Calcium intake- especially during periods of rapid growth, pregnancy, and lactation - is important in the prevention of osteoporosis, and vitamin D is crucial to its absorption. Vitamin D is synthesized in the skin under the influence of sunlight. Encouraging people to go outside for 15 a day may help them to intheir body stores of the vitamin. This daily exposure coupled with two glasses of milk enriched with vitamin D are the best sources of calcium. More is not necessarily better, though. Excess amounts of vitamin D compete with calcium and have even been associated with bone loss [The GNP Newsletter. 1990; 27:1,2].