Chromium in the diet

01 December 2008

Chromium is an essential trace element that enhances insulin function and influences carbohydrate, protein and fat metabolism. It has been suggested that chromium could be used as an adjunct to weight loss and to improve blood sugar control in people with diabetes. This article examines current understanding in these areas and outlines recommendations for chromium consumption.

Where to find chromium (Cr)

When we speak about dietary chromium as needed by the human body, we refer to the trivalent form (Cr3+ or Cr(III)). Chromium is all around us; in the air, water and soil and is widely found in the food supply. Like other trace minerals the amount in foods is small and varies depending on exposure to chromium in the environment and during manufacture. In general, meat, shellfish, fish, eggs, wholegrain cereals, nuts, and some fruits and vegetables are good sources of chromium.

Table 1 Dietary sources of chromium1

Food

Chromium content (µg/100 g)

Mussel

128

Brazil nut

100

Oyster

57

Date (dried)

29

Pear

27

Brown shrimp

26

Wholemeal flour

21

Tomato

20

Mushroom

17

Broccoli

16

Barley (wholegrain)

13

Hazelnut

12

Pork chop

10

Maize (wholegrain)

9

Egg yolk

6

Beef

3

Herring

2

Function in the body

The biological significance of chromium came to light in the late 1950’s when brewers’ yeast was discovered to prevent the age-related decline in the ability to maintain normal blood sugar levels in rats. An organic chromium complex was identified as the active ingredient and this complex was labelled the ‘Glucose Tolerance Factor’ (GTF).2 The precise nature of the GTF and the mechanism by which it boosts insulin function in the body are still not fully understood but it may promote the uptake of insulin into cells by facilitating its transfer across cell membranes.

Blood sugar control

In type 2 diabetes, although the pancreas is producing enough insulin, muscle cells and other tissues become resistant to the action of insulin, which results in poor control of blood glucose levels. A number of studies have examined the effect of chromium supplements in those with type 2 diabetes. A recent meta-analysis pooled the results of 41 studies and found that chromium supplements do appear to improve blood sugar control in people with type 2 diabetes, but the authors state that well-designed clinical trials are still required before any firm claims can be made.3 No benefits of chromium supplements on blood glucose have been found in people without diabetes.

Weight loss

Because chromium has an effect on glucose and fat metabolism, researchers have explored its potential to promote weight loss and enhance body composition (i.e. less fat, more muscle). Although some early studies found that chromium supplements led to greater weight and fat loss compared with the placebo, others did not. A recent double-blind, randomised trial, where women were fed similar diets (constant energy and nutrients) with or without chromium supplements, found that chromium supplements had no greater effect on weight or fat loss than the placebo.4

Safe intakes

Research on the essentiality of chromium is still scarce. However, based on intakes from typical diets the nutrition societies in Germany, Austria and Switzerland currently consider daily intakes of 30-100 µg as adequate for adolescents and adults.5 This is in line with the very recent EU recommended dietary allowance of 40 µg Cr3+ per day.6 Dietary surveys show that average adult European diets contain between 60 µg (Germany) and 160 µg (Sweden) chromium per day.5

While it is unlikely that harmful amounts of chromium could be consumed from regular foods, chromium can be added in the manufacture of foods, and chromium supplements have become popular. There is some concern that high doses of chromium may have adverse effects on DNA and that their use as nutritional supplements and insulin enhancers should be reconsidered.7 However, the European Scientific Committee on Food stated:

‘In a number of limited human studies, there was no evidence of adverse effects associated with supplementary intake of chromium up to a dose of 1 mg chromium/day.’5

Eat a varied diet

As chromium is found widely in foods, eating a varied balanced diet should provide all the chromium you need. Currently, no evidence supports the use of chromium supplements for the general population.

References

  1. Food Composition and Nutrition Tables, 7th revised and completed edition, Ed. SW Souci, W Fachmann, H Kraut.Wissenschaftliche Verlagsgesellschaft mbH, Stuttgart, 2008.
  2. Schwarz K and Mertz W. (1959) Chromium III and the glucose tolerance factor. Archives of Biochemistry and Biophysics 85:292-295
  3. Balk EM, Tatsioni A, Lichtenstein AH, Lau J, Pittas AG. (2007) Effect of chromium supplementation on glucose metabolism and lipids: a systematic review of randomised controlled trials. Diabetes Care 30:2154-2163
  4. Lukaski HC, Siders WA, Penland JG. (2007) Chromium picolinate supplementation in women: effects on body weight, composition and iron status. Nutrition 23:187-195
  5. Scientific Committee on Food (2003) Opinion of the Scientific Committee on Food on the tolerable upper intake level of trivalent chromium. Available at: http://ec.europa.eu/food/fs/sc/scf/out197_en.pdf
  6. Commission Directive 2008/100/EC of 28 October 2008. Available at: http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2008:285:0009:0012:EN:PDF
  7. Levina A and Lay PA. (2008) Chemical properties and toxicity of chromium (III) nutritional supplements. Chemical Research in Toxicology 21:563-571