Vitamin D and the A-Z Health Benefits

If I had to put my finger on one of the most essential and yet undervalued micronutrients that our body requires on a daily basis, I would say “Vitamin D”! Yes the ‘sunshine vitamin’. Iron, water, vitamin C, vitamin B12, these are other vital nutrients that our bodies depend on for proper cellular function, but I believe Vitamin D in adequate or insufficient levels may have the most dramatic impact on one’s overall health to thrive or (just) survive. With massive amounts of research suggesting that Vitamin D can protect us against osteoporosis and fragility fractures, reduce the risk of depression, reduce cancer cell growth, improve hypertension (ie. lower high blood pressure), reduce the risk of stroke and myocardial infarctions (ie. heart attacks), reduce cognitive (memory) decline, and can contribute to one’s longevity…. why are are more people not talking about this Super Vitamin!? Well actually, they are! Beyond the scientific community, many people are getting on board the Vitamin D train, and appreciating the astounding health benefits of this small but mighty nutrient. The following article explains the ins-and-outs of Vitamin D - everything from what exactly it is; to how easy it is to obtain more of it; to how much we need, and the different forms available - all based on current research. Let’s explore everything there is to know about Vitamin D… and if you would prefer to just read the summary, then skip to the The US Endocrine Society’s Clinical Practice Guidelines.

So what exactly is Vitamin D? 

There are varying definitions out there, but Vitamin D (also known as “calcitriol”) is a fat-soluble vitamin (meaning it’s absorbed by the small intestines in the presence of fat, and excreted by the kidneys). It is considered a nutrient and a hormone. Following Ultraviolet B (UVB) light hitting your skin during sun exposure, a process is triggered in your skin that will cause ‘pre’-Vitamin D3 (scientifically known as Cholecaliferol) to undergo several changes which continue in the liver, until the final process in the kidneys, where Calcidiol (25-hydroxcholecalciferol) is converted into its ‘active’ Vitamin D form, Calcitriol (1,25-dihydroxycholecalciferol D3 or 1,25-dihydroxyvitamin D, for short). This ‘active’ vitamin D is essential for maintaining both calcium and phosphorous serum levels that will play an important role in calcium absorption and deposition, and subsequent bone health (such as your long bones and teeth). And according to Harvard Health Publishing by Harvard Medical School, ‘many tissues in the body, including skin, skeletal muscle, adipose (fat) tissue, immune cells, blood vessels, have vitamin D receptors on them’[2,3,4], which is why its no surprise that it has many other functions outside of bone health, including a role in our immune systems and reducing inflammation.

Harvard clarifies two (of what I believe to be key) definitions: ‘Deficiency’- a term often used inappropriately, which refers to “specific health problems resulting from the lack of/or inability to use a specific nutrient.” Vitamin D ‘deficiency’ occurs when the serum level falls below <20ng/mL. Physicians and researchers often refer to the bone disorder, Rickets, as a good example of a condition resulting from a ‘true’ vitamin deficiency, as Vitamin D deficiency is directly attributed to skeletal deformities in childhood, and increased risk of fractures later in life. In contrast, the term, ‘Insufficiency’ - refers to “lower than optimal levels of vitamin D, which may increase your risk of numerous health problems”[2]. Vitamin D ‘insufficiency’ occurs when serum levels are between 20-29ng/mL[3]. So, for the majority of us- when we are talking about the lack of Vitamin D in our diets and every day lives, it is likely more accurate to say we are vitamin D ‘insufficient’ than ‘deficient’.

Classification of Vitamin D:

Further classification of Vitamin D:

The unfortunate downside of having a Vitamin D insufficiency or deficiency as we’ve already touched on, is that it can progress into more troublesome and detrimental conditions impacting our health. Current and past research has shown that low vitamin D levels, particularly serum levels <20ng/mL, have been linked to a 30-50% increased risk in breast cancer, colon cancer, and prostate cancer [5,6]. The archives of General Psychiatry in the Netherlands, reported a relationship between Vitamin D deficiency and depression in men and women between 65-95 years of age [7]. The archives of Internal Medicine reported doubled risk of cardiovascular causes and death overall, in men and women (mean age of 62). According to the Journal of the American Medical Association (JAMA), other conditions such as multiple sclerosis (MS), diabetes, and autoimmune conditions such as osteoarthritis, have also been linked to, and could be prevented by, Vitamin D [2,8]. 

In the cardiac journal, Circulation, the Framingham Heart Study (which began in 1948 and is ongoing) has assessed over thousands of subjects over past decades, and found that patients with serum Vitamin D levels <15ng/mL (ie. deficient levels) had a 60% higher risk of heart disease [9], with other medical journals have added that individuals with levels <15ng/mL are three-times more likely to develop hypertension [10].

Furthermore, what about the subpopulations that deem themselves “healthy”? A study conducted at a hospital in Boston, Massachusetts found that ’32% of healthy students, physicians, and residents at a Boston hospital were found to be vitamin D–deficient’, regardless of having a glass of milk, daily multivitamin, and consuming salmon once a week. [11] 

What does this tell you? Personally, it suggests that even if you believe you are healthy, asymptomatic, or immune to Vitamin D insufficiency/deficiency… well, you are incorrect. Anyone, even those that embody a healthy lifestyle, are susceptible to lacking this vital micronutrient. Which means we all have to be hyper-vigilant about ensuring we get enough of it, in one form or another, every single day! 

The silver lining...

Just as we’ve discussed all of the health downsides of a lifestyle and diet devoid of Vitamin D, the opposite is true when one ensures there is an adequate amount to surplus of Vitamin D in our lives. In a study based on 980 women, Garland et al found that a high vitamin D intake was associated with a 50% lower risk of breast cancer, in comparison to low vitamin D levels [12]; other studies have suggested protection against heart disease (indirectly suppressing inflammation or directly strengthening the arterial walls)[13]; significant improvements in depressive symptoms [14]; a smaller rise in plasma glucose when subjects received 700IU of Vitamin D/day, which suggests a correlation between Vitamin D and type 2 diabetes [15]; a 20% reduction in hip fractures when individuals supplemented with ~800 IU of Vitamin D/day, funnily enough due to strengthened muscle (not due strengthened bone, as I assumed) [16]; a 40% lower rate of Influenza A infection in children when given 1200 IU Vitamin D/day [17] …the list of the positive benefits Vitamin D can have on your health, goes on and on.

So why are so many people Vitamin D deficient/ insufficient in the first place? 

Well, the problem is twofold: (i) overly effective government vocalisation about the negative effects of sun-exposure and its contribution to skin cancer and (ii) people’s geographical location. Regarding the media, what the government/media is reporting is true- too much exposure to harmful UV sunlight can contribute to the development of skin cancer; However, this message has been trumpeted so loudly that it has created another problem, Vitamin D deficiency, in year-round sunny countries such as Australia, where Vitamin D deficiency should not be occurring and is avoidable. Many Australians are Vitamin D deficient because they don’t expose any of their skin to sunlight for the minimum requirement of 10-15 minutes each day, to receive the necessary UVB rays. Unlike Australia, Canadians have the opposite problem - they are not Vitamin D deficient because of too much skin coverage, rather, they are not receiving enough UVB light (and subsequent Vitamin D production) based on their geophysical location. Places like  Canada, Iceland, the UK, Russia are all at a very high latitude (ie. furthest from the equator), and are thus, competing against unmodifiable factors, such as the cold winter weather and limited minutes during a day to reasonably extract UVB rays from the sun. In fact, there are periods during the winter months in Canada, where it wouldn’t matter how long a Canadian exposed themselves to the sun (regardless of the elements), they wouldn’t receive enough UVB rays purely due to the tilt of the sun and the fact that the solar UV light is absorbed into the atmosphere. Alternatively, if one lives at a lower latitude (ie. closer to the equator, such as, in Central/South America, Australia/New Zealand), where the summer months last for more months of the year, there are more opportunities to be outside and receiving UBV rays from the sun. Of important mention - Vitamin D deficiency can also result in individuals with chronic conditions such as, Celiac sprue/gastric bypass / inflammatory bowel disease or end-stage liver disease, where the absorption or synthesis of Vitamin D has been inhibited.

Of current and significant relevance, are growing bodies of evidence suggesting that their is a relationship between infectivity and severity of Covid-19 to Vitamin D levels. Prior to the pandemic, research reported that Vitamin D supplementation was beneficial in protecting against the risk of acquiring acute respiratory viral infection due to its immuno-modulatory effects on our adaptive and innate immune systems. Continuing this research, a recent study published by Charoenngam et al. (2021), suggests that Vitamin D supplementation may be used as a primary preventative or adjunctive treatment of Covid-19 [4]. While long-term results from the study are still pending, it is no surprise that the researchers suggested taking Vitamin D regardless of the study outcomes, as there is no downside to Vitamin D supplementation, and numerous health benefits to be gained. I couldn’t agree more.

How do we obtain more Vitamin D?

Here are 3 practical ways:

(i) Vitamin D can be ingested through Vitamin-D rich foods, such as:

Milk, yogurt, raw mushrooms, almonds, salmon, canned tuna, and trout, to name a few. Interestingly ’freshwater’ rainbow trout contains the highest amount of Vitamin D by a long-shot!)- it just might require you to eat much larger quantities of certain foods to get near the required dose of Vitamin D that might more easily be achieved from a single supplement. However, this is still a good way to boost your vitamin D level, if you can’t get outside due to the cold weather.

(ii) Vitamin D may also be taken orally in one of two supplemental forms: 

Vitamin D2 (i.e. Ergocalciferol, found in plants or fungi) OR Vitamin D3 (ie. Cholecalciferol found in animals and humans). So which is better? While both are well absorbed by the intestines[3], studies based on seven randomised trials show and agree that D3 supplementation happens to increase serum levels more efficiently due to its longer half-life (compared to D2), this is particularly true for people requiring additional supplementation as an adjunctive treatment for Vitamin D deficiency [18]. 

(iii) The last, and what I believe to be a far superior form and choice:

Focusing on getting outside (if the elements permit) and exposure (a swim-suit level of exposure) for 10-15 minutes every day! Sun exposure allows our skin to obtain and utilise enough UVB light that your body can then convert from its natural Vitamin D3 (Cholecalciferol) form into the active Vitamin D (as mentioned above), while limiting your time and exposure to the cancer-provoking UVA rays. I have more than one reason for why I believe natural sunlight exposure is superior to supplemental forms of vitamin D, and I will explain why shortly.

What TIME should we be going outside to absorb Vitamin D?

If you are aiming for the optimal level of Vitamin D purely from sunlight, then approximately midday is the best time to get outside, as that is when the UV index will likely be the highest. And if you really want to take your Vitamin D knowledge to the next level, you can calculate the amount of vitamin D you are getting by using a UV (UltraViolet light) index calculator. The ‘UV index’ identifies the strength of the sun and predicted UV radiation levels on a 1-11+ scale (1=low radiation, 11+= severe radiation). It is specific to a particular location, day, time, and current weather (ie. cloudy). UVB rays are the specific rays that skin requires to produce Vitamin D, and is only synthesised in the skin when the UV index is greater than >3. In every country, the UV index will be different, but generally speaking the UV index will be highest around midday and approximately half that value at 10AM or 2PM. This may seem a bit contradictory, but the purpose of being in the sunlight at midday (when the UV index is highest), is that it maximises the amount of beneficial UVB rays you are exposed to in the briefest period possible- while reducing the overall length of time you are in the sun, and being exposed to harmful UVA rays. You can look up the UV index for your country/location online, to see what time of day is best for optimal Vitamin D exposure. Generally speaking, (and taking into consideration where you are geographically in the right conditions)- 10-15 minutes of swimsuit skin exposure (ie. arms, legs and face are exposed) to sunlight each day, during the months of spring, summer and fall; is sufficient sunlight to produce/and meet the daily Vitamin D requirements. And interestingly, according to Nair and Maseeh (2012), when the skin becomes slightly pink in the 24 hours following sunlight exposure, it is equivalent to consuming 10,000-25,000IU of Vitamin D [19].

This is a link to a UV index calculator, specific to each province in Canada, but you can download apps for your phone, as well: https://weather.gc.ca/forecast/public_bulletins_e.html?Bulletin=fpcn49.cwao

I believe now is a good time to add - that while I am encouraging you to enhance your vitamin D absorption, using the UV index to your advantage, I am in no way telling you to throw caution to the wind and get burned! 10-15 minutes of high UV index sun should be sufficient, while also practicing safe sun practice: wearing a hat, sunglasses, and light long-sleeve material (beyond 15 minutes). Additionally, if you don’t always have the time or means to access the UV index specific to your geographic location, it’s helpful to know that as a rough guide, when your shadow is shorter than you are (suggesting the angle of the sun is greater than 45 degrees and thus, the UV index is at its greatest), you are getting outside at the right time to get enough Vitamin D from the sun.

How much Vitamin D should I be aiming for daily?

The truth of the matter is, there is no consensus among the medical and scientific journals on a concrete number for recommended daily intake; and there are no guidelines for screening or treatment of vitamin D deficiency or insufficiency [20]. But if you understand that it is very easy to become Vitamin D deficient, while extremely difficult and rare to reach toxic levels of Vitamin D, it makes the idea of oral supplementation a lot less daunting. Before commencing any supplementation, heading to your GP for standard lab-work for a standard serum level of Vitamin D will be beneficial, safe, and a wise starting place.

According to the Sunlight Institute of Canada, ’90% (or more) of our vitamin D requirement comes from exposure to sunlight. Without sun exposure, 1,000 IU of vitamin D per day is required.’ [21]

Institute of Medicine (IOM) recommended daily intake (RDI):

(**These numbers have increased 200 IU (International Units) per age group, at least twice since 2014).

400 IU per day (for children <14)

600 IU per day (for Adults 14-70) --> (Harvard has since changed their recommendations to: 800-1000 IU)

800 IU per day (for Adults 71+)

4000IU per day = upper limit  

The US Endocrine Society’s Clinical Practice Guidelines (and what I go by): 

(**All recommendations are to maintain vitamin D levels above the optimal level of 30ng/mL)

400-1000 IU per day (for children <1 yo) 

600-1000 IU per day (for children >1-18 yo)

1500-2000 IU (for adults 19-50)

1500-2000I IU (for adults 50-70, and 70+)

1500- 2000 IU (for pregnant and lactating women)

As the IOM's RDI recommendations have fluctuated over the last 8 years, it seems to make the most sense to direct your daily intake based on healthy serum levels, and what the Australian government agrees is the best indicator of choice, as it takes into account both dietary and cutaneous vitamin sources[23]. This requires a bit of extra effort on your own part to trial-and-error titrating the specific daily (IU) dose you require and a few extra lab visits, until you ensure you’ve optimised your serum Vitamin D level to between 40-60ng/mL. If you direct your daily intake based on your serum levels, then you will know whether you need to increase your daily requirement from the above recommendations. (FYI: 100 IU of standard supplementation raises serum levels 1 ng/mL).

All resources (IOM, Harvard University, US Endocrine Society) do seem to agree on the following: 

Recommended healthy serum Vitamin D levels of: 40-60ng/mL  

Toxic serum levels: 85-150ng/mL (this takes an obscene amount of supplementation to reach).

Extra tidbits of knowledge.

Additionally, I would like to mention, tinted windows/air pollution and cloud cover can block the UVB wavelength, which means your skin will NOT be able to make Vitamin D in these settings. And contrarily, all UV light does penetrate water, meaning you need to be careful how much sun expose you or your children are receiving when swimming outside. Sun-tanning beds expose one to both UVA and UVB, so avoid them. And if you live geographically 37 degrees in latitude north (above) or south (below) the equator, you are at greater risk of vitamin D ‘insufficiency’.

Do I need supplements if I’m getting outside?

The simple answer is, no, you do not need supplements if you are meeting the required amount of Vitamin D from your time outside in sunlight. Ideally, receiving Vitamin D from sun-exposure is superior to taking supplements, as being outside provides the additional benefits of improving one’s physical and mental health by stimulating the release natural “happy hormones”, endorphins and serotonin. Also, the chances of one over-dosing on Vitamin D are rare, as there is a substantial window of safety; particularly in the case of accidental over-dose on Vitamin D, before one would ever reach toxic levels to cause harm (ie. >150ng/ml). And according to the University of Calgary, in countries such as Canada that experience cold winter months, there are times of the year where sunlight exposure (and UV intensity) are diminished, and as such, require one to supplement to meet the adequate daily Vitamin D dose.

The take home message: 

When its spring, summer or fall months, the UV index is high (being at least 3 or greater), and the sun is shining, you should be get outside at the peak of the day for 10-15 minute to get adequate amounts of Vitamin D! Conversely, the farther you live from the equator or when the UV index is low (less than 3) during certain seasons, ie. winter, ensure you are ingesting alternative forms of Vitamin D, whether it be by consuming more Vitamin D-rich foods or upping your volume of supplementation (with likely increased efficacy in the Vitamin D3 supplemental form). Your bones, mental health, and well, every fibre of your being will thank you!

Happy sun-searching!

-Dr. Kristyn Bell

References:

1. Holick MF. Vitamin D: important for prevention of osteoporosis, cardiovascular heart disease, type 1 diabetes, autoimmune diseases, and some cancers. South Med J. 2005 Oct;98(10):1024-7.

2. Harvard Medical School. How much vitamin D do you need? 2019. https://www.health.harvard.edu/staying-healthy/how-much-vitamin-d-do-you-need. Online.

3. Holick MF. "Vitamin D Deficiency," New England Journal of Medicine (July 19, 2007), Vol. 357, No. 3, pp. 266–80.

4. Charoenngam N, Shirvani A, Holick MF. Vitamin D and Its Potential Benefit for the COVID-19 Pandemic. Endocr Pract. 2021 May;27(5):484-493. doi: 10.1016/j.eprac.2021.03.006. Epub 2021 Mar 17. PMID: 33744444; PMCID: PMC7965847

5. Garland CF, Garland FC, Gorham ED, et al. The role of vitamin D in cancer prevention. Am J Public Health 2006;96:252-261

6. Giovannucci E, Liu Y, Rimm EB, et al. Prospective study of predictors of vitamin D status and cancer incidence and mortality in men. J Natl Cancer Inst 2006;98:451-459

7.  Vitamin D and Depression. Archives of General Psychiatry. 2008. 

8. Munger KL, Levin LI, Hollis BW, Howard NS. Serum 25 hydroxy Vit D levels and risk of MS. JAMA 2006; 296:2832-2838

9. Wang TJ, Pencina MJ, Booth SL, Jacques PF, Ingelsson E, Lanier K, et al. Vitamin D deficiency and risk of cardiovascular disease. Circulation. 2008;117:503–11.

10. Forman JP, Giovannucci E, Holmes MD, Bischoff-Ferrari HA, Tworoger SS, Willett WC, et al. Plasma 25-hydroxyvitamin D levels and risk of incident hypertension. Hypertension. 2007;49:1063–9.

11. Tangpricha V, Pearce EN, Chen TC, Holick MF. Vitamin D insufficiency among free-living healthy young adults. Am J Med. 2002 Jun 1;112(8):659-62. doi: 10.1016/s0002-9343(02)01091-4. PMID: 12034416; PMCID: PMC3091001.

12. Garland CF, Garland FC, Gorham ED, et al. The role of vitamin D in cancer prevention. Am J Public Health 2006;96:252-261

13. Wang TJ, Pencina MJ, Booth SL, Jacques PF, Ingelsson E, Lanier K, et al. Vitamin D deficiency and risk of cardiovascular disease. Circulation. 2008;117:503–11.

14. Jorde R, Sneve M, Figenschau Y, Svartberg J, Waterloo K. Effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects: Randomized double blind trial. J Intern Med. 2008;264:599–609.

15. Pittas AG, Harris SS, Stark PC, Dawson-Hughes B. The effects of calcium and vitamin D supplementation on blood glucose and markers of inflammation in nondiabetic adults. Diabetes Care. 2007;30:980–6.

16. Harvard School of Public Health Nutrition Source. Vitamin D and health. [Last accessed on 2010 Aug 30]. Available from:

17. Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010;91:1255–60.

18. Antoine Aoun, Jessica Maalouf, Myriam Fahed & Flora El Jabbour (2020) When and How to Diagnose and Treat Vitamin D Deficiency in Adults: A Practical and Clinical Update, Journal of Dietary Supplements, 17:3, 336-354, DOI: 10.1080/19390211.2019.1577935

19. Nair R, Maser A. Vitamin D: The “sunshine vitamin”. Journal of Pharm and Pharmacotherapies. 2012; 3(2): 119-120.

20. Judd SE, Tangpricha V: Vitamin D deficiency and risk for cardiovascular disease. Am J Med Sci 338: 40– 44, 2009.

21. Sunlight Institute Canada. https://sunlightinstitute.org/sun-exposure-vitamin-d-common-sense-approach-health/ [online]. 2022.

22. Michael F. Holick, Neil C. Binkley, Heike A. Bischoff-Ferrari, Catherine M. Gordon, David A. Hanley, Robert P. Heaney, M. Hassan Murad, Connie M. Weaver, Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline, The Journal of Clinical Endocrinology & Metabolism, Volume 96, Issue 7, 1 July 2011, Pages 1911–1930.

23. Australian Government. Nutrient Reference Values. Vitamin D. https://www.nrv.gov.au/nutrients/vitamin-d [online]. 2022.