Vitamin D supplementation. It's so popular. Let’s find out why.
Def.: Vitamin D
Vitamin D is a fat-soluble vitamin. Other fat-soluble vitamins include vitamin A, D, E and K.
When the body obtains (from sunshine!) or consumes (from vitamin D foods!) a sufficient amount of these fat-soluble vitamins, the remaining can be stored in the liver and fatty tissues. Unlike the more rapidly-used and eliminated water-soluble vitamins B and C, fat-soluble vitamins can be stored, and then eliminated more slowly.
Vitamin D is often obtained from the sun. So, what happens when the opportunity for sun exposure is diminished during the winter months? Well, we can pull stores from our liver and fat.
Form Follows Function:
Like lots of biological functions, our body needs to perform conversions before we can actively use Vitamin D. To convert Vitamin D to it's active form, we need the help of 3 organs – our skin, liver and kidney.
When our skin is exposed to UVB rays, 7-dehydrocholesterol from the skin is converted to cholecalciferol and travels to the liver and is converted to calcidiol, or 25-hydroxyvitamin D.
Calcidiol, or 25-hydroxyvitamin D then travels to the kidney where it is converted to the metabolically active form of vitamin D called calcitriol, or 1,25 dihydroxyvitamin D.
After Vitamin D is converted in the skin, liver and kidneys, it’s ready to be useful. Finally.
Vitamin D promotes calcium absorption from our food in the small intestine and increases calcium levels in the body.
High levels of calcium in our blood (hypercalcemia) from too much calcium, or calcium intake with an imbalance of cofactors such as vitamin D, vitamin K2, phosphorus and magnesium can result in calcification of the cardiovascular system and soft tissues, and also cause kidney stones.
Low levels of calcium in our bones (osteoporosis) is often associated with too low of calcium intake and too low of calcium absorption. Increased calcium absorption, with the help of cofactors like vitamin D and vitamin K2, can place calcium in the bone and increase bone mineralization.
Plays well with others:
- Alongside Vitamin A, helps aids immune system, skin health and eyesight
- Alongside Vitamin K2, deposits calcium into our bones
- Alongside magnesium, maintains calcium balance and aids in muscle contraction and relaxation
- Alongside phosphorus and calcium, mineralizes bones and teeth
The most popular assessment of Vitamin D is a serum test of calcidiol, or 25-hydroxyvitamin D.
The Vitamin D council indicates a desirable range serum level to be 40 – 80 ng/mL.
A 2012 study of 25 pastoral Maasai and 25 Hadzabe hunter-gatherers living in Tanzania had a mean serum 25(OH)D concentrations of Maasai and Hadzabe of 47 ng/mL and43 ng/mL, respectively.
Remember, too much or too little Vitamin D with an imbalance of synergistic nutrients can lead to physiological imbalances.
“Excessive sun exposure does not result in vitamin D toxicity because the sustained heat on the skin is thought to photodegrade previtamin D3 and vitamin D3 as it is forme… Intakes of vitamin D from food that are high enough to cause toxicity are very unlikely. Toxicity is much more likely to occur from high intakes of dietary supplements containing vitamin D.”
Quick tip: Get your serum Vitamin D levels checked in the spring months. Assess your levels to determine if you need less, more or a maintenance dose of sun exposure for proper Vitamin D levels.
3 Ways to Incorporate Vitamin D - Food, Sunshine and Supplementation
Get some sun:
Vitamin D is synthesized from 7-dehydrocholesterol on the outer cell membrane of skin cells following exposure to UVB radiation.
UVA vs. UVB – does it really matter? Yes!
UVA rays penetrate the skin more deeply than UVB rays. UVA rays are associated with skin aging, wrinkling and pigmentation. UVA rays have been shown to damage skin cells in the basal layer of the epidermis which is the outermost skin later, where most skin cancers occur. UVA rays don’t burn your skin, so you’re not aware you’re getting to much sun, like you do with UVB rays.
UVB rays do not penetrate as deeply as UVA rays. UVB rays allow the synthesis of Vitamin D to occur. Unlike UVA, UVB will turn the skin pink and begin to burn – a good indication to get out of the sun. UVB rays are highest at midday. UVA rays are present all day, so you won’t burn, but can cause premature skin aging and more dangerous skin cancers, like melanoma.
UVA rays act as the bouncer at the club. When we’ve had enough UVB rays and Vitamin D intake, UVA rays break down the vitamin D formed in your skin to prevent an overdose of Vitamin D.
Chemical sunscreens allow in the UVA rays that cause sun damage, but block the UVB rays that produce Vitamin D – crazy, right?! If you’re going to go for a sunscreen, try zinc oxide. It sits on top of your skin and acts as a physical barrier to scatter and reflect the UVA and UVB rays.
If you will be outside for a long period of time, cover up with tightknit clothing and a big floppy hat. Loosely knit clothing will block UVB rays, but not UVA rays.
Takeaway: Get some midday sun exposure without sunscreen. Start at 5-10 minutes, and work your way to 20 minutes or so, depending the amount of melanin in your skin, age, location on the planet, time of day, etc.
Vitamin D3 (cholecalciferol) is found in animal foods, such as beef liver, seafood and eggs. 4 ounces of salmon has over 500 micrograms of Vitamin D3.
Vitamin D2 (ergocalciferol) is found in very small doses in plants and mushrooms. One cup of portabella mushrooms has 20 micrograms of Vitamin D2. However, the conversion of D2 into the active form of D3 is poor.
Takeaway: In sum, if adequate sun exposure is not available, eat Vitamin D3-rich foods to receive a bioavailable form of Vitamin D.
While supplementation is popular, it’s not for everyone. If you’re receiving measured sun exposure and eating plenty of Vitamin D-rich foods, this may be enough to ensure optimal Vitamin D status.
If living in northern latitudes or during winter months, it may be advantageous to supplement with cod liver oil or take a Vitamin D3 supplement. However, a blood test is the best method to determine if supplementation is needed.
Takeaway: Remember, Vitamin D is a fat-soluble vitamin and stored in the body, so it’s important to know your levels before mega-dosing on Vitamin D.
If getting your daily dose of Vitamin D is a reason for you to go for a walk or stroll through a park, then let that be your reason. In addition to moderated sunshine, eat animal-based foods and get a blood test to check your status.