Why do I need B vitamins?
B vitamins are an important class of vitamins that help support your red blood cells and your nervous system. Some of the benefits are already well known. Women who are pregnant or planning to become pregnant need plenty of folic acid -- also known as vitamin B-9, or folate -- to prevent a serious type of birth defect known as neural tube defects (these include spinal bifida.) B vitamins are also important for energy levels.
The vitamins also provide a host of other benefits. Among other things, vitamin B6 helps keep blood sugar within a normal range, vitamin B12 protects against anemia, and folate (folic acid) helps prevent changes to your DNA that could lead to cancer.
How much should I be getting?
According to the latest guidelines, most adults should get 400 micrograms of folic acid a day, pregnant women should get at least 600 mcg, and breast feeding women should get 500 mcg. Younger adults need 1.3 milligrams of B-6; after age 50, women need 1.5 mg and men need 1.7 mg. adults need 2.4 micrograms of B-12. Pregnant and lactating women need a little more of both.
What are the best food sources?
Leafy green vegetables, citrus fruits, orange juice, liver, and dried peas and beans are all good sources of folate. All enriched grains -- most notably white flour and white rice -- are now fortified with at least 100 mcg of folic acid per serving. B-6 is found in meats, fruits, and vegetables. One banana will give you a third of what you need for the day. B-12 is found in meat, fish, and dairy products. Vegans can find it in brewer's yeast.
Should I take a supplement?
If you're pregnant or even considering the possibility of having a baby, you should definitely take extra steps to make sure you're getting enough folic acid. For most, that means a prenatal vitamin or multivitamin. The next best alternative would be a daily bowl of fully fortified cereal, such as Total.
Older people may need a supplement to get enough B-6 and B-12. About half of people over age 50 eventually fall short on these two vitamins, partly because they have trouble absorbing them from their food. People who are strict vegetarians or who have a digestive problem such as Crohns disease or celiac disease may have trouble getting enough B-12 into their systems. Again, multivitamins can likely make up for the shortfall. Some older people may need to get injections of B-12.
Can I get too much?
A multivitamin contains safe levels of all three B vitamins. Too much folic acid can mask a B-12 deficiency, however, which can cause nerve damage.
It's not possible to overload on the folate naturally found in foods. But since folic acid is in so many different foods and supplements, some experts worry that people who aren't pregnant may be getting too much. At least one has recommended alternate eating vitamin-enriched cereal and taking a daily multivitamin, just to be on the safe side.
Too much B-6 can cause nerve damage, but it takes a lot. The NIH says that adults can safely get 100 mg, which is more than 50 times the recommended daily allowance.
B-12 has never been shown to be dangerous at any level.
National Institutes of Health. Office of Dietary Supplements. Vitamin B12. 2010. http://ods.od.nih.gov/factsheets/VitaminB12-QuickFacts/
National Institutes of Health. Office of Dietary Supplements. Vitamin B6. 2007. http://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/
National Institutes of Health. Office of Dietary Supplements. Folate. 2009. http://ods.od.nih.gov/factsheets/folate/
Mayo Clinic. Vitamin deficiency anemia. Causes. 2009. http://www.mayoclinic.com/health/vitamin-deficiency-anemia/DS00325/DSECTION=causes