Dear Doctors: I have read that older adults may not get enough vitamin D in winter. My father-in-law is 73. He’s from Florida but spending a year with us in Maine. He can’t be outdoors all the time like he is at home. How important is vitamin D? How do we know if he’s getting enough?
Answer: Vitamin D is often referred to as the “sunshine vitamin.” It’s essential to human health and well-being and is produced by the body in response to exposure to sunlight.
It helps the body absorb calcium and maintain proper blood levels of calcium and phosphorus — functions critical to the growth and maintenance of healthy teeth and bones.
Research shows the vitamin also has an anti-inflammatory effect, helps fight infection and can reduce cancer cell growth in some situations.
Vitamin D receptors are found throughout the body and in several organs. This suggests additional roles for the nutrient that haven’t been identified.
Children, teenagers and adults up to 70 are advised to get 600 international units, or IU, a day of Vitamin D. Absorption becomes less efficient as we age, so older adults are advised to get 800 IU. For infants up to 12 months old, the recommendation is 400 IU daily.
While the nutrient is found in foods such as fatty fish, beef liver, egg yolks, cheeses and some mushrooms, most people don’t eat enough of these to fulfill our daily requirement. So some prepared foods are fortified with the nutrient, like dairy products, many breakfast cereals and some brands of orange juice.
Then, there’s sunshine. Ultraviolet rays in sunlight hitting the skin trigger a chemical reaction. With an assist from the kidneys, liver and other cellular structures, our bodies manufacture vitamin D.
For those with light skin, 15 to 30 minutes of full sunlight on bare arms, legs or torso at least two or three times a week will do the trick. Melanin offers a protective effect, so people with darker skin need longer exposure.
People with any kind of history or risk of skin cancer should rely on diet and supplements.
Clothing and sunscreen either partially or completely block UV light, which hinders or prevents vitamin D formation. In northern latitudes, with shorter days, weaker sunlight and weather that keeps people indoors, getting enough vitamin D naturally can be a challenge.
You can learn your vitamin D status with a blood test. If it’s low, a doctor can offer guidance.
Dr. Eve Glazier and Dr. Elizabeth Ko are internists at UCLA Health.
