PHILADELPHIA (CBS) – Researchers at the Mayo Clinic say vegans may be low on certain important nutrients.

Doctors say people who eat a strict plant-based diet, excluding all meat, dairy, fish and eggs, should have their levels of B-12, Iron, Calcium and other nutrients closely monitored.

“We found that some of these nutrients, which can have implications in neurologic disorders, anemia, bone strength and other health concerns, can be deficient in poorly planned vegan diets,” says Heather Fields, M.D., Community and Internal Medicine at Mayo Clinic.

The study found that some vegans rely heavily on processed foods and may not eat a sufficient variety of fruits, vegetables and whole grains.

Contrary to popular belief, she says, “Vegans have not been shown to be deficient in protein intake or in any specific amino acids.”

The review was recently published in the Journal of the American Osteopathic Association.