Vitamin D: Benefits & How to get it

Introduction to Vitamin D

Vitamin D is a fat-soluble vitamin that acts more like a hormone in the body due to its influence on various systems. There are two primary sources of vitamin D: exposure to sunlight and dietary intake. When your skin is exposed to UVB sunlight, it converts a precursor of vitamin D into its active form.

Extensive reviews on vitamin D status in the world have been published over the last decades. Although vitamin D status can be considered satisfactory in some countries, vitamin D deficiency still is very common in many countries throughout the world and in many higher risk groups. [1]

Vitamin D is necessary for the absorption of calcium in the intestines, which is essential for bone health [2]. Without adequate vitamin D, the body struggles to absorb calcium efficiently, which can lead to weakened bones and increased susceptibility to fractures. [3]

In recent years, researchers have uncovered numerous other roles for vitamin D beyond bone health. In this article we will cover the roles vitamin D plays in the body, the benefits to having sufficient vitamin D levels, where to get it from and strategies to maintain adequate levels.

Understanding Vitamin D

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that acts as a hormone in the body. It is not a single molecule but a group of compounds. The two major forms of vitamin D are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).

Different Forms of Vitamin D (D2 and D3)

Vitamin D2 and D3 are the two main forms of vitamin D. Vitamin D2 (Ergocalciferol): This form of vitamin D is primarily obtained from plant sources. [4]

Vitamin D3 (Cholecalciferol): Vitamin D3 is the more potent and biologically active form of vitamin D. 

It can be synthesised by the body when the skin is exposed to sunlight (UVB radiation) and is also found in some animal-based food sources.

While both forms help you meet your vitamin D requirements, they differ in a few important ways. Here are the differences between vitamin D2 and D3:

  • Sources: Vitamin D2 is present in plants and yeast, while D3 comes from animal sources such as fish oil, egg yolks, and liver. [5]
  • Structure: Both play the same role in the body, but vitamins D2 and D3 have slightly different molecular structures. The main difference is that vitamin D2 has a double bond in its structure, whereas D3 has a single bond.
  • Effectiveness: Research suggests that vitamin D3 is more efficiently absorbed and utilised by the body than vitamin D2. A 2017 review of 32 randomised controlled trials found that vitamin D3 raised blood levels of vitamin D more effectively than vitamin D2 [5]. However, the review also said researchers needed more evidence before they could be sure how the two types affected different groups of people, such as people of different ages, sexes, and ethnicities [6].

How Vitamin D is synthesised in the Skin

When your skin is exposed to UVB sunlight, it triggers the synthesis of vitamin D [7]. The process begins with a cholesterol precursor in your skin, which, when activated by UVB radiation, converts to cholecalciferol (vitamin D3). This newly formed vitamin D3 is then transported to the liver and kidneys, where it is converted into its active hormonal form.

Factors Influencing Vitamin D Production

Several factors can influence the production of vitamin D in the skin:

  • Geographic Location: The amount of sunlight available varies depending on your geographical location and the time of year. People living in regions with limited sunlight during the winter months are more susceptible to vitamin D deficiency. [8]
  • Skin Pigmentation: Darker skin contains more melanin, which reduces the skin's ability to produce vitamin D in response to sunlight. [9]
  • Sunscreen Use: The use of sunscreen with a high sun protection factor (SPF) can block UVB radiation and hinder the production of vitamin D.
  • Ageing: As we age, our skin becomes less efficient at producing vitamin D [10].
  • Time of Day: The production of vitamin D is most effective when the skin is exposed to direct sunlight during the midday hours.

Understanding these factors is essential for maintaining vitamin D levels.

Benefits of Vitamin D

Maintaining optimal vitamin levels is important for overall health and well-being. Here are some reasons why:

May help support the Immune system

Vitamin D has been found to modulate both the innate and adaptive immune responses. It inhibits B cell proliferation, blocks B cell differentiation and immunoglobulin secretion, suppresses T cell proliferation, and facilitates the induction of T regulatory cells. Vitamin D deficiency is associated with increased susceptibility to infection and autoimmunity. Excessive training may lead to increased risk of illness and upper respiratory tract infections (URTIs), therefore, maintaining adequate levels of vitamin D is essential for a functional immune system and overall health[11][12].

May help athletic performance

Vitamin D has been linked to improved athletic performance. It influences muscle protein synthesis, muscle strength, muscle size, reaction time, balance, coordination, endurance, inflammation, and immunity—all important to sports health and athletic performance. Increasing vitamin D levels has been associated with increases in muscle protein synthesis, ATP concentration, strength, jump height, jump velocity, jump power, exercise capacity, and physical performance. Therefore, maintaining adequate levels of vitamin D could potentially enhance athletic performance and prevent future injuries[13][14].

A key point to note is that it is more about treating a deficiency of vitamin D than simply increasing vitamin D levels (4). 

May aid mood regulation

Vitamin D has been associated with mood regulation and mental health. Some studies suggest that vitamin D supplementation may effectively alleviate symptoms of depression and reduce the occurrence of negative emotions. However, the results are not consistent across all studies, and more research is needed to fully understand the relationship between vitamin D and mood disorders. Nevertheless, maintaining adequate levels of vitamin D could potentially contribute to improved mental health and quality of life[15,16].

May help strengthen bones and teeth

Vitamin D plays a crucial role in the health of our bones and teeth. It aids in the absorption and retention of calcium and phosphorus, essential minerals for tooth mineralisation and bone health. When vitamin D levels are low or unregulated, teeth may weaken, making individuals more susceptible to fractures, cavities, and decay. In fact, vitamin D deficiency has been linked to increased risk of tooth decay and gum disease. Therefore, maintaining adequate levels of vitamin D is vital for the strength and health of our bones and teeth [17].

Sources of Vitamin D

Sun exposure

Optimal sun exposure for vitamin D synthesis depends on several factors, including your skin type, geographical location, and the time of day. Here's what you need to know:

  • Time of Day: The best time for vitamin D synthesis is during midday when the sun is at its highest point in the sky. This is when UVB radiation, required for vitamin D production, is most abundant.
  • Duration: For individuals with light to medium skin tones, spending approximately 10 to 30 minutes in the sun, a few times a week, with your face, arms, and legs exposed, is usually sufficient to generate an adequate amount of vitamin D. However, people with darker skin may require more sun exposure because their skin contains more melanin, which reduces the skin's ability to produce vitamin D [9].

Vitamin D deficiency is common in the winter months with studies showing levels drop (18). This is where being proactive with your vitamin D intake and supplementation can help.

Seasonal variation in serum vitamin D concentrations (mean (95% confidence interval)) among 7,437 white British (1958 British birth cohort) at age 45. Dark red bar = male, red bar = female.
Seasonal variation in serum vitamin D concentrations (mean (95% confidence interval)) among 7,437 white British (1958 British birth cohort) at age 45. Dark red bar = male, red bar = female.

Dietary sources

Foods that are naturally high in vitamin D3 come from mainly animal sources [19]. These may include

  1. Salmon: 100 grams of cooked salmon contains 526 IU of vitamin D, or 131% of the Recommended Daily Value (DV).
  2. Rainbow trout: 100 grams of cooked rainbow trout contains 645 IU of vitamin D, or 161% of the DV.
  3. Mushrooms: 100 grams of mushrooms contain 10 IU of vitamin D, or 2% of the DV.
  4. Egg yolk: 1 large egg yolk contains 18 IU of vitamin D, or 4% of the DV.
  5. Canned tuna: 100 grams of canned tuna contains 236 IU of vitamin D, or 59% of the DV.
  6. Sardines: 100 grams of sardines contain 480 IU of vitamin D, or 120% of the DV.
  7. Cod liver oil: 1 tablespoon of cod liver oil contains 1,360 IU of vitamin D, or 340% of the DV.
  8. Beef liver: 100 grams of braised beef liver contains 42 IU of vitamin D, or 10% of the DV.

In addition to natural food sources, you can also obtain vitamin D from fortified foods and supplements. Fortified foods, like fortified dairy products and cereals, have vitamin D added during processing. Supplements, such as vitamin D spray or capsules, can be an effective way to ensure you're meeting your daily requirements, especially if you have limited sun exposure or dietary restrictions.

It's important to note that while natural food sources and fortified foods can contribute to your vitamin D intake, it may be challenging to get enough from diet alone. Supplements can provide a convenient and reliable way to maintain optimal vitamin D levels.

Recommended dietary allowances (RDAs) for Vitamin D

The only way to know if you are deficient is by having your blood levels measured.

Talk to your GP to get levels tested. Anything under 30 nmol/l is considered deficient, and anything above 50 noml/l is considered adequate.

To treat a deficiency it is recommended to supplement as deriving enough from food alone is challenging. Below is a table that shows the RDA for vitamin D [19].

However, these targets are often cited in the research as being too low for the majority of people (REF). 

Thus, higher doses of vitamin D than currently recommended are needed to bring most individuals to 75 nmol. This is where supplementation of 2000-3000iu per day may be required. (20)

According to the U.S. National Academy of Medicine, the safe upper limit is 4,000 IU (100 mcg) per day (21). 

It may be a sensible strategy to use the higher dose if you are in the severly deficient and insufficient ranges and a more maintenance dose of 1000-3000 iu once you are between 50 and 100nnmol/l [19]

Strategies to help maintain Vitamin D Levels

Balancing Sun Exposure and Protection.

Optimal Sun Exposure: Aim for approximately 10 to 30 minutes of sunlight exposure to the face, arms, and legs a few times a week during midday hours. This is typically sufficient for vitamin D synthesis for individuals with light to medium skin tones. For those with darker skin, longer exposure may be required.

Use Sunscreen Wisely: To balance sun protection and vitamin D synthesis, apply sunscreen with a high sun protection factor (SPF) after the initial 10-30 minutes of unprotected sun exposure.

Sun Safety Tips

While midday is the best time for vitamin D synthesis, it's also when the sun's UV radiation is most intense. Be cautious to prevent sunburn and skin damage [22].

Use protective clothing, such as hats, sunglasses, and long sleeves, to shield your skin from excessive sun exposure.

Adequate hydration is essential, especially in warm weather, to prevent overheating while spending time outdoors.

Lifestyle modifications for enhanced vitamin D absorption

Regular Physical Activity:

Engaging in physical activity outdoors is an excellent way to get both sun exposure and exercise. Just be mindful of sun safety guidelines.

Activities like walking, jogging, and weight lifting can help maintain bone health, enhancing the effects of vitamin D on calcium absorption.

Maintaining a Healthy Weight:

Maintaining a balanced diet and a healthy weight can positively impact vitamin D absorption and overall health. Obesity can lead to lower bioavailability of vitamin D, so managing your weight is essential [23]


Vitamin D is a fat soluble vitamin that plays an important role in overall health, exercise performance and wellbeing. Deficiency is fairly common due to limited sunlight exposure and a small selection of rich dietary sources. If you don’t spend much time in the sun and rarely eat fatty fish, consider supplementing.

The blood 25(OH)D concentration is the best indicator of vitamin D status. A blood vitamin D concentration of >50 nmol/L but preferably 75-100 nmol/L should be maintained. “Suboptimal” vitamin D status is linked to increased risk for acute illness, inflammatory injury, stress fracture, muscle pain/weakness and suboptimal muscle performance. 

Regular consumption of vitamin D-containing foods alone is not likely to maintain sufficient vitamin D status. Sensible sun exposure (5 to 30 min of exposure to arms, legs and back at close to solar noon several times a week), regular vitamin D supplementation (1000-3000 IU/day), or a combination of dietary intake, sun exposure and supplementation are required to achieve sufficient status. Our Vitamin D Spray delivers 3000IU of vitamin D per spray.

In winter months, vitamin D supplementation is needed for people living at >35° north or south

Frequently Asked Questions (FAQs)

Q1) What is vitamin D and how is it obtained by the body?

A1) Vitamin D is a fat-soluble vitamin that acts as a hormone in the body. It can be obtained through exposure to sunlight, which converts a precursor in the skin to its active form, or through dietary intake.

Q2) What are the main forms of Vitamin D, and how do they differ?

A2) The two main forms of Vitamin D are D2 (ergocalciferol) and D3 (cholecalciferol). D3 is more biologically active and can be synthesised by the body when the skin is exposed to sunlight, while D2 is primarily obtained from plant sources.

Q3) What are the benefits of maintaining sufficient Vitamin D levels?

A3) Maintaining adequate levels of Vitamin D contributes to supporting the immune system, improving athletic performance, aiding mood regulation, and strengthening bones and teeth.

Q4) What are the primary sources of Vitamin D?

A4) The primary sources of Vitamin D are sun exposure, where UVB radiation triggers its synthesis in the skin, and dietary sources like fatty fish, egg yolks, and fortified foods.

Q5) How can I maintain optimal Vitamin D levels, especially in regions with limited sunlight?

A5) To maintain optimal Vitamin D levels in regions with limited sunlight, you can consider a combination of sensible sun exposure, regular Vitamin D supplementation (1000-3000IU per day), and a dietary intake of Vitamin D containing foods. 


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