Key Takeaways (expand)
- Chromium is a trace mineral present in small amounts in every food group.
- Within the body, chromium is mostly found in the form of trivalent chromium (Cr3+), although it can exist in a number of other oxidation states as well.
- Chromium’s main function is in serving as a cofactor for chromodulin—an oligopeptide that potentiates the effects of insulin, in turn allowing the body to effectively use carbohydrates.
- Chromium can also improve insulin sensitivity by reducing markers of oxidative stress and inflammation.
- As a result of its effects on insulin, chromium may play a protective role against type 2 diabetes: studies show chromium supplementation can boost the efficiency of insulin, improve glucose intolerance, and reduce fasting blood sugar levels in people already diagnosed with diabetes.
- Chromium may likewise help protect against gestational diabetes, although the evidence is currently inconsistent and limited to observational studies.
- Along with its role in carbohydrate utilization, chromium influences protein and fat metabolism; however, there’s not much evidence to suggest chromium itself can increase muscle mass or promote weight loss in most people.
- Despite a lack of evidence for weight loss specifically, chromium supplements have shown potential for reducing cravings, food intake, and binge behavior in people who are overweight and/or have binge eating disorder.
- Some research suggests chromium supplementation can improve blood lipid profiles (lowering triglycerides and LDL cholesterol, while raising HDL cholesterol); however, these effects may be limited to people with low baseline levels of chromium.
- Chromium interacts with several other nutrients, including competing with iron for transferrin binding sites and subsequently interfering with iron metabolism.
- Chromium absorption may be enhanced by vitamin C and niacin, and inhibited by a high intake of simple sugars.
- Little research exists on the effects of chromium deficiency, but chronic insufficiency may be a contributor to type 2 diabetes.
- The richest sources of chromium are kidneys, liver, oysters, broccoli, green beans, mushrooms, leafy green vegetables, nuts, tomatoes, egg yolks, Brewer’s yeast, and blackstrap molasses.
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Chromium is a trace element that doesn’t get as much attention as some other “heavy hitter” minerals (like iron or calcium), but that doesn’t mean it’s not important for health! Chromium was first discovered in 1797 by a French chemist named Nicholas Louis Vauquelin, who was analyzing a bright red mineral found in a Siberian gold mine—at the time, referred to as Siberian red lead. Along with lead, the mineral contained a previously unknown metallic element that produced colorful compounds when mixed with various solutions. Vauquelin named this new element chromium from the Greek word chroma, meaning color. In fact, the green color in emerald is caused by chromium, as is the red in rubies!
Chromium’s main function is in the potentiation of insulin, allowing the body to effectively use carbohydrates. It also influences the metabolism of fat and protein.
Chromium is found in small amounts in every food group, but is most abundant in foods such as kidneys, oysters, liver, broccoli, green beans, leafy green vegetables, mushrooms, nuts, egg yolks, and tomatoes. Brewer’s yeast and blackstrap molasses are also good sources of chromium. Unlike most minerals and vitamins, the amount of chromium in different foods hasn’t been thoroughly documented. And, chromium levels can vary dramatically among different samples of the same foods due to variations in local soil conditions, water conditions, and agricultural processes!
The Biological Roles of Chromium
Among the trace minerals, chromium is somewhat shrouded in mystery. In fact, some debate exists about whether it’s truly essential—although we certainly have enough evidence to show it plays a role in human health!
Chromium can exist in a number of oxidation states, but within the body, exists mostly in the form of trivalent chromium (Cr3+), which is the form believed to play a role in insulin function. When blood sugar levels rise, specialized cells in the pancreas (called beta-cells) respond by secreting insulin, which then binds to insulin receptors on the surface of cells. By activating those receptors, the insulin directs the cells to take up glucose—in turn providing them with energy and removing glucose from the blood stream. When this system is running properly, the body is able to maintain blood glucose level within a narrow range (which is imperative, because both low blood sugar and high blood sugar can cause problems!); but, when insulin sensitivity decreases in tissues and the pancreas fails to produce enough insulin to maintain normal blood sugar levels, it can lead to impaired glucose tolerance and eventually type 2 diabetes.
Where chromium comes in is by serving as a cofactor for chromodulin—an oligopeptide that can potentiate the effects of insulin. Scientists are still trying to figure out the exact mechanism of action, but it appears that chromodulin can enhance the cascade of signaling events that happen when insulin binds to the insulin receptor. One proposed model suggests that chromodulin itself binds to the insulin receptor and upregulates insulin signaling molecules, causing greater translocation of glucose transporters (GLUT-4) to the cell membrane and ultimately improving glucose absorption.
In a mouse model of diabetes, chromium was able to alter the activity of the insulin-degrading enzyme (the major enzyme responsible for breaking down insulin), leading to reduced insulin degradation and slower clearance in the blood—making the insulin more available to bind to the insulin receptor and increasing the entrance of glucose into cells. This same study also found that chromium enhanced insulin signaling. Likewise, some in vitro experiments, as well as studies using animal models of insulin resistance and diabetes, have shown that chromium can inhibit the activity of certain negative regulators of insulin signaling (such as protein tyrosine phosphatase-1B)—suggesting a potential role for chromium in improving existing insulin resistance. But, these findings haven’t been consistent, and much more research (especially in humans!) is needed.
Other suggested mechanisms for the effects of chromium on insulin sensitivity are that chromium reduces markers of oxidative stress and inflammation, both of which are associated with insulin dysregulation.
Interactions with Other Nutrients
Chromium also has some notable interactions with other nutrients. For instance, it competes with iron for one of the binding sites on transferrin, an important protein that facilitates iron transport. Not only can chromium supplementation potentially decrease transferrin saturation (an indicator of iron deficiency) and interfere with iron metabolism, but iron excess may also interfere with chromium transport and possibly impact insulin function. In fact, one of the possible reasons genetic iron overload disorders increase the risk of diabetes could be due to excess iron preventing chromium uptake by transferrin, leading to insulin resistance!
In both animal and human studies, vitamin C has been shown to enhance the absorption of chromium; the same is true for niacin (vitamin B3). Conversely, diets high in simple sugars (such as sucrose) have been shown to increase the excretion of chromium in the urine, likely due to the increased insulin demands that accompany high sugar consumption. And, although little is known about potential interactions between chromium and pharmaceutical drugs, rodent studies suggest that large doses of antacids containing calcium carbonate or magnesium hydroxide can reduce chromium absorption, whereas non-steroidal anti-inflammatory drugs (such as aspirin) can increase its absorption.
Chromium in Health and Disease
Evidence about how chromium impacts health is currently ambiguous. Part of the reason is that blood levels of chromium don’t necessarily reflect dietary intake, and the chromium content of foods is highly variable and often unknown—making it difficult to track chromium consumption and nutritional status (and therefore, hard to establish links between chromium and disease risk!). That being said, the available evidence does suggest chromium could play a role in the prevention of some diseases, especially those related to impaired glucose tolerance.
Chromium, Blood Sugar, and Type 2 Diabetes
A variety of controlled trials—with participants ranging from healthy adults to malnourished children to type 2 diabetics—have shown that chromium supplementation can boost the efficiency of insulin, improve blood lipid profiles, and in some cases, improve impaired glucose tolerance. Studies that included supplementation specifically with chromium picolinate (the best-absorbed form) have demonstrated some improvement in risk for type 2 diabetes, as well as for cardiovascular disease.
Among people who already have type 2 diabetes, chromium supplementation could be particularly beneficial. For example, a controlled trial of 180 diabetics found that supplementing with 1000 micrograms of chromium per day, for a period of four months, reduced fasting blood sugar by up to 19% compared to placebo; chromium supplementation was also associated with reduced insulin concentrations and lower glycated hemoglobin A1c in this study. Some smaller trials also found that chromium supplementation improved insulin concentrations, fasting glucose, and blood lipids among type 2 diabetics.
However, not all studies have confirmed these effects, and others have shown no impact of chromium supplementation on diabetes-related biomarkers or blood sugar control (or, have shown benefit only for people who had the lowest initial insulin sensitivity and highest fasting blood sugar). Baseline chromium status, genetics, severity of insulin resistance, the presence of diabetes medications (which could mask or negate the effects of chromium), and chromium dose and duration could all play a role in these mixed results. So, while it does seem that chromium supplementation could have therapeutic value for blood sugar disorders, much more research is needed to identify who can benefit the most—as well as what chromium intakes are needed in order to see those benefits!
Chromium and Gestational Diabetes
Some research has also evaluated the effects of chromium on gestational diabetes—a condition where the pancreas fails to produce or use enough insulin during pregnancy. Here, too, findings have been mixed. Some observational studies have found no link between blood levels of chromium and gestational diabetes, glucose tolerance, or insulin resistance in pregnancy; however, given that blood levels of this nutrient don’t necessarily represent dietary intake, these findings might not be very informative. Conversely, a cross-sectional study of pregnant women in India found significantly lower blood chromium among those who had gestational diabetes compared to those who didn’t. And, a trial of chromium supplementation (4 micrograms daily per kg of body weight, for a period of eight weeks) led to a reduction in fasting blood sugar and insulin concentrations in women with gestational diabetes. Once again, more research is needed to expand on this limited and sometimes mixed evidence.
Chromium and Blood Lipids
The results of studies of chromium supplementation on blood lipid profiles have also been inconsistent. In some studies, chromium supplementation was able to reduce total cholesterol, LDL cholesterol, and triglyceride levels, as well as raise levels of HDL cholesterol; but in other studies, no such effect was observed. It’s possible that chromium supplementation only improves blood lipids in people whose dietary intake is initially low. And, given the current lack of tools for assessing chromium status, it may be hard to identify the deficient individuals who would fall into this category.
Chromium and Body Composition
Due to its role in macronutrient metabolism (via potentiating insulin), it’s been hypothesized that chromium could help increase muscle mass and/or promote weight loss. However, among the existing trials looking at chromium supplementation and lean body mass or body fat, little evidence exists that this is the case. The studies using the most accurate measurements of body composition (such as underwater weighing or dual energy x-ray absorbtiometry) haven’t found a beneficial effect of chromium supplementation on muscle mass or body fat. Similarly, controlled studies of chromium supplementation have shown minimal benefit (at best!) for weight loss or fat loss. A meta-analysis of 11 randomized controlled trials did find that supplemental chromium picolinate, at doses of up to 1000 micrograms daily for eight to 24 weeks, led to about a 1.1 pound reduction in body weight; but, this wasn’t enough to qualify as clinically significant.
Chromium, Cravings, and Food Intake
More compellingly, some studies have found that supplemental chromium can reduce food intake, cravings, and binge behavior. One trial of patients with binge eating disorder found that supplementation with either 600 micrograms or 1000 micrograms of chromium daily led to significant reductions in fasting blood sugar, as well as reductions in binge frequency, body weight, and symptoms of depression—although the limited statistical power of the study made it hard to establish the significance of these findings. Another trial found that eight weeks of chromium picolinate supplementation led to a reduction in hunger levels, food intake, and fat cravings among overweight women. However, as with chromium research in general, more (and larger) studies are needed to confirm these findings.
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Health Effects of Chromium Deficiency
As with its health benefits, the effects of chromium deficiency or insufficiency haven’t been extensively studied. Some likely cases of chromium deficiency have occurred from long-term intravenous feeding that lacked supplemental chromium, producing symptoms similar to those of diabetes—including greater insulin requirements and impaired glucose tolerance, both of which improved after chromium supplementation. These cases, along with the evidence for chromium’s impact on insulin, suggest that chromium insufficiency could be a contributor to type 2 diabetes. But, much more research is needed to say this definitively!
Some studies have shown that people engaging in endurance running have greater urinary calcium loss, suggesting there may be increased chromium demands on those who exercise regularly (and potentially raising the risk of deficiency among this population). Interestingly, weight lifting has also been shown to increase urinary chromium excretion, but also enhances its absorption, leading to no real net loss.
Problems From Too Much Chromium
Although chromium is valuable in trace amounts from food, too much—especially from environmental sources—can be toxic. This is particularly true for exposure to hexavalent chromium (Cr4+), which is a known carcinogen and has much higher toxicity than the trivalent chromium (Cr3+) found in the body. For example, hexavalent chromium from contaminated drinking water, fume inhalation from heated chromium, or chromium-containing dust inhalation has been shown to cause cancer, respiratory problems, skin inflammation, dermatitis, and ulcers.
By contrast, even relatively high intakes of trivalent chromium (such as from dietary supplements) are likely to be safe, both due to the lower overall toxicity of this form of chromium and due to the low absorption and rapid excretion of excess ingested chromium. Studies of up to 1000 micrograms daily of supplemental chromium for a period of months have generally failed to find adverse effects. However, in rare and isolated instances, chromium picolinate supplementation has led to kidney failure and impaired liver function; the risk of these effects may be highest in people with pre-existing kidney or liver disease.
How Much Chromium Do We Need?
The adequate intake level for chromium for adults up to the age of 50 is 35 micrograms a day for men and 25 micrograms daily for women (45 micrograms while breast-feeding, and 30 micrograms while pregnant). For adults 51 years and older, the adequate intake is set at 30 micrograms daily for men and 20 for women. Given how much is still yet to be discovered about chromium and its effects on human health, shooting for these adequate intake levels—rather than aiming for a high intake of chromium—is the most evidence-based recommendation available.
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