With the days getting shorter, we started freaking out about becoming vitamin D deficient, and the SAD lamps were coming out of storage. But how common is that and what does it mean for your health? We ask the experts.
Vitamin D deficiency (which is exactly what it sounds like: a suboptimal level of vitamin D in your body) is often confused with Seasonal Affective Disorder (SAD). And it’s easy to see why: both conditions have similar symptoms like fatigue and depression and research shows that low levels of vitamin D might contribute to SAD. But vitamin D deficiency can have long-term consequences for your health, while SAD is a mood disorder that is most commonly linked to symptoms only during certain times of the year.
So what exactly is Vitamin D? “Even though we call it a ‘vitamin,’ vitamin D is actually more of a hormone, so it acts as a chemical messenger in the body,” explains Dr. Marilyn Tan, clinic chief at the Endocrine Clinic at Stanford Healthcare. “It’s most critical for bone health and maintaining calcium levels in the body but there’s a lot of interest in [vitamin D’s role in] other conditions like diabetes, heart disease, cancer, depression, and even COVID-19.” (A study published in March 2021 found that people who had tested positive for COVID-19 were more likely to also have low vitamin D levels, but Dr. Tan cautions that this is extremely preliminary research. “Causation and correlation are different things,” she says, meaning more research is needed before any definite links can be established.)
It’s hard to estimate exactly how many people are vitamin D deficient since most people aren’t getting regularly tested Dr. Tan explains. One recent study estimated that of the U.S. adult population, 40 percent aren’t getting enough vitamin D. “We know that there are higher rates if your skin is darker,” Dr. Tan adds. That same study found that vitamin D deficiency was more common among Black people (82 percent) and those of Hispanic descent (63 percent).
Here’s everything you need to know about vitamin D deficiency this winter.
Sources of vitamin D
While vitamin D is found in many food sources (think: fish and eggs, plus vitamin-D fortified foods like milk, orange juice and cereal) the main way our bodies get vitamin D is by actually producing it using sunlight. People with light skin and those under 50, tend to produce more vitamin D this way, according to the Cleveland Clinic. This is why vitamin D deficiency is most often linked with the cold, dark winter months when time in the sun isn’t as common.
Should you get a vitamin D test?
So, how do you know if you’re D deficient? Unfortunately, “the most common symptom is that it’s asymptomatic,” says Dr. Tan. Vitamin D deficiency typically presents as fatigue, muscle weakness, or depression — all things you might write off as the result of a stressful period at work or case of SAD, rather than a vitamin deficiency.
The lack of symptoms doesn’t mean, it’s a-okay to live with vitamin D deficiency forever. “In the long-term, there are health issues that can be associated with disruptions of this calcium and vitamin D balance, most notably osteoporosis,” says Dr. Tan. It’s also been linked to heart disease and high blood pressure, diabetes, and certain types of cancer including prostate and breast cancer, according to the Cleveland Clinic.
Even given the risks, doctors don’t always agree about how often you should get tested. “There are two schools of thought,” explains Dr. Tan. Some doctors advocate that it’s worth getting regularly screened via a simple blood test because it’s an easily detectable, treatable contributor to disease. “However, there is also a concern that universal screening creates a lot of unnecessary healthcare costs,” she says since there is a wide range of individual risk factors. For example, if you are a light-skinned person living in Florida where you get plenty of sunlight year-round, you’re much less likely to be vitamin D deficient than a dark-skinned person living in Minnesota, where you might spend a large portion of your year cooped up inside. “I think it’s something to talk about with your doctor,” says Dr. Tan.
How to boost your vitamin D levels
How much vitamin D is enough? It doesn’t take as much time in the sun as you might think — “Ten or 15 minutes of exposure [per day] is sufficient for the average person,” says Dr. Tan. (More than that and you’re opening yourself up to another health risk: cancer-causing UV rays.)
If your vitamin D levels are low, your doctor might suggest a supplement. The Health and Medicine Division of the National Academies of Sciences, Engineering, and Medicine recommends getting 600 IU in your diet each day. But beware: it is possible to take too much Vitamin D. “There can be vitamin D toxicity, which can lead to high calcium levels and other consequences,” says Dr. Tan.
Vitamin D is a fat-soluble vitamin, she explains, which means it can last in the body for a long time (unlike a water-soluble vitamin, any excess of which is simply eliminated when you pee). The maximum daily recommended amount of Vitamin D is 4,000 IU, according to the Health and Medicine Division of the National Academies of Sciences, Engineering, and Medicine. More than that can cause hypercalcemia, a buildup of calcium in your blood. In the short-term, it can cause nausea and vomiting, but long-term it can cause more serious consequences like kidney stones. This is why it’s so important to talk to your healthcare provider before taking any new supplements.
And what about SAD lamps? “SAD lamps, or phototherapy, haven’t been well-studied for vitamin D deficiency,” says Dr. Tan. If you think you might be vitamin D deficient, you’re better off talking to your doctor about the best supplement.
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