When to take Vitamin D | PlanYourVitamins.com

What is vitamin D good for?

Short answer: Vitamin D has potential benefits for bone health, the immune system, calcium absorption, cell function, cardiovascular health, the nervous system, diabetes, depression, cancer prevention, mental health and inflammatory bowel disease.

Vitamin D is an essential, fat-soluble vitamin that plays a fundamental role in the absorption and distribution of calcium and phosphorous, not only keeping our bones healthy, but also, together with vitamin K, ensuring that calcium doesn't end up being deposited in places where it doesn't belong.

Vitamin D also promotes healthy cell growth and cell function, promotes healthy nervous system function, and is crucial for a functional immune system, reducing the risk of developing health conditions and illnesses, and allowing us to overcome infection sooner, which is why it is so ubiquitous in the treatment of respiratory illnesses like the common cold and flu.

Vitamin D actually refers to a family of compounds that includes vitamins D1, D2, and D3.

Vitamin D3: From sunlight & animal-sourced foods

Vitamin D3, also known as cholecalciferol, is the form of vitamin D that is produced by our bodies when our skin is exposed to sunlight. I'm sure you are all aware by now that sufficient sunlight exposure on our skin is how we must obtain the bulk of our vitamin D intake, but did you know that it is actually the cholesterol contained within our skin that synthetizes vitamin D when it is irradiated with the sun's ultraviolet waves? Well now you do! The connection between vitamin D, calcium and cholesterol is also hinted at in cholecalciferol's peculiar name.

Taking full advantage of good weather is a great way to achieve healthy levels of vitamin D intake.

While healthy and regular sunlight exposure is the easiest and most efficient (and arguably the cheapest) way to reach our required intake of vitamin D, vitamin D3 can also be found in certain animal-sourced foods such as fatty fish, liver and eggs, although it is not feasible to achieve the entirety of our vitamin D intake through diet alone.

To put it into perspective, approximately half an hour of exposure to direct sunlight (provided clothing, seasonal and meteorological conditions are met) can easily give you the full daily quota of recommended vitamin D, while you would need to eat more than half a kilogram of fatty fish in order to achieve this through diet alone. Obviously, in reality, we naturally eat much less than that.

That said, every little helps, and you should definitely seek to include fatty fish in your diet often, if not for its complimentary vitamin D3 content, then at least for the host of other health benefits it provides.

Vitamin D2: An inferior synthetic alternative

Vitamin D2 on the other hand is the synthetic form of vitamin D, and it is often used for fortifying foods, such as cereals and plant-based milk alternatives, due to its low cost. Vitamin D2 can also be found in certain species of mushrooms that have been exposed to ultraviolet radiation.

We are able to absorb both types of vitamin D, however research has shown that vitamin D3 is significantly more efficient, both at raising as well as maintaining, adequate vitamin D levels in our body.

Sufficient sunlight exposure

However, it is important to remember that anything that interferes with our body's ability to create vitamin D through our skin, including liver disease, kidney disease, increased melanin, or simply our lifestyle choices or obligations of remaining indoors and/or covered up, can cause vitamin D deficiency.

In fact, if you live far from the equator, there's a definite possibility that you are deficient in vitamin D to some degree, and this is where vitamin D supplementation comes in handy, especially during the winter months.

Vitamin D deficiency

So, now that you know how to get your daily dose of vitamin D, let's dig deeper into the actual health benefits of vitamin D, or rather, the effects that result from vitamin D deficiency.

Low levels of vitamin D have been associated with an increased risk of heart disease, hypertension, heart failure, and strokes, as well as increased risk of respiratory infection. In fact, this is one of the main reasons we succumb to the common cold and the flu with such apparent ease during the winter months, when our immune system is at its weakest from lack of sunlight exposure.

The winter months are when we are most susceptible to illness, as our immune system is at its weakest from reduced vitamin D intake.

Vitamin D deficiency is also associated with an increased risk of type 1 and type 2 diabetes, arthritis, and autoimmune diseases such as inflammatory bowel disease. Studies show that vitamin D supplementation significantly reduces the risk of developing type 2 diabetes in people that have pre-diabetes.

We're not done yet, it gets worse. A deficiency in vitamin D has been linked to an increased risk of developing several types of cancer.

Role in mental health

Furthermore, researchers have observed that many people that suffer from depression have low Vitamin D levels, although low Vitamin D levels are also in turn associated with lower outdoor activity and overall unhealthier lifestyles, making it hard to distinguish the correlation from the causation within the context of depression.

That said, studies have been able to demonstrate that vitamin D does play an important role in mood regulation and can decrease the risk of depression. A study featuring over 7,500 people revealed that vitamin D supplementation improved symptoms in those that were experiencing negative moods and emotions.

I think we all intuitively know that being outside in the fresh air and sunlight is beneficial for our mood, but the scientific explanation for that, or at least one of the main reasons, might be as simple as vitamin D.

When should I take vitamin D?

Short answer: Vitamin D is best taken with breakfast, or with the first meal of the day, preferably including fatty foods (fish, meat, eggs, dairy, avocado, olive oil, nuts, seeds).

Vitamin D is best taken early in the day if possible, and as it is a fat-soluble vitamin, it is recommended to take it together with a meal that incorporates dietary fat, such as fatty fish or meat, dairy products, avocados, nuts or seeds, in order to maximize its absorption.

What does vitamin D combine well with?

Short answer: Vitamin D has been shown to work well together with astaxanthin, fish oil, krill oil, magnesium, omega-3, quercetin, ubiquinol, vitamin B12, vitamin K and zinc.

Vitamin D with omega-3, for cardiovascular health

As vitamin D is best taken along with a meal that includes high-fat foods, it can be beneficial to combine it together with your omega-3 supplement of choice, such as fish oil or krill oil, if you are taking any.

Furthermore, research shows that combined supplementation of vitamin D with omega-3 fatty acids is able to significantly reduce insulin levels and inflammation while increasing HDL "good" cholesterol levels.

Vitamin D with magnesium, for bone, muscle & cognitive health

Magnesium is also known to combine well with vitamin D, and for a variety of reasons. The primary reason is that the enzymes that are responsible for metabolizing vitamin D all require a certain amount of magnesium to work.

In other words, if you don't have enough magnesium in your body, you will not be able to make the most of any vitamin D supplement. In fact, magnesium deficiency can result in insufficient levels of vitamin D, which may result in low intestinal calcium absorption, and lead to brittle bones, an increased risk of fracture, and increased risk of developing osteoporosis.

In addition to this, taking magnesium with vitamin D benefits muscle health, as they are both crucial for regulating normal muscle function. Specifically, vitamin D helps regulate muscle contraction, while magnesium helps regulate muscle relaxation.

The combination of magnesium and vitamin D is also known to promote neurotransmitter production, which helps regulate mood. Studies show that depression during adolescence could be caused by vitamin D deficiency for this precise reason.

Vitamin D with zinc, for increased absorption

Another mineral that combines well with vitamin D is zinc, as they share a synergistic relationship. Specifically, zinc is known to enhance the activity of vitamin D, while vitamin D is known to influence zinc's absorption. That said, zinc is best taken on an empty stomach, so you may need to find a compromise and take zinc with a meal if you want to take advantage of combining taking it at the same time as vitamin D.

Vitamin D with vitamin K, for bone health

As mentioned earlier in this article, vitamin D and vitamin K work together as a team to ensure calcium is distributed correctly throughout the body.

One of vitamin D's primary functions is to ensure that your blood has adequate levels of calcium, while vitamin K promotes the accumulation of calcium in your bones (and not elsewhere), making a supplemental combination of vitamin D and vitamin K perfect for promoting bone health.

Vitamin D with ubiquinol

Research also shows benefits to combining vitamin D with CoQ10, which you may also know as ubiquinol. Some studies show that this combination proves effective for supporting cardiovascular health and kidney health, and one animal-study in hypertensive rats was able to confirm the synergy between both components, especially in regards to their antioxidant properties.

Vitamin D with ubiquinol, astaxanthin and vitamin B12

Another study suggests that supplementing ubiquinol and vitamin D together with astaxanthin and vitamin B12 could increase energy levels, physical endurance and muscle health. This could be especially beneficial for those who are on a diet that is low in vitamin B12, such as people following vegan or vegetarian diets.

Vitamin D with quercetin, for cancer prevention

It has also been noted in some studies that vitamin D and quercetin show strong synergetic effects when taken together, by inhibiting the proliferation of cancer cells.

What should I avoid taking vitamin D with?

Short answer: Avoid taking vitamin D supplements at the same time as calcium.

Avoid with calcium

While it is known that one of vitamin D's main functions involves assisting in the absorption and distribution of calcium, it is not necessary to take them at the same time, and in fact in one study it was revealed that there is actually an increased risk of stroke when vitamin D and calcium are taken together in supplemental doses.

While these two supplements are often recommended to be taken together, and some supplement formulations even combine the two, taking high doses of both can lead to a condition known as hypercalcemia, which means that there is too much calcium in the blood.

In addition to cardiovascular issues, and the risk of calcium being deposited in the artery walls, this condition can also increase the risk of kidney stones.

So, in order to avoid any potential interaction, it would be advisable to take your calcium and vitamin D supplements separate, at least two hours apart.

What are natural sources of vitamin D?

If you are interested in achieving your daily vitamin D intake through your diet, rich sources of vitamin D include:

Beef liver
Cheese
Eggs
Trout
Mackerel
Tuna
Salmon
Pork
Mushrooms

Only a few select foods, such as the flesh of fatty fish, or certain species of mushrooms that have been exposed to UV light, naturally contain anything above trace amounts of vitamin D, and dietary intake is estimated to account for roughly only 10% of a person's total Vitamin D intake. We must get the vast majority of our Vitamin D through sunlight exposure, or alternatively, via supplementation.

Vitamin D data sources & further reading

Last updated by Asklepios on 30th January, 2025