Chromium is a metallic element that exists in seven forms in nature (Cr0 to Cr6+), most of which are toxic, but the trivalent form (Cr3+) is essential for healthy in tiny amounts.
Our chromium levels are highest just after birth, then rapidly decrease with age, especially in men. Some experts believe this reflects a widespread nutritional deficiency and may be related to premature ageing and the increased risk of heart disease and diabetes that occurs in older people.
Chromium health benefits
Chromium was first recognised as important for human health in the 1950s, but it was another 40 years before its role in glucose control was fully recognised.
Chromium increases the number and activation of insulin receptors, so that more insulin can bind to cells to improve insulin sensitivity and optimise the uptake of glucose by cells. Chromium may do this by forming a complex, together with vitamin B3 and three amino acids, called chromium dinicotinic acid glutathione. Also known as Glucose Tolerance Factor (GTF) this complex has proven difficult to isolate and characterise and remains controversial, although yeast supplements are believed to provide chromium ready incorporated into the GTF form.
Chromium is also involved in the production of energy from glucose, and protein synthesis, especially in muscle cells. It has effects on the liver to lower ‘bad’ LDL-cholesterol levels, and may suppress hunger pangs through a direct effect on the satiety centre in the brain.
The EU has authorised health claims that chromium contributes to:
- normal macronutrient metabolism
- the maintenance of normal blood glucose levels.
Food sources of chromium
Most dietary chromium is obtained from:
- red meats
- fats and oils
- wholegrain cereals (especially barley)
- egg yolk
- fruit and vegetables (especially broccoli)
- herbs and spices such as black pepper and thyme.
Processing can reduce the chromium content of foods by at least 80%.
Plants do not need chromium and do not selectively absorb it. The amount of chromium they supply will therefore depend on how much is present in the soil in which they are grown.
Chromium deficiency is thought to be common. According to some estimates, as many as 90% of adults are deficient as most people get less than the recommended intake from their diet. Of the chromium that is present, only around 2 per cent is in the usable (trivalent) form.
One US study of 22 people following a diet designed to be ‘well-balanced’ found that chromium intakes ranged from 8.4mcg to 23.7 mcg with an average of 13.4 mcg chromium per day. This is significantly lower than the recommended daily amount (40mcg in the EU and 120mcg in the US).
Symptoms that can result from chromium deficiency are uncertain by may include:
- Poor glucose tolerance
- alcohol intolerance
- raised cholesterol and triglyceride levels
- muscle weakness
- hunger pangs
- mood changes such as nervousness, irritability, confusion or depression
- reduced fertility.
Chromium and diabetes
Low levels of chromium have been linked with poor glucose tolerance and a dietary lack of chromium appears to be a risk factor for type 2 diabetes. Some researchers have even suggested that type 2 diabetes is the result of long-term chromium deficiency, although this is controversial.
Studies assessing the effects of chromium supplements on glucose control in people with type 2 diabetes have provided conflicting results. The best way to evaluate these is to pool all the data and perform a meta-analysis.
When researchers did this with the results from 25 trials, involving almost 2,000 people, chromium supplements were found to significantly improve glycaemic control with reductions in HbA1c (-0·55%), fasting blood glucose levels, triglycerides and improved cholesterol balance – including a rise in ‘good’ HDL-cholesterol.
The beneficial effects on glucose and triglycerides levels were most marked with supplements providing chromium in the form of chromium picolinate, at doses of greater than 200 mcg per day.
Cinnamon supplements can also improve glucose control.
Chromium and heart disease
Chromium levels are lower in people with coronary heart disease than in the general population, and chromium deficiency may be an independent risk factor for cardiovascular disease.
Chromium levels were assessed from toenail clippings in healthy men from nine different countries, and compared with those of men experiencing their first non-fatal heart attack. This showed that average toenail chromium concentrations were significantly lower in those with the heart attack. These results add to the increasing evidence that chromium plays a role in cardiovascular health.
Chromium and weight loss
Because chromium has an effect on appetite, hunger pangs and fat metabolism, it is widely used as a slimming aid. When combined with a sensible diet and regular exercise, chromium supplements may help some people to lose weight – but probably only if they are deficient in chromium.
Data from 11 clinical trials suggested that including a chromium supplement in a weight loss regime resulted in a significantly greater weight loss compared with placebo, of half a kilogram over 8 weeks, which is not a massive difference but better than nothing.
In general, the more carbohydrate you eat, and the higher the glycaemic index of your diet, the more chromium you need.
Supplements usually contain either chromium picolinate, chromium polynicotinate or yeast bound (GTF) chromium. Intakes of 200mcg to 1000mcg chromium per day are considered both safe and adequate for glucose control.
The tolerable upper limit for chromium is significantly higher at 10mg (10,000mcg) per day from both food and supplements. However, I don’t advise taking more than 1000mcg (1mg) per day in supplement form.
Chromium supplements are better absorbed when taken with a source of vitamin C (eg orange juice).
Chromium side effects
Chromium supplements are safe at usual therapeutic doses. Very high intakes can damage the liver and kidneys, and cause an irregular heart rhythm, but these toxic side effects are rare.l
Do not exceed recommended doses as this may affect zinc and iron absorption.
Have chromium supplements improved your glucose control? Please share your experience below.