Vitamin D is made from cholesterol. Your body must have vitamin D to absorb calcium and promote bone growth. Too little vitamin D results in soft bones in children (rickets) and fragile, misshapen bones in adults (osteomalacia). You also need vitamin D for other important body functions. It helps regulate the immune system and the neuromuscular system. Vitamin D also plays major roles in the life cycle of human cells. Saturated fats and cholesterol are very important for the human body and should not be avoided. Grains, sugar and industrial seed oils, however should be avoided for optimal health.