We are rapidly approaching the shortest day of the year. This means our opportunity for adequate sun exposure is shortened. Although excessive sun exposure to the skin can cause skin damage and increase the risk of skin cancer, some limited sun exposure is important for vitamin D metabolism.
Vitamin D is a fat soluble nutrient necessary for proper calcium and phosphorus homeostasis and ultimately bone metabolism. Fortunately, the bone disease known as rickets is rare due to the availability of vitamin D in our diet. However, osteoporosis is common. Adequate calcium and Vitamin D intake can promote bone health. How much vitamin D do you need and how can you get it?
Proper levels of vitamin D are dependent on dietary intake and sun exposure. Vitamin D levels tend to fluctuate depending on the changes in the seasons. Generally it is recommended that between 5-30 minutes of sun exposure twice a week is adequate. The amount of skin exposed and skin pigmentation can be factors to consider when determining the amount of exposure. Darker skin and less skin exposed will require longer time in the sun. Sun block can inhibit the beneficial effects of sun in vitamin D metabolism.
Interestingly, there are few foods that naturally contain vitamin D. Fish like salmon, tuna, mackerel, and fish oils along with eggs, beef liver, and mushrooms are natural sources of vitamin D. However, the major source of vitamin D is foods that are fortified with vitamin D like milk, juices, yogurt, cheese, and cereals. Milk has up to 100 units per cup. Vitamin D supplements over the counter generally have 100-400 units and many are combined with a calcium supplement.
There is some difference in opinion about whether vitamin D levels need to be checked routinely. The US Preventive Services Task Force recently concluded that there is not enough evidence to show a benefit to having routine levels of vitamin D checked in otherwise healthy people. There is controversy about what the normal levels actually are. In addition some of the claims made about benefits for the heart and circulation have not been substantiated. Also, since the levels measured in the blood fluctuate, it is difficult to monitor response to treatment with vitamin D.
Bone strength and health can be supported by taking adequate vitamin D and calcium. The recommended daily allowances for Vitamin D are at least 600 units for adults up to age 70 and at least 800 units for those over 70. Some people take large doses of vitamin D, but 4000 units daily is considered the maximum safe dose. Calcium supplements are available combined with Vitamin D. Calcium supplements with 500-600 mg calcium combined with 400 units of vitamin D taken twice daily will generally provide adequate amounts of these nutrients. This is especially beneficial for women in their menopause to help prevent complications of osteoporosis.
You can help keep your bones healthy with regular activity, limited sun exposure, and a diet that includes calcium and vitamin D. Stay healthy my friends.
By: P. Michael Shattuck, M.D. – Community Health Network Family Physician
