By: Shweta Soni, MD

Why do I need Vitamin D?
How much do I need in a day? What are the various ways to get it? What will happen if I remain deficient in Vitamin D? If I eat oily fish, drink enough milk, and go out in sun, should I still worry about being deficient?
If these questions flash through your mind then please read on. Interestingly, Vitamin D deficiency is pandemic with more than half of the world’s population at risk.

What is Vitamin D, and why is it essential in a healthy diet?
Vitamin D is a fat soluble vitamin obtained from food and sun and performs various functions in our body. It enables normal mineralization of bone and is important for tooth attachment like calcium; but calcium needs vitamin D to be absorbed or else it gets lost in feces. There have been suggestions of possible anti cancer activity and the deficiency increasing susceptibility to several chronic diseases.

Are there any types of Vitamin D?
There are two types: Vitamin D2 (from yeast and plant) and Vitamin D3 (from oily fish and photosynthesis).
It was previously thought Vitamin D3 more effective than Vitamin D2 but much uncertainty remains.

What are the various sources of Vitamin D?
There are three main sources of Vitamin D. It can be synthesized in the skin on exposure to UVB light at a specific wavelength range from the precursor cholesterol (7-dehydrocholesterol); an inactivated hormone present in skin. It can be obtained through dietary sources (naturally or via fortification). If the other two sources become insufficient then there are supplements available.

Why can’t I get enough synthesized in my skin?
There are many factors or hurdles that play a role in the process: Sunscreen impedes absorption of UVB so skin wont synthesis enough vitamin. With age, the levels of precursor in skin (7-DHC) lowers, so again less Vitamin synthesis. Melanin (pigment which provides color to skin) competes with the precursor (7-DHC) for UVB radiation, so darker skins synthesize less Vitamin D. Other factors like season, geographic Latitude, time of day, cloud cover, skin cover, and smog affect UV ray absorption and the synthesis. So if you living on East coast, all these factors impair sufficient vitamin D synthesis in the skin.

What are the various dietary sources of Vitamin D?
Natural food sources are the main sources of vitamin D. These include fatty fish (Mackerel, Salmon, Tuna contain around 300 IU per 3.5 oz), egg yolk (20 IU /egg) and cod liver oil (400 IU/ tsp). Options for vegetarians are very limited. Fortunately the U.S. has been fortifying milk, cereal and Orange Juice with 100 IU of Vitamin per serving. Irradiated Shitake Mushrooms may also have some vitamin D.
In the United States, the 100% Daily Value used for product labels is 800 IU/day and typical American diets provide only about 100 IU/day.

What are various supplements available?
The natural sources should always be utalized first. Alternatives are over the counter supplements available such as Caltrate (600 mg calcium carbonate with 400 IU Vitamin D/tablet), CitraCal Petites (400 mg calcium citrate with 500 IU Vitamin D/tablet), Viactive (500 mg calcium with 500 IU Vitamin D and 40 mcg Vitamin K), Tums (500 mg calcium carbonate without Vitamin D) and vitamin D3 (cholecalciferol) supplements. There are prescriptions medications available as well in high doses which your physician may prescribe if the need arise.

Is there any test available to find out if you are deficient in it?
You can request a blood test from your physician for Vitamin D 25-OH level to see if you are deficient (< 20 ng/mL) or insufficient (20 to 30 ng/mL) in it.

How rampant is deficiency?
Studies have shown that 50% of seniors in North America and 66% of individuals internationally fail to maintain healthy bone density and tooth attachment resulting from inadequate vitamin D levels. Prevalence in the U.S. dialysis population is much higher at 97%.

What are the various symptoms of Vitamin D deficiency?
Symptoms are mostly non-specific and vague and may be similar to many other diseases. The most common complaints have been muscle pain or aches and Muscle weakness .Pain when pressure is applied to breast bone or shin is another common symptom.

What are the risk factors for Vitamin D deficiency?
Various studies has proven that everyone  is at risk for deficiency even if following risk factors are absent but these risk factors puts you at much more risk. Risk factors are: Obesity, Elderly, Sedentary, Dark-skinned persons, exclusively breast-fed babies, Medications that interact with vitamin D, Chronic liver or kidney disease and Malabsorption Syndromes (e.g. Celiac Sprue, Crohns disease)

How does Vitamin D deficiency manifest?
It can manifest as loss of bone mineral density (osteoporosis), fractures and falls, osteomalacia and rickets. Studies also suggest correlation between the deficiency and various chronic pain syndromes, low mood and worse cognition.

Can excess of Vitamin D be harmful?
Yes. It is an extremely rare but real problem. The safe upper limit for Vitamin D is 1000IU/d for infants and 2000 IU for children and adults. The toxicity almost always occurs from overuse of supplements and not from excessive sun exposure.

Can the prescription medicines you are taking interact with Vitamin D?
Yes. Some drugs such as Antacids, anti-seizure medications and steroids reduce the potency of Vitamin D so you would need more vitamin D than recommended. Other drugs such as digoxin and thiazides can increase the potency of vitamin D. Better still is to discuss with your physician if you are already taking any prescription medicines or dietary supplements.

What are the recommended daily doses of Vitamin D for healthy persons?
There are different recommendations as per different guidelines.
At risk and elderly populations are recommended 800-1000 IU daily.
Adult healthy population: 400-600 IU daily. Infants and children: 200-400 IU daily. Talk to your physician to discuss the recommended dose for you based on your risk factors.

Vitamin D has many important biological functions. Its Deficiency is prevalent worldwide and presentation of deficiency is mostly nonspecific. Good news is that it’s easy and generally safe to replace. All research shows vitamin D supplementation impact functional outcomes and quality of life.