Chromium
What is it?
Chromium is an essential trace mineral. It occurs naturally in three different forms with one particular form (chromium III) making up the majority of dietary chromium. The average adult body contains between 0.4 and 6 mg of chromium and older people usually have lower levels. There is a wide geographical variation in chromium levels and population studies suggest that the incidence of diabetes and heart disease is lower in areas where chromium intakes are relatively high.
What it does in the body
Metabolism
Chromium is essential for normal sugar metabolism. It is a component of a compound called glucose tolerance factor (GTF) which works with insulin to move glucose into cells where it can be used to generate energy. Optimal chromium intake appears to decrease the amount of insulin needed to maintain normal blood sugar.
Insulin also plays a role in fat and protein metabolism, thus chromium is necessary for these processes to occur normally. Adequate chromium intake is essential to maintain healthy cholesterol levels.
Absorption and metabolism
Absorption of chromium from food is poor with only 2 to 10 per cent of dietary intake being absorbed. Organic chromium is absorbed more efficiently than inorganic chromium. Absorbed chromium binds to proteins, including transferrin, which transport it in the bloodstream. Chromium absorption is enhanced by the presence of oxalates and it is also higher in cases of iron deficiency. Absorption may decline with age.
Most absorbed chromium is eliminated through the kidneys. Chromium may be stored in the skin, fat, brain, muscles, spleen, kidneys and testes.
Deficiencies
Symptoms of chromium deficiency include high blood fat and cholesterol levels and diabetes-like symptoms of glucose intolerance, weakness, depression, confusion, weight loss, thirst, hunger and frequent urination.
Diets high in refined and processed foods, such as flour and sugar, excessive losses from the body in some diseases, alcoholism, prolonged slimming regimes and pregnancy may lead to chromium deficiency. Infection and physical trauma appear to increase chromium requirements and strenuous exercise appears to increase chromium excretion, increasing the risk of deficiency when intake is marginal.
Tissue levels of chromium tend to decrease with age. British researchers involved in a study published in 1997 analyzed chromium levels in hair, sweat, and serum samples obtained from over 40 000 patients.1 The results showed highly significant age-related decreases which may play a part in the increased risk of diabetes and atherosclerosis in older people. Marginal chromium deficiency may be relatively common, with as many as 50 per cent of people in the USA consuming less than the recommended 50 mcg per day. Preventing chromium deficiency is very important as this is easier than treating the complications which arise as a result.
Diabetes
Chromium deficiency is relatively common in patients with Type II diabetes and may impair the function of GTF, causing the uptake of glucose into cells to become less efficient. Impaired chromium metabolism may also play a role in diabetes of pregnancy.2 High insulin levels also seem to increase chromium excretion. Chromium deficiency may also lead to hypoglycemia or low blood sugar.
Heart disease
Chromium deficiency may also play a role in heart disease. Poor dietary intake may be linked to higher blood cholesterol levels and therefore increased risk of atherosclerosis. Patients with advanced heart disease often have low chromium levels in their blood. On a population level, decreased chromium levels correlate with increased heart disease.
Sources
Good sources of chromium include liver, egg yolk, brewer's yeast, certain spices such as black pepper and thyme, beef, poultry, broccoli, whole grain cereals, bran, wheatgerm and oysters. The chromium content of food varies with the location in which the food is grown. The table below can be used as a guide.
Food refining and processing remove most of the chromium from food. Hence a diet high in these foods will not contribute much chromium but will require it for metabolism, thus leading to depletion of the body's chromium stores.
Cooking food in stainless steel pots causes chromium to leach into the food if it is acidic and can be an additional source of dietary chromium. Hard tap water can also be a source.
| Food | Amount | Chromium (mcg) |
|---|---|---|
| Skim milk powder | 100g | 34 |
| Brown sugar | 100g | 27 |
| All Bran | 100g | 26 |
| Ham | 100g | 26 |
| Cheddar cheese | 100g | 24 |
| Corned beef | 100g | 20 |
| Wheatbran | 100g | 19 |
| Cod, smoked | 100g | 18 |
| Split peas, dried | 100g | 13 |
| Soybean flour | 100g | 17 |
| Pork sausage | 100g | 16 |
| Beef sausage | 100g | 15 |
| Mackerel, canned | 100g | 14 |
| Oysters, canned | 100g | 14 |
| Wheatgerm | 100g | 13 |
| Spinach | 100g | 13 |
| Brown lentils, dried | 100g | 13 |
| Lamb chops | 100g | 13 |
| Beefsteak, mince | 100g | 9.0 |
| Yeast extract | 10g | 8.7 |
| Yellow butter beans | 100g | 8.0 |
| Sweetcorn | 100g | 7.0 |
| Chicken, dark meat | 100g | 7.0 |
| Potato | 100g | 5.0 |
Recommended dietary allowances (RDA)
There is no RDA for chromium. Estimated safe requirements are between 50 and 200 mcg per day. It is difficult to test chromium levels accurately as there are no reliable established tests and it is possible that chromium accumulates in the tissues while being quickly cleared from blood serum.
Supplements
Chromium supplements are available in various forms including chromium picolinate, chromium chloride, chromium polynicotinate and chromium-enriched yeast. Biologically active forms of chromium such as chromium picolinate and yeast GTF are better absorbed than chromium chloride. GTF is found in brewer's yeast and is considered the most biologically active and absorbable form of chromium. The supplement doses effective in studies are in the region of 200 to 400 mcg per day. Chromium may be more effective if given with niacin, as the nicotinic acid form of niacin is part of GTF.
Toxic effects of excess intake
Little is known about the toxic effects of large doses of the form of chromium found in food and supplements. There have been reports of adverse effects, including irregular heartbeat, with people taking above the recommended 250 mcg dose.
A 1995 study found that chromium supplements caused severe damage to chromosomes of cells grown in the laboratory.3 However, no studies have yet been done to confirm these potential carcinogenic effects. As toxic effects were not seen with other forms of chromium; including chromium nicotinate, nicotinic acid, and chromium chloride hexahydrate; the researchers concluded that the toxic effects were due to the picolinate part of the molecule.
Therapeutic uses of supplements
Diabetes
Chromium supplements have been successfully used to treat Type I and Type II diabetes, diabetes in pregnancy, and hypoglycemia. Chromium supplementation has been shown to lower fasting glucose levels, improve glucose tolerance and lower insulin levels in Type II diabetics. This helps to keep blood levels stable, thereby preventing damage to blood vessels and organs caused by high levels of blood sugar. The greatest benefits are seen in those who have severe deficiencies. Chromium acts to increase insulin sensitivity by improving insulin binding, insulin receptor number, insulin internalization, beta cell sensitivity and insulin receptor enzymes.4
According to the results of a Chinese study published in 1997, daily chromium supplements may help control blood sugar levels and insulin activity in Type II diabetics. The study, conducted by researchers at the US Department of Agriculture and Beijing Medical University, involved 180 Type II diabetics. Chinese people were chosen because of the likelihood that they had not previously used supplements. The participants were divided into three groups: one group was given 1000 mcg of chromium picolinate, the second was given 200 mcg and the third group was given a placebo. After two months, the researchers assessed blood sugar and cholesterol levels. In the 1000 mcg group, levels were significantly reduced. In the 200 mcg group, it took four months to see a reduction in blood sugar levels and this was not as significant as that seen in the first group.5
Chromium supplements have been shown to reduce blood fat levels in Type II diabetics. In a study done in 1994 in San Antonio, Texas researchers found that chromium picolinate supplements taken for a period of two months significantly reduced triglyceride levels in 14 men and 16 women.6
Hypoglycemia
Research suggests that chromium supplements may improve the symptoms of hypoglycemia in some people.7
Heart disease
Chromium supplements have been shown to improve blood cholesterol and lipid levels in both diabetic and nondiabetic subjects. In those whose body levels of chromium are low, chromium seems to reduce total and harmful LDL cholesterol levels while raising beneficial HDL cholesterol levels.
In a study published in 1996, researchers assessed the effects of daily supplements of 200 mcg of chromium and nicotinic acid on blood glucose and lipids, including total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides. The patients were 14 healthy adults and five adults with Type II diabetes mellitus. The results showed lowered total and LDL cholesterol, triglycerides, and glucose concentrations in patients with Type II diabetes.8
Weight loss
Limited research suggests that moderate increases in chromium, in the form of chromium picolinate, may cause weight loss, reduce fat and increase muscle mass. Because of these reports, chromium picolinate supplements have become very popular.
Researchers involved in a 1997 study done in Austria assessed the effects of chromium yeast and chromium picolinate on lean body mass in 36 obese patients during and after weight reduction with a very low calorie diet. During the 26 week treatment period, subjects received either placebo or 200 mcg chromium yeast or 200 mcg chromium picolinate in a double-blind manner. After 26 weeks, chromium picolinate supplemented patients showed increased lean body mass whereas the other treatment groups still had reduced lean body mass.9
In a 1997 study done at the University of Texas at Austin, researchers examined the effects of 400 mcg of chromium and exercise training on young, obese women. The results showed that exercise training combined with chromium nicotinate supplementation resulted in significant weight loss and lowered the insulin response to an oral glucose load.10
Other uses
Some animal studies have shown that chromium picolinate supplements can prolong life. Further research is needed but this effect may be due to lowering of blood glucose levels similar to that seen in life-prolonging calorie restriction studies.
Chromium may help to boost the bone-building effects of insulin and may have a role in the maintenance of bone density and prevention of osteoporosis.11 High chromium yeast has also been used to treat acne with some success.12
Interactions
Antacids may decrease chromium absorption and may aggravate an existing deficiency. Sugar increases chromium excretion.
Cautions
Diabetics may benefit from chromium supplementation but as their insulin requirements may change as a result, their use of supplements should be monitored by a doctor.