Large dose of vitamin B12 can provide quick burst of energy
DEAR DOCTOR: I’m almost 90 years old and always tired. I took two capsules of 2,000 mcg vitamin B12 the other night, and felt stronger and not as tired. Is it safe?
DEAR READER: My first thought is that you might have B12 deficiency, caused either by inadequate intake or by inadequate absorption of B12. Animal products such as meat, dairy and eggs are the only sources of B12 in humans, and the recommended daily allowance is 2.4 micrograms per day. The average intake of an individual in the United States is approximately 3.4 micrograms per day, but if you follow a vegan diet, you obviously lack sources of B12.
If your intake is sufficient, it may be your ability to absorb B12 that is compromised. This can occur if you have inflammation of your stomach lining or disorders of the small intestine, such as Crohn’s disease. Antacids and proton pump inhibitors such as Prilosec, Protonix, Prevacid, Aciphex, Zantac and Pepcid also can lead to deficiency.
Also, age can be a risk factor for B12 deficiency. Significant B12 deficiency can lead to anemia, nerve damage and
dementia.
Many of my patients, who are not B12 deficient, feel greater energy and improvement of their health with B12 injections. I am not certain why this happens, and it doesn’t appear to have a lasting effect. It is possible that extra amounts of B12 can improve the metabolic function and allow the vitamin to be utilized better.
Water-soluble vitamins, like B12, can be tolerated at higher doses without adverse effects upon the body, and the National Academy of Medicine has not established an upper limit of vitamin B12 intake.
Before continuing the B12, I would recommend getting your levels tested with your doctor. If you show a deficiency, your doctor may want to investigate and gauge how much of the vitamin you might need.
Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.
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