The effect of selenium deficiency on health remains uncertain, particularly in relation to Kashin-Beck disease. Also, selenium interacts with other minerals, such as zinc and copper. High doses of Se supplements in pregnant animals might disturb the Zn:Cu ratio and lead to Zn reduction; in such treatment cases, Zn levels should be monitored. Further studies are needed to confirm these interactions. In the regions (e.g. various regions within North America) where low selenium soil levels lead to low concentrations in the plants, some animal species may be deficient unless selenium is supplemented with diet or injection. Ruminants are particularly susceptible. In general, absorption of dietary selenium is lower in ruminants than other animals, and is lower from forages than from grain. Ruminants grazing certain forages, e.g., some white clover varieties containing cyanogenic glycosides, may have higher selenium requirements, presumably because cyanide is released from the aglycone by glucosidase activity in the rumen and glutathione peroxidases is deactivated by the cyanide acting on the glutathione moiety. Neonate ruminants at risk of white muscle disease may be administered both selenium and vitamin E by injection; some of the WMD myopathies respond only to selenium, some only to vitamin E, and some to either. It has been suggested that selenium supplementation may help prevent cancer incidence in people, but research has established there is no evidence to support such claims.