Chromium

Chromium is an ingredient in total parenteral nutrition (TPN), because deficiency can occur after months of intravenous feeding with chromium-free TPN.[115] It is also added to nutritional products for preterm infants.[116] Although the mechanism of action in biological roles for chromium is unclear, in the United States chromium-containing products are sold as non-prescription dietary supplements in amounts ranging from 50 to 1,000 μg. Lower amounts of chromium are also often incorporated into multi-vitamin/mineral supplements consumed by an estimated 31% of adults in the United States.[114] Chemical compounds used in dietary supplements include chromium chloride, chromium citrate, chromium(III) picolinate, chromium(III) polynicotinate, and other chemical compositions.[7] The benefit of supplements has not been proven.[7][117]

Approved and disapproved health claims[edit]

In 2005, the U.S. Food and Drug Administration had approved a Qualified Health Claim for chromium picolinate with a requirement for very specific label wording: "One small study suggests that chromium picolinate may reduce the risk of insulin resistance, and therefore possibly may reduce the risk of type 2 diabetes. FDA concludes, however, that the existence of such a relationship between chromium picolinate and either insulin resistance or type 2 diabetes is highly uncertain." At the same time, in answer to other parts of the petition, the FDA rejected claims for chromium picolinate and cardiovascular disease, retinopathy or kidney disease caused by abnormally high blood sugar levels.[118] In 2010, chromium(III) picolinate was approved by Health Canada to be used in dietary supplements. Approved labeling statements include: a factor in the maintenance of good health, provides support for healthy glucose metabolism, helps the body to metabolize carbohydrates and helps the body to metabolize fats.[119] The European Food Safety Authority (EFSA) approved claims in 2010 that chromium contributed to normal macronutrient metabolism and maintenance of normal blood glucose concentration, but rejected claims for maintenance or achievement of a normal body weight, or reduction of tiredness or fatigue.[120]

Given the evidence for chromium deficiency causing problems with glucose management in the context of intravenous nutrition products formulated without chromium,[115] research interest turned to whether chromium supplementation would benefit people who have type 2 diabetes but are not chromium deficient. Looking at the results from four meta-analyses, one reported a statistically significant decrease in fasting plasma glucose levels (FPG) and a non-significant trend in lower hemoglobin A1C.[121] A second reported the same,[122] a third reported significant decreases for both measures,[123] while a fourth reported no benefit for either.[124] A review published in 2016 listed 53 randomized clinical trials that were included in one or more of six meta-analyses. It concluded that whereas there may be modest decreases in FPG and/or HbA1C that achieve statistical significance in some of these meta-analyses, few of the trials achieved decreases large enough to be expected to be relevant to clinical outcome.[125]

Two systematic reviews looked at chromium supplements as a mean of managing body weight in overweight and obese people. One, limited to chromium picolinate, a popular supplement ingredient, reported a statistically significant −1.1 kg (2.4 lb) weight loss in trials longer than 12 weeks.[126] The other included all chromium compounds and reported a statistically significant −0.50 kg (1.1 lb) weight change.[127] Change in percent body fat did not reach statistical significance. Authors of both reviews considered the clinical relevance of this modest weight loss as uncertain/unreliable.[126][127] The European Food Safety Authority reviewed the literature and concluded that there was insufficient evidence to support a claim.[120]

Chromium is promoted as a sports performance dietary supplement, based on the theory that it potentiates insulin activity, with anticipated results of increased muscle mass, and faster recovery of glycogen storage during post-exercise recovery.[117][128][129] A review of clinical trials reported that chromium supplementation did not improve exercise performance or increase muscle strength.[130] The International Olympic Committee reviewed dietary supplements for high-performance athletes in 2018 and concluded there was no need to increase chromium intake for athletes, nor support for claims of losing body fat.[131]

Fresh-water fish[edit]