Although the vast majority of studies of chromium supplementation reveal no side effects except mild gastrointestinal upset, they tend to be of short duration (a few weeks to a few months). Recent anecdotal reports, however, have suggested a variety of adverse side effects such as anemia, memory loss and DNA damage – in most cases for a particular form of chromium known as chromium picolinate
A handful of laboratory studies have shown that the supplemental form of chromium (chromium III) provided as the picolinate form, causes DNA breakage in isolated cells. Such DNA effects are thought to lead to genetic mutations and cancer, but it is important to note that these cell studies in the test tube are a long way removed from the case of a human ingesting an essential trace mineral. In one of the most publicized studies, Dartmouth researchers demonstrated that chromium picolinate is absorbed into cells intact (at least in the test tube), where it appeared to cause breaks in chromosomal DNA in hamster ovary cells (a common model for cancer researchers). The upshot of the study was that other chromium salts, such as nicotinate and chloride, were not taken up into the cells as efficiently as the picolinate version.
There have been a few case reports of adverse effects following high dose chromium supplementation. In one, a 24-yr-old female body builder developed rhabdomyolysis, a serious condition causing muscle and kidney toxicity, after ingesting 1200 mcg of chromium picolinate over 48 hours. This is 6-24 times the daily recommended allowance of 50-200 mcg. Another case of toxicity following chromium picolinate ingestion (1200-2400 mcg for 4-5 months) involved a 33-yr-old woman who was taking it to enhance weight loss. The supplement increased blood chromium levels to 2-3 times normal and caused anemia, blood abnormalities, liver dysfunction, and renal failure.
Both case reports demonstrate the fact that intakes of chromium picolinate at levels above the recommended dosage should be avoided. An animal study conducted by the USDA, fed rats a diet rich in chromium picolinate for 24 weeks and found no adverse side effects and there are no clinical studies that show harmful effects in humans from supplements containing chromium picolinate. It would seem prudent, however, to avoid excessive intake of supplements containing chromium picolinate and, where possible, select supplements which use alternate forms of chromium such as nicotinate, chloride or other amino acid chelates.