Chromium influences carbohydrate, fat, and protein (protein) metabolism as an essential component of the so-called glucose tolerance factor (GTF).
Influence on insulin action – improvement of glucose tolerance
Glucose tolerance factor represents the biologically active form of chromium. Its exact structure has not yet been clearly elucidated. The GTF appears to consist of one or more similar trivalent chromium complexes. Two molecules of vitamin B3 (nicotinic acid) and one molecule each of glycine, cysteine and glutamate – glutamic acid – are bound to one chromium atom.Furthermore, it is suspected that aspartate – aspartic acid – could also be a component of the GTF. This was confirmed by a study on various tissues from which a chromium-binding oligopeptide with a low molecular weight of 1,500 was isolated. This consists of glycine, cysteine, glutamate and aspartate and was named “chromodulin” by Vincent.Chromodulin acts via activation of a specific enzyme. It is responsible for activating the tyrosine kinase activity of the insulin receptor. In this way, chromodulin-containing GTF controls the binding of insulin, a glucose-lowering (blood sugar-lowering) peptide hormone, to the insulin-specific receptor.Ultimately, this potentiates insulin action on target cells and accelerates the uptake of glucose and amino acids into liver, muscle, and fat cells, thereby decreasing the circulating amounts of glucose, insulin, as well as glucagon – glucose-increasing peptide hormone – in serum after glucose loading. As a result of increased influx of glucose and amino acids into liver, muscle, and adipose tissue, intracellular glycogen, protein, and triglyceride synthesis is stimulated.Other hypotheses for activation of insulin action by chromium:
- Cr+3 as a component of glucose tolerance factor promotes the formation of insulin-insulin receptor complexes, which enable interactions between insulin and insulin-sensitive tissues
- Chromium, through its influence on gene expression, regulates the formation of a molecule that enhances insulin action
Influence on lipid profile – triglycerides, LDL and HDLThe essential trace element chromium is able to reduce the lipid concentration of total and LDL cholesterol and triglyceride levels. At the same time, chromium causes serum HDL cholesterol to increase.Thus, the trace element prevents the formation of atherosclerotic plaques-deposits of blood lipids, thrombi, connective tissue, and calcium-in the walls of blood vessels.Chromium deficiency may be associated with the following symptoms:
- Decreased glucose tolerance (impaired glucose utilization).
- A 50% reduction in the incorporation of glucose into muscle and liver glycogen.
- Hyperglycemia (increased blood glucose levels).
- Hyperlipidemia (lipid metabolism disorder) – increased serum LDL and triglyceride levels.
- Abnormalities of nitrogen metabolism.
- Weight loss
In patients on long-term parenteral nutrition who complained of hyperglycemia with peripheral neuropathy (disease of the peripheral nervous system), ataxia (disorders of balance regulation and coordination of movement), and weight loss, the beneficial effect of chromium on glucose tolerance was discovered. Glucose tolerance means the ability to tolerate the intake of a certain amount of glucose without pathological (abnormal) blood and urine glucose levels.Under chromium administration, there was a significant improvement in symptoms.In general, an intravenous intake of > 20 µg chromium per day is considered standard for parenteral nutrition.
Influence on diabetes mellitus
Chromium also plays an essential role for diabetics in the form of the glucose tolerance factor.Diabetics often suffer from chromium deficiency – too little chromium in the diet – as a result of which the glucose tolerance factor can only be formed inadequately. Due to the low supply of chromium or GTF, diabetes mellitus is usually accompanied by hyperglycemia (elevated blood glucose levels).As the extent of glucose metabolism disorder (glucose intolerance) increases, the need for chromium increases in diabetics.A diabetes diet augmented with chromium supplementation resulted in the following observations:
- Improved glucose tolerance
- Increased (fasting) blood glucose levels
- Decreased insulin levels
- Lower total cholesterol and triglyceride levels
- Increased HDL cholesterol levels
Further studies in adult diabetics found significant improvement in diabetes control with daily administration of 180-1,000 µg chromium.However, a recent meta-analysis of 15 randomized clinical trials found no effect of supplemental chromium on glucose or insulin concentrations in nondiabetics. Based on some of the studies from China examined in this meta-analysis, the corresponding effect of chromium in diabetics was judged to be inconclusive.
Significance for weight reduction
The essential trace element chromium is said to have a weight-reducing effect – but compared with exercise, this effect is vanishingly small.For example, a study of 154 adults who received 200 and 400 µg of chromium picolinate per day, respectively, over a period of 10 weeks on a calorie-restricted diet showed an increased proportion of lean body mass (lean body mass), especially muscle mass, and a loss of body fat. In contrast, in another study of 33 overweight women who consumed 200 µg of chromium picolinate daily for 12 months on a hypocaloric diet, no effects on body weight or body composition were observed.
