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Supplementing with Vitamin-D

Posted 28th November 2013 by Josh Schouten

Vitamin-D is a fat-soluble nutrient and is one of the 24 micronutrients critical to human survival. Vitamin-D is found naturally in eggs and fish and is sometimes added to dairy products, but the sun is the major natural source.

Your body produces vitamin-D from cholesterol, provided it gets adequate amounts of UV light from sun exposure. However, there are only sufficient amounts of UV light coming from the sun when the UV index is 3 or higher. If you live in the UK you need to be aware of the UK Vitamin-D Crisis.

Supplemental vitamin-D is implicated in wide-ranging benefits, such as increasing cognition, immune health, bone health, and well-being; reducing the risks of cancer, heart disease, diabetes, and multiple sclerosis; and increasing testosterone levels in deficient populations.

There is a lot of controversy surrounding the prescribed doses of vitamin-D supplements. The controversy is not about if we should take the supplement it’s more a question of how much should we be taking? With vitamin-D, it is not a case of more is better and many studies have found a U-shaped curve associated with the benefits of vitamin-D levels.  Each person is an individual and, depending on the time of year, your body composition (i.e. the more body fat you have the more vitamin-D you will need), exposure to sunlight, dietary fat absorption problems and even your age will determine the required dosage of vitamin-D.


In the early 1900s, rickets (a bone disease attributed to vitamin-D deficiency) was rampant among poor children in the United States and England who were living in polluted industrialised cities with smoky skies. Around this same time, cod liver oil (an omega-3 fatty acid) was found to be useful in the prevention of rickets because it contained substantial amounts of vitamin-D.

Dr. Neil Binkley of the University of Wisconsin Osteoporosis Clinical Research Program, cited studies of blood levels in people who get their vitamin-D naturally from the sun.[2]  That includes surfers, farmers, construction workers and some cultures in Africa. These groups of people were shown to have average plasma levels in the range of 40-50 ng/ml.

The Vitamin-D Council recommends ranges for vitamin D3 are between 32-100 ng/mL. They then say, “Reference ranges represent the range of values that the majority of the population will fall between and are not indicative of values which would be considered optimal.” Very insightful and useful information to share with a society that has little awareness of the importance of vitamin-D!

From the studies cited above it seems the human body may stop naturally synthesising vitamin-D when levels reach 50ng/ml.  If this were the case, would it be wise to force feed vitamin-D into the system?


Vitamin-D toxicity can result in hypercalcemia (too much calcium in the blood), which can cause nausea, anorexia, constipation, confusion, and nephrolithiasis (kidney stones).  Although toxicity is very rare, there have been some occurrences of individuals who accidentally overdosed on vitamin-D and experienced health complications as a result.


It is recommended to take vitamin-D supplementation in the vitamin D3 (cholecalciferol) form rather than D2 (ergocalciferol) due to better utilisation in the body, and to take it with meals to avoid potential feelings of nausea and better aid absorption.

There are many factors that can affect your individual absorption rate of vitamin-D.  Everybody is an individual and one of the best recommendations is to get your vitamin-D levels tested (see essential nutrients) two or more times each year.

By testing D3 at the end of summer, you will be able to see if your sun exposure during the summer months was enough to maintain vitamin-D levels. If you do not spend enough time in the sun, you should change your lifestyle and get out doors more often. You should not need to supplement with vitamin-D during the summer unless you work night shifts.  It amazes me when my clients for vitamin-D levels are low in the middle of summer. You only need to spend 10-30minutes in the sun each day to top up vitamin-D levels.

The RDA for vitamin D is currently set at 400-800IU/day, but this is likely too low for adults. The RDA might just be enough to prevent you from getting rickets, is it enough to maximise the health benefits?

The safe upper limit in the United States is currently defined as 2,000IU/day, and in Canada it’s 4,000IU/day. However, research suggests that the true safe upper limit is 10,000IU/day [1]

Many studies have concluded that vitamin-D needs to be between 30-32ng/mL for optimal health. To achieve this, a daily intake of at least 1000 IU of D3 is required and it is highly probable that substantially higher amounts are required to achieve the recommended levels for certain populations. For moderate supplementation, a dose of 1,000-2,000IU vitamin D3 is sufficient to meet the needs of 50-95% of the population and should be seen as the lowest effective dose range.

The best way to figure this out is to test your D3 at the end of winter after you’ve been supplementing with 1000IU per day.  If your scores are low you should increase the dosage next winter and find a balance that works for you.  If your body fat percentage increases you will need more vitamin-D, fat people burn more vitamin-D!  As we get older our skins ability to synthesise vitamin-D slows down and we also need increase the dosage.

Vitamin-D should be taken with meals that contain a source of fat (such as fish oil). There have been anecdotal reports of it causing trouble sleeping when taken later at night, so it might be best to take it earlier in the day.

If you are deficient in vitamin-D you need to boost your D3 to normal levels as quickly as possible.  I suggest following Charles Poliquin’s advice on “How I Replenish My D3 Levels


Are you aware of the benefits of vitamin-D?  Did you know?

  1. The risk of falls in the elderly (and subsequently, rate of bone fractures) appears to be significantly reduced with vitamin-D supplementation at 700 IU or greater (more)
  2. There appears to be less risk of cardiovascular disease and related cardiovascular complications with supplementation of 1,000 IU of vitamin-D (more)
  3. The association between serum vitamin-D at 37ng/mL and colorectal cancer is approximately a halving of risk (more)
  4. A decrease in bone fracture risk (nonvetebral and hip) appears to exist when supplemental doses of vitamin-D are taken above 800 IU (more)
  5. Both correlational and intervention studies note that higher cohorts of serum vitamin-D have less blood pressure than lower cohorts (more)
  6. Mixed effects on overweight/obese persons, but it appears that normalising a deficiency may aid fat loss in persons of higher body weight (more)
  7. Cohorts of people with higher serum vitamin-D appear to die less frequently than cohorts with less serum vitamin-D in D (more)
  8. An improvement in insulin secretion is noted in diabetics (type II mostly) and in persons at risk for diabetes when supplementing with vitamin-D (more)
  9. Improvements in insulin sensitivity can occur secondary to increasing pancreatic insulin secretion (more)
  10. The decrease in triglycerides is present after long term ingestion of vitamin-D, (more)
  11. May reduce the risk of catching the flu (more)
  12. Appears to be somewhat effective at reducing the occurrence of asthma attacks in youth (more)
  13. An increase in testosterone has been noted in men with 3,332 IU of vitamin-D over the course of a year (more)
  14. An improvement in muscular and neural functionality in the elderly is thought to underlie the reductions of fall risk and reduced bone fracture rate seen in elderly cohorts (more)
  15. An increase in lean mass has been noted in dieting obese women relative to control (2,000IU) and a trend to reduce lean mass relative to control has been noted in exercising healthy persons (4,000IU); there appears to be potential for both effects with vitamin-D  supplementation (more)
  16. A decrease in symptoms associated with tuberculosis are noted with vitamin-D (more)
  17. The risk of developing MS is significantly reduced by both sunlight, latitude, and supplemental vitamin-D (more)
  18. There is less risk of breast cancer associated with vitamin-D supplementation (more)
  19. Appears to be associated with less risk of pancreatic cancer (more)
  20. May reduce the incidence of type 1 diabetes in offspring and adults when supplemented (for the former, but the mothers) (more)
  21. There appears to be a lower relapse rate in multiple sclerosis patients when vitamin-D is present at higher concentrations (more)
  22. A inverse correlation between vitamin-D and Depression (lower vitamin-D status being related to more depressive symptoms) (more)

The list could go on as new studies are being released every year that show endless health benefits of vitamin-D. Our society today sees less sunlight and spends more time indoors than ever before.  Micronutrients are critical to our health and our survival, no wonder we are fatter and sicker than ever!


Did you know that athletic performance peaks in the summer when vitamin-D levels peak, and is at its lowest in the winter when vitamin-D levels are at their lowest?

The medical literature indicates that the sufficient levels of vitamin-D will make you faster, stronger, improve your balance and timing, etc. Athletes who are deficient in D3 will not be performing to the highest level. How much D3 can improve your athletic ability depends on how deficient you are to begin with. D3 acts as a hormone in our bodies and we use it for cell signalling (so our cells can talk to each other). At the end of the day athletic performance comes down to speed and your bodies’ ability to react to the environment around it.

Peak athletic performance also depends upon the neuromuscular cells in your body and brain having access to the steroid hormone, activated vitamin-D. How much activated vitamin-D is available to your brain, muscle, and nerves depends on much 25-hydroxy-vitamin-D is in your blood. In turn, how much 25-hydroxy-vitamin D is in your blood depends on how much vitamin-D you put in your mouth or how often you expose your skin to UVB light.

Some other very interesting studies have found a direct association between physical performance and vitamin-D levels. That is, the higher your vitamin D level, the better your athletic performance between 30 to 50 ng/ml, above which further improvements in athletic performance were not seen.


When supplementing with the fat-soluble vitamin-D you should eat foods that contains monounsaturated fats to improve absorption for example olive oil.

Other vital micronutrients to be paired with vitamin-D are as follows:

Zinc – Helps vitamin-D bind to its receptor

Magnesium – is Vitamin-D’s most important cofactor


  1. Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safetyAm J Clin Nutr. (1999)
  2. Binkley NRamamurthy RKrueger D. Low vitamin D status: definition, prevalence, consequences, and correction.  Rheum Dis Clin North Am. 2012 Feb