Everything you need to know about proper— and safe—vitamin D supplementation

Once thought to only prevent rickets and broken bones, this versatile vitamin has now been shown to help stave off a whole host of chronic diseases that plague the body and brain…

I’m talking about vitamin D.

In fact, every month, there are more new studies published on the many health benefits of this essential nutrient.

But despite this newfound knowledge, many people still continue to have insufficient vitamin D levels in their blood. There are various reasons why, but what it all adds up to is the need to take a high-quality vitamin D supplement each and every day.

And yet, even this basic, commonsense advice is subject to controversy. Debate rages over how much vitamin D people should take, and whether they can actually get enough D without taking any supplements at all.

Well, allow me to answer some common questions (and misconceptions) about vitamin D, based on the science—so that you can be an informed consumer of vitamin D supplements, once and for all.

How are your vitamin D blood levels?

First and foremost, the best way to know if you are D deficient is through a blood test. Ask your doctor for a 25-hydroxyvitamin D, or 25(OH)D, test. It measures the levels of vitamin D in your blood in tiny units of nanograms per milliliter (ng/mL). I recommend it twice a year—at the end of winter (late March) and at the beginning of fall (late September).

The U.S. Institute of Medicine (IOM) recommends that vitamin D blood levels be at least 20 ng/mL. But that’s strictly for prevention of outright deficiency that leads to bone disease.

To prevent other diseases associated with low levels of D—including Alzheimer’s and dementia, common cancers (like lung cancer, see page 1), diabetes, high blood pressure, and immune system dysfunction—research shows your blood levels should be much higher. I recommend aiming for 50 to 75 ng/mL.

If your levels are lower than that, you most likely need to supplement with vitamin D. Which leads me to my next topic…

How much D should you take?

Based on its recommendation that “healthy” vitamin D levels could be as low as 20 ng/mL, the IOM issued correspondingly low “optimal” intakes of D. The recommended U.S. dietary allowances (RDA) are a measly15 mcg (600 IU) daily for people ages 1 to 70 years, and 20 mcg (800 IU) for those who are older.

But even a decade ago when these recommendations were updated, research showed that the dosages were too low to maintain optimum health. And now, as we know far more about vitamin D’s role in the body and brain, these dosages are laughable.

That’s why, based on the latest science, I routinely recommend 250 mcg (10,000 IU) of vitamin D per day. This dosage is perfectly safe alongside the 25(OH)D test—and oftentimes necessary to get your blood levels where they need to be.

Look for a high-quality D supplement from a brand you trust. And remember, you can even find D in easy-to-use liquid form, alone or together with the potent marine carotenoid astaxanthin.

And since D is fat soluble, I recommend taking supplements with food to properly absorb the nutrient. Opt for foods that naturally contain healthy fats, like avocados, olives and olive oil, nuts, and seeds.

And speaking about food…

Can I get enough D from my diet alone?

Consuming a healthy, balanced diet is the basis for determining the optimal amounts of dietary supplements you should take. After all, dietary supplements are meant to supplement the diet—not substitute for an unhealthy diet.

But when it comes to D, the problem is that very few foods naturally contain good amounts of this vitamin.

Fatty fish like salmon is the best source of vitamin D. But one recent study found that an average-sized wild-caught salmon (the only kind I recommend eating) contains about 10 mcg (400 IU) to 20 mcg (800 IU) of D—meaning you’d need to eat an entire school of fish to get the recommended 250 mcg (10,000 IU) a day!1

In addition, red meat and egg yolks are also reasonable sources of vitamin D. But, as with fish, you’d have to eat huge quantities to get adequate levels of D per day.

I should also warn you that foods “fortified” with vitamin D, like milk and cereal, are still inadequate. And you don’t want to be eating bowls of highly processed carbs, typically with added sugars, in cereals anyway. (Not to mention that the sugar and high-fructose corn syrup in processed foods can interfere with vitamin D levels in the blood.)

But there are some foods that are symbiotic with vitamin D…

Is there anything I can consume to boost my D levels?

Research shows that magnesium—either in food or supplements—plays an essential role in the synthesis and metabolism of vitamin D.

One study of participants in the huge NHANES (National Health and Nutrition Examination Study) found that higher intakes of magnesium were associated with reduced risks of vitamin D deficiency.2

Plus, people who had low vitamin D levels but high magnesium intake were less likely to die from cardiovascular diseases or colon cancer.

Good food sources of magnesium include nuts, seeds, leafy greens like spinach, beans, and whole grains. You can also supplement your healthy, balanced diet with 150 mg of magnesium daily. (Just stay away from magnesium glutamate, magnesium aspartate, and magnesium oxide.)

Another way to get magnesium is to absorb it through your skin. Two easy ways to do this are through soaking in Epsom salts or spending time in seawater (while getting some sun)—which leads me to the next question…

Do I still need vitamin D supplements if I spend time in the sun?

There’s a reason why D is called the sunshine vitamin. The sun’s rays are essential for natural activation of D through our skin.

But, as I’ve often mentioned, in latitudes north of Atlanta or Los Angeles, the sun’s rays aren’t high enough in the sky from October to March, nor strong enough to allow your body to naturally produce D. That’s why supplements are especially crucial in the winter months.

But what about during the summer, when you’re outside, actively soaking up the sun? Well, the problem is, your ability to make your own vitamin D from ultraviolet (UV) rays begins to drop as you get older.

In fact, one study found that people between the ages of 8 to 18 years produce more than twice the amount of vitamin D in skin exposed to sunlight than those ages 77 to 82.3

So even if you spend time in the sun without sunscreen (which prevents your skin from making vitamin D at all), it may simply not be enough. (And isn’t, in most cases.) That’s why I still recommend dietary supplements in order to maintain adequate levels of the sunshine vitamin—even in the warmer months.

Which leads me to the final “Frequently Asked Question” about this essiential nutrient…

Can I “overdose” on vitamin D?

Even though the recommended RDA for vitamin D is woefully low, some doctors warn against taking higher dosages. They harbor an irrational fear about “toxicity” or “overdose” at this level. (I know because, years ago, I was brainwashed into believing some of these baseless concerns as well.)

But as I routinely report, and as I thoroughly explained in the May 2018 issue of Insiders’ Cures, the way vitamin D has been measured makes the doses seem much higher than they actually are.

Thankfully, the Food and Drug Administration (FDA) recently provided guidance for updating units of measurement for certain nutrients on supplement facts labels—including vitamin D.

That’s why you’ll see me write out the amounts using the newly enforced measurement—micrograms (mcg)—and the formerly used measurement—international units (IU).

As you’ll see, 10,000 IU of vitamin D is just 250 mcg (or 0.25 milligrams [mg]). That’s miniscule compared to the doses of other nutrients. For example, the RDA of vitamin C (which is also too low) is almost 200 times higher than that amount—at 46 mg!

Plus, as I reported in the September 2019 issue, you can count the actual cases of clinical toxicity associated with vitamin D on your fingers. And they all occurred under circumstances so rare and unusual, the vast majority of doctors won’t encounter them even once in their lifetimes.

So don’t be afraid to supplement with 250 mcg (10,000 IU) of vitamin D daily. And remember to get your blood levels screened regularly. Then, continue to eat a healthy, balanced diet…and have fun in the sun this summer!


1”Vitamin D in Wild and Farmed Atlantic Salmon (Salmo Salar)—What Do We Know?” Nutrients. 2019 May; 11(5): 982.

2“Magnesium, vitamin D status and mortality: results from US National Health and Nutrition Examination Survey (NHANES) 2001 to 2006 and NHANES III.” BMC Med. 2013 Aug 27;11:187.

3“Aging decreases the capacity of human skin to produce vitamin D3.” J Clin Invest. 1985 Oct;76(4):1536-8. doi: 10.1172/JCI112134.