Good nutrition keeps the mind and body sharp during our twilight years.

That’s especially true with vitamin B12. It is crucial for warding off dementia, depression, anemia and nervous system problems. For seniors, it can be particularly hard to maintain healthy levels of B12. That’s because the body tends to get worse at absorbing B12 as we age. Medications commonly taken by seniors can also impede B12 absorption.

So, for seniors, monitoring B12 levels is crucial. A recent study by Canadian researchers looked at the prevalence of B12 deficiency among new residents at nursing homes, and then assessed it a year later. The findings were published in the journal Applied Physiology, Nutrition, and Metabolism.

The researchers found that seniors who change their living arrangements and their doctors have a heightened risk of B12 deficiency. Among the 412 residents included in the study, nearly 14 percent were low in B12 when they moved into a long-term care facility. About 38 percent of them had levels that were not quite deficient, but less than ideal. Fewer than half of the people in the study — almost 48 percent — had normal B12 levels.

But there was marked improvement within the group after a year in long-term care: The number of seniors with a B12 deficiency had been cut in half.

The study also revealed an interesting detail about B12 supplements: People taking them orally were less likely to be deficient than those who got B12 injections.

Still, it’s better to keep B12 levels up with a healthy diet. By getting plenty of the vitamin from natural sources such as seafood, dairy, poultry and meat, you can skip the shots and pills.