D3 (cholecalciferol): Comes from animals Research suggests that D3 may be more effective in raising and maintaining vitamin D levels. When purchasing vitamin D supplements, be sure to purchase ...

Another key difference between the two forms of vitamin D is their source. “Vitamin D2 is usually produced by plants when exposed to sunlight,” Dr. Jiang says. Meanwhile, vitamin D3 is found in animal ...

For reference, a 3-ounce portion of rainbow trout contains about 16 mcg of vitamin D, while a cup of vitamin D-fortified milk contains about 3 mcg, per WebMD. Other foods high in ...