For various reasons, many Americans aren't getting enough vitamin D for optimal health. Vitamin D keeps your bones healthy by helping your body absorb calcium, and it plays a role in immune function, regulating cell growth and reducing inflammation. The recommended intake for adults under 70 is 600 international units per day and 800 for those over 70 years old. Vitamin D is found in fatty fish such as tuna and salmon, as well as fortified foods like ready-to-eat cereals. Milk naturally contains trace amounts of vitamin D and is fortified to increase vitamin D content.
Not Getting Enough Sun
Lack of sunlight is the primary cause of vitamin D deficiency, according to a review the American Journal of Clinical Nutrition published in April 2008. Spending too much time indoors, living in a northern climate where sunlight is weaker and less direct, and having darker skin are all factors. Vitamin D is made in your skin when it's exposed to ultraviolet rays, so sunlight in moderation is your body's main source. Vitamin D is found in few foods and typically in small amounts, so you're unable to get enough from food alone.
Being overweight or obese increases your risk of vitamin D deficiency. Scientists aren't completely sure why, but one theory is that carrying extra pounds reduces the amount of vitamin D available in your body. Pregnancy increases your need for vitamin D to support the health of yourself and your baby. Many pregnant women take vitamin D as directed by their doctor before, during and after pregnancy to keep levels sufficient. Older adults represent another population at risk for vitamin D deficiency. Due to thinning skin that comes with age, older adults may have a harder time producing vitamin D.
Symptoms and Testing
While severe vitamin D deficiency may result in pain or weakness in your bones, you may not have symptoms if you have a less severe deficiency. Or, the symptoms may be vague, seemingly unrelated and difficult to pinpoint. Symptoms that you're not getting enough vitamin D include fatigue and general aches and pains. The only way to find out whether you're deficient is to have your doctor test your vitamin D level. A concentration of 20 nanograms per milliliter or higher is adequate for overall health.
How to Get Enough Vitamin D
The two main ways to get enough vitamin D are by increasing your sun exposure or taking dietary supplements. The amount of sun you need depends on your complexion. A fair-skinned person may only need to expose her bare skin for 15 minutes. Talk to your doctor about whether this is a good option for you. Some people, such as those who have or are at risk for skin cancer, must protect themselves from UV ray exposure. If you're unable to get enough sunlight, taking supplements is a good way to meet your vitamin D needs. Talk to your doctor before taking supplements, however.