Like HowStuffWorks on Facebook!

Ultimate Guide to B Vitamins


Getting Enough B Vitamins

­As you can see, the B vitamins are essential for an astonishing array of life f­unctions. Fortunately, most of us will get all of the B vitamins we need by eating a well-balanced diet. Some people swear by a B-complex supplement every day, but based on the wide variety of foods containing these vitamins, a supplement may not be necessary.

Researchers from the Hope Heart Institute say that up to 30 percent of people over age 50 have lost the ability to absorb adequate vitamin B12 from meat or dairy products. Other people need only 2.4 mg. a day -- the amount found in three ounces of beef -- but researchers recommend that older Americans eat fortified cereal or grains or take a daily vitamin supplement. (If you need extra calories and protein, a supplement drink, containing all the appropriate vitamins, is an alternative.) Check the chart below for a quick, but thorough, look at the basics of the B-complex vitamins:


Recommended Daily Allowance (RDA)* in mg (B12 is in µg) Food Sources Importance When You Take Too Much When You Take Too Little
Thiamine (B1) I=0.3-0.4; C=0.7-1.0; A=1.0-1.5 cereal, bread, meat, rice, yeast, corn, nuts carbohydrate metabolism, nervous system none known beriberi (anemia, paralysis), movement & memory effects
Riboflavin (B2) I=0.4-0.5; C=0.8-1.2; A=1.2-1.8 grains, milk, meat, eggs, cheese, peas maintains skin, mucous membranes, eyes, nerve sheaths None known skin & oral problems, anemia
Niacin (B3) I=5-6; C=0.8-1.2; A=1.2-1.8 meat, milk, eggs, fish, legumes, potatoes healthy skin, nerves & GI tract, metabolism of food flushing, itching, cramps, nausea, skin eruptions pellagra (diarrhea, dermatitis, dementia)
Pyridoxine (B6) I=0.3-0.6; C=1.0-1.4; A=1.4-2.0 organ meats, brown rice, fish, butter, soybeans metabolism of food, amino acids nerve damage skin & nerve damage, confusion, mouth irritation
Folic acid (B9) I=25-35; C=50-100; A=150-180 yeast, liver, green vegetables, whole grain cereal DNA, hemoglobin synthesis, formation of blood cells, protein metabolism convulsions, disrupted zinc absorption anemia, mouth irritation, poor growth
Pantothenic acid N/A; made by our intestines meats, legumes, whole-grain cereals breakdown of carbohydrates, lipids, amino acids diarrhea none known
Biotin N/A; made by our intestines beef liver, egg yolk, brewer's yeast, mushrooms functions as coenzyme in caroboxylation reactions none known scaly dermatitis
B12 I=0.3-0.5; C=0.7-1.4; A=2.0 liver, meat, eggs, poultry, milk metabolism of food, blood cell formation, DNA synthesis none known pernicious anemia, mouth irritation, brain damage

*I=infant; C=child; A=adult. Please note that vitamin ranges account for differences in age and gender. Some of the vitamins should be increased during pregnancy and for lactating mothers.

For more information on vitamins and related topics, check out the links on the next page.


More to Explore