What the research says

Research on the use of vitamin B-12 for specific activities and conditions shows:

• Heart and blood vessel disease. People with heart and blood vessel disease, also called cardiovascular disease, may have high levels of a compound called homocysteine. Vitamin B-12 and other B vitamins may help lower homocysteine levels. But researchers haven't found that lowering homocysteine levels lowers the risk of heart and blood vessel disease.
• Athletic performance and increasing energy. There's no proof that taking vitamin B-12 supplements or injections boosts energy or improves athletic performance.