Getting adequate vitamin D is essential to maintaining healthy bones. Without it, your body wouldn't be able to absorb calcium efficiently. Think of the relationship between calcium absorption and vitamin D as that of a locked door and a key. Vitamin D is the key that unlocks the door that allows calcium to leave the intestines and enter the bloodstream. If you don't get enough vitamin D, the "door" remains locked and your body will simply excrete the calcium without putting it to use.

There are two ways to get vitamin D: from sunlight and from food. Your body (more specifically, your skin) produces vitamin D following direct exposure to sunlight. The amount varies depending on what time of day it is, the season, the latitude and your skin pigmentation. Usually 10-15 minutes of sunlight exposure several times a week to your face, arms and hands is sufficient. Sunscreen, window glass, clothing and air pollution all slow down the body's production of vitamin D – however, this is not to say that you should stop using sunscreen or start walking around without your clothes! Instead, try eating foods that either contain vitamin D naturally (like egg yolks, saltwater fish and liver) or those that are vitamin D-fortified (like milk and other dairy products). A multivitamin can also help you meet your daily vitamin D requirement. Your intake of vitamin D should be between 400 and 800 international units (IU) each day. Do not exceed more than 800 IU (unless directed by your doctor), because large doses of vitamin D can be harmful. Check the charts below to determine how much vitamin D is right for your age as well as how much is contained in certain foods.