Discount brokerages require a minimum age of 18. However, you can create a sub-account under your dads name (as long as he signs some sort of consent form) and these sub-accounts don't have a minimum age requirement.
Vitamin D deficiency rickets can be caused by a lack of vitamin D in the diet, a lack of exposure to the sun, or malabsorption syndromes in which there is an inability of the intestines to adequately absorb nutrients from foods.
A more severe lack can cause serious problems such as rickets (in children) and osteomalacia (in adults), described below. Treatment is with vitamin D supplements. Some people are more at risk of vitamin D deficiency, and so are recommended to take vitamin D supplements routinely. lack of vitamin D is very common. Vitamin D is mostly made in the skin by exposure to sunlight. Most foods contain very little vitamin D naturally, though some are fortified (enriched) with added vitamin D. A mild lack of vitamin D may not cause symptoms but can cause tiredness and general aches and pains.