WHAT IS VITAMIN D?

Vitamin D is an oil (fat) soluble vitamin, meaning it dissolves and is stored in fat.

It helps absorb dietary calcium and phosphorus from the gut.  It also suppresses release of parathyroid hormone (PTH); PTH can increase bone breakdown.  Consequently, Vitamin D has a pronounced impact on bone health and stability.  There are also Vitamin D receptors in most body cells; thus, while not fully understood, Vitamin D appears to have positive roles in immune system and muscle function, and cardiovascular health.

HOW DO I GET VITAMIN D?

Your body gets Vitamin D through 2 main sources:

1)      your skin can make it after sun exposure (photoisomerization)

2)    you can eat it in foods or supplements

The amount of sunlight needed to make adequate amounts of vitamin D depends on various factors.  These include age, skin color, geographic location, season of the year, sun screen use, and other medical problems.  Dark-skinned and elderly people make less Vitamin D after sun exposure.  Also, obese individuals may only make half as much Vitamin D for a given exposure than non-obese people.  With a move to a more indoor lifestyle, recommendations that people avoid unprotected sun exposure via clothing and sunscreen, and with obesity on the rise, it is difficult to maintain adequate Vitamin D levels via sun exposure alone.

Vitamin D occurs naturally in some foods, specifically fatty fish, cod liver oils, and to a lesser extent in eggs.  Certain products are fortified with Vitamin D.  In America, this is primarily milk and dairy products, though others have come on the market.  Overseas, cereals and other grains are often fortified with Vitamin D.

Vitamin D deficiency occurs via one or more of the following reasons:

1)      insufficient sun exposure or reduced synthesis from sun exposure

2)    inadequate intake via foods or supplements

3)    absorption problems (common in digestive and bowel disorders)

4)    liver or kidney problems (both organs are necessary to make Vitamin D functional in the body)

WHAT ARE THE PROBLEMS ASSOCIATED WITH LOW VITAMIN D?

The most notable and proven problems associated with Vitamin D deficiency include poor bone health (osteopenia and osteoporosis) and increased risk of fractures.  Randomized controlled trials have shown Vitamin D replacement to decrease risk of falls and fractures in elderly patients.  Many randomized controlled trials have also shown benefits in treating and preventing bone loss in post-menopausal women, and in patients using corticosteroids (prednisone or similar agents).

In addition to its benefit to bone health, many preliminary studies suggest vitamin D deficiency is also associated with decreased immune system function, as well as development of colon cancer, multiple sclerosis, rheumatoid arthritis and cardiovascular disease.  Patients with Vitamin D deficiency are also more likely to report symptoms of muscle cramps and weakness, fatigue, and bone pain.  These are preliminary studies and there is no definitive evidence that replacing Vitamin D prevents or treats these disorders.

HOW MUCH IS ENOUGH?

Vitamin D levels are best measured using a blood test called the 25-OH vitamin D concentration.

Levels less than 10 are quite dangerous and can lead to a profound problem of bone softening called Rickets in children, and Osteomalacia in adults; this level of deficiency is uncommon these days.

There are different opinions on what levels people should maintain.  Generally levels below 30 are considered to be insufficient.  Most studies support maintaining levels above 30 for proper bone health.  Since data is incomplete on other benefits of Vitamin D, proper levels have not been established.  Since toxicity has not been seen at levels less than 80 and usually not till levels greater than 100, I usually try to maintain levels in the 40-60 range.

HOW DO I TREAT AND PREVENT VITAMIN D DEFICIENCY?

There are many different types and dosages of Vitamin D supplements available.  Most supplements are either Vitamin D2 (ergocalciferol) or Vitamin D3 (cholecalciferol).  There are also other versions of Vitamin D available, but these are generally only needed in patients that have notable liver or kidney disease.  Recent evidence suggests Vitamin D3 is more potent than Vitamin D2 and thus I recommend Vitamin D3 use in most cases

A rough guide is that Vitamin D levels will increase by about 6-8 for every 1000 units of supplement taken daily over a 2-3 month period.  The increase is more pronounced in patients with greater deficiency and tapers off once people are at normal levels.

In patients with marked deficiency (levels less than 20), I usually recommend 5-7000 units daily for 2-3 months.  For those with moderate deficiency (levels 20-30), I usually recommend about 2000 units daily for 2-3 months.  After initial treatment, I’ll either recheck levels, or just move people back to maintenance dosages.

For patients with normal levels and limited natural sources, I recommend 1-2000 units daily, though some people will need more.  For patients taking more than 2000 units daily for prolonged periods of time, monitoring of blood levels is necessary.

Increasing sun exposure can also improve levels.  In best case scenarios, near full body sun exposure can be the equivalent of taking 10,000 units daily.  However, due to increased skin cancer risk and the variability in Vitamin D production via sun exposure, generally oral supplementation is preferred.

CAN I TAKE TOO MUCH VITAMIN D?

Yes, however Vitamin D toxicity is uncommon.  Generally problems do not occur until levels are greater than 100 (though can occur at levels above 88).  Also, supplements increase Vitamin D levels less so as level rise.

Symptoms of Vitamin D toxicity are usually caused by elevated calcium levels (hypercalcemia) that occur.  These could include weakness, fatigue, sleepiness, headache, loss of appetite, dry mouth, metallic taste, nausea, vomiting, abdominal cramps, constipation, diarrhea, dizziness, ringing in the ears, trouble walking, skin eruptions, hypotonia in infants, muscle pain, bone pain, and irritability.

It is important to check Vitamin D levels periodically if you are taking more than 2000 units daily, or notably change your sun exposure while on supplements.  Also be sure to look at all your supplements, not just your actual Vitamin D.  Most multivitamins contain at least 400 units of Vitamin D and Vitamin D can be found in a variety of other supplements.  Remember, it is the total Vitamin D from ALL your supplements that contributes to your daily dose.

Primary References: Up To Date, Inc. and Natural Medicines Comprehensive Database