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Feeling Down? It might be a Lack of Vitamin D

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Unlike other vitamins, the body actually makes vitamin D. This vitamin is synthesized in the skin from sunlight and a metabolite of cholesterol. Its role in depression has been well studied and now, there is conclusive proof that vitamin D deficiency is common among depressed patients. But can vitamin D supplementation brighten your mood? How does vitamin D work to provide relief for depression? How can you maximize the amount of vitamin D your body makes? This article provides answers to these questions.

The Health Benefits of Vitamin D

Vitamin D is also affectionately called the “Sunshine Vitamin” because it is naturally made in the skin on exposure to sunlight.

Vitamin D refers to a family of secosteroids named from vitamin D1 to vitamin D5. Of these secosteroids, the most important ones to humans are vitamin D2 or cholecalciferol and vitamin D3 or ergocalciferol.

The primary benefit of vitamin D is for the intestinal absorption of calcium and phosphate to help promote bone health. Therefore, vitamin D deficiency can cause bone diseases such as rickets and osteomalacia.

However, new studies are finding new benefits for vitamin D. For example, vitamin D is now known to possess antioxidant, anti-inflammatory and immunomodulatory properties.

It is also essential for the division and differentiation of cells as well as for neuromuscular functions.

Although the body can make vitamin D from sunlight, it is still recommended that the vitamin be obtained from dietary and supplement sources. Dietary sources of vitamin D include mushrooms, fatty fish, fish liver oils, whole eggs, and cooked beef liver. In addition, vitamin D is also commonly added to staple foods in most countries.

The different forms of vitamin D (ergocalciferol and cholecalciferol) obtained from foods and supplements are converted to calcidiol in the liver. Calcidiol is also known as calcifediol. It is the metabolite measured in the serum to determine the vitamin D levels with laboratory tests.

Calcidiol is also a prohormone. It is converted to calcitriol, the bioactive form of vitamin D.

Some calcidiol is converted to calcitriol in the kidneys. The calcitriol from this source functions as a hormone and it is responsible for the regulation of calcium and phosphate levels in the blood. This functional role of calcitriol helps maintain bone health.

Calcidiol can also be converted to calcitriol in other sites besides the kidneys. The calcitriol made outside the kidneys is known to influence cellular growth, inflammatory processes, and neuromuscular activities.

Although we still do not fully understand the many roles of vitamin D in the body, scientists are finding new insights into how vitamin D affects different organs and systems in the body. For example, low levels of vitamin D are now associated with certain cancers, multiple sclerosis, influenza, asthma, and tuberculosis.

For some of these disorders, vitamin D supplementation may provide relief for symptoms.

Vitamin D Synthesis from Sunlight

The form of vitamin D produced in the skin in response to sunlight is vitamin D3 or cholecalciferol. It is produced from a metabolite of cholesterol known as 7-dehydocholesterol.

As much as 10,000 – 20,000 IU of vitamin D can be produced from 7-dehydrocholesterol in 30 minutes of whole-body exposure to sunlight. However, a number of factors can affect the production of this vitamin from sunlight.

The wavelength of Ultraviolet Light

Vitamin D3 is made from 7-dehydrocholesterol in the skin only in response to the UVB type of ultraviolet light. The specific wavelength of UVB light required is in the range, 270 – 300 nm, and production is at its peak between 295 nm and 297 nm.

These ideal UVB wavelengths represent the range at which sunlight has a UV index greater than 3.

Although the UV lamps used in tanning beds mostly emit UVA light, 4 – 10% of the UV light from these lamps is UVB light that has a UV index greater than 3. Therefore, tanning beds can also increase vitamin D production in the skin.

Sunlight with UV index greater than 3 occurs daily in the tropics, daily during the summer and spring in temperate regions, less frequently during winter and rarely at the poles.

The Angle of the Sun’s Ray

The angle at which sunlight enters the earth’s atmosphere is also important to the production of vitamin D in the skin. When sunlight comes through the atmosphere at a low angle, most of the UVB light is blocked and vitamin D production is at its lowest.

Sunlight enters the atmosphere at low angles early and late during the day and also all-day during the winter months.

One way of knowing when the angle of sunlight is too low for vitamin D production is to check the length of your shadow. When your shadow is longer than you are tall, then the angle of sunlight is too low and vitamin D production is also low.

Time of the Day

The time of day can also determine how much vitamin D is produced in the skin. Basically, the optimal time of the day for vitamin D synthesis is when UVB light is at its peak, between the 270 nm and 300 nm, and when the UV index is higher than 3.

The right time of the day, therefore, is around noon especially between 10 in the morning and 12 at noon. However, the ideal range depends on the latitude.


The latitude of your location can also determine the months during which you get enough sunlight for vitamin D production. Generally, the farther you live away from the equator, the less sunlight you get and the less vitamin D you make.

People living between 0 and 35 degrees north and south of the equator usually get all-year-round sunlight ideal for vitamin D production.

Latitudes 40 – 50 degrees north will experience low angle sunlight (and low vitamin D production) between November and March. Above 50 degrees north of the equator, the vitamin D winter extends from October to April.

On the other hand, latitudes 40 – 50 degrees north of the equator experience vitamin D winter from December to February.

Skin Type

Skin type can also determine how much vitamin D is made. There are generally 6 skin phototypes ranging from Type I to Type VI.

Skin phototypes are classified by the amount of melanin produced in the skin. Therefore, Type I skin is extremely white, pale and fair skin while Type VI corresponds to black-skinned individuals.

The protection offered by the Type VI skin phototype against sun damage by ultraviolet light is a disadvantage for vitamin D production. The high levels of skin pigment that shields dark-skinned people from easily getting sunburned, also mean that the amount of UVB light penetrating the skin is low.

Therefore, people with skin Type VI need six times more sun exposure to make the same amount of vitamin D as those with skin Type I. This is also the reason why dark-skinned people are prone to vitamin D deficiency when they living far away from the equator.

Other Factors

There are other factors that can also affect the amount of vitamin D produced in the skin. Age is one such factor.

People older than 60 years or younger than 20 years need longer exposure to sunlight because the level of 7-dehydrocholesterol in their skins is lower than adults aged 20 – 60 years. To compensate for a lower amount of vitamin D precursor, the longer exposure time may be required.

The part of the body exposed to sunlight is also important. The production of vitamin D varies by body part with the torso producing the highest while the face and hands produce very little.

Ideally, 40% of the body’s skin surface should be exposed to sunlight for optimal vitamin D synthesis.

Any factor that blocks sunlight from reaching or penetrating through the skin can also reduce vitamin D production. Therefore, sunscreens can reduce the amount of vitamin D produced in the skin. In fact, a sunscreen with an SPF value of 8 can reduce vitamin D production by as much as 95%.

In addition, sunlight can be filtered, absorbed or scattered by clouds and air pollutants. Therefore, people living in places with heavy cloud cover or considerable particulate air pollutants may experience low vitamin D production.

Lastly, although sunlight can pass through glass, UVB light is mostly blocked. Therefore, workers spending too much time indoors may mistake the natural illumination afforded by a glass office for the kind of sun exposure that promotes vitamin D synthesis.

Vitamin D and Depression

There is increasingly strong evidence that vitamin D may be linked to depression. This link is established because:

  • Low levels of vitamin D have been shown to be common in depressed patients
  • Vitamin D supplementation has been proven to relieve the symptoms of depression

Although there is no large-scale, placebo-control study to investigate the link between vitamin D deficiency and depression, there is overwhelming evidence from numerous small studies and clinical data to indicate that such a link exists.

However, it is still unclear whether it is vitamin D deficiency that causes depression or depression that causes vitamin D deficiency. Or, indeed how vitamin D is specifically linked to mood.

Still, it is now certain that disorders known to be caused or worsened by vitamin D deficiency are also associated with a high risk of depression. Such disorders include Alzheimer’s disease, hypertension, kidney disease, heart disease, obesity and bone fracture in postmenopausal women.

Therefore, many have suggested that vitamin D may improve mood in depressed patients simply because it contributes to lowering the risk or relieving the symptoms of those disorders that are vitamin D-sensitive. This suggests that when healthy, people do not feel down.

However, there are indications that vitamin D may indeed have direct effects on the mood. For example, vitamin D can reduce the production of inflammatory cytokines.

This action can reduce inflammation in the neurons and neurotransmitter pathways that control mood.

More importantly, vitamin D is concentrated in specific parts of the brain such as the amygdala and hippocampus. These are areas known to control mood, emotion, and behavior.

Furthermore, vitamin D is needed in the brain for the release of the neurotransmitters also known to improve mood. Such neurotransmitters include dopamine, serotonin, and norepinephrine.

Standard antidepressants target these neurotransmitters by increasing their production and/or activities.

Studies on Vitamin D and Depression

Does Vitamin D Deficiency Cause Depression?

A number of scientific debates have discussed the newfound link between vitamin D and depression, why more studies are needed to gain a better understanding of this link and how it can be targeted in the treatment of depression.

One such review was published in 2009 in the journal, Nutrition Reviews. While the author took the cautious approach, many others are quite optimistic.

For example, the authors of a 2007 paper published in the journal, Medical Hypotheses, were confident that vitamin D supplements should be included in the standard care of depressed patients especially where sun exposure and dietary intake of the vitamin are low.

The researchers of a 2008 study published in the Archives of General Psychiatry tested the vitamin D-depression link in a large population in the Netherlands.

In a cohort study involving 1,282 residents aged 65 – 95 years, the researchers correlated depression scores with the serum levels of calcidiol (the vitamin D prohormone measured to give a status of the vitamin) and parathyroid hormone (the hormone that drives the conversion of calcidiol to calcitriol, the bioactive form of vitamin D).

The results showed that the occurrence and severity of depression are strongly correlated with low vitamin D levels and high parathyroid hormone levels in the elderly.

The low vitamin D and high parathyroid hormone levels are the classic signs of vitamin D deficiency.

A study similar to this one was published in the American Journal of Geriatric Psychiatry in 2006. In this study, the researchers investigated the possible links between vitamin D deficiency and low mood as well as cognitive impairment in the elderly.

The study involved 80 participants, 40 of whom suffered from mild Alzheimer’s disease. By measuring the serum levels of calcidiol and correlating with scores from cognitive function tests and standard depression scales, the researchers were able to demonstrate that vitamin D deficiency was associated with depression and cognitive impairment in the elderly.

A 2012 study published in The British Journal of Psychiatry compared depressive symptoms in participants with high and low vitamin D levels. The study also determined whether vitamin D supplementation can improve depression symptoms in those with vitamin D deficiency.

The researchers found that the participants with low vitamin D levels were more depressed than those with high levels of the vitamin.

Curiously, they also found that supplementation with 40,000 IU/week of vitamin D3 did not significantly improve depressive symptoms in the low vitamin D group.

Vitamin D and Depression in the Different Disease States

Because anxiety and depression are very common symptoms in fibromyalgia patients, a group of researchers compared the levels of vitamin D to the severity of the disease in a number of patients.

In a study published in 2007 in the journal, Clinical Rheumatology, vitamin D levels were measured in 75 fibromyalgia patients.

The results of the study showed that low levels of vitamin D were common among fibromyalgia patients (13.3% with vitamin D deficiency, 56% with insufficient levels and 30.7% with normal levels). In addition, patients with vitamin D deficiency had higher anxiety and depression scores than those with sufficient levels of the vitamin. Those with normal vitamin D levels had the least anxiety and depression scores.

The study demonstrates the vitamin D level is strongly associated with anxiety and depression in fibromyalgia patients and its level should be considered during treatment.

A similar finding was obtained from a 2010 paper published in the American Heart Journal.

In that study, the link between vitamin D and depression was investigated in people with cardiovascular disease. There were over 7,000 participants aged 50 years and above in this study and with different types of heart diseases.

The results showed that vitamin D levels significantly affected the moods of patients with cardiovascular diseases. Low levels of the vitamin were strongly associated with depression and depression was at its highest during the winter months when vitamin D levels were at their lowest.

A 2008 study published in the Journal of Internal Medicine also supported this conclusion although in another group of patients.

In this study, the vitamin D levels and depression scores were measured in a group of overweight and obese individuals. A total of 441 participants aged 21 – 70 were recruited for this study.

Some of the depressed, obese participants with low vitamin D levels were given high doses of vitamin D.

The results showed that low levels of vitamin D were strongly correlated with depression and that vitamin D supplementation provided relief from depressive symptoms.

In a 1999 study published in The Journal of Nutrition, Health and Aging, the researchers tested the hypotheses that vitamin D levels can influence SAD (Seasonal Affective Disorder, a form of depression that occurs in certain seasons).

The study involved 15 SAD patients. Eight of them were given 100,000 I.U of vitamin D while the others received phototherapy (broad-spectrum light therapy in the wavelengths between 280 nm and 320 nm).

The course of therapy was 1 month and vitamin D levels were measured before the study and a week into the study. The participants were also evaluated on 3 depression standard scales (including the Hamilton Depression Scale and the SAD-specific SAD-8 Depression Scale) at the beginning of the study and 1 month later.

The results showed that vitamin D levels improved in both groups (74% in the vitamin D supplement group and 36% in the phototherapy group). However, only the subjects receiving vitamin D supplements improved on the depression scales.

This study shows that vitamin D is an effective treatment for SAD.

Just as importantly, it hints that even though phototherapy can raise vitamin D levels, it may not improve depressive symptoms as much as vitamin D supplements.





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