Chromium is an essential nutrient for humans and animals. The main physiologic role of Cr is to increase insulin action or sensitivity in peripheral tissues. Dietary Chromium supplementation increases cellular uptake of glucose (Mooradian and Morley 1987). 
Chromium increases glucose tolerance through a Cr-dependent oligopeptide that activates insulin receptor tyrosine kinase activity. This in turns leads to the translocation of glucose transporter-4 from an intracellular vesicular compartment to the plasma membrane, stimulating glucose uptake into skeletal muscle and adipose tissue (Czech and Corvera 1999).
High Chromium Yeast contains a glucose tolerance factor (Mertz 1976). Although the chemical composition and structure of the glucose tolerance factor have not been identified completely.(NRC 1997).
High Chromium Yeast supplementation improved glucose tolerance in elderly subjects  but this effect of high Chromium Yeast supplementation (160 μg Cr/d) was not repeated in elderly subjects with stable impaired glucose tolerance (Uusitupa et al. 1992).
High Cr yeast did not affect either plasma insulin or plasma C-peptide response in elderly subjects (Usitupa et al. 1992). The inconsistent effects of dietary Cr supplementation on glucose tolerance and insulin response may result from uncontrolled factors, such as nutritional, metabolic and stress status.
Peripheral plasma insulin concentration does not precisely reflect insulin secretion although it has been used to indicate insulin secretion in most Chromium studies.
Chromium may affect the hepatic extraction of insulin from the portal blood because chromium was shown to reduce insulin-binding percentage by porcine hepatic plasma membranes (Ward et al. 1994). Increased peripheral insulin concentration may increase glucose uptake by skeletal muscle and adipose tissue.
Improvement in glucose tolerance may benefit the utilization of glucose and improve the long-term efficiency of growth in pigs.
(from The Journal of Nutrition)
On Fish, there has been an increasing interest in the potential effect of dietary chromium on the health of fish, particularly with respect to their metabolism and growth. Information as to the role of this mineral on their immune response, is limited however.
A study was to assess the effects of dietary Chromium Yeast supplementation on the immune response of rainbow trout (Oncorhynchus mykiss):
Juvenile rainbow trout (56 g average weight) were fed three semipurified diets containing different levels of Chromium (1540, 2340 and 4110 ppb), obtained by supplementing a basal diet with 800 or 2570 ppb Chromium Yeast, for 6 weeks. After this, time differences in their immune response were examined.
A positive influence was observed on serum lysozyme activity at this time in fish maintained on the high Chromium diet. The respiratory burst of head-kidney macrophages was also examined, and statistical differences were found in the level of respiratory burst elicited by macrophages from both groups of fish fed supplemented Chromium Yeast after 3 and 6 weeks of feeding (absorbance at 3 weeks: 0.118, 0.166. 0.151 and 6 weeks 0.114, 0.168, 0.151 for the 1540, 2340 and 4110 ppb groups).
Macrophages of fish receiving diets supplemented with Chromium also had a greater ability to phagocytose after 6 weeks than the control fish. The results of the study show that chromium yeast is able to modulate the immune response of rainbow trout, and this effect appears to be both dose- and time-dependent.
Another experiment to evaluate the effect of Chromium on growth, Feed efficiency on fish:
A 60-day feeding experiment was conducted to Labeo rohita fingerlings. Four isonitogenous (crude protein 35%) and isocaloric (4150Kcal/Kg). Experimental feeds were prepared by supplementing different levels of dietary Chromium:
- The control (0.0 mg kg-1),
- T1 (0.4 ppm Chromium),
- T2 (0.8 ppm Chromium) and
- T3 (1.2 ppm Chromium)
* Weight gain WG (%), specific growth rate (SGR), feed efficiency ratio (FER) and protein efficiency ratio (PER) and apparent net protein utilisation (ANPU %) were significantly improved (p<0.05) when Chromium was supplemented at 0.8 ppm. The protein retention (PR %) value increased with the dose of Chromium, showing the highest value in T2 group.
* Chromium supplementation significantly increased (p<0.05) liver glycogen in T1 and T2 groups but decrease was observed at high level of Chromium supplementation in T3 group.
* Chromium supplementation significantly reduced (p<0.05) serum cholesterol and triglycerides in all the experimental groups compared to control showing the highest reduction in T2 group. * Similarly, highest muscle protein as well as lowest liver AST and ALT were observed in T2 group.
The results of the present study indicates that growth, feed utilisation and biochemical parameters in Labeo rohita can be significantly improved by feeding the fingerlings with Chromium supplemented at dose of 0.8 ppm.