Should You Take Vitamin D Year-Round?

You might already be pretty familiar with this “sunshine vitamin”, but when it comes to Vitamin D, there’s a lot to know. It’s role in regulating immune function, for example, is especially interesting given the recent research correlating a link between high vitamin-D levels and better outcomes for those infected with COVID-19. (1

But it’s not just your immune system that benefits from vitamin D: It plays a role in everything from cell growth, to bone health and even muscle strength and energy levels. Every cell in your body has a vitamin D receptor—highlighting how crucial it is for our health. Chances are, if you live in a colder climate, you might not be getting enough vitamin D.

We’re covering all the basics around vitamin D, including why you need it for your health and the best ways to source it. 

What is Vitamin D?

Vitamin D is unlike most vitamins, because it actually functions as a steroid hormone that’s produced in the body when your skin is exposed to sunlight. (2) Vitamin D is a fat-soluble vitamin, meaning it is absorbed well with fats, and that it can be stored in fat cells in the body. 

It's responsible for a variety of functions in the body including maintaining homeostasis of calcium and phosphorus, bone mineralization, proper skeletal development and regulating the immune system. 

While the best way to source vitamin D is through exposure to the sun, most people aren’t spending enough time outdoors, increasing the risk of vitamin D deficiency. This is especially true in colder climates, where sunshine is limited throughout the winter months.

In the UK, for example, 1 out of 3 people are deficient in vitamin D due to working indoors during peak daylight hours, cloudy days throughout the year, and limited skin exposure. 

Different types of Vitamin D

There are two main types of the precursor vitamin D that can be found in foods and supplements: 

Vitamin D2: this is a plant-based source of vitamin D found in mushrooms that have been exposed to UV light, fortified foods and supplements.

Vitamin D3: this is an animal-based source of vitamin D, found in oily fish, liver, eggs yolks and supplements. This is also the kind produced from skin exposure to the sun. (3)

When it comes to absorption, vitamin D3 is a better source for raising blood levels of vitamin D, as it’s almost twice as effective as vitamin D2. (4)

Why We Need It: Health Benefits of Vitamin D

It Improves Bone Health: one of vitamin D’s biggest roles is in supporting bone health, as vitamin D deficiency causes calcium to be pulled from the bones, leading to conditions like rickets or osteoporosis. (5) In fact, research shows that in elderly women in particular, vitamin D can help to prevent osteoporosis, as well as falls and fractures. (6) Vitamin D deficiency has also been observed in people with rheumatoid arthritis, and while research is limited, it may have benefits in arthritic pain relief. (7)

It Might Help With Depression: vitamin D actually plays a powerful role in mood regulation, and supplementation with vitamin D may help prevent and lessen symptoms of depression. (8, 9)

It Improves Muscle Health and Strength: Not only is vitamin D important for bone health, it also plays a part in muscle tissue and physical performance. Vitamin D supplementation has been shown to increase strength, reduce the risk of falling and potentially affect muscle fibre composition. (10) A systematic review found that vitamin D supplementation also helped to improve upper and lower limb strength. (11)

It Regulates Immune Function: Immune cells, like B cells, T cells and antigens have vitamin D receptors, as vitamin D plays a crucial role in modulating immune response. In fact, evidence suggests that vitamin D deficiency is linked to a variety of autoimmune conditions, including rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease and diabetes. (12) Another study found that vitamin D supplementation in children was also able to reduce their risk of getting the flu. (13, 14

How to Get it

Sun Exposure: Sun exposure is one of the best ways to get vitamin D, however, for a lot of us that may not be possible. Research in the UK suggests that about 15 minutes in midday summer sun, wearing a t-shirt and shorts, is enough to keep people with lighter skin out of deficiency (if not in an optimal range), but people with darker skin are more likely to be deficient. (15

People with darker skin may need to spend anywhere from 30 minutes to three hours in the sun to reduce their risk of deficiency (16

Sun exposure also comes with it’s own risks: it ages the skin, it increases the risk of skin cancer and can lead to skin discoloration and damage. (17, 18, 19) Research is also still mixed as to whether or not sunscreens play a role in limiting the production of vitamin D, however short term studies show there might be little, if any impact on blood levels of vitamin D. (20)

Diet: there are also few sources of vitamin D in our food supply, offering up both vitamin D2 and D3. Again, D3 is the better option when looking at food sources, but D2 provides a plant-based source of vitamin D. 

Cod liver oil is an excellent source of vitamin D3, providing three times the RDA. (21) Other food sources of vitamin D3 include salmon, trout, tuna and egg yolks. Sources of D2 include mushrooms that have been exposed to UV light and fortified foods.

While food sources of vitamin D are a great addition, diet alone may not be sufficient in preventing deficiency: a 3oz piece of salmon, for example, contains 74% of the RDA for vitamin D, while one egg only provides 7%.

Should you Supplement?

Certain populations may require supplementation to have optimal blood levels of vitamin D, particularly during winter months. The only true way to know how much you need to supplement with is by having your blood levels measured.

However, here are some factors that could put you at higher need for supplementation:

  • Older populations. Older adults may be at a bigger risk of deficiency due to the decreased ability to synthesize vitamin D, and the lack of sun exposure as a result as a result of limited mobility (22)
  • Not enough sun exposure. People living in colder climates, away from the equator are more likely to require supplementation as vitamin D is not produced during winter months (which in some places can run from October to March). (23) It is often recommended that these populations consume at least 1000 IU daily. (24)
  • Fat malabsorption and compromised gut health. Because vitamin D is a fat-soluble vitamin, those with difficulties absorbing fat—people with ulcerative colitis, Crohn’s disease or liver disease, for example—may require extra supplementation. (25)
  • High body fat percentage. It seems that people with a higher BMI are more likely to be deficient in vitamin D, although research is still unclear as to why that is. (26)
  • Darker skin. People with darker skin and higher melanin levels produce less vitamin D when exposed to the sun, and therefore may require supplementation. (27
  • Nutrient deficiencies. Magnesium deficiency, which is one of the most common nutrient deficiencies, can affect vitamin D levels, due to its role in assisting vitamin D production. (28) Vitamin A and K are other nutrients that are important in the optimization of vitamin D. (29, 30)

How to Choose the Right Supplement 

When choosing a vitamin D supplement, vitamin D3 is the preferred source as it is more biologically active, and has been shown to be more effective at raising blood levels of vitamin D in comparison to D2. (31)

Another great quality to look for in a vitamin D supplement is the inclusion of vitamin K2. Vitamin K2, another fat-soluble vitamin that people are often deficient in, helps to ensure that vitamin D is deposited in your bones and teeth as needed, as opposed to soft tissue. (32

Lastly, while the dose is based around individual needs, recommendations for maintenance is around 2000 IU, while requirements to replete a deficiency can vary between 5,000-10,000 IU per day. (33

While vitamin D toxicity can happen, it’s quite rare and is typically seen in extremely high doses for extended periods of time (34) In fact, one study looking at 17,000 people found that intakes above 20,000 IU per day still did not show signs of toxicity. (35) For reference, the upper limit of harmless intake is set at 4,000 IU. (35)

The average range for daily supplementation if you don’t have access to the sun, sits somewhere between 1,000-4,000 IU/per day. 

Inner Vitality’s Vitamin D3 with K2 is made with Cholecalciferol D3—the kind made by your skin—as well as vitamin K2 MK7, made from naturally fermented nato. Research shows that vitamin K2 MK7 is a more bioavailable form of K2, to ensure that calcium is properly utilized in the body while preventing vitamin D toxicity. (36

At a dose of 3000 IU per day, Inner Vitality offers a high strength dose of vitamin D that can be particularly beneficial for daily maintenance of immune function and bone health throughout the winter months.

Key Takeaways 

Vitamin D is crucial for our health, especially when it comes to regulating our immune system and maintaining bone health. While sunlight exposure and food sources are good ways to increase vitamin D levels, they may not be sufficient on their own, especially if you live somewhere with a long winter season, spend a lot of time indoors or have darker skin. 

Supplementation can be a really beneficial (and easy!) way to maintain vitamin D levels, especially in colder climates that are farther away from the equator. Vitamin D3 is the preferred form for supplementation, however vegans may prefer D2 sources as it is plant-based. 

With all that said, who’s ready to get out and get a little bit of sun today?

You might already be pretty familiar with this “sunshine vitamin”, but when it comes to Vitamin D, there’s a lot to know. It’s role in regulating immune function, for example, is especially interesting given the recent research correlating a link between high vitamin-D levels and better outcomes for those infected with COVID-19. (1

But it’s not just your immune system that benefits from vitamin D: It plays a role in everything from cell growth, to bone health and even muscle strength and energy levels. Every cell in your body has a vitamin D receptor—highlighting how crucial it is for our health. Chances are, if you live in a colder climate, you might not be getting enough vitamin D.

We’re covering all the basics around vitamin D, including why you need it for your health and the best ways to source it. 

What is Vitamin D?

Vitamin D is unlike most vitamins, because it actually functions as a steroid hormone that’s produced in the body when your skin is exposed to sunlight. (2) Vitamin D is a fat-soluble vitamin, meaning it is absorbed well with fats, and that it can be stored in fat cells in the body. 

It’s responsible for a variety of functions in the body including maintaining homeostasis of calcium and phosphorus, bone mineralization, proper skeletal development and regulating the immune system. 

While the best way to source vitamin D is through exposure to the sun, most people aren’t spending enough time outdoors, increasing the risk of vitamin D deficiency. This is especially true in colder climates, where sunshine is limited throughout the winter months.

In the UK, for example, 1 out of 3 people are deficient in vitamin D due to working indoors during peak daylight hours, cloudy days throughout the year, and limited skin exposure. 

Different types of Vitamin D

There are two main types of the precursor vitamin D that can be found in foods and supplements: 

Vitamin D2: this is a plant-based source of vitamin D found in mushrooms that have been exposed to UV light, fortified foods and supplements.

Vitamin D3: this is an animal-based source of vitamin D, found in oily fish, liver, eggs yolks and supplements. This is also the kind produced from skin exposure to the sun. (3)

When it comes to absorption, vitamin D3 is a better source for raising blood levels of vitamin D, as it’s almost twice as effective as vitamin D2. (4)

Why We Need It: Health Benefits of Vitamin D

It Improves Bone Health: one of vitamin D’s biggest roles is in supporting bone health, as vitamin D deficiency causes calcium to be pulled from the bones, leading to conditions like rickets or osteoporosis. (5) In fact, research shows that in elderly women in particular, vitamin D can help to prevent osteoporosis, as well as falls and fractures. (6) Vitamin D deficiency has also been observed in people with rheumatoid arthritis, and while research is limited, it may have benefits in arthritic pain relief. (7)

It Might Help With Depression: vitamin D actually plays a powerful role in mood regulation, and supplementation with vitamin D may help prevent and lessen symptoms of depression. (8, 9)

It Improves Muscle Health and Strength: Not only is vitamin D important for bone health, it also plays a part in muscle tissue and physical performance. Vitamin D supplementation has been shown to increase strength, reduce the risk of falling and potentially affect muscle fibre composition. (10) A systematic review found that vitamin D supplementation also helped to improve upper and lower limb strength. (11)

It Regulates Immune Function: Immune cells, like B cells, T cells and antigens have vitamin D receptors, as vitamin D plays a crucial role in modulating immune response. In fact, evidence suggests that vitamin D deficiency is linked to a variety of autoimmune conditions, including rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease and diabetes. (12) Another study found that vitamin D supplementation in children was also able to reduce their risk of getting the flu. (13, 14

How to Get it

Sun Exposure: Sun exposure is one of the best ways to get vitamin D, however, for a lot of us that may not be possible. Research in the UK suggests that about 15 minutes in midday summer sun, wearing a t-shirt and shorts, is enough to keep people with lighter skin out of deficiency (if not in an optimal range), but people with darker skin are more likely to be deficient. (15

People with darker skin may need to spend anywhere from 30 minutes to three hours in the sun to reduce their risk of deficiency (16

Sun exposure also comes with it’s own risks: it ages the skin, it increases the risk of skin cancer and can lead to skin discoloration and damage. (17, 18, 19) Research is also still mixed as to whether or not sunscreens play a role in limiting the production of vitamin D, however short term studies show there might be little, if any impact on blood levels of vitamin D. (20)

Diet: there are also few sources of vitamin D in our food supply, offering up both vitamin D2 and D3. Again, D3 is the better option when looking at food sources, but D2 provides a plant-based source of vitamin D. 

Cod liver oil is an excellent source of vitamin D3, providing three times the RDA. (21) Other food sources of vitamin D3 include salmon, trout, tuna and egg yolks. Sources of D2 include mushrooms that have been exposed to UV light and fortified foods.

While food sources of vitamin D are a great addition, diet alone may not be sufficient in preventing deficiency: a 3oz piece of salmon, for example, contains 74% of the RDA for vitamin D, while one egg only provides 7%.

Should you Supplement?

Certain populations may require supplementation to have optimal blood levels of vitamin D, particularly during winter months. The only true way to know how much you need to supplement with is by having your blood levels measured.

However, here are some factors that could put you at higher need for supplementation:

  • Older populations. Older adults may be at a bigger risk of deficiency due to the decreased ability to synthesize vitamin D, and the lack of sun exposure as a result as a result of limited mobility (22)
  • Not enough sun exposure. People living in colder climates, away from the equator are more likely to require supplementation as vitamin D is not produced during winter months (which in some places can run from October to March). (23) It is often recommended that these populations consume at least 1000 IU daily. (24)
  • Fat malabsorption and compromised gut health. Because vitamin D is a fat-soluble vitamin, those with difficulties absorbing fat—people with ulcerative colitis, Crohn’s disease or liver disease, for example—may require extra supplementation. (25)
  • High body fat percentage. It seems that people with a higher BMI are more likely to be deficient in vitamin D, although research is still unclear as to why that is. (26)
  • Darker skin. People with darker skin and higher melanin levels produce less vitamin D when exposed to the sun, and therefore may require supplementation. (27
  • Nutrient deficiencies. Magnesium deficiency, which is one of the most common nutrient deficiencies, can affect vitamin D levels, due to its role in assisting vitamin D production. (28) Vitamin A and K are other nutrients that are important in the optimization of vitamin D. (29, 30)

How to Choose the Right Supplement 

When choosing a vitamin D supplement, vitamin D3 is the preferred source as it is more biologically active, and has been shown to be more effective at raising blood levels of vitamin D in comparison to D2. (31)

Another great quality to look for in a vitamin D supplement is the inclusion of vitamin K2. Vitamin K2, another fat-soluble vitamin that people are often deficient in, helps to ensure that vitamin D is deposited in your bones and teeth as needed, as opposed to soft tissue. (32

Lastly, while the dose is based around individual needs, recommendations for maintenance is around 2000 IU, while requirements to replete a deficiency can vary between 5,000-10,000 IU per day. (33

While vitamin D toxicity can happen, it’s quite rare and is typically seen in extremely high doses for extended periods of time (34) In fact, one study looking at 17,000 people found that intakes above 20,000 IU per day still did not show signs of toxicity. (35) For reference, the upper limit of harmless intake is set at 4,000 IU. (35)

The average range for daily supplementation if you don’t have access to the sun, sits somewhere between 1,000-4,000 IU/per day. 

Inner Vitality’s Vitamin D3 with K2 is made with Cholecalciferol D3—the kind made by your skin—as well as vitamin K2 MK7, made from naturally fermented nato. Research shows that vitamin K2 MK7 is a more bioavailable form of K2, to ensure that calcium is properly utilized in the body while preventing vitamin D toxicity. (36

At a dose of 3000 IU per day, Inner Vitality offers a high strength dose of vitamin D that can be particularly beneficial for daily maintenance of immune function and bone health throughout the winter months.

Key Takeaways 

Vitamin D is crucial for our health, especially when it comes to regulating our immune system and maintaining bone health. While sunlight exposure and food sources are good ways to increase vitamin D levels, they may not be sufficient on their own, especially if you live somewhere with a long winter season, spend a lot of time indoors or have darker skin. 

Supplementation can be a really beneficial (and easy!) way to maintain vitamin D levels, especially in colder climates that are farther away from the equator. Vitamin D3 is the preferred form for supplementation, however vegans may prefer D2 sources as it is plant-based. 

With all that said, who’s ready to get out and get a little bit of sun today?