If neglected, vitamin D insufficiency can result in rickets in children, osteoporosis in adults, and negative effects on pregnant women. Although additional research is required, it may also be connected to cancer, diabetes, and heart disease. neurological symptoms and vitamin D insufficiency Numerous neurological issues, such as weariness, memory loss, and difficulties focusing, can be brought on by vitamin D insufficiency. This means taking a vitamin D supplement to correct a vitamin D deficit may help you focus better.