Vitamin B-12 is most likely ineffective at repelling mosquitoes, according to Joe Conlon, an adviser for the American Mosquito Control Association. Despite claims to the contrary, double-blind scientific studies show no evidence whatsoever that taking B vitamins helps to make humans less attractive to mosquitoes.
Vitamin B-12 is crucial for healthy red blood cells and nerve cells. A deficiency of vitamin B-12 can lead to muscle weakness, memory problems and fatigue, as stated by WebMD. The recommended dietary allowance of vitamin B-12 for men and women 14 years of age and older is 2.6 micrograms per day. High doses of vitamin B-12 do not appear to be dangerous, but they may cause acne. Good food sources of vitamin B-12 include meats, fish, poultry, dairy products and fortified cereals.