Vitamin D is different from any other vitamin. If you get enough exposure to the sun, your body makes all the vitamin D it needs. Imagine how wonderful the warmth of the sun feels on your skin. Now consider that as you are basking in the rays, you are fortifying your body with this important nutrient. Sounds like time well spent to me!
Why is Vitamin D Important?
Vitamin D is essential for bone health. Vitamin D and calcium work together to keep your bones strong. When vitamin D is lacking, only about 10-15% of your dietary calcium is absorbed by your body. Your body needs adequate vitamin D for calcium to do its job.
Vitamin D has other roles in the body too. It aids in cell growth, the immune system and reducing inflammation in the body. There is also some evidence that getting enough vitamin D may lower your risk of certain cancers, including those of the colon, breast, prostate, skin, and pancreas.
How much Vitamin D do You Need?
According to the Office of Dietary Supplements, http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/ : the following amounts are recommended:
Male and female aged 1-70: 15 mcg/day (600 IU)
Male and female over 70: 20 mcg/day (800 IU)
Sources of Vitamin D
You can get the required amount of vitamin D solely from sun exposure, but here are several factors to consider:
- Exposure of arms and legs for 5 to 30 minutes, between 10 a.m. and 3 p.m., twice per week is generally adequate.
- Sunscreen almost entirely blocks the ultraviolet light necessary for your body to make vitamin D.
- The sun delivers more radiation in the summer months.
- The sun delivers different amounts of radiation depending on where you live. Areas closer to the equator have more intense sunlight.
- 80% or more of the sun’s UV rays penetrate clouds but window glass blocks these rays.
- Lighter skinned people absorb these rays more quickly than darker skinned people.
- People over 70 years of age have a 75% reduction in their ability to produce vitamin D through sun exposure. This is why they require more vitamin D in their diet.
- Infants are born with stores of vitamin D that last about 9 months.
A rule of thumb is to expose your hands, arms and face to the sun for about one-third the time it would take you to burn. Doing this two to three times per week should provide you with adequate vitamin D. (Disclaimer: This rule of thumb is stated in my Nutrition book, but please be careful exposing your unprotected skin to the sun for any amount of time. My dermatologist would be very disappointed in me for suggesting you do this for even a minute. I’m just stating the facts as I have learned them and everyone can make their own choices.) Now back to the learning!
You can get adequate vitamin D through your diet as well, however, few foods naturally contain this nutrient. For this reason, many foods are fortified with vitamin D including milk, breakfast cereal, orange juice, yogurt and breads and grains.
Vitamin D is found naturally in oily fish (such as swordfish and salmon) and in fish oils (such as cod liver oil). Egg yolk, butter and liver also supply some vitamin D, but the amount depends on the amount of vitamin D consumed by the animal source.
Plants are a poor source of vitamin D.
Vitamin D Deficiency
In adults, a deficiency can cause a skeletal problem called osteomalacia or “soft bones” and also contributes to osteoporosis.
Besides skeletal issues, vitamin D deficiency has been linked to increased risk for cardiovascular disease, multiple sclerosis, rheumatoid arthritis and type I diabetes.
Vitamin D Toxicity
Vitamin D is a fat soluble vitamin and like most other fat soluble vitamins, your body stores the excess in the liver for future use. If you consume too much, you can exceed the liver’s storage capacity and vitamin D becomes toxic in your body.
Sun exposure does not cause vitamin D toxicity, but high supplement doses can.
Vitamin D toxicity is severe and causes a condition called hypercalcemia, which is a high concentration of calcium in the blood. This affects many tissues in the body and can result in bone loss, kidney stones and can affect the central nervous system.
Large doses of vitamin D should only be taken under a physician’s supervision.
Insel,P., Ross,D., McMahon,K., Bernstein,M., Nutrition Fourth Edition. Burlington: Jones & Bartlett, 2013