B-12 and weight loss

Recently, vitamin B-12 has been linked to weight loss and energy boosts, but are these claims for real? A lot of doctors and nutritionists lean toward no.

Vitamin B-12 plays a major role in a number of the body’s essential functions, including DNA synthesis and the formation of red blood cells. It also helps the body convert fats and proteins into energy and aids in the breakdown of carbohydrates.

B-12 deficiency can lead to several ailments, most notably megaloblastic anemia, which is caused by a low red blood cell count. The most common symptom of megaloblastic anemia is fatigue. This form of anemia, as well as other health issues associated with B-12 deficiency, can be easily treated with injections of the vitamin.

Claims that B-12 can boost energy and aid in weight loss come from the incorrect assumption that the effect it has on people with megaloblastic anemia will be the same in people with normal levels of vitamin B-12.

Most people get vitamin B-12 through their food. The vitamin is naturally present in certain animal protein-based foods, such as:

  • shellfish
  • meat and poultry
  • eggs
  • milk and other dairy products

Vegetarian sources of B-12 include:

  • certain plant milks that are fortified with B-12
  • nutritional yeast (seasoning)
  • fortified cereals

Since most B-12 sources are derived from animal-based sources, deficiency is common among vegetarians and vegans. If you don’t eat meat, fish or eggs, eating fortified foods or taking a supplement may be recommended.

Other groups of people at risk for B-12 deficiency include:

  • older adults
  • people who are HIV-positive
  • people who have undergone gastrointestinal surgery
  • people with certain digestive disorders, specifically Crohn’s disease and celiac disease
  • people taking proton-pump inhibitors or other stomach-acid reducers for longer than 2 years

Celiac disease is the autoimmune disorder that causes gluten intolerance. Older adults — or those who have undergone stomach surgery — generally have lower levels of stomach acid. This can result in reduced B-12 absorption from animal protein and fortified foods.

For these people, B-12 found in supplements might be a better option if available in a sublingual or injectable form. These forms do not require the same digestive action for B-12 absorption as the form available in whole foods or fortified foods. Also, people who take the diabetes drug metformin are at higher risk for B-12 deficiency.


There are many ways for people at risk for B-12 deficiency to add more of the vitamin to their diet. Like just about any vitamin and mineral on the market, B-12 supplements are available in pill form at supermarkets and pharmacies. B-12 is also present in vitamin B-complex supplements, which combine all eight of the B vitamins into a single dose.

You can get larger doses of B-12 through an injection, which is the way weight loss facilities often administer the supplement. This form does not depend on the digestive tract for absorption.

Doctors typically suggest injections of higher-than-average doses of B-12 for people diagnosed with megaloblastic anemia and other health problems associated with a B-12 deficiency. This type of injection often requires a doctor’s prescription.


Foods where B-12 is not naturally present, such as breakfast cereals, can also be “fortified” with the vitamin. Fortified foods can be useful for people who are at risk for deficiency, such as vegans, due to low intake from their food supply.

Those with physiological changes — such as reduced stomach acid levels and/or abnormal digestive function — still may not be able to prevent a B-12 deficiency by eating fortified foods. Check the nutritional information on food labels to see if it’s been fortified.

The National Institutes of Health (NIH) recommends 2.4 micrograms (mcg) of vitamin B-12 per day for anyone over the age of 14. This recommended daily intake may also increase for those with decreased absorption. There’s no difference in the recommended intake for men and women. Pregnancy increases the recommended dose for women, both during the pregnancy as well as after if the mother chooses to breastfeed her child.

As any doctor or nutritionist will tell you, there’s no magical weight-loss cure. Those looking to adopt a healthier lifestyle or drop some pounds should be wary of supplements that claim to help you lose weight without proper lifestyle changes to affect your diet and exercise routine.

Thankfully, there are no reported risks in taking large doses of vitamin B-12, so those who have tried injections to lose weight have no need to worry.

However, there’s also no reported evidence to support the claim that vitamin B-12 will help you lose weight in those without a deficiency. For those with a diagnosed deficiency, B-12 treatment may improve energy levels which could in turn increase activity and promote weight management.