Vitamin D3 plays many vital roles in the human body. Like most vitamins, proper dosage and form will make the difference in terms of how well it’s absorbed and utilized by the body. In this vitamin D3 overview, I’ll outline its role in human nutrition, good sources of D3, supplement facts, and recommended dosage.

Vitamin D3 in Human Nutrition:

Vitamin D3 is an essential component in human health because it helps our bones remain strong by preventing demineralization. Some studies even claim that bone density can be predicted simply by assessing the alleles in our DNA that encode for vitamin D

Having adequate amounts of D3 can positively affect a person’s mood during months with very little sunlight. In countless studies, a positive correlation has been found between poor mood and vitamin D3 deficiency, which could explain the onset of seasonal depression in many people. (Other studies have shown, however, that once a person’s D3 requirements are met, increasing dosage won’t necessarily lead to an increase in mood. Thus maintainance is key.)

Most cells in our bodies have vitamin D receptors. As a result, vitamin D3 has a huge effect on potential gene expression and cell behavior. Vitamin D also plays a major role in immune function, helping the body to effectively fight infections and disease

Vitamin D helps to balance phosphorous and calcium concentrations, ensuring proper assimilation, as well as assist in the absorption of magnesium

Vitamin D Deficiency:

Inadequate intake of vitamin D, or not enough sunlight, can aggravate osteoporosis, cause bone disease, as well as bone and muscle weakness and sensitivity

Because sunlight is a good source of vitamin D, wearing sunscreen can severely decrease one’s ability to produce this vitamin

Old age also plays a role in leading to a potential D3 deficiency, as one’s kidneys gradually lose their ability to convert D3 into a usable form. This may also be linked to inadequate bone density and osteoporosis in the elderly

As stated earlier, a D3 deficiency may lead to seasonal depression and anxiety during months when sunlight is rare

Having a more melanin in your skin may reduce the amount of sunlight that is converted to vitamin D

Having liver problems could lead to improper assimilation of vitamin D3, as this is the first site where D3 is metabolized in the body

Other factors like Crohn’s and celiac disease might severely decrease how much vitamin D is absorbed through the digestive tract, leading do deficiency issues down the road

Caffeine can also block the absorption of vitamin D, as well as various vitamins and minerals by interfering with cell receptors. Limit coffee/caffenated tea intake to less than 3 cups a day, and supplement with vitamin D3, preferably away from caffeinated drinks

Cortisol, a hormone that is produced by acute or chronic stress, may also interfere with vitamin D3 absorption. While acute stress usually doesn’t pose a problem, chronic stress can deplete the body of this vitamin, as well as having many negative effects. Practice reducing stress levels on a daily basis

Vitamin D Toxicity:

On the very rare occasion, vitamin D toxicity can occur. These symptoms may include: kidney stones, increased blood calcium levels, nausea and loss of apatite. Supplementing with a lowdose of vitamin A (2,5003,000

IU) can work to regulate vitamin D3, reducing the likelihood of toxicity. Too much vitamin A can work against vitamin D, so be careful when supplementing with these two. My rule of thumb is 1:2 ratio, A:D

The average daily intake of vitamin D is roughly 5,000 IU/day, though 10,000 IU/day is also acceptable. A dose of 50,000 IU/day over a long period of time could lead to vitamin D toxicity, though this far exceeds the recommended daily dose and should not be considered

Forms and Sources of Vitamin D:

Vitamin D, when absorbed by the body, takes on several different forms in the liver, kidneys, and bloodstream. When supplementing with vitamin D, however, all you need to know is whether to take vitamin D3 or D2. Both are absorbed by the body, but D3 is synthesized much more readily, having a greater effect on the body. Research has found that D2 is markedly less powerful because it is typically synthesized in plants

Plants do not contain vitamin D, but they do contain sterols, which are unsaturated alcohols like cholesterol, that can be irradiated to produce vitamin D. Mushrooms and the human skin contain different types of sterols that can be converted to vitamin D, which is why sun exposure is so important

Egg yolks, fatty fish, cod liver oil, and milk (fortified with vitamin D,) are other good sources of vitamin D, though the quantity and availability might vary widely among them. In essence, vitamin D is typically lacking in the human diet, so acquiring it solely from food isn’t the best method

Sunlight is the best and most natural source of potential vitamin D3 because one’s body can produce it on its own, no supplement necessary. When unprotected skin is exposed to sunlight, UVB rays spark a chemical reaction, producing preD3 and, when metabolized, D3.

For best absorption, avoid having calcium at the same time

Recommended Dosage:

Roughly 20 minutes of sun exposure per day is recommended for one’s skin to properly convert sunlight to D3. In order to ensure proper absorption, refrain from washing the oils off your skin, and using sunscreen prior to sun exposure

If sunlight is rare, and/or assimilation of D3 is difficult, try supplementing with vitamin D3. The average recommended dosage is 45000 IU/ day. If you know you’re deficient, increase the dosage to 1000 IU/ 25 lbs of body weight per day. If you get adequate sun exposure every day, less might be needed to maintain healthy levels of D3. Only a blood test will verify this.

Vitamin D3 is fat soluble, so supplements should be taken with a saturated fat source (coconut oil, butter, ghee, etc.) in order to ensure proper absorption

Research has also shown that magnesium and D3 work together. Magnesium converts D3 into its activated form, while D3 can help magnesium be better absorbed by the body. Try taking them together

Because vitamin D3 has a positive effect on the absorption of vitamin K2, A, and zinc, it might make sense to take these vitamins at the same time as well to optimize their effectiveness

Brands I recommend (soyfree): Natural Stacks D3 (5,000IU) and Life Extension D3 (5,000IU)

Note: Only a blood test will verify if you are deficient in vitamin D, though many people, especially those living in the northern hemisphere, suffer from some degree of deficiency. Considering how unlikely vitamin D toxicity is, some supplementation is probably better than none. If in doubt, always refer to a professional.