Vitamin D

Vitamin D is a fat-soluble vitamin that plays an essential role in many physiological processes in the human body.

Vitamin D is something we get from our diet and exposure to the sun’s rays. It is common for the colder months, where individuals spend less time outside for the deficiencies to become problematic. Unlike our ancestors who spent a lot of time under the sun, today even in warmer climates, people stay a lot of the time indoors and may lack Vitamin D even in warmer sunny-all-year-round countries. Be wary of a Vitamin D deficiency, as it can be a major hindrance to your health, health span, and longevity

Vitamin D is a crucial nutrient that plays several important roles in our body:

  1. Promotes bone health: Vitamin D is essential for calcium absorption and helps maintain proper levels of calcium and phosphorus in the blood, which are important for building and maintaining strong bones. Vitamin D deficiency can lead to conditions such as osteoporosis or rickets (1,2).
  2. Supports immune function: Vitamin D plays a role in regulating the immune system and can help reduce the risk of certain infections, such as respiratory tract infections(3,4).
  3. Regulates cell growth and differentiation: Vitamin D is involved in regulating the growth and differentiation of cells, including those in the skin, prostate, colon, and breast. There is also some evidence to suggest that vitamin D may play a role in reducing the risk of certain types of cancer (5,6).
  4. Helps regulate insulin levels: Vitamin D may play a role in regulating insulin secretion and glucose metabolism, which can help reduce the risk of developing type 2 diabetes(7,8).
  5. Supports heart health: Some studies have suggested that vitamin D may help reduce the risk of heart disease and stroke, possibly by helping to regulate blood pressure and inflammation(9).

Vitamin D is a vital nutrient that plays several important roles in our body. It is important to maintain adequate levels of vitamin D through sun exposure, diet, and supplements if necessary, to support overall health and wellbeing.

There are two primary forms of vitamin D: D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D2 is mainly found in plant sources, while vitamin D3 is produced in the skin of animals and humans after exposure to ultraviolet B (UVB) radiation.

The main dietary sources of vitamin D are fatty fish, liver, egg yolks, and fortified foods such as milk and cereal. However, most people meet their vitamin D needs through exposure to sunlight, which triggers the production of vitamin D3 in the skin. The amount of vitamin D that a person can produce from sunlight exposure depends on factors such as skin color, age, and geographic location.

Once in the body, vitamin D is converted into its active form, calcitriol, which acts as a hormone and regulates the absorption of calcium and phosphorus in the intestines. This, in turn, helps to maintain healthy bones and teeth. Vitamin D is also involved in other processes in the body, including immune function, cell growth and differentiation, and muscle function.

Vitamin D deficiency is a common health issue, especially among people who live in areas with limited sun exposure or who have a diet low in vitamin D-rich foods. Severe vitamin D deficiency can lead to a condition called rickets in children, which causes weakened and deformed bones, and osteomalacia in adults, which causes bone pain and muscle weakness. Therefore, it is important to maintain adequate vitamin D levels through a combination of sun exposure, diet, and supplementation if necessary.

Sources of Vitamin D

The percentage of vitamin D that forms via exposure to sunlight versus dietary sources can vary depending on factors such as geographic location, season, and dietary habits. However, in general, it is estimated that approximately 80-90% of vitamin D in the body is synthesized in the skin through exposure to sunlight, while the remaining 10-20% comes from dietary sources.

Sunlight

%
We get up to 80% of our Vitamin D from sunlight

Dietary sources

%
We get up to 20% of our Vitamin D from food

Sunlight and Vitamin D3

When skin is exposed to ultraviolet B (UVB) radiation from the sun, a cholesterol derivative in the skin called 7-dehydrocholesterol is converted into vitamin D3 (cholecalciferol). The process of vitamin D3 formation is initiated when UVB radiation penetrates the skin and causes a photolytic cleavage of the bond between C9 and C10 on 7-dehydrocholesterol. This reaction yields pre-vitamin D3, which isomerizes rapidly to form vitamin D3.

However, several factors can hinder the formation of vitamin D3 from sun exposure. These include:

  1. Season and latitude: At higher latitudes and during the winter months, the sun’s angle is too low for UVB radiation to penetrate the atmosphere and reach the skin. Therefore, people who live in these regions may have reduced vitamin D3 production from sun exposure.
  2. Time of day: UVB radiation is most intense during midday when the sun is highest in the sky. Therefore, sun exposure during midday may be more effective at promoting vitamin D3 production.
  3. Skin pigmentation: Melanin, the pigment that gives skin its color, absorbs UVB radiation and reduces the amount of vitamin D3 that can be produced in the skin. Therefore, people with darker skin may require longer sun exposure times to have adequate amounts of vitamin D3.

On the other hand, several factors can enhance vitamin D3 production from sun exposure. These include:

  1. Amount of skin exposed: The more skin that is exposed to the sun, the more vitamin D3 can be produced.
  2. Age: As people age, their skin becomes less efficient at producing vitamin D3. Therefore, older adults may require more sun exposure or a higher dietary intake of vitamin D to maintain adequate levels.
  3. Altitude: At higher altitudes, there is less atmosphere to absorb UVB radiation, which means that sun exposure at high elevations can be more effective at promoting vitamin D3 production.
  4. Use of sunscreen: Sunscreen with a sun protection factor (SPF) of 30 or higher can significantly reduce vitamin D3 production in the skin. Therefore, it is recommended to get some sun exposure without sunscreen for a short time before applying it.

Overall, a balance of moderate sun exposure, dietary intake, and possibly supplementation if necessary, can help ensure adequate vitamin D levels.

Dietary sources of Vitamin D

a table that lists the vitamin D content of some common foods that are naturally rich in vitamin D per 100-gram serving:

Food (100g)Vitamin D (IU)
Salmon, cooked988
Tuna, canned in water, drained236
Sardines, canned in oil, drained193
Mackerel, cooked360
Beef liver, cooked42
Egg yolk, cooked37
Cheese, Swiss6
Mushrooms, raw0*
These are just examples, showing that food is not that good a source of vitamin D, it is best to get it through sunlight exposure

* Not all mushrooms contain vitamin D, only those that were exposed to sunlight or ultraviolet prior to packing… Very few of the mushrooms available at supermarkets are high, or even contain Vitamin D.

Note that the amount of vitamin D in these foods can vary depending on factors such as how the food is prepared and the animal’s diet. It is also important to keep in mind that while these foods are good sources of vitamin D, it can be challenging to obtain enough vitamin D through diet alone, especially in areas with limited sun exposure.

Geographic and dietary differences

Certain groups may particularly benefit from vitamin D supplementation:

  • Elderly: As skin ages, it becomes less efficient at producing vitamin D. The elderly also tend to have reduced dietary intake and sun exposure.
  • Individuals with Darker Skin: Higher melanin levels reduce the skin’s ability to produce vitamin D.
  • Individuals with Limited Sun Exposure: Those living at northern latitudes, wearing covering clothing, or mostly staying indoors may need supplements.
  • People with Malabsorption: Conditions like celiac disease, Crohn’s disease, and cystic fibrosis can reduce vitamin D absorption.
  • Obese Individuals: Vitamin D can be sequestered in body fat, reducing its bioavailability.

In countries such as the USA and UK, where sunlight exposure can be limited due to climate or lifestyle factors, it is particularly important to obtain vitamin D through dietary sources or supplements. Foods that are naturally rich in vitamin D include fatty fish (such as salmon and tuna), egg yolks, and beef liver. Some foods, such as milk, yogurt, and cereals, are also fortified with vitamin D to help increase intake. However, even with these sources, many people may still struggle to get enough vitamin D, and supplementation may be necessary to meet recommended intake levels.

Climate and geographic location

Latitude and longitude have a significant impact on exposure to sunlight, which is the primary source of vitamin D for humans. At higher latitudes, the angle of the sun’s rays is lower, and the atmosphere scatters more of the UVB radiation that is needed to produce vitamin D. Therefore, people living in areas closer to the equator generally have higher vitamin D levels than those living farther away.

The climate also plays a role in vitamin D production, as cloud cover can reduce the amount of UVB radiation that reaches the skin. In regions with a lot of cloud cover or precipitation, people may have a higher risk of vitamin D deficiency.

The worst countries for vitamin D deficiency and insufficiency are typically those located at high latitudes, with little exposure to sunlight. For example, countries in northern Europe, such as Norway, Sweden, and Finland, have high rates of vitamin D deficiency, as do countries in the Middle East, such as Saudi Arabia and Iraq.

It may be surprising that people living close to the equator may struggle with Vitamin D deficiency, but there are a few good reasons.

  1. High temperatures: In many Middle Eastern countries, the weather is hot and sunny, which may seem like it would lead to higher levels of vitamin D production. However, because of the extreme heat, many people spend a lot of time indoors, in air-conditioned environments. This reduces their exposure to sunlight and may contribute to vitamin D deficiency.
  2. Traditional dress: Many people in the Middle East wear clothing that covers most of their skin, such as abayas or burqas. This reduces their skin’s exposure to sunlight and can also contribute to vitamin D deficiency.
  3. Limited outdoor activities: Due to the high temperatures and cultural norms, outdoor activities may be limited in some Middle Eastern countries. People may be less likely to engage in activities that involve spending time outside, which can further reduce their exposure to sunlight. The same problems can happen to those living in colder climates and in urban environments where sun exposure is rare, especially in the colder months.

In the United States, states in the northern part of the country, such as Alaska, Maine, and Vermont, also have higher rates of vitamin D deficiency compared to states located closer to the equator, such as Hawaii and Florida.

How long does vitamin D stay in the body?

The amount of time that vitamin D stays in the system can vary depending on a variety of factors, including the individual’s age, health status, and level of sun exposure or dietary intake. Some studies suggest that vitamin D has a half-life of about 2-3 weeks in the blood, meaning that it takes that amount of time for the body to eliminate half of the vitamin D that is present in the bloodstream.

The rate at which vitamin D is used up for various functions can also vary depending on the individual and their needs. For example, if an individual is deficient in vitamin D, their body may use up more vitamin D to help support bone health, immune function, and other processes that rely on vitamin D. Conversely, if an individual has sufficient vitamin D levels, their body may use less of it for these same functions.

Symptoms of vitamin D deficiency

Vitamin D is necessary and the body will tell you with various symptoms that it is not getting enough Vitamin D. You may notice the following symptoms when low on Vitamin D:

  1. Bone and muscle pain: Vitamin D plays a crucial role in regulating bone health, and a deficiency in vitamin D can cause bone and muscle pain. Studies have shown that vitamin D supplementation can help improve bone and muscle pain in individuals with vitamin D deficiency(10).
  2. Muscle weakness: Vitamin D is important for muscle function and strength, and a deficiency can lead to muscle weakness. Studies have found that vitamin D supplementation can help improve muscle strength and function in individuals with vitamin D deficiency(11).
  3. Fatigue: Vitamin D deficiency has been associated with fatigue and low energy levels. Studies have shown that vitamin D supplementation can help improve fatigue in individuals with vitamin D deficiency(12).
  4. Mood changes: Vitamin D deficiency has been linked to an increased risk of depression and other mood disorders. Studies have found that vitamin D supplementation can help improve mood in individuals with vitamin D deficiency(13).
  5. Impaired wound healing: Vitamin D is important for skin health and wound healing. Studies have shown that vitamin D deficiency can impair wound healing, and that vitamin D supplementation can help improve wound healing in individuals with vitamin D deficiency(14).

Many of these symptoms are problems by themselves. So keep yourself checked. Some people may not notice or ignore these symptoms, also these symptoms may indicate larger unrelated problems, but Vitamin D is so important that it ought not to be ignored. Try to fix yourself some sunlight when you are feeling the symptoms described above.

Vitamin D deficiency tests

There are two main ways to check for vitamin D levels: a blood test or a 25-hydroxy vitamin D (25(OH)D) test, which is the most accurate way to assess vitamin D status.

Blood tests can measure the amount of 25(OH)D in the blood, which is the best indicator of vitamin D status. The test is typically done by drawing blood from a vein in the arm, and the results can be used to determine if an individual is deficient, insufficient, or has adequate levels of vitamin D.

The accuracy of vitamin D tests can depend on a variety of factors, including the type of test used, the laboratory performing the test, and the timing of the test. Some studies have shown that different laboratories can produce different results for the same sample, so it is important to use a reputable laboratory for testing.

Another factor that can affect the accuracy of vitamin D tests is the timing of the test. Vitamin D levels can fluctuate throughout the year, with higher levels typically seen in the summer months when there is more sun exposure. Therefore, it may be best to test vitamin D levels during the winter months when levels are expected to be lower.

It is also important to note that there is no universally accepted definition for vitamin D deficiency or insufficiency. Different organizations and experts may use different cutoff values for determining vitamin D status, which can affect the interpretation of test results.

Correcting Deficiencies

For individuals with vitamin D deficiencies, oral supplementation can be very effective. The dose required to correct a deficiency will depend on the severity of the deficiency and individual factors like age, body weight, and level of sun exposure.

How long does it take for symptoms to dissipate?

The amount of time it takes for vitamin D deficiency symptoms to dissipate can vary depending on the individual’s age, health status, and the severity of their deficiency. Additionally, the source of vitamin D (sun exposure, supplements, or dietary intake) can also affect the rate at which symptoms improve.

In general, it can take several weeks to months for vitamin D levels to increase and for symptoms of deficiency to improve with supplementation or dietary changes. For example, a study published in The American Journal of Clinical Nutrition found that it took 16 weeks of vitamin D supplementation to achieve a significant improvement in muscle strength in elderly individuals with vitamin D deficiency.

Sun exposure can also increase vitamin D levels, but the amount of time it takes to see an improvement in symptoms can vary depending on factors such as the individual’s skin pigmentation, time of day, and latitude. For example, a study published in the Journal of Investigative Dermatology found that it took 2-3 weeks of sun exposure to increase vitamin D levels in individuals with fair skin living in the northern hemisphere during the summer months.

Vitamin D deficiency and aging

There is some evidence to suggest that vitamin D deficiency may be associated with accelerated aging, but more research is needed to fully understand this link.

Aging is a complex process that involves the accumulation of cellular damage over time. Studies have shown that vitamin D plays a role in regulating cellular processes that are important for maintaining healthy aging, such as inflammation, oxidative stress, and DNA repair.

Here is an overview of vitamin D’s role in these processes:

  1. Cell signaling: Vitamin D acts as a hormone that regulates several cellular processes, including cell proliferation and differentiation, apoptosis, and inflammation. By regulating these processes, vitamin D can play a role in maintaining healthy aging.
  2. Nutrient sensing: Vitamin D plays a role in nutrient sensing pathways, such as the insulin-like growth factor (IGF-1) pathway, which is important for maintaining cellular homeostasis and regulating cell growth and differentiation.
  3. DNA repair: Vitamin D is involved in DNA repair processes, such as base excision repair and nucleotide excision repair. By promoting DNA repair, vitamin D can help prevent mutations and maintain genomic stability, which is important for healthy aging.
  4. DNA maintenance: Vitamin D also plays a role in DNA maintenance, including maintaining telomere length, which is important for preventing genomic instability and maintaining healthy aging.

Some studies have suggested that vitamin D deficiency may be associated with accelerated aging, as indicated by shorter telomeres (the protective caps at the end of chromosomes that shorten with age) and other markers of cellular aging. However, other studies have not found a significant association between vitamin D levels and telomere length or other markers of aging.

It is important to note that the relationship between vitamin D deficiency and aging is likely complex and multifactorial, and more research is needed to fully understand this link. Additionally, while vitamin D may play a role in maintaining healthy aging, it is just one of many factors that contribute to overall health and aging.

Vitamin D Supplementation

Vitamin D supplementation can be administered by various methods, including oral supplements (pills), additives to food or beverages, and intravenous (IV) drips. Here is an overview of the effectiveness of each method:

  1. Oral supplements (pills): Oral vitamin D supplements are the most common form of vitamin D supplementation. These supplements can come in various forms, such as tablets, capsules, or liquids, and can be taken daily or weekly. Studies have shown that oral vitamin D supplements can effectively increase vitamin D levels and improve vitamin D deficiency symptoms. The effectiveness of oral vitamin D supplementation can depend on the dose, duration of treatment, and the form of vitamin D used.
  2. Additives to food or beverages: Vitamin D can be added to certain foods or beverages, such as milk, orange juice, or cereal. While this can be an effective way to increase vitamin D intake, the amount of vitamin D in these foods is often limited and may not provide enough vitamin D to meet daily requirements or treat vitamin D deficiency.
  3. Intravenous (IV) drips: IV vitamin D supplementation is typically reserved for individuals with severe vitamin D deficiency or malabsorption issues. While IV vitamin D can rapidly increase vitamin D levels, it is not a common or recommended method of vitamin D supplementation. This method should only be used under the guidance of a healthcare professional.

Exposure to sunlight in moderate amounts, perhaps taking a daily walk outside if the weather permits, is perhaps the best way to keep your Vitamin D levels up, if not – oral supplements or pills have been shown to be effective in increasing Vitamin D levels.

Look after yourself. Vitamin D is one of those free micronutrients that is essential and, essentially free – we can get it from walking outside in the sun. Do not underestimate its importance for our body’s functions.

References

  1. Holick, M. F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), 266-281. https://doi.org/10.1056/NEJMra070553
  2. Dawson-Hughes, B., Mithal, A., Bonjour, J. P., Boonen, S., Burckhardt, P., Fuleihan, G. E., … & Yoshimura, N. (2010). IOF position statement: vitamin D recommendations for older adults. Osteoporosis International, 21(7), 1151-1154. https://doi.org/10.1007/s00198-010-1285-3
  3. Aranow, C. (2011). Vitamin D and the immune system. Journal of investigative medicine, 59(6), 881-886. https://doi.org/10.2310/JIM.0b013e31821b8755
  4. Martineau, A. R., Jolliffe, D. A., Hooper, R. L., Greenberg, L., Aloia, J. F., Bergman, P., … & Goodall, E. C. (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ, 356, i6583. https://doi.org/10.1136/bmj.i6583
  5. Garland, C. F., Gorham, E. D., Mohr, S. B., & Garland, F. C. (2009). Vitamin D for cancer prevention: global perspective. Annals of epidemiology, 19(7), 468-483. https://doi.org/10.1016/j.annepidem.2009.03.021
  6. Deeb, K. K., Trump, D. L., & Johnson, C. S. (2007). Vitamin D signalling pathways in cancer: potential for anticancer therapeutics. Nature Reviews Cancer, 7(9), 684-700. https://doi.org/10.1038/nrc2196
  7. Pittas, A. G., Lau, J., Hu, F. B., & Dawson-Hughes, B. (2007). The role of vitamin D and calcium in type 2 diabetes. A systematic review and meta-analysis. Journal of Clinical Endocrinology & Metabolism, 92(6), 2017-2029. https://doi.org/10.1210/jc.2007-0298
  8. Forouhi, N. G., Ye, Z., Rickard, A. P., Khaw, K. T., Luben, R., Langenberg, C., … & Wareham, N. J. (2013). Circulating 25-hydroxyvitamin D concentration and the risk of type 2 diabetes: results from the European Prospective Investigation into Cancer (EPIC)-Norfolk cohort and updated meta-analysis of prospective studies. Diabetologia, 56(10), 2173-2182. https://doi.org/10.1007/s00125-013-2960-5
  9. Wang, L., Song, Y., Manson, J. E., Pilz, S., März, W., Michaëlsson, K., … & Liu, S. (2012).
  10. Holick, M. F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), 266-281.
  11. Bischoff-Ferrari, H. A., Dietrich, T., Orav, E. J., Hu, F. B., Zhang, Y., Karlson, E. W., & Dawson-Hughes, B. (2004). Higher 25-hydroxyvitamin D concentrations are associated with better lower-extremity function in both active and inactive persons aged ≥ 60 y. The American Journal of Clinical Nutrition, 80(3), 752-758.
  12. Forrest, K. Y., & Stuhldreher, W. L. (2011). Prevalence and correlates of vitamin D deficiency in US adults. Nutrition Research, 31(1), 48-54.
  13. Jorde, R., Waterloo, K., Saleh, F., & Haug, E. (2008). Vitamin D deficiency does not predict depressiveness in middle-aged and older Europeans. Tidsskrift for den Norske Laegeforening: tidsskrift for praktisk medicin, ny raekke, 128(22), 2570-2573.
  14. Xie, Z., Komuves, L., Yu, Q. C., Elalieh, H. Z., Ng, D. C., Leary, C., & Chang, S. (2002). Lack of the vitamin D receptor is associated with reduced epidermal differentiation and hair follicle growth. Journal of Investigative Dermatology, 118(1), 11-16.
  15. Forrest KY, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutr Res. 2011 Jan;31(1):48-54. doi: 10.1016/j.nutres.2010.12.001. PMID: 21310306.