Previous studies have used single vitamin D measurements to investigate effects on bone. (sciencedaily.com)
Single vitamin supplements became available in the US in the 1930s, and multivitamins went on sale a decade later. (newscientist.com)
There are also many different types of supplements, such as multivitamins, omega fats, single vitamins like vitamin D, single nutrients like magnesium, and so much more. (mindbodygreen.com)