible information about the role of vitamins and minerals in health and disease. Each Fact Sheet in this series received extensive review by recognized experts from the academic and research communities.
The information is not intended to be a substitute for professional medical advice. It is important to seek the advice of a physician about any medical condition or symptom. It is also important to seek the advice of a physician, registered dietitian, pharmacist, or other qualified health professional about the appropriateness of taking dietary supplements and their potential interactions with medications.
The Clinical Nutrition Service and the ODS thank the expert scientific reviewers for their role in ensuring the scientific accuracy of the information discussed in these Fact Sheets, along with the Nutrition Education Subcommittee of the NIH, the U.S. Department of Agriculture (USDA) Dietary Guidance Working Group, and the Department of Health and Human Services Nutrition Policy Board Committee on Dietary Guidance.
Reviewers of Chromium Fact Sheet:
William Cefalu, MD, Pennington Research Lab, LA
Merlin Lindermann, DVM, University of Kentucky
Hank Lukaski, PhD, USDA, Grand Forks, ND
Richard Anderson, PhD, USDA, Beltsville, MD
Barbara Stoecker, PhD, Oklahoma State University