Vitamin D is essential for intestinal calcium and phosphorous absorption. Ergocalciferol (Vitamin D2) is a vegetarian form of vitamin D. Magnesium works with calcium and other minerals in bone formation. Moreover, it is involved in over 300 enzymatic reactions, including in energy (ATP) production, as well as cardiac and smooth muscle contractions. HEALTH CLAIM: Adequate calcium and vitamin D as part of a healthful diet, along with physical activity, may reduce the risk of osteoporosis later in life.