Have you had your vitamin D level tested lately?

I’ve been shouting from the rooftops for years that everyone — adults and children alike — should be getting their vitamin D levels tested on a regular basis. But unfortunately, the message must not be getting out there as loudly as I’d like. Otherwise, why would 80 percent of Americans still be deficient in this essential nutrient?

So, just in case you need another reason to get your blood levels checked, here’s a pretty important one: New research shows that low vitamin D levels are linked to cognitive decline.

This isn’t the first study to find an association between vitamin D and brain health. But what set this one apart is that more than half of the study participants were African American or Hispanic. Vitamin D deficiency is especially common in these groups because the larger amounts of melanin in darker skin make it more difficult to synthesize vitamin D.

And in this particular study, low levels of vitamin D were associated with accelerated decline in episodic memory and executive function, the two cognitive functions that are most strongly associated with Alzheimer’s disease (AD) and dementia.

One thing that shocked me when I read this study was just how low the participants’ levels of vitamin D were. Researchers found the average vitamin D level among the participants was just 19.2 ng/mL. Of course, according to their analysis, this dismal level is only slightly below the 20 ng/mL they consider “adequate” for healthy people. And here is where the problem lies.

You and I both know that’s not nearly enough. In fact, all of the studies on the health benefits of vitamin D indicate that the higher the number, the better the health outcomes. I mean if I read those studies, why haven’t these researchers?

Anyway, as expected, the researchers found vitamin D levels varied by race/ethnicity, with lower levels in African Americans (17.9 ng/mL) and Hispanics (17.2 ng/mL) relative to whites (21.7 ng/mL). The prevalence of vitamin D deficiency also differed by race/ethnicity, with rates higher in African Americans (42.5%) and Hispanics (28.1%) than in whites (13.3%).

This is downright atrocious. How did their doctors allow them to have such low levels of vitamin D? If you ask me, this is malpractice.

The fact is unless your vitamin D level is optimal, you’re at serious risk for all sorts of disorders, from osteoporosis to heart disease to diabetes, and now even Alzheimer’s.

Solet’s take a few minutes to go over the basics of exactly how to reach that optimal level.

First, have your vitamin D 25 OH blood level checked.Then repeat this every 6 weeks until you reach at least 80 ng/mL. And after that, continue to have it checked every six months to make sure it stays where it needs to be.

To produce vitamin D naturally, you need to be exposed to the sun’s UVB rays during the peak sunlight hours of 10am-3pm (without sunscreen) for at least 20 minutes a day. Believe it or not, there’s actually an app called D-Minder that can help you keep track of your efforts. It takes into account your location, weather conditions, skin tone, age, what type of clothing you’re wearing, etc. And then it computes how much UV radiation you’re getting, and how many units of vitamin D your body is making. It also lets you know when to get out of the sun so you don’t burn.

But keep in mind, the farther away from the equator you live, the scarcer the UVB rays — especially during the winter months.

Also keep in mind that if you have dark skin, you’ll need about 25 times more exposure to sunlight as someone who is light skinned to produce the same amount of vitamin D.

And the older you get, the harder it is to metabolize vitamin D. After age 50 it takes twice as long in the sun to get the same amount at age 25.

As you’ve probably gathered, even with the best of intentions, it’s difficult to consistently get vitamin D naturally through the sun’s rays. So it’s also important to take a vitamin D supplement every single day. I recommend at least 5,000 IU, but I’ve found higher doses, up to 10,000 IU per day, are often necessary — especially in the winter, when sunlight is fleeting.

Of course, it doesn’t hurt to get some additional vitamin D through food too. Wild caught salmon, mushroom, oysters, liver, and eggs are all good sources.

The takeaway here is to keep regular tabs on your levels, get safe sun when you can, and please, if you take no other nutritional supplement, make sure to take vitamin D3.