Vitamin D – “the sunshine vitamin”

If you shun the sun, suffer from milk allergies, or adhere to a strict vegan diet, you may be at risk for vitamin D deficiency. Most of this “sunshine vitamin” (80% to 90%), is produced by the body in response to skin being exposed to sunlight.

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Why is it important for us?

Vitamin D, unfortunately an imprecise term, actually is a group of fat-soluble steroids (hormone) serving several important functions in the body. These include:

• promoting absorption of calcium, iron, magnesium, phosphate, and zinc from the gut. Our body cannot absorb calcium from food in absence of vitamin D.
• helping deposit the bone minerals phosphorous and calcium in bones and teeth to make them strong and healthy.
• promoting bone and cell growth.

In humans, the most important compounds in this group are vitamin D₃ (cholecalciferol) and vitamin D₂ (ergocalciferol).

How do we get it?

The best source of vitamin D, specifically D₃ is sunlight on the skin. The vitamin forms under the skin (dermal synthesis) in reaction to a type of ultraviolet ray called UVB. About 15 minutes of sun exposure (without sunscreen) is usually enough to build up vitamin D levels. It’s important to wear a sunscreen if you’re going to be outside for longer than 15 minutes, to protect against the sun’s damaging rays.

The necessary exposure time varies with age, skin type, clothing, diet, and an individual’s current vitamin D levels. Several factors can influence the amount of sun exposure you need, including the time of year (UVB rays being more powerful in the summer than in winter), altitude, latitude, cloud cover, and the time of day (the sun’s rays are more direct during the middle of the day).

Body fat acts like a kind of storage battery for vitamin D. During periods of sunlight, vitamin D is stored in fatty skin layer and then released when sunlight is gone.

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Ultraviolet B radiation that stimulates vitamin D production, can’t penetrate glass.  So even if you’re taking in sunlight through a window, you won’t get the benefit of vitamin D production.

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Vitamin D is largely absent from the food supply. Though it occurs naturally in a small number of foods, it is difficult to obtain enough amounts from diet alone.

Foods that are naturally high in vitamin D include: fatty fish such as herring, mackerel, sardines and tuna, fish liver oils, beef, cheese, egg yolks and mushrooms.

To make vitamin D more available, it is added to dairy products (milk, yogurt and cheese), juices, soya and breakfast cereals in small amounts, that are then said to be “fortified with vitamin D.” 

In many countries, all margarines and infant formula milks are fortified with vitamin D.

Vitamin D is also made in the laboratory as medicine.

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The risk for vitamin D deficiency in people over 65 years of age is very high. Surprisingly, as many as 40% of older people even in sunny climates don’t have enough vitamin D in their systems because:

• They have fewer “receptors” in their skin that convert sunlight to vitamin D. 
• They have trouble absorbing vitamin D even if they do get it in their diet.
• They have more trouble converting dietary vitamin D to a useful form due to aging kidneys.

Health Risks of Vitamin D Deficiency

Vitamin D is directly related with the bone health. It’s insufficiency results in rickets (defective bone growth) in children, and osteomalacia (soft bones), Osteopenia (low density of bones) and osteoporosis (porous bones) in adults. These skeletal diseases are the result of inadequate bone mineralization or demineralization. Rickets causes bowed legs, knock knees, and weak bones in children. In adults, the deficiency causes variety of symptoms like back pain, joints pain, muscle weakness and whole body pain, and fractures due to thin and brittle bones.

It impaires the immune system functioning, putting you at a higher risk for autoimmune diseases like rheumatoid arthritis, lupus, multiple sclerosis, and skin conditions including leucoderma, psoriasis, etc. Vitamin D in forms known as calcitriol or calcipotriene is applied directly to the skin for a particular type of psoriasis with benefits.

It affects your ability to use insulin to process blood sugar, putting you at a higher risk for type 1 and type 2 diabetes.

Low levels of vitamin D result in bigger concentrations of calcium build up in the arteries, forming plaques, causing high blood pressure and increase the risk of stroke or heart attack.

Improving the levels of Vitamin D3 reduces the risk of developing cancers specifically of the breast, prostate and colon by almost 30 to 50% because it plays a very important role in maintaining the cell growth.

Low levels of vitamin D have been found in patients with depression. A D3 supplementation is known to perk them up as they experience a reduction of negative symptoms – both cognitive and physical such as food cravings, unexplained lethargy, hypersomnia, and sleep disturbances.

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Vitamin D deficiency is often mistaken for fibromyalgia, chronic fatigue or peripheral neuropathy.

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Tests for Vitamin D Deficiency

The most accurate way to measure how much vitamin D is in your body is the 25-hydroxy vitamin D blood test. Levels are expressed in nanomoles/liter (nmol/L) or nanograms/milliliter (ng/mL). (1 nmol/L = 0.4 ng/mL)

According to the Office of Dietary Supplements (ODS), the results can indicate the following:

• deficiency: less than 30 nmol/L (12 ng/mL)
• potential deficiency: between 30 nmol/L and 50 nmol/L (12 ng/mL – 20 ng/mL)
• normal levels: between 50 nmol/L and 125 nmol/L (20 ng/mL – 50 ng/mL)
• high levels: higher than 125 nmol/L (50 ng/mL)

If your vitamin D levels are low and you’re having symptoms of bone pain, your doctor may recommend a special scan to check for bone density. This painless scan helps to evaluate a person’s bone health.

Treatment for Vitamin D Deficiency

The  daily recommended dietary allowance (RDA) for eating foods containing vitamin D and/or taking supplements to optimize bone health is:

• ages 0 to 12 months: 400 international units (IU)
• ages 1-70 (including pregnancy and lactating): 600 IU
• ages 70 and above: 800 IU

Blood levels of less than 20 nanograms per milliliter of Vitamin D is generally considered inadequate, requiring treatment. Treatment for deficiency involves getting more vitamin D — through diet and supplements.

How much is too much?

Taking vitamin D for long periods in higher doses is UNSAFE. It can cause unnecessary calcium build up in the blood leading to formation of kidney stones, and increase the risk of atherosclerosis – hardening of the arteries, causing damage to your blood vessels and heart.

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The Institute of Medicine has set the upper tolerable limit at 4,000 IU for vitamin D per day.

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Some side effects of taking too much vitamin D include muscle aches, weakness, fatigue, sleepiness, headache, loss of appetite, dry mouth with consequent excessive thirst, metallic taste, nausea, vomiting, etc.

How can vitamin D deficiency be prevented?