Vitamin D is a hot topic in the news lately. Research studies show more and more evidence that vitamin D possesses many important benefits. For example, emerging research suggests the possible role of vitamin D in protecting against cancer, heart disease, bone fractures, autoimmune diseases, influenza, type 2 diabetes, and even depression.
Vitamin D is absolutely essential for allowing us to absorb calcium into our bodies and create strong bones, not to mention maintain them. In medical school, they taught us about the risks of severe vitamin D deficiencies (namely Rickets and Osteomalacia). They also taught us that vitamin D deficiency is almost unheard of in the first world (probably because cases of Rickets and Osteomalacia are so rare).
It turns out that a deficiency of vitamin D in first world countries is much more prevalent than my professors suspected. In addition, vitamin D seems important for more than simply making and maintaining strong bones. My professors overlooked a couple of possibilities; patients may have only mild, yet symptomatic, deficiencies in vitamin D and that vitamin D may have other protective effects in the body against many other unrelated disorders.
What is vitamin D and why is it so important?
Vitamin D is absolutely critical in order for us to absorb calcium from our food and move it into our bones. Without vitamin D, our bones would be brittle, deformed, or just completely useless to us (exactly as occurs in Osteomalacia or Rickets). Vitamin D intake is crucial to anyone who is at risk for bone related problems such as osteoporosis. Expectant and nursing mothers should be careful to maintain adequate levels (but not too much) of vitamin D to prevent birth defects and maintain the health of their babies.
Vitamin D2 and D3, what do the numbers mean?
Our bodies process vitamin D through many stages (denoted by the subscript numbers) before it reaches a form which is “active” vitamin D. The active vitamin D is what actually does the work in our body, be it mediating calcium and phosphate in the blood or helping to grow and repair bones.
Vitamin D supplements are available over the counter in either D2 or D3 forms. No matter the form you buy, it’s a safe bet that ultraviolet light (UV) had a big part in creating it, just like in our skin. Vitamin D supplements are, quite literally, sunshine in a bottle.
Vitamin D3 : This type of vitamin D is made by your skin (and the skin of most land animals) when it is exposed to UV light (usually through direct sunlight). Vitamin D3 is put into many brands of fortified milk (either directly or by exposing the milk to UV light). Actual supplements of vitamin D3 are created using artificial methods involving UV light directed at animal products (e.g., wool grease or “lanolin”), just like UV light affects our skin.
The only significant, natural dietary sources of vitamin D3 in foods are fatty fish (e.g. cod liver oil, mackerel, tuna, salmon, sardines), liver, chicken eggs (if the chickens were fed vitamin D supplements), fortified milk, and fortified grain products (mainly cereals). In the American diet, fortified foods provide the most vitamin D3 of any source.
Vitamin D2 : This type of vitamin D naturally occurs in yeast and fungi (who also happen to need and use vitamin D). The precursor to vitamin D2 is a chemical called “ergosterol” (created by these organisms as part of their cell membranes). When ergosterol gets exposed to UV light, you guessed it, vitamin D2 is the result.
Just about the only source of Vitamin D2 is supplements, which are usually created using ergosterol from yeast or mushrooms exposed to UV light. Since it comes from non-animal sources, vitamin D2 is the only type of vitamin D which is okay for vegans to consume.
But, which one is better?
While some reports of differing efficacy between D2 and D3 (favoring D3) caused recent controversy, much of the confusion surrounding these reports has since been understood and clarified. Vitamin D2 and D3 are equally effective in increasing total available vitamin D in your body when taken as daily supplements.
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| Vitamin D deficiency can lead to many bone related problems such as Osteoporosis. |
Vitamin D deficiency, more common than you might think.
An estimated 1 billion people worldwide, across all ethnicity and age groups, suffer vitamin D deficiency. There are several reasons for this deficiency, but usually it results from either inadequate dietary intake (malnutrition) or inadequate sun exposure. Inadequate sun exposure can happen for several reasons:
- Increasingly indoor lifestyle
- Avoiding sunlight because of fear of skin cancer
- Living in far Northern or Southern latitudes geographically
What happens when we don’t get enough vitamin D?
Subtle symptoms of mild vitamin D deficiency can include loss of appetite, diarrhea, insomnia, vision problems, or a burning sensation in the mouth and throat. Because these symptoms are so vague and could potentially be caused by many other conditions, many doctors may not consider that vitamin D deficiency could be a possible cause.
Extreme vitamin D deficiency basically prevents calcium from reaching the bones. This leads to bone softening (ostemalacia), rickets, osteoporosis, or bone related birth defects in babies.
How can I make sure to get enough vitamin D?
Sunlight is the natural source of vitamin D for almost all land animals, and therefore it is for us as well. We evolved to make use of UV light to produce vitamin D3, and our skin is one of nature’s most efficient ways of doing so. In fact, spending as little as 10 minutes in direct sunlight 3 times a week (arm out the window on a drive home is probably enough) is enough to maintain healthy levels of vitamin D. In the winter months of many latitudes, however, there is hardly enough direct sunlight to allow significant UV light to even reach us, so our bodies may not be able generate D3 well, if at all. Supplementing through diet or nutritional supplements is necessary under these conditions.
It is also helpful to know that taking vitamin D in conjunction with calcium has a synergistic effect, increasing your body’s total absorption of both. Since vitamin D regulates the body’s absorption and levels of calcium, having both present in a supplement makes your body’s job that much easier. Some supplement manufacturers are starting to include calcium in their vitamin D supplements for just this reason.
Too much of a good thing - Can you take too much vitamin D?
While vitamin D is an essential part of keeping your body functioning at peak health, too much can be very unhealthy. Fortunately, you don’t have to worry about Hypervitaminosis-D (too much vitamin D in your body) from being out in the sun for too long.
Since the sun is the original, and most natural (i.e., which we evolved to use), source of vitamin D available, we have an inbuilt method of keeping levels in check. Vitamin D3 in the skin is destroyed by UV light (a process called photo-degrading) when there is too much of it around. Once we reach an optimal dose from sunlight (UV) exposure, our body simply lets the UV light destroy any excess. That is a pretty elegant solution. However, when we start supplementing vitamin D, especially in areas where it is necessary in winter months, it is possible to overdo it and get sick from too much.
If you were to take a large (>10,000 IU) dose of vitamin D3 and not encounter any direct sunlight (it is winter, after all), the natural method of UV degradation of Vitamin D3 in your skin would not take place. Even that small excess could cause symptoms such as nausea, vomiting, constipation, headache, sleepiness, and weakness. Much more vitamin D than that can raise blood calcium concentrations, and an acute toxicity can cause hypercalcemia and hypercalciuria.
Vitamin D2, however, gets transformed into the active form of vitamin D in your body through another biochemical route (conversion to D4) and is therefore not subject to this risk. However, it is always important to avoid taking too much of any supplement for several reasons, not the least of which is that you could get sick, or it might be just a waste of money.
Dr. Rebecca’s Recommendations about vitamin D
Since both vitamin D2 and D3 supplements have shown equal effects in raising overall vitamin D levels in the body, the choice is up to you. Vegans, obviously, may only wish to use vitamin D2 supplements, but everyone else may be able to use either. The risks associated with supplements of D3 are minimal, provided that you are careful to not take an excessive amount when you are not spending much time in the sun.
While many studies seem to conflict on the matter of just how much vitamin D is optimal to take per day, there is some agreement that doses between 1000 - 4000 IU (25 - 100mcg) per day may be optimal. While the FDA and other government agencies continue to suggest that the RDI (Recommended Daily Intake) of vitamin D is only 400 IU (10 mcg), mounting evidence suggests that this level is far too low to maintain optimal health. The RDI for vitamin D needs to be (and likely will be) revised upwards to a minimum of 1000 - 4000 IU per day.
Above 4000 IU per day, research has shown diminishing returns (taking more becomes less and less useful for your body) for vitamin D. There simply isn’t any increase to blood serum levels of active vitamin D when supplemented at or above these levels. In addition, the risk of hypervitaminosis-D, especially when there is insufficient sunlight to photo-degrade any excess, increases markedly.
In some cases, clinicians may recommend doses up to 10,000 IU per day. A high dose such as this may have its place in treating patients who have a severe deficiency of vitamin D and they require a rapid rebuilding of their bodies stores. Patients who are undergoing orthopedic surgery procedures may need these kinds of larger daily doses in preparation for upcoming surgery and for the necessity of bone healing after surgery. Doses at this level require careful monitoring by a trained and licensed health care provider in order to make sure there are no adverse effects.
While higher doses of vitamin D may have their place, it is important to always seek the advice of a knowledgeable and qualified health care practitioner who understands the benefits and risks of vitamin D supplementation for your particular health, lifestyle, and geographic circumstances. We suggest that if you are concerned about your levels of vitamin D, you have a doctor test your blood serum levels of vitamin D in order to determine if you require additional supplementation, and discuss all available options to that end before proceeding with any treatment or supplementation. As with any supplement, it is important to make sure that you get a quality product from a company you trust to be committed to making the healthiest product possible.
Conclusion:
Vitamin D is vitally important because it strengthens our bones and appears to help protect us from many chronic illnesses. You may well have a deficiency of vitamin D if you don’t get adequate amounts in your diet, don’t spend time in the sun, overuse sunscreen, or live in a very northern or southern latitude.
Vitamin D can be replenished safely through:
- Diet -- Fish oil (especially cod liver oil), oily fish, liver, fortified milk, fortified grains or "fortified" eggs.
- Spending a small amount of time each day in direct sunlight (A good rule of thumb is that if your shadow is shorter than your height, you will likely be generating vitamin D3).
- Taking supplements (Vitamin D2 or D3)
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Articles / References
Protean Manifestations of Vitamin D Deficiency
Vitamin D Supplementation: An Update
Vitamin D deficiency
More evidence and explanation here about the equivalency of vitamin D2 and D3, as well as much more information about vitamin D.
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Researched and written by Dr. Rebecca Malamed, M.D. with assistance from Mr. Malcolm Potter.
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