Short days, heavy coats, and indoor routines make winter in Massachusetts a prime setting for low vitamin D. Because our skin synthesizes vitamin D from sunlight, levels often drop in late fall and winter, especially at northern latitudes. While mild deficiency may be silent, a notable dip can show up as fatigue, generalized aches, low mood, frequent colds, or slow bone healing. Over time, deficiency increases the risk of bone loss and fractures. This guide ...