Vitamin B12 enjoys a reputation as a weight loss aid, but it's one that isn't warranted, according to the Office of Dietary Supplements, or ODS. Weight loss clinics often administer intramuscular B12 injections which purportedly boost your metabolism, and online supplement peddlers allude to the "energy vitamin's" weight loss benefits. Doctors use this vitamin to treat health conditions associated with B12 deficiency; however, vitamin B12's value as a weight loss aid is unproven.
About Vitamin B12
Vitamin B12 is a vital nutrient needed for healthy nerve and red blood cells, as well as DNA synthesis, according to the Mayo Clinic website. This water-soluble vitamin has the unique capacity to store in your body for a number of years, making B12 deficiency uncommon in healthy people. Older individuals, vegetarians and vegans are most at risk for vitamin B12 deficiency. If your body cannot absorb or use the vitamin B12 it has stored, vitamin B12 deficiency can occur. Vitamin B12 deficiency is characterized by constipation, a flagging appetite, weight loss, muscle weakness and fatigue, and sometimes tingling in the hands and feet, states the ODS.
B12 as a Medical Treatment
There's excellent evidence to suggest that vitamin B12 treats pernicious anemia, a condition that prevents normal absorption of the vitamin, as well as megaloblastic anemia and deficiencies caused by inadequate dietary intake of vitamin B12. According to MayoClinic.com, vitamin B12 is administered orally, intramuscularly or intranasally to treat these conditions. However, vitamin B12 injections are sometimes offered to address general fatigue. MayoClinic.com indicates that some evidence exists to suggest that a patient's overall well-being may be enhanced with vitamin B12 injections, but more clinical trials are needed.
Vitamin B12 and Weight Loss
Because vitamin B12 exerts its effect on your metabolism, as well as its use in treating medical conditions caused by vitamin B12 deficiency -- specifically symptoms of fatigue -- the leap of logic is that vitamin B12 increases energy and boosts metabolism in otherwise healthy adults. However, the ODS states that vitamin B12 supplements and injections don't appear to affect your physical performance absent a nutritional deficit. You're unlikely to experience increased energy from vitamin B12 injections, or any form of vitamin B12, unless you had a deficiency to begin with, points out Mayo Clinic nutritionist Katherine Zeratsky.
Recommended B12
The recommended dietary allowance, or RDA, of vitamin B12 for males and females 14 years of age and older is 2.4 mcg, according to the ODS. Pregnant women need 2.6 mcg, and breastfeeding women should get 2.8 mcg. Dietary sources of vitamin B12 include fish, meat, poultry, milk and milk products. Plant-based foods generally don't contain vitamin B12; however, breakfast cereals are often fortified with this vitamin, making these a good choice for vegetarians and vegans.
Bottom Line
Because vitamin B12 is rarely toxic, no safe upper limit is established, states the ODS. However, if you intend to used vitamin B12 to lose weight, tell your treating physician, Zeratsky advises. Vitamin B12 can interfere with the effectiveness of medications you take. The best way to lose weight is to avoid methods that claim to be quick and easy, she says. Eat a healthier diet and incorporate exercise into your lifestyle. If you're concerned that you may not be getting adequate amounts of vitamin B12, consult with your doctor or eat more vitamin B12-rich foods.
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