The essentiality of Chromium, particularly in its trivalent form (Cr3+), is praised in most publications dealing with the speciation of chromium. Especially the ambivalence of chromium, with the trivalent form being considered essential, while the hexavalent species is classified as carcinogen, is a very strong argument to differentiate the two species by means of speciation analysis. Yet, the essentiality of Cr(III) for human nutrition has been a subject of debate in more recent years.
For many years, chromium in its trivalent state [Cr(III)] was considered an essential trace element necessary for the normal metabolism of carbohydrates, fats, and proteins. However, recent research has challenged this view, leading to some re-evaluation of its status as an essential nutrient. Here’s what is currently known:
Historical Perspective on Chromium Essentiality
Discovery and Early Research: Chromium's potential essentiality was first suggested in the 1950s, when studies indicated that it might be involved in glucose metabolism. Researchers observed that chromium supplementation improved glucose tolerance in animals and humans with glucose intolerance, leading to the hypothesis that chromium is an essential nutrient. K. Schwarz, W. Mertz, Chromium(III) and the glucose tolerance factor. Arch. Biochem. Biophys., 85/2 (1959) 292-295. DOI: 10.1016/0003-9861(59)90479-5
Chromodulin Hypothesis: It was believed that chromium, in the form of a complex known as chromodulin (also referred to as low-molecular-weight chromium-binding substance, LMWCr), played a role in enhancing insulin signaling, thus aiding in glucose uptake. This theory contributed to chromium's classification as an essential trace element. J.B. Vincent, The biochemistry of chromium. J. Nutr., 130/4 (2000) 715-718. DOI: 10.1093/jn/130.4.715
Recent Research and Re-Evaluation
Controversy and Skepticism: Over the past two decades, the idea that chromium is essential has been increasingly questioned. Some studies have failed to demonstrate a clear biological role for chromium, and the chromodulin hypothesis has faced challenges due to a lack of consistent evidence. D.M. Stearns, Is chromium a trace essential metal?. BioFactors, 11/3 (2000) 149-162. DOI: 10.1002/biof.5520110301 J.B. Vincent, Chromium: Is it essential, pharmacologically relevant, or toxic?. Met. Ions Life Sci., 13 (2013) 171-198. DOI: 10.1007/978-94-007-7500-8_6
Human Studies: Many controlled studies on humans have shown mixed results regarding chromium supplementation’s effects on glucose metabolism, weight loss, and other health outcomes. Some studies report mild benefits, particularly in people with type 2 diabetes or insulin resistance, while others show no significant effects. R.A. Anderson, Chromium as an essential nutrient for humans. Regul. Toxicol. Pharmacol., 26/1 (1997) S35-S41. DOI: 10.1006/rtph.1997.1136 H.C. Lukaski, Chromium as a supplement. Ann. Rev. Nutr., 19/1 (1999) 279-302. DOI: 10.1146/annurev.nutr.19.1.279
Regulatory and Scientific Consensus: Organizations like the European Food Safety Authority (EFSA) and the U.S. National Academy of Medicine have recognized the lack of conclusive evidence for chromium’s essentiality. In 2014, EFSA concluded that chromium is not essential for human nutrition because no chromium deficiency syndrome has been clearly identified, and no specific biological role for chromium has been definitively established. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on Dietary Reference Values for chromium. EFSA Journal, 12/10 (2014) 3845. DOI: 10.2903/j.efsa.2014.3845
Toxicity Concerns: While trivalent chromium (Cr3+) is considered relatively safe, hexavalent chromium (Cr6+) is highly toxic and carcinogenic. This distinction is important in discussions about chromium’s health effects, particularly concerning occupational exposure and environmental contamination. R.A. Anderson, N.A. Bryden, M.M. Polansky, Lack of Toxicity of Chromium Chloride and Chromium Picolinate in Rats. J. Am. Col. Nutr., 6 (1997) 273–279. DOI: 10.1080/07315724.1997.10718685 D. Bagchi, S.J. Stohs, B.W. Downs, M. Bagchi, H.G. Preuss, Cytotoxicity and Oxidative Mechanisms of Different Forms of Chromium. Toxicology, 180 (2002) 5–22. DOI: 10.1016/S0300-483X(02)00378-5
Current Understanding
Nutritional Status: The current consensus leans towards the view that chromium is not essential for humans. However, some individuals may experience mild benefits from supplementation, particularly in cases of impaired glucose metabolism. Institute of Medicine (US), Panel on Micronutrients, Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. The National Academies Press, (2001). DOI: 10.17226/10026
Research Gaps: The role of chromium in human health remains an open question, with some scientists advocating for more research to definitively determine whether it should be classified as essential or not. The lack of evidence for chromium essentiality does not preclude chromium being considered a bioactive element with beneficial effects when supplemented in higher than nutritional or physiological (supranutritional) amounts M. Hummel, E. Standl, O. Schnell, Chromium in metabolic and cardiovascular disease. Horm. Metabol. Res., 39/10 (2007) 743-751. DOI: 10.1055/s-2007-985847
Supplement Use: Despite the controversy, chromium supplements, particularly in the form of chromium picolinate, are still widely used, often marketed for weight loss or improved glucose metabolism. The effectiveness and safety of such supplements are still under scrutiny. D.D.D. Hepburn, J.M. Burney, S.A. Woski, J.B. Vincent, The nutritional supplement chromium picolinate generates oxidative DNA damage and peroxidized lipids in vivo. Polyhedron, 22/3 (2003) 455-463. DOI: 10.1016/S0277-5387(02)01369-4
In summary, while chromium was once considered an essential trace element, recent evidence suggests that it may not be essential for human nutrition. The debate continues, with some scientists calling for more research to clarify chromium's role in human health. Based on the actual state of research, the best classification for chromium probably is that it is a supranutritional or pharmacological beneficial element that can alter a biochemical pathway or biological structure in a therapeutic manner.