Chromium (Cr) is a naturally occurring element found in rocks, animals, plants, and soil, predominantly in its insoluble trivalent form [Cr(III)]. Like many trace metal elements, chromium is essential to life at low concentrations, playing a key role in glucose, fat and protein metabolism by potentiating the action of insulin (this article will give you a concise overview of its beneficial actions) yet toxic to many systems at higher concentrations.
Another important aspect to point out is that metals don’t occur in just one state and their different states have different potencies and actions on the human body, therefore it is important to differentiate and refer to them separately. Chromium for instance has several oxidation states (or valence states) ranging from chromium (II) to chromium (VI).
Chromium is widely used in numerous industrial processes and as a result is a contaminant of many environmental systems. This type of “industrial chromium”, otherwise known as soluble hexavalent chromium Cr(VI), is a different molecule with different actions on the body: it is a toxic industrial pollutant that is classified as human carcinogen by several regulatory and non-regulatory agencies [1–2].
Cr(VI) can induce toxicity at the cellular, biochemical and genetic levels. This study done on rats shows dose- and time-dependent effects on DNA damage after 24, 48, 72, and 96 hours of exposure to potassium dichromate .
Hexavalent chromium was initially thought to be man-made but recently, naturally occurring hexavalent chromium has been found in ground and surface waters at values exceeding the World Health Organisation limit for drinking water of 50 µg of Cr(VI) per liter .
Sources of Exposure to Cr(VI)
Non-occupational exposure occurs via ingestion of chromium containing food and water whereas occupational exposure occurs via inhalation.Breathing high levels of chromium (VI) can cause irritation to the lining of the nose, and nose ulcers. Even though the principal route of human exposure to chromium is through inhalation, and the lung is the primary target organ, significant human exposure to chromium has also been reported to take place through the skin [5, 6]: the widespread incidence of dermatitis noticed among construction workers is attributed to their exposure to chromium present in cement  . Exposure to Cr(VI)-containing compounds is known to cause multiorgan toxicity such as renal damage, allergy and asthma, and cancer of the respiratory tract in humans.
Chromium (III) compounds are much less toxic and do not appear to cause these problems. Some individuals are extremely sensitive to both chromium(VI) and chromium(III), and allergic reactions consisting of severe redness and swelling of the skin have been noted.
An increase in stomach tumours was observed in humans and animals exposed to chromium(VI) in drinking water.
How Cr(VI) Harms the Body: Oxidative damage
Cr(VI) compounds are powerful oxidising agents and thus tend to be irritating and corrosive. Cr(VI) is much more toxic systemically than Cr(III).
Being a soluble compound, Cr(VI) can pass through cell membranes with ease. It can be absorbed by the lung and gastrointestinal tract, and even to a certain extent by intact skin.
Once inside the body, Cr(VI) enters many types of cells and under physiological conditions can be reduced by hydrogen peroxide (H2O2), glutathione (GSH) reductase, ascorbic acid, and GSH to produce reactive intermediates, including Cr(V), Cr(IV), thiylradicals, hydroxyl radicals, and ultimately, Cr(III). Any of these species could attack DNA, proteins, and membrane lipids, thereby disrupting cellular integrity and functions [8, 9]. This should highlight the importance of plant-derived anti-oxidants and most importantly of the body’s endogenous antioxidant system involving glutathione in the detoxification and elimination of toxic chromium from the body.
First, do not confuse Cr(VI) with Cr(III): trivalent (chromium 3+), which can be found in foods, and hexavalent (chromium 6+), which is considered toxic and unsafe for humans and isn’t meant to be acquired from foods. So far, I’ve been referring mainly to Cr(VI).
Chromium as Cr(III) is an essential trace mineral that is well-researched in regard to blood sugar and diabetes control, heart health, weight management and brain health.
These are some of the symptoms of a possible chromium deficiency in the body.
Beneficial Effects of Chromium Supplementation
- Control of Hyperglycaemia, Insulin Resistance, Diabetes
Chromium is known to help enhance the role of insulin, the critical hormone that controls blood sugar and helps bring glucose into cells. In this study, people with diabetes were administered 100 microg Cr as chromium picolinate two times per day and the results showed significant beneficial effects on HbA1c, glucose, insulin, and cholesterol variables.
Chromium (in the form chromium picolinate or CrPic) has been associated with a reduction in obesity and less weight gain. This study found that chromium supplements effectively helped modulate food intake in healthy, overweight, adult women who reported craving carbohydrates.
- Brain Health, Longevity and Anti-Ageing
Because chromium is capable of improving glucose levels and insulin response, it may act as a beneficial modulator of brain function and is associated with a reduction of age-related alterations of the brain. This also fits well into an anti-ageing theory since aging is often associated with a reduction of effective insulin activity in the brain. This study suggests that chromium picolinate may have a longevity effect by keeping the hypothalamus in a more youthful state, by better regulating appetite in elderly adults and preventing negative effects on brain neurons caused by aging.
However, chromium is very controversial when it comes to its benefits vs.harmful actions.
While some medical researchers believe chromium deficiency is very prevalent, especially in people who don’t properly respond to insulin (overweight people and those who eat a poor diet), other researchers still find it hard to verify a specific biological role of chromium in the body. Furthermore, in 2014, the European Food Safety Authority published a report stating that chromium has no proven beneficial effects on health in otherwise healthy adults, so chromium was removed from the list of essential nutrients.
I would speculate that since chromium exerts its beneficial action in extremely small amounts (the RDI is about 20-50mcg/day), the positive effects achieved with supplementation are due to long-term severe chromium deficiency. Chromium deficiency is most likely caused by malabsorption as it occurs in cases of gut dysbiosis and intestinal inflammation, conditions that are prevalent in overweight individuals. The elderly are known to have less efficient digestive systems, hence they are also at risk of deficiency. Thus, the inability to absorb enough chromium from dietary sources is a pertinent hypothesis that fully explains the positive effects of supplementation.
Given the current state of available medical evidence, I would recommend that people rely on food sources of chromium as a much healthier way to obtain the right amount of this nutrient.
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