Vitamin D: Why You Need It

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About 32% of Canadians are deficient in vitamin D, a statistic that rises to 40% during the winter months. Vitamin D deficiency is also relatively common in the United States. According to data from the National Health and Nutrition Examination Survey (NHANES) conducted between 2011 and 2014, approximately 29% of U.S. adults had a deficiency in vitamin D.

Combined with the fact that foods (unless they have been fortified) naturally do not contain significant amounts of vitamin D, means that to ensure you get enough vitamin D, you can either expose some skin to sunlight, or orally supplement the vitamin.

Regardless of the source, experts typically safely recommend 1000 IU per day to maintain adequate levels, especially during the autumn and winter months.

Vitamin D3 vs D2

Vitamin D3 and vitamin D2 are both forms of vitamin D, but they differ in their sources, metabolism, and effectiveness in raising vitamin D levels in the body.

Vitamin D3 (cholecalciferol) is produced naturally in the skin when exposed to sunlight and is also found in some animal-based foods, such as fatty fish, eggs, and dairy products. Vitamin D3 is also available as a supplement in the form of tablets, capsules, and drops.

Vitamin D2 (ergocalciferol) is produced by some plants and fungi, and is also available as a supplement in the form of tablets, capsules, and injections.

Research suggests that vitamin D3 is significantly more effective than vitamin D2 at raising and maintaining vitamin D levels in the body. This is because vitamin D3 is more easily converted into the active form of vitamin D in the body and has a longer half-life than vitamin D2.

Additionally, some studies have suggested that vitamin D2 may be less effective at preventing and treating vitamin D deficiency compared to vitamin D3. This is especially true for people with conditions that affect vitamin D absorption, such as inflammatory bowel disease, cystic fibrosis, and obesity.

However, it is important to note that vitamin D2 is not completely useless. Vitamin D2 is still effective at raising vitamin D levels in the body, and can be a useful alternative for people who cannot tolerate vitamin D3 or who are following a plant-based or vegan diet.

Overall, vitamin D3 is considered to be the preferred form of vitamin D supplementation for most people, but the choice between vitamin D3 and vitamin D2 may depend on individual circumstances and healthcare provider recommendations.

Health benefits of Vitamin D

Some of the general health benefits of taking vitamin D supplements include:

Improving bone health: Vitamin D helps the body absorb calcium, which is essential for strong bones. Taking vitamin D supplements may help improve bone density and reduce the risk of osteoporosis, particularly in older adults.
Supporting the immune system: Vitamin D plays a role in immune system function and may help reduce the risk of certain infections, such as respiratory tract infections.
Improving brain function: Some research has suggested that vitamin D may have a positive impact on brain function, including cognitive function and memory. However, more research is needed to fully understand this potential benefit.
Reducing the risk of heart disease: Some research has suggested that vitamin D may help reduce the risk of heart disease by helping to lower blood pressure and reducing inflammation. However, more research is needed to fully understand this potential benefit.
Reducing the risk of other diseases: Some research suggests that vitamin D may help reduce the risk of other diseases, including diabetes, multiple sclerosis, and certain types of cancer. However, more research is needed to fully understand these potential benefits.
Improving mood: Low vitamin D levels have been linked to an increased risk of depression, and some studies have suggested that taking vitamin D supplements may help improve mood.

Specific medical conditions

Vitamin D supplementation has been researched for a wide range of medical conditions, and there is evidence to suggest that it may provide benefits for several of them. Here are some specific examples:

Multiple Sclerosis: There is evidence to suggest that vitamin D may play a role in reducing the risk of multiple sclerosis (MS) and slowing the progression of the disease. Several studies have found that individuals with MS tend to have lower vitamin D levels, and that vitamin D supplementation may help to reduce disease activity.
Depression: Some studies have suggested that vitamin D supplementation may help to improve symptoms of depression, particularly in individuals with low vitamin D levels. However, more research is needed to confirm this association.
Type 2 Diabetes: Vitamin D may help to improve insulin sensitivity and blood sugar control in individuals with type 2 diabetes. Several studies have found that vitamin D supplementation can improve glycemic control and reduce the risk of complications in individuals with diabetes.
Hypertension: There is evidence to suggest that vitamin D supplementation may help to lower blood pressure in individuals with hypertension. Several studies have found that vitamin D supplementation can reduce systolic and diastolic blood pressure, although the magnitude of the effect may be small.
Cardiovascular disease: Some studies have suggested that vitamin D supplementation may help to reduce the risk of cardiovascular disease and improve cardiovascular health.
Asthma: Vitamin D may help to reduce airway inflammation and improve lung function in individuals with asthma. Several studies have found that vitamin D supplementation can reduce asthma exacerbations and improve symptoms.
Rheumatoid arthritis: Vitamin D may help to reduce inflammation and improve symptoms in individuals with rheumatoid arthritis. Several studies have found that vitamin D supplementation can improve joint pain and function.
Cognitive decline: Some studies have suggested that vitamin D supplementation may help to improve cognitive function and reduce the risk of cognitive decline and dementia in older adults.
Inflammatory bowel disease (IBD): Vitamin D may help to reduce inflammation in individuals with IBD, such as Crohn’s disease and ulcerative colitis. Several studies have found that vitamin D supplementation can improve symptoms and reduce disease activity.
Chronic kidney disease: Vitamin D plays a critical role in kidney function, and several studies have found that vitamin D supplementation can improve kidney function and reduce the risk of complications in individuals with chronic kidney disease.
Psoriasis: Vitamin D may help to reduce inflammation and improve symptoms in individuals with psoriasis. Some studies have found that vitamin D supplementation can improve skin lesions and reduce disease severity.
Autoimmune disorders: Vitamin D may help to regulate the immune system and reduce inflammation in individuals with autoimmune disorders, such as lupus and multiple sclerosis. Some studies have found that vitamin D supplementation can improve symptoms and reduce disease activity.
Polycystic ovary syndrome (PCOS): Vitamin D may help to improve insulin sensitivity and reproductive function in women with PCOS. Some studies have found that vitamin D supplementation can reduce insulin resistance and improve menstrual regularity.
Allergic rhinitis: Vitamin D may help to reduce inflammation and improve symptoms in individuals with allergic rhinitis, such as seasonal allergies. Some studies have found that vitamin D supplementation can reduce allergy symptoms and improve quality of life.
Periodontal disease: Vitamin D may help to improve oral health and reduce the risk of periodontal disease. Some studies have found that vitamin D supplementation can improve gum health and reduce inflammation.
Migraine headaches: Some studies have suggested that vitamin D supplementation may help to reduce the frequency and severity of migraine headaches.
Non-alcoholic fatty liver disease (NAFLD): Vitamin D may help to improve liver function and reduce inflammation in individuals with NAFLD. Some studies have found that vitamin D supplementation can improve liver enzymes and reduce disease severity.
Chronic obstructive pulmonary disease (COPD): Vitamin D may help to improve lung function and reduce exacerbations in individuals with COPD. Some studies have found that vitamin D supplementation can improve symptoms and reduce the risk of complications.
Prostate cancer: Some studies have suggested that vitamin D supplementation may help to reduce the risk of prostate cancer and improve outcomes in individuals with prostate cancer.
Endometriosis: Vitamin D may help to reduce inflammation and improve symptoms in individuals with endometriosis. Some studies have found that vitamin D supplementation can reduce pain and improve quality of life.
Urinary tract infections (UTIs): Vitamin D may help to reduce the risk of UTIs and improve outcomes in individuals with UTIs. Some studies have found that vitamin D supplementation can improve immune function and reduce the severity of symptoms.
Sarcopenia: Vitamin D may help to improve muscle strength and reduce the risk of sarcopenia (age-related muscle loss). Some studies have found that vitamin D supplementation can improve muscle function and reduce the risk of falls.

Links to obesity

There is some evidence to suggest that there may be a link between vitamin D status and obesity. Several studies have found that individuals with obesity tend to have lower levels of vitamin D in their blood compared to those who are not obese. However, it is not clear if low vitamin D levels are a cause or a consequence of obesity.

One possible explanation for this link is that vitamin D may play a role in regulating appetite and metabolism. Vitamin D receptors are present in areas of the brain that control food intake and energy expenditure, and animal studies have shown that vitamin D deficiency can lead to overeating and weight gain. Additionally, vitamin D may also affect the function of adipose tissue (body fat), which could further impact obesity risk.

While some studies suggest that vitamin D supplementation may help with weight loss and improve metabolic health, results have been mixed and more research is needed to fully understand the relationship between vitamin D and obesity. Therefore, maintaining a healthy weight through a balanced diet and regular exercise is still the most effective way to manage obesity risk.

Links to all-cause mortality

There is evidence to suggest that maintaining adequate vitamin D levels may be associated with a reduced risk of all-cause mortality, or death from any cause.

Several studies have found that individuals with low vitamin D levels may have a higher risk of mortality compared to those with adequate levels. For example, a meta-analysis of 32 prospective cohort studies found that low vitamin D levels were associated with a significantly increased risk of all-cause mortality.

The exact mechanisms behind this association are not fully understood, but it is thought that vitamin D may play a role in reducing inflammation, improving cardiovascular health, and supporting immune function, all of which are important for overall health and longevity.

While more research is needed to confirm the relationship between vitamin D status and mortality risk, maintaining adequate vitamin D levels is an important part of overall health and may help to support longevity.

Vitamin D overdose

Taking too much vitamin D for prolonged periods of time can lead to several health risks. As a fat-soluble nutrient, vitamin D has a longer retention in the body as compared to water-soluble vitamins, such as Vitamin B12.

Documented reports of people overdosing on Vitamin D are rare, and usually involve doses of over 10,000 IU per day for long periods of time. Taking a daily dose of 1000-2000 IU is generally considered safe and unlikely to cause any adverse effects.

Nevertheless, some of the risks of vitamin D overdose include:

Kidney damage: High levels of vitamin D can cause damage to the kidneys, which can lead to kidney stones and other complications. This risk is considered low for a healthy person, but it may be higher for those with existing kidney problems.
Calcium buildup in the blood: Vitamin D helps the body absorb calcium, but an overdose of vitamin D can lead to a buildup of calcium in the blood (hypercalcemia), which can cause confusion, muscle weakness, and fatigue. This risk is considered rare for a healthy person.
Heart problems: High levels of calcium in the blood can also lead to heart problems, such as irregular heartbeats and cardiovascular disease. This risk is considered low for a healthy person, but it may be higher for those with a pre-existing heart condition.
Digestive problems: An overdose of vitamin D can cause digestive problems, such as nausea, vomiting, and diarrhea. This risk is considered low for a healthy person.

Who should be careful?

While vitamin D supplements are generally safe for most people when taken in appropriate doses, there are some groups of people who should be careful or avoid taking vitamin D supplements altogether. These include:

People with hypercalcemia or high blood calcium levels: Vitamin D can increase calcium absorption, and high doses of vitamin D can lead to hypercalcemia, which can cause nausea, vomiting, confusion, and other symptoms.
People with kidney disease: Vitamin D is processed by the kidneys, and people with kidney disease may have difficulty processing vitamin D. In some cases, vitamin D supplements can cause high blood levels of calcium and phosphorus, which can contribute to kidney damage.
People with certain medical conditions: People with certain medical conditions, such as sarcoidosis, lymphoma, and tuberculosis, may have higher levels of vitamin D in their blood and should avoid taking vitamin D supplements without first consulting with their healthcare provider.

Risks of Vitamin D deficiency

Vitamin D plays an important role in many functions of the body, so deficiency can lead to a number of health problems. Some potential health risks of vitamin D deficiency include:

Weakened bones: Vitamin D helps the body absorb calcium, which is important for maintaining strong bones. Deficiency can lead to weakened bones, increased risk of fractures, and osteoporosis.
Immune system dysfunction: Vitamin D plays a role in regulating the immune system, so deficiency may increase the risk of infections, autoimmune diseases, and certain types of cancer.
Increased risk of chronic diseases: Vitamin D deficiency has been associated with an increased risk of chronic diseases such as cardiovascular disease, diabetes, and certain types of cancer.
Muscle weakness and pain: Vitamin D deficiency can cause muscle weakness and pain, as well as difficulty walking or climbing stairs.
Mood disorders: Low levels of vitamin D have been linked to an increased risk of depression, seasonal affective disorder (SAD), and other mood disorders.

It is important to note that the severity of these health risks may vary depending on the degree and duration of vitamin D deficiency.

Who is at higher risk?

Certain groups of people are at greater risk of being deficient in vitamin D. These include:

People with limited sun exposure: Vitamin D is produced by the body in response to sunlight exposure, so people who spend a lot of time indoors or who live in areas with limited sunlight exposure may be at risk of deficiency.
People with dark skin: Melanin, which gives skin its color, can reduce the skin’s ability to produce vitamin D in response to sunlight exposure. This means that people with darker skin may need more sun exposure to produce the same amount of vitamin D as someone with lighter skin.
Older adults: As people age, their skin becomes less efficient at producing vitamin D in response to sunlight exposure. Older adults are also more likely to spend time indoors and may have a decreased ability to absorb vitamin D from their diet.
People with obesity: Vitamin D is stored in fat tissue, so people with obesity may have lower levels of vitamin D available for use by the body.
People with certain medical conditions: Certain medical conditions, such as Crohn’s disease, celiac disease, and liver disease, can interfere with the body’s ability to absorb vitamin D from food.

Vitamin D dose

Generally, the recommended daily intake for vitamin D for most adults is between 600-800 IU (International Units), or 15-20 mcg per day. However, some people may need higher doses, especially if they are at risk of vitamin D deficiency.

Most clinicians will recommend Vitamin D at a steady 1000-2000 IU (25-50 mcg) per day orally, since it is a safe, effective way to increase Vitamin D status. Some recommend higher doses of up to 5000 IU (125 mcg) per day for certain people to manage specific conditions.

Another way to take Vitamin D is via a single large dose, given once a week or less. This is best for people who cannot take a daily supplement for any given reason. Doses given in this fashion can be upwards of 10,000-25,000 IU (250-625 mcg), or sometimes more at one time, and can be given orally, or via injection.

Getting Vitamin D

From the sun

The skin is able to produce significant amounts of vitamin D from sun exposure. However as we age, our skin has less and less capacity to produce vitamin D from the sun.

The types of rays required are specifically UVB rays, as UVA rays do not significantly stimulate vitamin D production in the skin. The amount of time is dependant on your skin type and shade, where you live, and time of day and year.

Generally, a larger area of the skin (such as a bare back) must be exposed for around 10 minutes to obtain a good daily dose of vitamin D (~1000 IU).

Unfortunately, during winter months, this becomes difficult to achieve, and some people turn to tanning salons to obtain the necessary dose.

Tanning beds?

Tanning beds are not a good way to get vitamin D for several reasons.

Tanning beds emit UV radiation, which can increase the risk of skin cancer, premature aging, and other skin damage.
Tanning beds do not necessarily produce the same type of UV radiation that stimulates vitamin D production in the skin. Vitamin D synthesis in the skin is triggered by UVB radiation, which is different from the UVA radiation emitted by most tanning beds. This means that tanning beds may not actually provide adequate levels of vitamin D, even with prolonged use.
Tanning beds are not a regulated source of vitamin D, meaning that the amount of UV radiation emitted can vary widely depending on the type of bed, the length of the session, and other factors.

If you do choose this method, it is important to choose low-pressure beds that have a good amount of UVB light, rather than high-pressure beds which only have UVA light.

From supplements

Supplements are the easiest and safest way to obtain your daily dose of vitamin D. Two different forms exist on the market; however vitamin D3 (cholecalciferol) is far more common. Vitamin D is a fat soluble vitamin, and supplements typically exist in 3 different forms: tablet (dry), liquid (drops), and capsule (gelcaps).

Tablet formulations of vitamin D tend to have the longest shelf lives, be the easiest to find, and may be combined with other nutrients. Because this form is dry, consuming tablets with a fatty meal will help improve absorption, and is usually recommended to get the full dose from the tablet. For example:

Vitamin D (tabs) – 1 tablet per week.

Liquid formulations tend to be more cost effective, and easier to take in larger doses. Most formulations suspend the vitamin in some sort of oil base, making it easier to absorb into the body without relying on concomitant food intake. Fancier formulations are designed to further improve absorption and bioavailability in the body. For example:

Vitamin D (drops) – 4 drops per day.

Capsule formulations are liquid formulations that have been encapsulated or sealed in a gelcap. This gives the capsule a longer shelf life than the liquid form, while retaining the good absorption of the liquid forms. For example:

Vitamin D (gelcaps) – 1 gelcap per day.

From the diet

Foods naturally do not naturally contain significant amounts of vitamin D. Obtaining sufficient amounts of vitamin D from these sources can be difficult. Here is a list of some natural foods that contain vitamin D:

Food	Vitamin D
Cod liver oil	250 mcg (10,000 IU)
Salmon	13.3-25 mcg (532-1,000 IU)
Sardines	6.8-8.5 mcg (272-340 IU)
Tuna fish	3.7-11.9 mcg (148-473 IU)
Beef liver	1.6-50 mcg (64-2,000 IU)
Egg yolks	1.1 mcg (44 IU)
Cheese	0.5-2.5 mcg (20-100 IU)
Mushrooms	0.1-5.5 mcg (4-220 IU)

Natural vitamin D content of various foods (per 100 g)

Fortified foods make up the bulk of vitamin D obtained in the diet. The most obvious fortified sources are found in dairy products, such as milk and yogurt. Orange juice and cereals are also frequently fortified in North America.

In Canada, milk is fortified by law with 35-40 IU/100 mL, as is margarine at ≥530 IU/100 g. Check the label of your food to determine how much vitamin D has been added.