Douglas Laboratories Ultra Preventive X - 120 Tablets Douglas Laboratories Ultra Preventive X now contains Metafolin, a patented, natural form of (6S) 5-methyltetrahydrofolate (5-MTHF) as well as 1,000 IU of vitamin D3 per serving. 5-MTHF is the naturally occurring, predominant form of folate commonly found in cells and is essential for overall health, as it participates as a cofactor in a reaction that involves the remethylation of homocysteine to methionine. Unlike synthetic folic acid, 5-MTHF can be used directly by the body, without the need for an additional conversion via the enzyme (5,10-methylenetetrahydrofolate reductase (MTHFR)). In certain populations, the body's ability to convert folic acid to 5-MTHF by use of this enzyme may be compromised due to genetic differences. Metafolin contains only the S isomer of 5-MTHF and has been shown to be the only form of folate to be able to cross the blood-brain barrier. Additional vitamin D3 (also known as cholecalciferol) has been added to this formula as numerous scientists now feel that supplementation with vitamin D at levels greater than previously thought necessary is critical to helping maintain overall health. Studies show that a high percentage of adults in North America and other developed areas eat less than the minimum daily allowance of 10 or more essential nutrients. Adequate amounts and proper balance of these nutrients are needed not only for maintaining good health, but also for the dietary management of the body's structure as well as the optimum functioning of its various systems, including the immune and gastrointestinal systems. Ultra Preventive X has been carefully developed to contain the right proportions of vitamins, minerals, trace elements, and other nutrients without danger of toxic build-up or other side effects.