Vitamin B3 is a water-soluble vitamin which is part of the vitamin B complex. Like all B vitamins, niacin helps your body convert food to the energy it needs. Vitamin B3 plays an important role in controlling and lowering cholesterol levels. In addition, most diabetic patients are better able to control their blood glucose levels with the help of vitamin B3, while also lowering their risk of high blood cholesterol and heart disease, two problems that are commonly seen in patients with diabetes. Vitamin B3 is found in a range of foods, but especially good sources include chicken, fish, brown rice, avocado and peanuts.