Vitamin D – Think You Get Enough? Think Again

Vitamin D is synthesized by the body when sunlight hits our skin. It’s found in fish and eggs, many of us struggle to get enough.

Vitamin D

Deficiencies and even insufficiencies leave people susceptible to health problems.

Vitamin D3 is the best form and 2000 IU per day should sort most people out.

The RDA you read on food packets is not enough for an adult. You have been warned!

Vitamin D Key Points

  • Vitamin D supplementation helps: Bones, Immunity, Testosterone, Mood, Cognition, Heart
  • It is essential for survival
  • It is fat soluble (so goes well with a Fish Oil / Omega-3 supplement)
  • Goes well with Vitamin K
  • Goes well with Calcium
  • The Recommended Daily Allowance (RDA) of 400-800 IU is NOT sufficient for adults
  • 2000 – 4000 IU per day has been shown to be safe.
  • 4000 IU per day is upper safe limit but some studies show 10000 per day can be
  • People of Northern Latitudes get insufficient amounts in general
  • Fortified Foods and Milk are generally under-dosed
  • D3 is the most efficient form
  • A Vitamin D3 supplement is highly recommended
how to get more vitamin D

Vitamin D Overview

Like all other vitamins, Vitamin D is necessary for human life. The sun’s radiation triggers Vitamin D’s synthesis when it hits the skin, but certain food groups, namely fish and eggs contain it.

Also, some dairy products and many infant foods are fortified with Vitamin D to boost the daily amount consumed, although this is often not enough to make much of a difference.

Bone strength, mood, cognitive function, immunity and testosterone production are all improved with optimal levels of Vitamin D. It is also known to reduce the risk of diabetes, cardiovascular disease, MS and certain cancers.

It is fat soluble and is produced from the body’s cholesterol when the skin is exposed to UV light. The level of UV required means that much of the world’s population cannot synthesize enough Vitamin D, particularly the northern latitudes where winters are harsh and long.

Even in latitudes exposed to more sun, overuse of sunscreen can diminish Vitamin D synthesis as it blocks some of the UV-B light which directly influences the process (see ‘Did You Know’ section below).

The RDA (recommended daily allowance) is currently 400 to 800 IU (equal to 10 to 20 micrograms respectively). This is actually not enough for adults, but while – technically – deficiencies are the minority, there are many benefits to getting more than the RDA.

Supplementing with Vitamin D is the most practical option because a dosage several times the recommended daily allowance is tolerable, and highly beneficial. Getting the equivalent from food would be almost impossible, and getting the equivalent from the sun may not be possible.

Did You Know…?

…that sunscreen can actually prevent the synthesis of Vitamin D by blocking the UV-B light from the sun. Chronic sunscreen use could be a factor in some Vitamin D deficiencies, especially in parts of the world that experience a hot summer and a long winter.

But sunscreen protects me…

The problem is that this has not been widely supported by scientific evidence. Sunscreen has been around a long time, and while it may prevent sun burn to a degree, that doesn’t seem to be synonymous with the real danger: melanoma, cancer.

So sunscreen is a conspiracy…oh please!

Well, put it this way: as the usage of sunscreen rises, so do the number of cases of skin cancer worldwide. How could this be? – It might come back to Vitamin D plus a bit of common sense….

By preventing the synthesis of Vitamin D, the sunscreen is in turn reducing the amount of metabolites of Vitamin D. These metabolites are helpful in preventing cancer.

Secondly, the skewed level of confidence people have for staying in the sun all day because they have applied a thin layer of sunscreen is a large factor in explaining why cases of skin melanoma are on the rise.

What should we do about this…?

It may be prudent to reduce the amount of direct strong sunlight you expose yourself to. It may also be just as effective to rely on more physical methods of protection, such as hats, umbrellas and parasols.

Point takeaway: don’t stay out in the sun all day thinking your sunscreen is like a shield. Get some responsible sun, and where you can, block it physically.

And, of course, a Vitamin D3 supplement will certainly help.

NOTE: It would be highly irresponsible of us to suggest you lose the sunscreen, but hopefully you can see that this is information to help you realize it is not a panacea for all sun related health issues, and may even be inhibitory to Vitamin D synthesis if used excessively.

ref: Garland et al. Could sunscreens increase melanoma risk? 1992 []

Vitamin D benefits

Types of Vitamin D Supplements

Supplements will be in the form of Vitamin D3 – or cholecalciferol – because it is more readily absorbed than other types, primarily D2 (Ergocalciferol).

Vitamin D2 mostly comes from plants whereas D3 is sourced from animals and fish, cod liver oil being one of the best examples. While both are available in supplement form, there is an argument that D2 should NOT be, as it is not as efficient.

D3 is also more stable in powder form, which has implications to manufacturers of powdered supplements looking to add it into their products.

Recommended Daily Allowance – Not So Recommended

The RDA for Vitamin D is still 400 – 800 IU.  The number 400 was arrived at because it was the minimum amount required for the prevention of rickets in children.

These days, 400 IU is known to be insufficient and sourcing additional Vitamin D from nutritional intake is highly recommended, as is supplementing if necessary.

Some products like milk are made with Vitamin D fortification. Vitamin D fortified foods are generally under-dosed also.

Many multi-vitamins today contain only 800 IU, and so it may be worth purchasing a separate Vitamin D3 supplement.

The current safe upper limit in the US and Canada is 4000 IU per day, though some research studies have used more than double that in their trials. Dosage will be discussed in further detail later in this article.

Benefits of Vitamin D Supplementation

Here are some of the main benefits of Vitamin D, based on and supported by scientific research:

Lifespan – Vitamin D deficiency appears to be correlated to shorter lifespans. This is fairly standard for any of the 24 essential vitamins and micronutrients. Rather than specifically extend life, supplementation may be an aid in preventing early deaths.

Cancer prevention – a scientific paper looking at the effects of a minimum of 1000 IU per day of Vitamin D estimated that billions of dollars of cancer treatment has been saved due to its overall preventative effects.

  • Neuro-protection
  • Anti-Depressive (more reliably in circumstances where D deficiency is causing depression)
  • Reduced risk of Heart Disease
  • Reduced Blood Pressure (for people with hypertension)
  • Reduced risk of Type 2 Diabetes and complications of Type 1 Diabetes.
  • Improved Muscle Recovery post exercise (also, insufficient amounts of Vit D will cause reduction in muscle hypertrophy and impairments to physical function)
  • Increased Power Output (when correcting deficiency)
  • Reduced risk of Bone Fractures
  • Normalized Testosterone Levels
  • Increased Luteinizing Hormone production

Scientific Support for Vitamin D – Testosterone

There are many studies involving Vitamin D, looking at many potential benefits of supplementation and negatives of deficiencies.

The below section outlines one area which has little evidence in terms of volume, but is promising nonetheless: testosterone.

Scientific references used for the rest of this article can be found after the Conclusion and Recommendations section.

Boosting low testosterone levels


There aren’t many studies conducted to test Vitamin D’s effect on testosterone levels but one which stands out was conducted over a year. In total 165 participants finished the year, and 54 of them were men.

A dose of 3332 IU (83 mcg) or placebo was given daily. After the course, a significant increase in total testosterone, both bioactive and free testosterone was observed in the Vitamin D group compared to baseline values. The increase was not seen in the placebo group.

It is important to note that both groups were deficient in Vitamin D and were at the low end of the testosterone reference spectrum.
Conclusions can obviously be drawn with respect to the efficacy of Vitamin D supplementation to correct a deficiency related decline in Testosterone levels. It has a significant effect in this situation.

Whether or not supplemental levels of Vitamin D (above those which normalize testosterone production) will boost testosterone production to higher-than-average levels has not been studied.

Pilz S et al. Effect of vitamin D supplementation on testosterone levels in men. 2011 []

Usage and Dosage Guidelines

There appears to be a tangible difference between the term ‘deficient’ and ‘insufficient’ where Vit D is concerned.

The RDA of 400 – 800 IU will prevent a ‘deficiency’ but is widely considered to be insufficient in light of current scientific knowledge.

Certain factors such as geography (i.e. latitude), occupation (exposure to the sun), diet (ingestion of richer sources) and so on, are determining factors in the calculation of an appropriate dose.

People who live in parts of Canada, the northern parts of the US, UK, Europe and similar latitudes may not synthesize any Vitamin D from sunlight for several months each year.

Supplementation of between 1000 and 2000 IU will be of great advantage to people living in these areas.

The upper safety limit in the US and Canada is about 4000 IU. Some studies have tested much higher dosages but a decent base of supplementation will be in the aforementioned 1000 to 2000 IU range.

This way, whatever is sourced from nutrition and the sun is a bonus.

Vitamin D3 is the best variant to use as the body can utilize it more efficiently within its own metabolic process.

Also, given that it is fat soluble, taking it alongside another fish oil supplement or a source of healthy fat is the ideal method of ingestion.

Is Supplementing Vitamin D Safe – Are There Side Effects?

Provided the dosage stays below the upper safety limit (around 4000 IU, but perhaps best kept at 2000 IU), there are no negative side effects associated with Vitamin D supplementation.

IMPORTANT: Consult your doctor if you are unsure of the optimal dosage for yourself. This article has been written with a general readership in mind. This is why a dose of 2000 IU has been recommended, as it would be virtually impossible to get too much additional Vitamin D from the sun and diet alone.

Having said this, you may be a candidate for an even higher daily dose, hence why it is then necessary to consult a doctor so as to more accurately determine your individual needs.

Conclusion and Recommendations

Is there a pandemic of Vitamin D deficiency?…perhaps not.

Insufficiency, however, is a different story.

It’s clear that the recommended daily allowance skirts just about the amount needed for mothers to avoid leaving their offspring with rickets, but it’s probably not enough for adults to maintain optimal health.

Nor do most of us seem to get enough from our diets and sunshine alone, especially in the northern parts of the world.

Office jobs, poor nutrition and excessive slathering-on of sunscreen may all combine to explain some of the problem, but lying out in the sun unprotected and filling our face with eggs and fish all day is definitely not the solution.

The happy medium comes in the form of Vitamin D3 supplements. Without knowing each individuals daily habit, a 2000 IU per day dose will probably set right any deficiencies and insufficiencies, and stay well away from the 4000 IU upper safety limit.

Scientific References (Examples)


Parker J et al. Levels of vitamin D and cardiometabolic disorders: systematic review and meta-analysis. 2010 []

Dobnig H et al. Independent association of low serum 25-hydroxyvitamin d and 1,25-dihydroxyvitamin d levels with all-cause and cardiovascular mortality. 2008. []

Bone Health

Bischoff-Ferrari HA et al. Prevention of nonvertebral fractures with oral vitamin D and dose dependency: a meta-analysis of randomized controlled trials. 2009 []

Mortality and Life Expectancy

Bjelakovic G et al. Vitamin D supplementation for prevention of mortality in adults. 2011 []


Pilz S et al. Effect of vitamin D supplementation on testosterone levels in men. 2011. []

Multiple Sclerosis (notable reduction in risk)

Munger KL et al. Vitamin D intake and incidence of multiple sclerosis. 2004 []


Gorham ED et al. Optimal vitamin D status for colorectal cancer prevention: a quantitative meta analysis. 2007[]

Crew KD et al. Association between plasma 25-hydroxyvitamin D and breast cancer risk. 2009. []

Garland CF et al. Vitamin D and prevention of breast cancer: pooled analysis. 2007. []

Skinner HG et al. Vitamin D intake and the risk for pancreatic cancer in two cohort studies. 2006. []


Mohr SB et al. The association between ultraviolet B irradiance, vitamin D status and incidence rates of type 1 diabetes in 51 regions worldwide. 2008. []


Carrillo AE et al. Impact of vitamin D supplementation during a resistance training intervention on body composition, muscle function, and glucose tolerance in overweight and obese adults. 2013 []

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