As this trace mineral begins its integration into foods, conclusive research remains to be conducted on toxicity and optimal dosage amounts for various conditions. Todd Runestad scans the literature.
The recent establishment of a daily chromium requirement of 35mcg for men and 25mcg for women by the Institute of Medicine in the US has raised its profile. Few foods are good chromium sources, a recent USDA analysis found. Cereals, particularly high-bran cereals, contribute variable but potentially important amounts of chromium.2 However, food processing strips chromium from foods, particularly when grains and sugars are refined.3 Some researchers have long believed the rising rate of type II diabetes is due in part to chromium depletion in the food supply.4
Chromium appears to make insulin function more efficiently by enhancing the uptake of glucose from the blood into the cell. Chromium increases the number of insulin receptors on the cell membrane and enhances insulin binding to cells. It also activates insulin receptor kinase, leading to increased insulin sensitivity.5 Because of chromium's role in insulin activity, researchers have looked at using the trace mineral to help diabetics control their blood-sugar levels. Additionally, work has been done on chromium's utility in depression and cholesterol management.
There is evidence that suggests chromium may be useful in the management of diabetes, but at levels much higher than the daily amount recommended to stave off deficiency conditions. A seminal study in this area was conducted in 1997 by Richard A. Anderson, PhD, and colleagues at the US Department of Agriculture, Beltsville Human Nutrition Research Center, in conjunction with Beijing Medical University Hospital.6 In a randomised, placebo-controlled trial, 180 Chinese adults with type II diabetes took either 200mcg/day chromium picolinate, 1,000mcg/day or placebo. Fasting glucose levels were lower in the 1,000mcg/day chromium group than placebo (chromium, 7.1mmol/l; placebo, 8.8mmol/L ). Two-hour glucose values were also significantly lower after both two and four months (four-month values: placebo, 12.3mmol/L; 1,000mcg/day chromium, 10.5mmol/L). Plasma total cholesterol also decreased after four months in the 1,000mcg/day group. Just as important, after two months, haemoglobin values remained elevated (8.5 per cent) in the placebo group but dropped to what is considered only slightly elevated levels (7.5 per cent) in the 200mcg/day group and dropped significantly (6.6 per cent) in the 1,000mcg/day group. Diabetics should not self-administer larger doses because of danger of dropping below normal blood-glucose levels.
Another well-designed, long-range, placebo-controlled study enrolled 76 patients with established atherosclerotic disease, 25 of whom had diabetes, who were treated daily with 250mcg chromium chloride for seven to 16 months. Measurements were taken at baseline, three months and at the conclusion of the study. Serum triglycerides were significantly lower in the chromium-treated patients than in the patients who received placebo, and serum high-density lipoprotein (HDL) increased in the patients who received chromium, suggesting an improvement in insulin sensitivity. There was no change in serum cholesterol or blood glucose during the study.7
Despite this good news for diabetics and those with insulin resistance, chromium does not appear to be for everyone. Blood-sugar levels in people with good glucose tolerance who do not need additional chromium do not respond to supplemental chromium, nor do levels change in those consuming adequate chromium and well-balanced diets. Researchers believe this shows that chromium is essentially a food, with pharmacological action in large doses for certain disease conditions, and will therefore benefit only those who are chromium-deficient or have abnormal blood-sugar values.8
How much chromium is enough? Some studies with 150mcg chromium chloride show no effect on carbohydrate and lipid metabolism.9 Others with 200mcg chromium chloride show no effect on non-insulin-dependent diabetics.10 As mentioned above, 1,000mcg appeared to work better than 200mcg.6
When chromium picolinate was introduced in the mid-1990s, it was heralded as another supplement to aid in weight loss, particularly by losing body fat and not lean muscle mass. In a randomised, double-blind, placebo-controlled study, 154 patients received either 200mcg/day or 400mcg/day chromium picolinate for 72 days. Both chromium groups had significantly higher positive changes in body composition compared to placebo.11
A follow-up study by the same researchers found that those taking either 200mcg/day or 400mcg/day chromium picolinate lost significantly more weight than placebo over a 90-day period. Without any loss of fat-free mass, the chromium groups lost 7.79kg and 7.71kg vs. 1.81kg and 1.53kg for the placebo groups.12
However, a study of 16 young men taking 200mcg/day chromium picolinate for 12 weeks showed no change in strength, lean body mass or body fat.13 One head-to-head study pitting chromium picolinate against a newer chromium derivative, niacin-bound polynicotinate, found 400mcg/day chromium polynicotinate for eight weeks resulted in significant weight loss in young obese women, but no changes were seen in either the picolinate or placebo groups. Equivocal studies like these took some of the air out of the chromium picolinate balloon for its weight-loss uses (though the research was sponsored by a supplier of chromium polynicotinate).
Chromium has been implicated as a factor in the maintenance of normal lipid and carbohydrate metabolism. A study using 220mcg/day chromium polynicotinate taken for 90 days by 26 healthy adults showed no improvements in normal blood-lipid levels.14 This is not entirely surprising, as other studies also find no benefit from chromium in normal subjects with normal blood-sugar levels.
The first report of chromium's ability to significantly reduce serum triglycerides in a group of non-insulin-dependent diabetic patients was in 1994. In a prospective, double-blind, placebo-controlled study, 28 patients received 200mcg/day chromium picolinate for two months. Although there was no change seen in HDL or LDL cholesterol, triglyceride levels dropped 17.4 per cent.15
While positive studies continue to be published,6 other findings report no benefit. For example, an uncontrolled, eight-week pilot study in the UK using only 100mcg/day chromium found no significant changes in insulin and lipoprotein concentrations among 12 type II diabetics.16
Toxicity And Interactions
Few serious adverse effects have been associated with excess intake of chromium from food, which is why the Institute of Medicine declined to establish a tolerable upper intake level when it set minimum requirements for chromium. Animal studies have found that supplemented chromium chloride and picolinate are non-toxic, though it does accumulate in the liver and kidney.17 One human case study, however, reported that a woman who took 1,200-2,400mcg/day chromium picolinate for five months developed serious renal impairment.18
Its toxicity and metabolic function at doses exceeding 2,000mcg/day is presently unknown. And not enough research has been done on toxic build-up of some of the metallic minerals, including chromium, in the body, especially when their bioavailability has been enhanced, as is the case with most forms other than chromium chloride.
Animal studies have concluded that vitamin C enhances chromium absorption.19 Other animal studies have found that amino acids double the absorption of chromium.20 As might be expected, antacids have been found to reduce chromium absorption and retention in rats.21
The future of chromium lies in research at laboratories and in clinical settings, as well as in government houses. Already, new research at Oxford University found that chromium may have antidepressant properties by increasing the availability of tryptophan for brain serotonin synthesis in rats.22
Additional research is still needed to conclusively determine the safety and toxicity of chromium—especially in regards to the many forms of the trace mineral and particularly in relation to optimal doses for various conditions. As food formulators begin incorporating chromium into meal replacement bars and specialty beverages, more research is needed into dietary factors that affect chromium absorption. Also, as might be expected in people with insulin resistance who attempt to treat themselves with functional foods, research is needed to determine chromium's efficacy with sporadic use.
1. Food and Nutrition Board (FNB), Institute of Medicine (IOM). Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc (2002). http://books.nap.edu/books/0309072794/html/197.html
2. Anderson et al. Chromium content of selected breakfast cereals. J Food Comp Anal 1988;1:202-8.
3. Anderson RA. Chromium. In: Mertz W, ed. Trace Elements in Human and Animal Nutrition, Vol I. San Diego: Academic Press 1987. P 225-44.
4. Boyle Jr E, et al. Chromium depletion in the pathogenesis of diabetes and atherosclerosis. South Med J 1977 Dec;70(12):1449-53.
5. Anderson RA. Chromium in the prevention and control of diabetes. Diabetes Metab 2000 Feb;26(1):22-7.
6. Anderson RA, et al. Elevated intakes of supplemental chromium improves glucose and insulin variables in individuals with type 2 diabetes. Diabetes 1997 Nov;46(11):1786-91.
7. Abraham AS, et al. The effects of chromium supplementation on serum glucose and lipids in patients with and without non-insulin-dependent diabetes. Metabolism 1992 Jul;41(7):768-71.
8. Anderson RA. Chromium, glucose intolerance and diabetes. J Am Coll Nutr 1998;17(6):548-55.
9. Rabinowitz et al. Effects of chromium and yeast supplements on carbohydrate and lipid metabolism in diabetic men. Diabetes Care 1983 Jul-Aug;6(4):319-27.
10. Uusitupa MI, et al. Effect of inorganic chromium supplementation on glucose tolerance, insulin response, and serum lipids in noninsulin-dependent diabetics. Am J Clin Nutr 1983 Sep;38(3):404-10.
11. Kaats G, et al. Effects of chromium picolinate supplementation on body composition: a randomized, double-masked, placebo-controlled study. Curr Therapeut Res 1996 Oct;57(10):747-56.
12. Kaats GR, et al. A randomized, double-masked, placebo-controlled study of the effects of chromium picolinate supplementation on body composition: a replication and extension of a previous study. Curr Ther Res 1998;59:379-88.
13. Hallmark MA, et al. Effects of chromium and resistive training on muscle strength and body composition. Med Sci Sports Exer 1996 Jan;28(1):139-44.
14. Wilson BE, Gondy A. Effects of chromium supplementation on fasting insulin levels and lipid parameters in healthy, non-obese young subjects. Diabetes Res Clin Pract 1995 Jun;28(3):179-84.
15. Lee NA, Reasner CA. Beneficial effect of chromium supplementation on serum triglyceride levels in NIDDM. Diabetes Care 1994 Dec;17(12):1449-52.
16. Trow LG, et al. Lack of effect of dietary chromium supplementation on glucose tolerance, plasma insulin and lipoprotein levels in patients with type 2 diabetes. Int J Vitam Nutr Res 2000 Jan;70(1):14-8.
17. Anderson RA, et al. Lack of toxicity of chromium chloride and chromium picolinate in rats. J Am Coll Nutr 1997 Jun;16(3):273-9.
18. Cerulli J, et al. Chromium picolinate toxicity. Ann Pharmacother 1998 Apr;32(4):428-31.
19. Davis ML, et al. Effects of over-the-counter drugs on chromium retention and urinary excretion in rats. Nutr Res 1995;15:201-10.
20. Dowling HJ, et al. Effects of amino acids on the absorption of trivalent chromium and its retention by regions of the rat small intestine. Nutr Res 1990;10:1261-71.
21. Kamath SM, et al. Absorption, retention and urinary excretion of chromium-51 in rats pretreated with indomethacin and dosed with dimethylprostaglandin E2, misoprostol or prostacyclin. J Nutr 1997;127:478-82.
22. Attenburrow MJ, et al. Chromium treatment decreases the sensitivity of 5-HT2A receptors. Psychopharmacology (Berl) 2002 Feb;159(4):432-6.