How Much Vitamin D Do You Need? (For Immunity, Preventing/Fighting Cancer, Bone Health, Sleep, Etc.)

Hey Everyone. Drew here, health & nutrition coach and personal trainer, answering a nutrition-related question from my friends over at Atlantic Spine Clinic in Mt Pleasant. Let’s get right into it. Today’s Question- How much vitamin D should a healthy adult consume on a daily basis? What is the best way to get your daily dose? A great question. But before answering it, let’s cover some important background info on vitamin D first.

Vitamin D is an essential fat soluble vitamin that’s unique in that it often acts more like a hormone than a vitamin in the body. Vitamin D3 plays a major role skeletal, immune system and endocrine health, and a somewhat more minor role in cardiovascular and neurological health (vitamin D2 is another, less effective, form of vitamin D and ideally should be avoided). Deficiencies in vitamin D have been linked to several diseases, including sleep disorders, thyroid diseases, bone diseases (including rickets, osteomalacia & osteoporosis), diabetes, chronic pain, autoimmune diseases, cardiovascular disease, Alzheimer’s, dementia and serious gastrointestinal diseases like Crohn’s and ulcerative colitis, as well as 17 different types of cancer. [1-2]

Several studies suggest that vitamin D deficiency is rampant in the United States, such as a 2018 study from the Cureus Journal of Medical Science that looked at data from nearly 5000 American adults and found that more than 40% were deficient in vitamin D, including >80% African Americans and >60% of Hispanics. [3]

Why is this the case? For starters, very few foods naturally contain vitamin D. The top 2 food sources are salmon and eggs. A 4oz serving of salmon only contains around 400 international units, and 3 eggs only contain around 125 IU. So it’s nearly impossible to obtain adequate vitamin D from food alone. [4]

The other 2 options are sunlight & supplements. Although vitamin D is a relatively cheap supplement, the majority of Americans still don’t consume it on a regular basis. In fact, data from 2011 found that only 21% of Americans regularly consume a vitamin D supplement, although data from recent years suggest that number is increasing. [5-6]

With sunshine, the further away from the equator we get, the more difficult it is to obtain adequate vitamin D from the sun. The risk of vitamin D deficiency is higher for those living above the 37th parallel, and a large percentage of Americans live north of this line of latitude. [7]

Also, it’s important to know that a few conditions must be met for the body to produce vitamin D from sunshine. The sun generally needs to be above 50 degrees on the horizon, otherwise the atmosphere tends to block the UVB rays needed for vitamin D production. This is why it’s generally impossible to get vitamin D from the sun in winter months, regardless of how warm or sunny it is. Also, thick cloud cover, most clothing and sunscreen can also block UVB rays from reaching the skin. There are even certain liver and kidney conditions that can also interfere with the body’s ability to produce the metabolically active form of vitamin D.

Some studies have also shown that the elderly are at an increased risk of deficiency, due in part to their body’s reduced ability to convert vitamin D into its most useful metabolic form. [8-9]

So the reason that vitamin D deficiency in America is so widespread has to do with all these factors. Most still don’t regularly consume a vitamin D supplement. Many Americans live in northern climates where getting vitamin D from the sun is nearly impossible for many months out of the year. As a society we spend more time indoors than we used to. We’ve been conditioned for several decades now to cover up with clothing or wear high SPF sunscreen if we’re going to be exposed to the sun. And then there’s the widespread prevalence of kidney & liver diseases, both of which are among the top 15 causes of death for Americans. And finally there’s an increasing percentage of the population who are elderly. For instance, in 1920 less than 5% of Americans were over 65; today that number is over 15%. [10]

In short, vitamin D is an incredibly important nutrient, but a large percentage of U.S. adults are deficient. The original question was “How much vitamin D should a healthy adult consume on a daily basis?” That really depends on the adult and their current vitamin D levels. So the first step is getting tested.

The current gold standard test is the 25-Hydroxy Vitamin D Blood Test. This test is relatively cheap and is almost always covered by insurance. The test results are either given in nanograms per milliliter or nanomoles per liter. I usually discuss vitamin D levels using ng/ml, and there are conversion calculators online if you need to convert nanomoles per liter to nanograms per milliliter.

In 2010, the Institute of Medicine (now known as the National Academy of Sciences) set the vitamin D deficiency threshold at 20 ng/ml. A year later, the Endocrine Society set their vitamin D deficiency threshold at 30 ng/ml. And to make matters more complicated, we also have other influential organizations like the GrassrootsHealth Nutrient Research Institute, as well as The Vitamin D Society of Canada, which recommend levels in the 40-60 ng/ml range. Some independent researchers suggest that optimal vitamin D levels go as high as 100 ng/ml, but many advocate for levels in the 40-80 ng/ml range. This is the range I recommend as well. [11-13]

Several studies back this up, such as one from 2012 that found that vitamin D levels in the 60-80 ng/ml range were most effective for treating 1500 patients with sleep disorders. [14]

So if 40 ng/ml is the minimum threshold to reach, how much daily vitamin D do we need to reach it? Well, The National Academy of Sciences (formerly the IOM) says 600 IU a day is the RDA and 4,000 IU a day is the tolerable upper limit for adults. The Endocrine Society says 1500-2000 IU a day is the RDA and 10,000 IU a day is the tolerable upper limit. [13]

A 2011 study in the journal Anticancer Research found that “the supplemental dose ensuring that 97.5% of the population achieved a vitamin D serum level of at least 40 ng/ml was 9600 IU per day.” [15]

It is for reasons like these that I often recommend adults supplement with a minimum of 5,000-10,000 IU a day of vitamin D, while having their blood vitamin D levels checked on a regular basis. In other words, many of these scientific findings suggest that the IOM significantly low balls the amount of vitamin D needed for optimal health.

But what about toxicity concerns with higher dose vitamin D protocols? Several studies have shown that, while 25 hydroxy vitamin D readings in the 90-150 ng/ml range are likely excessive, true vitamin D toxicity isn’t clinically defined until blood serum levels go above 150 ng/ml, and for this to happen a minimum of 40,000 IU a day needs to be taken for several months. [16-19]

In my opinion the best vitamin D supplements are those derived from fish. BlueBonnet is one of the few companies that make such a product. The vast majority of D supplements come from lanolin, which is produced by sheep. Most people will do fine with lanolin-derived vitamin D products but those who are more sensitive may develop a skin allergy. There are vegan vitamin D supplements available as well, such as those derived from lichen, which is a composite of fungus and algae.

The second part of the question was “What’s the best way to get your daily dose?” The research seems split here. Some research suggests that supplemental vitamin D is better at improving serum D levels, while other research seems to show that sunshine does a better job at raising levels in the body. [20-21]

While I am a big fan of people regularly getting exposure to sunshine, I’d offer 2 cautions- one, you want to avoid getting sunburned as much as possible. A zinc oxide based sunscreen is a safer option if you’re going to be exposed for longer periods of time. And two, if your skin isn’t healthy or you’ve had skin cancer or are at a higher risk of developing skin cancer, you might opt for taking supplemental vitamin D, even when you can get vitamin D from the sun. [22-23]

And lastly with vitamin D, if you’re going to take higher doses of supplemental vitamin D or you’re going to be exposed to vitamin D producing sunshine on a regular basis, you should consider taking a vitamin K2 supplement.

As some might know, vitamin D significantly increases calcium absorption, and vitamin K2 helps direct that calcium into the bones where the vast majority of it belongs. Too much calcium in the soft tissues has been linked to cardiovascular disease, kidney stones and hormonal disorders. [24-29]

Ok, let’s sum up!

  • Vitamin D is an important essential nutrient whose deficiency has been linked to several common disease conditions.

  • More than 40% of Americans are deficient in vitamin D, and the numbers for Hispanic and African Americans are much higher than that.

  • Not many foods contain notable amounts of vitamin D.

  • Several factors play a role in why vitamin D deficiency is so prevalent in the U.S.

  • The 25-Hydroxy Vitamin D blood test is a commonly run test and is helpful in identifying deficiency, sufficiency and toxicity.

  • Studies suggest that a vitamin D test results of 40-60 ng/ml is ideal for optimal health, and 60-90 ng/ml may be therapeutic for those dealing with certain acute and serious conditions.

  • Vitamin D derived from fish oil tends to be highly bioactive while also having low allergen potential.

  • Studies are split on whether sunshine or supplementation is most effective at raising 25-hydroxy vitamin D levels.

  • Vitamin D increases calcium absorption (and calcium levels in the blood), and Vitamin K2 plays an important role in regulating healthy blood and bone calcium levels.

Well that’s it! I hope you learned something helpful. If you’re interested in holistic health and nutrition coaching or personal training, reach out to me. I’d love to help. Until next time…


1 (May 2020 StatPearls on Vitamin D)

2 (2006; review suggesting avoidance of vitamin D2 in favor of vitamin D3)

3 (2018 study looking at NHANES data from 2012; found >40% of total population, with >60% Hispanics & >80% African Americans deficient)


5 (2014; nutritional supplement use data from 2007-2011, compiled by The Council for Responsible Nutrition (CRN))


7 (2010 article; “Populations living at a latitude higher than 37° north of the equator in the Northern Hemisphere are at the greatest risk of developing vitamin D deficiency. In the United States, this translates roughly to a line drawn between San Francisco and Richmond, Virginia.”


9 (April 2020 StatPearls on Vitamin D Deficiency)

10 (data on the elderly 65+ in the U.S., 1900-2050)

11 (2012 review highlighting differences between IOM’s baseline for vit D deficiency [20 ng/ml] and Endocrine Society’s [30 ng/ml])

12 (2011 article outlining Endocrine Society’s rationale for recommending >30 ng/ml as baseline for deficiency)


14 (2012; sleep disorders linked to vit D deficiency; 25(OH) vitamin D3 blood levels of 60-80 ng/ml needed for optimal sleep [notably higher than the 20-30 ng/ml baseline])

15 (2011 study showing 9600 IU/day needed for 97.5% of population to go >40 ng/ml)

16 (2018; case reports on vitamin D toxicity)

17 (2018 review on vitamin D toxicity; “…findings were consistent with the observation by Ekwaru et al. that Canadian adults who ingested up to 20,000 IU of vitamin D3 per day had a significant increase of 25(OH)D concentrations, up to 60 ng/ml, but without any evidence of toxicity.”)

18 (2013 review on vitamin D deficiency, sufficiency & toxicity; 90-150 ng/ml = excessive and >150 ng/ml = toxicity; 90 ng/ml is highest recorded reading through sunshine alone (no supplementation); “Vieth reported that vitamin D toxicity probably begins to occur after chronic consumption of approximately 40,000 IU/day”)

19 (2017; in case studies of 3 adult males, doses of 10k-60k IU/day for 2-6 yrs safely tolerated)

20 (2017; rat study showing sunshine more effective than supplementation at improving serum vitamin D levels)

21 (2011 study showing supplementation more effective than sunshine at improving serum vitamin D levels)

22 (2019 study on safety of zinc oxide as a sunscreen)

23 (2017 study on safety of zinc oxide as a sunscreen)

24 (2020; The combination of vitamin K and D can significantly increase the total bone mineral density and significantly decrease undercarboxylated osteocalcin, and a more favorable effect is expected when vitamin K2 is used.”)

25 (2019; “We propose therapeutic strategies with vitamin K2 treatment to prevent or hold progression of vascular calcification as a consequence of excessive calcium intake…supplementation of calcium—either with or without vitamin D—comes at the price of increased risk of vascular calcification. Clinical studies demonstrate that increased intake of vitamin K could be a promising complementary nutrient in supporting both bone health and protecting vascular calcification.”)

26 (2019; dangers of calcium supp for osteoporosis can increase CVD & CKD risk; points to need for vit K2 supp w/ calcium)

27 (2017; Vitamin K2 may be a useful adjunct for the treatment of osteoporosis, along with vitamin D and calcium, rivaling bisphosphonate therapy without toxicity. It may also significantly reduce morbidity and mortality in cardiovascular health by reducing vascular calcification.”)

28 (2017; Current evidence supports the notion that joint supplementation of vitamins D and K might be more effective than the consumption of either alone for bone and cardiovascular healthvitamin D and calcium supplementation along with vitamin K deficiency might also induce long-term soft tissue calcification and CVD”)

29 (2015; “Vitamin K2 promotes arterial flexibility by preventing accumulation of arterial calcium, and supplementation with it could correct calcium amounts in the body that are out of balance. Thus, calcium in tandem with vitamin K2 may well be the solution for bringing necessary bone benefits while circumventing an increased risk for heart disease”)

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