Avoiding too much sun and using sunscreen regularly are good habits, right? Yes, but. Though both practices will reduce your chances of skin cancer, they also have a potential downside that could play out as you age: Researchers at Duke-NUS (National University of Singapore) Medical School and Duke University have recently found a link between low vitamin D levels and increased risk of cognitive decline and impairment. In the first large-scale study in Asia to assess the association between vitamin D status and risk of cognitive impairment in the Chinese elderly, researchers studied 1,202 subjects who were 60 years of age or older. Low vitamin D levels signaled significant cognitive decline over time.
In the study, which appeared in The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, the subjects’ vitamin D baselines were recorded at the start of the study, and their cognitive abilities were assessed over the next two years. Regardless of gender and extent of advanced age, individuals with lower vitamin D levels at the start of the study were approximately twice as likely to exhibit significant cognitive decline (a decrease in cognitive score) over time. In addition, low vitamin D levels at the beginning of the study also increased the risk for future impairment (a drop in score indicating significant functional loss, likely dementia) by two-to-three times, the study found.
The concern about diminishing vitamin D levels in humans isn’t new. Scientific American reported in 2009 that a vitamin D deficiency among Americans was a growing problem, significant and alarming, especially among the African-American population. Citing results from a 2009 University of Colorado Denver School of Medicine (UCDSM) study, the magazine reported that in 2004, when data was collected as part of a federal government’s national health survey, just 23 percent of 13,369 people surveyed had a sufficient amount of vitamin D in their system (and only 3 percent of African-Americans did), compared to 45 percent between 1988 and 1994.
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“We were anticipating that there would be some decline in overall vitamin D levels, but the magnitude of the decline in a relatively short time period was surprising,” said the UCDSM study’s co-author Adit Ginde, then an assistant professor at that institution. Ginde linked vitamin D deficiency to catching more colds, and blamed the change on skin cancer prevention campaigns that resulted in an increased use of sunscreen and people wearing long sleeves. Using a sunscreen with as little as 15 SPF cuts the skin’s vitamin D production by 99 percent, the study noted. “We’re just starting to scratch the surface of what the health effects of vitamin D are,” Ginde said in the report. “There’s reason to pay attention for sure.”
Fast forward to 2016 and the news gets worse. We’ve known for decades that vitamin D is necessary for maintaining healthy bones and muscles, but with more research it appears that it also plays a significant role in maintaining healthy brain function. David Matchar, M.D., co-author of the Singapore study and professor and director of health services research at Duke-NUS Medical School in Singapore said that although the study took place in Asia, “It’s been shown in other populations that a similar pattern exists. Basically it seems to be a very general phenomenon that lower vitamin D levels are associated with subsequent cognitive decline.”
“We all like our brains, and we all like our bones, so there are two good reasons to pay attention to vitamin D adequacy.”
Matchar says that getting your vitamin D levels checked is pretty easy, and that you’re never too young to be mindful of keeping adequate levels of the nutrient in your system. “Your 40s and 50s are a good time to start supplementing if your levels are low,” he says. The Institute of Medicine recommends 600 international units (IUs) per day, 800 if you’re over 70. But vitamin D is fat-soluble (excess amounts are stored in your fat), Matchar cautions, so taking too much of it can cause a toxic build-up in your body.
Here are ten easy ways to get your daily dose of vitamin D:
1. Ditch the sunscreen … briefly. Sun exposure offers the best (and most natural) way to get your body to make vitamin D. A small amount of sun exposure without SPF will do it, no more than 20 to 25 minutes. But keep in mind the sun won’t provide your daily D dose at higher latitudes, including the northernmost United States, especially in the winter months (southern states fare better year-round). If you’re over 60, your skin is no longer as efficient at converting sunlight to Vitamin D, and if you have a dark complexion, the concentration of melanin in your skin acts as a barrier to sunlight. Basking in the sun near a window may feel good, but the glass blocks 100 percent of the sun’s beneficial rays. So even though the sun is your best source for vitamin D, your age, geographical location and skin tone might mean you need to supplement sunshine to get your daily D.
2. Go fish. Fatty fish such as sockeye salmon are a good source of vitamin D. A 3-ounce sockeye salmon fillet contains about 450 IUs of vitamin D. Trout, mackerel, tuna and eel are good choices, too.
3. Enjoy your catch from the can. Canned tuna fish and canned sardines both contain vitamin D, have a longer shelf life and are less expensive than fresh fish. Canned light tuna has the most vitamin D; about 150 IUs per 4 ounces. Canned albacore has about 50 IUs per 4 ounces, and canned sardines offer a little more than 40 IUs per two sardines.
4. Eat your magic mushrooms. No, not those. All mushrooms turn sunlight into vitamin D, just as humans do, but because mushrooms are typically grown in the dark, most of them don’t contain the vitamin. Specific brands, however, are grown under ultraviolet light, and those are D-rich. They offer 400 IUs of vitamin D per 3-ounce serving, about 1 cup of diced mushrooms. Check the label; it will tell you whether the mushrooms have been exposed to UV light.
5. Milk it. Most cow’s milk sold in the U.S. is fortified with vitamin D, but ice cream and cheese are not. An 8-ounce glass of milk contains at least 100 IUs of vitamin D, and a 6-ounce serving of yogurt contains 80 IUs, but the amount varies depending on the brand and how much D is added. Some soy and rice milks are also fortified. Check the food label. Like milk, some orange juices are also fortified with vitamin D, and one glass usually has around 100 IUs, but this can vary, so check the label before committing to a particular brand.
6. Pop a pill. You can get your daily D from a supplement and completely avoid sun exposure. The upper limit is 4,000 IUs for people ages 9 and older, and that includes all sources – food, sun and supplements. If you’re not sure what you need, consult your doctor.
7. Egg yourself on. Egg yolks give you about 40 IUs of vitamin D, but even if you love eggs, you don’t want to rely on them to give you your fully daily dose of D. That’s because one egg contains about 200 milligrams of cholesterol, nearly the limit of 300 mg a day recommended by the American Heart Association.
8. Add some morning crunches. A low-calorie, vitamin D-fortified cereal can help you fulfill part of your daily dosage, and if you pair it with fortified milk and fortified orange juice, you’re well on your way to getting all the D you need for the day.
9. Become a liver lover. A 3.5 ounce serving of cooked beef liver contains about 50 IUs of vitamin D along with other important nutrients like vitamin A, iron and protein. Keep in mind that beef is high in cholesterol too, so you may want to opt for more fins than hooves.
10. Hold your nose and swallow. Cod liver oil is a vitamin D powerhouse, and if you can stand it, a mere tablespoon of the stuff provides about 1,300 IUs, more than twice the recommended dietary allowance of 600 IUs per day, a good strategy if you’re vitamin D deficient or over 60.
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Matchar advises that if you are going to take advantage of the sun, do so when the UVB rays (the ones responsible for creating vitamin D) are their most potent, which is in the middle of the day. But, he cautioned, don’t overdo it. And if you’re 60 or older, your body may not be as efficient at converting UVB rays to vitamin D, so a combination of sun and supplements or food, as laid out in the ten recommendations above, is a wiser way to accomplish your daily D goal.
More research is needed to determine what truly optimal levels of vitamin D will help stave off cognitive decline, Matchar says, so in the meantime just be sensible. While recent research has focused on the brain, Matchar reminds us that “Vitamin D is also really good for our bones. We all like our brains, and we all like our bones, so there are two good reasons to pay attention to vitamin D adequacy.”