Sam Schwab Fitness: Vitamin D: What You Need To Know About Testing And Supplementation.

Vitamin D is a vitamin unlike any other, as we can make certain amounts of it in the body when exposing our skin to the sun. Adequate levels of it appear to be able to boost your performance in many areas, keep you from getting sick and slowing down the aging process. I became interested in vitamin D when a blood test during pregnancy showed that my wife had deficient levels of it, even though we were living in the tropics at the time, and would never have imagined that she was not getting adequate sun exposure. I have had several blood tests since then, at different times of year, and this year have experimented with supplementing vitamin D for the first time.

What is Vitamin D?

Vitamin D refers to a group of secosteroids responsible for increasing intestinal absorption of calcium, iron, magnesium, phosphate and zinc. The most important compounds for humans are vitamin D₃ (cholecalciferol) and vitamin D2 (ergocalciferol). [1]

Vitamin D controls the expression of over 1000 genes, 1/23 of the human genome, and helps balance your hormones. [2] Unlike other vitamins, your body can make its own vitamin D when you expose your skin to sunlight. Once the vitamin D is in your body it turns into a hormone. This hormone is sometimes called “activated vitamin D” or “calcitriol.” [3]

How do I get it?

The main source of vitamin D is from sun exposure which allows your body to produce it. There is also a very small amount in foods such as salmon, sardines and egg yolks. [4] It is not enough to rely on food sources though and for those at risk of deficiency, supplementation can help to achieve normal blood levels.

Why do I need it?

70% of people do not meet requirements for adequate vitamin D levels of 30 ng/ml which has been correlated with immune dysfunction, increased inflammation, weak and possibly deformed bones, brain dysfunction, reduced nerve growth factor, learning impairments, increased cancer risk and increased depression. Low vitamin D is also correlated with increased DNA damage and acceleration of telomere shortening which leads to accelerated aging. [5]

How do I know if I’m deficient in vitamin D?

Factors that contribute to vitamin D deficiency are the use of sunscreen, skin pigmentation, excess body fat, age and living above or below 37 degrees of latitude where it is difficult to get enough in the winter months. [5] The use of sunscreen sometimes is necessary, but getting 15 minutes of sun exposure, at a time of day that you do not risk getting sunburn, may be more beneficial than using it all the time. Melanin is an adaptation that serves as a natural sunscreen, but it also blunts the body’s ability to make vitamin D from UVB. Those with darker skin have more melanin and therefore also have a harder time producing vitamin D. Vitamin D is a fat soluble and a large amount of body fat means less vitamin D available in your blood stream. A 70-year-old makes 4 times less vitamin D from the sun than a 20-year-old. [5]

How much do I need to supplement?

Most multi-vitamins have around 250IU of vitamin D if they have any at all and stipulate that the recommended daily allowance (RDA) is 400IU. However this is a very low amount and to get enough vitamin D would mean taking in far too many of some other vitamins or minerals that are in the multi-vitamin. It has been shown that 4000IU of vitamin D daily were enough to bring the majority of adults who previously had deficient levels back up to non-deficient levels of 30 ng/ml without toxicity. This is about 6.5 times the adult RDA! [5]

Above all, the only way to know your levels is to get a blood test then use a vitamin D supplement and retest to see if you are supplementing enough. Ideal levels for lowest all-cause mortality are cited to be between 40 and 80 ng/ml. [5] It seems that the most effective way to supplement is with vitamin D drops so the dose can be adjusted easily.

My experience with Vitamin D testing and supplementation.

When I was living in sunny Rio de Janeiro, Brazil, my levels fluctuated between 40 ng/ml and 60 ng/ml with plenty of regular, year-round sun exposure. So, here in Auckland at around 36 degrees below the equator and with many winter days rained out or under full cloud cover, I’ve decided to experiment with taking a good vitamin D supplement for the duration of winter.

At the end of summer my blood levels were 44 ng/ml, so by the time next summer comes around, after a long, dark winter, I expect those levels would be out of the sweet spot, if not close to deficient levels of below 30 ng/ml. I have never supplemented with vitamin D until this winter, but I have been taking 5000IU per day since I took the first blood test in May. I will continue doing so until the end of winter, when I will get another blood test and see if that seems to be enough for me.

As I’ve already outlined in this article, your ideal dosage will depend on the amount of sun you get, how much sunscreen you use, where you live, your skin colour, your age and your body-fat levels. So if in doubt, get tested, as the amounts of vitamin D found in most multi-vitamins probably won’t be enough to keep you in the sweet spot.