Rare side effects can include diarrhea and excessive urination, but a more common side effect is Gatorade-colored urine: "Vitamin B2 supplementation is considered to be very safe," says Slavin.

The two types of water-soluble vitamins are vitamin C and B vitamins. Excess water-soluble vitamins ... B3 helps maintain normal nervous system function, and B2 keeps your skin and eyes healthy.

Your body needs vitamins A, C, D, E, K, and the eight B vitamins: thiamin (B1), riboflavin (B2 ... weak bones (vitamin D deficiency), muscle problems (vitamin E deficiency), or excess bleeding ...