While Vitamin D is important to the body in many ways, including brain health, immunity, cardiac function, bone health, and cancer resistance, roughly three-quarters of US citizens are deficient in the sunshine vitamin. How do we know if we’re getting enough?
Vitamin D requirements vary according to age group and which expert you ask. The National Institutes of Health vitamin D fact sheet lists vitamin D requirements for babies under 1 year of age as 400 IU daily, ages 1 to 70 need 600 IU daily while those over 70 need 800 IU daily. However, the Vitamin D Council says that infants need 1000 IU daily, children need 1000 IU per 25 pounds daily, and adults need 5000 IU daily.
Actually it’s difficult to determine a one-size-fits-all dosage for everyone because many variables affect vitamin D levels. Generally, females have lower levels than males and older people have lower levels than young people. People with dark skin are not able to produce as much vitamin D from sunlight as people with light skin. Obese people may have lower levels because excess fat binds some of the vitamin D and doesn’t allow it to circulate in the blood. The same goes for those with celiac disease or Crohn’s disease as their bodies do not handle fat properly. People who have had gastric bypass surgery may be unable to metabolize vitamin D because the area of the gut that processes it has been bypassed. Breast-fed babies get very little vitamin D from breast milk. These groups may be at higher risk of vitamin D deficiency but anyone who eats a poor diet and gets very little sunshine can be deficient in the sunshine vitamin.
It’s impossible to get enough vitamin D from food alone. Salmon, mackerel, tuna in water, eggs, cheese and fortified foods such as milk, plant-based milks, some orange juices, yogurt, margarine, and breakfast cereals contain small amounts. Sunshine is the richest source. Most experts agree that a few minutes of sunlight on the arms and legs several times a week during the middle of the day in summer months is sufficient. According to the Vitamin D Council, the body can produce 10,000 to 25,000 IU of vitamin D in just a little under the time it takes for your skin to turn pink. The great thing about this is that the body only generates what it needs so there is no risk of toxicity. On the other hand, since vitamin D is fat soluble and stored in the body, toxicity has been seen in some cases of patients taking large supplement doses. Vitamin D supplements can also affect some health conditions and/or interact with some medications.
Some dermatologists warn against skin cancer risk from sunlight while other doctors say there is no evidence that moderate amounts of sunlight without sunburn lead to cancer. A free app is available to help you keep track of your daily vitamin D. Developed by vitamin D expert, Dr. Michael Holick, it counts toward your target by applying all the factors that determine how much vitamin D you can get.
The only way to be sure you are getting the right amount of vitamin D is to have a 25(OH)D blood test. Partnering with Heartland Assays, the Vitamin D Council has recently released a home-testing kit. However health organizations vary in what result is considered sufficient. The Vitamin D Council says 40 to 80 ng/ml is sufficient, with 50 ng/ml being ideal, while the Endocrine Society says 30 to 100 ng/ml is sufficient and most testing laboratories call 32 to 100 ng/ml normal. Your doctor can best advise you for your particular health needs.