(HealthDay News) -- Vitamin B-12 is an essential vitamin that supports the nervous system, creation of red blood cells and production of DNA. It's primarily found in seafood, meat and dairy products.

If you have low levels of vitamin B-12, it could be because you're not eating enough of these products, or you're having trouble absorbing the vitamin from foods.

The American Academy of Family Physicians says possible reasons for poor absorption of vitamin B-12 include:

• An illness known as pernicious anemia, which kills stomach cells that absorb this vitamin.
• Crohn's disease, celiac disease or other intestinal problems that affect absorption.
• Abnormal growth of bacteria in the stomach.
• A side effect of prolonged use of certain drugs, including those that help manage heartburn or ulcers.
• A prior surgery on the intestines or stomach.