A. Robert M. Russell, MD, emeritus professor at Tufts Friedman School, answers: You have added an important caveat: You are on this diet for medical reasons, which I take to mean that you have been diagnosed with celiac disease. In patients with celiac disease, it is prudent to be taking a multivitamin-mineral supplement along with following a gluten-free diet. This is because the treated disease, although clinically silent, may still be causing some degree of poor absorption of certain vitamin and minerals. Your doctor will tell you if there is any reason to take more specific, higher-dose vitamins (e.g. vitamin D) or minerals (e.g. iron, calcium), depending on your test results and physical examinations.
In patients without celiac disease who nevertheless follow a gluten-free diet, a multivitamin-mineral supplement is optional. It is very possible to get all the nutrients one needs on a gluten-free diet by making nutrient-dense food choices (colored vegetables, fruits, meat, fish, calcium-rich foods such as milk or fortified products, etc.). Many gluten-free products have not been fortified, so making these right choices is wise.