How We Found the Best Vitamin D Supplement
We started by looking for popular brands that are readily available through online retailers (like Amazon and Vitacost) or at chain grocery stores and pharmacies. We found a bunch: 239 vitamin D supplements in a variety of forms, including softgels, tablets, gummies, liquids, and sprays. Then we talked to doctors, nutrition experts, and a vitamin manufacturer before looking at each product’s ingredients label, product purity, and dosage accuracy to find the best vitamin D supplement on the market.
First, we researched the differences between vitamin D3 and D2.
In our search for the best vitamin D supplement, we learned that there are actually two types of vitamin D: D2 (ergocalciferol), which comes from plants, and D3 (cholicalciferol), which is manufactured using fish oil or — more commonly — lanolin taken from sheep wool and subjected to ultraviolet (UV) radiation. This may sound scary, but UV radiation is what our bodies use to make natural vitamin D when our skin is exposed to sunlight.
Vitamin D2 isn’t as effective as D3, but that doesn’t mean it’s bad or completely ineffective.
Dr. Joe Feuerstein, associate professor of clinical medicine at Columbia University and director of integrative medicine at Stamford Hospital in Stamford, Connecticut, told us, “Vitamin D3 mimics the way our bodies make D from sunlight and it’s more easily absorbed, making it the best option for most people.” But he doesn’t rule out vitamin D2. “When patients are very deficient in vitamin D, the standard protocol is high-dose injections of D for a short time, and these higher pharmaceutical doses are always vitamin D2.”
Because vitamin D3 is more widely recommended and more available in stores, it’s a good choice for most people. But if you follow a vegetarian or vegan diet, plant-based vitamin D2 certainly isn’t a bad option either.
No third-party testing? No way.
The Food and Drug Administration (FDA) regulates food products, but not dietary supplements. So it’s anybody’s guess if what’s in a pill actually matches what’s on its bottle label. Some supplements contain lead or other contaminants, and product ingredients can vary widely. In fact, Labdoor, a reputable third-party testing company, found that the actual dosage of vitamin D supplements sometimes exceeded what was listed on the label by as much as 900 percent. That’s why we required all of our top picks to be vetted by at least one of three reputable, independent labs.
United States Pharmacopeial Convention (USP) – A scientific nonprofit that sets standards for quality and purity in medicines and food supplements in the US and more than 140 other countries.
Labdoor – A free consumer resource that focuses on testing dietary supplements for purity, accuracy, and value.
National Sanitation Foundation (NSF) – An independent organization that sets worldwide standards for consumer product safety.
Contenders cut: 208
We also looked for minimal additives — including other added supplements.
Ever wonder why vitamin D, like many supplements, contains glycerin, water, cellulose, or other fillers? We did too, so we asked Jamie Shuck, brand manager for Vitabiotics, one of the UK’s largest vitamin manufacturers. “Vitamin D is needed by the body only in tiny microgram amounts, which is barely a speck in its pure form — far smaller than a grain of rice and too small to even pick up,” Shuck explained. “Therefore, all vitamin D supplements must be formulated with other ingredients to increase the volume of the product, so customers are able to measure a safe and accurate dose.”
While it’s impossible to find a vitamin D supplement that contains just vitamin D, we did look for products that avoided questionable additives like sugar, flavoring, artificial color, and preservatives. And while we were at it, we went gluten-free, too — because you don’t need gluten in a vitamin supplement.
We also chose products containing only vitamin D with no other dietary supplements. According to the experts we talked to, almost everyone needs a vitamin D supplement, while only some of us need or want additional ingredients like calcium or CoQ10.
Dr. Feuerstein also made a strong case for eliminating proprietary blends: “The challenge with proprietary blends is it’s hard to know the specific dose of vitamin D in each pill,” he said, “and that makes it difficult to treat someone who has a vitamin D deficiency.”
It’s important to note that most of the vitamin D supplements you find in stores cannot be labeled vegetarian or vegan, even when no animal products are listed on the label. Vitamin D3 is commonly derived from lanolin, a product of sheep wool. Vegetarians might not take issue with this, but there’s another hang-up: Most vitamin D supplement manufacturers use softgels as a delivery method, too. Softgels allow vitamin D3 to be mixed with olive, soybean, safflower, or sunflower oil for better absorption. The vast majority of softgels, however, are made with gelatin — and all gelatin comes from animal products, like pigskin, pig and beef bones, cowhide, or fish bones. While supplement manufacturers list “gelatin” on the label, many fail to mention that gelatin comes from animal sources.
For vitamin D that is purely plant-based, look for vitamin D2 in tablet form, with packaging that indicates the product is vegan.
Contenders cut: 10
Each pill needed to include 2,000 IU of vitamin D and some form of fatty oil to help with absorption.
For years, the gold standard for dietary supplement dosage has been the Recommended Daily Allowance (RDA). The RDA is determined by the Institutes of Medicine (IOM), which bases RDAs on dosages that will meet the needs of roughly 50 percent of the population. If this sounds general, it is — and it helps explain why the experts we consulted believe the current Recommended Daily Allowance for vitamin D (600 IU per day, last updated in 2010), is not high enough to prevent a deficiency.
The current recommended daily allowance of vitamin D probably isn’t enough.
In fact, a 2014 study suggested that the IOM had made a “serious miscalculation” and that the actual RDA for vitamin D should be “10 times higher.” One thing that all of our experts did agree on was the fact that vitamin D is best absorbed by the body when taken with fatty foods. That’s why we also required all of our top picks to include some form of fatty oil from olives, soybeans, or some other healthy source.
Popular nutrition expert Dr. Andrew Weil recommends 2,000 IU of vitamin D3 per day for most people, and Dr. Feuerstein agrees: “If you follow the current RDA of vitamin D, which is 600 IU per day, I can pretty much guarantee that unless you’re a child, it won’t be anywhere near enough.” He recommends 2,000 IU per day for his adult patients, with higher doses for patients who have been diagnosed with a vitamin D deficiency.
In a 2007 New England Journal of Medicine article, Dr. Michael Holick, a physician and researcher from Boston University Medical Center, wrote: “I recommend to all of my patients that they should take 2,000-3,000 IU of vitamin D a day from dietary sources, sensible sun exposure, and supplements.” Most of the other experts we talked to agreed: 2,000 IU of vitamin D each day is going to be the best amount for most people to take.
Contenders cut: 8