Brain tumor research is a relatively modern science that parallels the explosion of molecular biology and modern neuroimaging. While the science is new, Mayo Clinic has a long history of brain cancer treatment and research stretching back over 100 years.
But not all vitamins are water-soluble, and the ones that are lipid-soluble, meaning they like to hang around in your body's fat, don't get flushed out. Instead, if you take too much of a lipid-soluble vitamin over a few weeks to a month, they sit in the liver and can build up to toxic levels, causing problems ranging from weak bones to liver damage, according to Katherine Zeratsky, a registered dietician nutritionist at the Mayo Clinic.
As Vitamin D is a fat soluble vitamin, it is possible to accumulate too much of it through oral supplementation. Your body has natural regulatory mechanisms in place to ensure that you never create more Vitamin D from sunshine than you need, but when you supplement with Vitamin D, you override this.