Vitamin D is an essential, fat soluble vitamin that is absorbed in the body through a process that occurs when sunlight hits your skin. Because it's fat-soluable vitamin D is stored in the body for long periods of time.
Vitamin D can refer to either vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D3 is the preferred vitamin D supplement.
Vitamin D in the body
There are three main ways your body can absorb adequate amounts of vitamin D. The most efficient is from direct sunlight. Ultraviolet rays from the turns a chemical in the skin into vitamin D3. It's then converted into an active form of D3 by the kidneys.
You can also get vitamin D through your diet, but taking a D3 supplement is most reliable since few foods contain sufficient amounts of the nutrient.
Vitamin D2 vs. D3
There are two types of vitamin D. The most natural form, vitamin D3, is created in the body when UVB (ultraviolet B) rays from the sun strikes the skin. Even foods that are a rich source of vitamin D, such as fish, almost always contain D3. The body can't make vitamin D2 -- meaning, it's not a naturally occurring nutrient.
Another benefit of vitamin D3 is that it may be less toxic than D2, according Mark A. Moyad, MD, "higher concentrations of D2 circulate in the blood when consumed (compared to vitamin D3). [In addition, D2] does not bind as well to the receptors in the human tissues compared to vitamin D3."
Vitamin D3 is more potent and stable than D2. Of the two, D3 stays active and circulates in the body longer.
Uses and functions
One of the most crucial reasons for getting the recommended daily allowance (RDA) of vitamin D is for the purpose of increasing calcium and phosphorus levels, maintain bone health, immunity, cell growth, and preventing a deficiency. Proper vitamin D levels prevents rickets and brittle bone disease. Vitamin D also helps control:
- High blood pressure
- Treating low calcium and phosphate levels due to other health issues
- Kidney disease (regulates calcium and facilitates bone growth)
- Skin conditions
- Stroke and heart attack prevention
- Fibroids: may shrink fibroids in rats
Regardless of where you live, the risk for vitamin D3 is high. In 2009, the Archives of Internal Medicine released a study indicating that
75% of kids and adults are deficient in vitamin D.
According to the Office of Dietary Supplements, it takes just a few minutes of unprotected exposure to the sun to get your RDA of vitamin D. "It has been suggested ... that approximately 5 to 30 minutes of sun exposure between 10 a.m. and 3 p.m. at least twice a week to the face, arms, legs, or back ... usually lead to sufficient vitamin D synthesis."
Vitamin D3 is naturally present in very few foods and is added to others. The Food and Nutrition Board (FNB) has established dietary reference intakes (DRI) indicating how much vitamin D3 you should take based on different variables. The recommended daily allowance (RDA), is "the average daily level of intake sufficient to meet the nutrient requirements of nearly all healthy people," according to the Office of Dietary Supplements.
Suggested vitamin D3 dosage:
|0-12 months||400 IU|
|1-13 years||600 IU|
|14-18 years||600 IU|
|19-50 years||600 IU|
|51-70 years||600 IU|
|>70 years||800 IU|
Few foods are a natural, rich source of vitamin D3. Foods that do provide significant amounts of the nutrient are typically fortified.
Eggs: the yolk of one large egg contains about 41 IUs per serving.
Cod liver oil: 1 tbsp. contains 1,360 IUs.
Sardines: two canned in oil or drained sardines contain 46 IUs of vitamin D3
Salmon: 3oz of cooked salmon contains 447 IUs.
Tuna: 3oz of tuna canned in water contains 154 IUs.
Beef liver: 3 oz of cooked beef liver contains 42 IUs.
Cheese: 1oz of Swiss cheese has 6 IUs.
Milk: 1 cup of skim, low-fat, and whole milk is fortified with 115 to 124 IUs of vitamin D3
Orange juice: 1 cup is fortified with about 137 IUs of vitamin D. Since vitamin D levels can vary between brands, be sure to read the label.
Margarine: 1 tbsp. of margarine is fortified with 60 IUs of vitamin D3.
Cereal: from 3/4 to 1 cup of boxed cereal contains about 40 IUs of D3 -- about 10% of the recommended daily allowance.
If you wear sunscreen, don't get out in the sun often, have dark skin, or cover up when in the sun, you could have a vitamin D3 deficiency. Women who breastfeed, obese people, and older individuals also have difficulty getting adequate amounts of vitamin D via ultraviolet B rays.
If you don't get enough vitamin D from the sun or food sources, your bones release calcium to help maintain electrolyte balance in the blood. This balance helps regulate your heartbeat and keeps muscles strong, but the process may compromise bone health. 
If children don't get enough vitamin D, they could develop rickets (soft bones), which can stunt their growth. Adults who don't get enough vitamin D are at risk for brittle bones diseases.
Vitamin D deficiency may be connected to depression because brain and nerve tissue have vitamin D receptor cells.
To determine whether you have a vitamin D3 deficiency, talk to your doctor about getting a blood test. Because there are few significant vitamin D3 deficiency symptoms, it's important to talk to your doctor about ways to ensure you're getting the RDA of the nutrient.
Symptoms of a vitamin D deficiency are: 
If you experience any other otherwise unexplained symptoms, consult your doctor for a check up to help discover the cause. 
On the other end of the spectrum, you may be getting too much vitamin D. This can cause dangerously high calcium levels. Look for the signs of toxicity such as lack of appetite, thirst, mood changes, urinating more than usual, market tiredness for no other apparent reason, nausea, vomiting, and constipation. 
Individuals who regularly supass the tolerable upper intake (UI) of vitamin D3 may be at risk for developing vitamin toxicity. Signs include:
Lack of interest in sex
Pain in the upper abdomen and back
Metallic taste in the mouth
Taking excessive amounts of vitamin D can also raise calcium blood levels, which can cause tissue and vessel calcification, and damage to the heart, kidneys, and liver. The good news is that the body can't produce too much vitamin D. There is no risk for vitamin D toxicity from sun exposure.
Bile acid sequestrates: cholestyramine, mineral oil, and orlistat, for example
Colestipol: cholesterol drug
Digoxin: controls heart rhythm
Diuretics: water pills, used for the treatment of liver disease, heart disease, and others
Please note that this is not an exhaustive list of medications that can interact negatively with vitamin D3. Consult your doctor regarding possible interactions between vitamin D3 and other medications.
Interactions may affect how a medication works or cause unwanted side effects. Check product labels (prescription and over-the-counter). If they have calcium, magnesium, phosphate, or vitamin D, ask your doctor or pharmacist how to safely use them.
It's best to take vitamin D3 (cholecalciferol) after you eat.
Vitamin D3 can be taken on a empty stomach or with food.
Allergic reactions to vitamin D3 are not likely, but if you develop a rash, swelling, dizziness, problem thinking clearly, irritability, boosted urine output, itchiness, have trouble breathing, or experience any other troubling symptoms, get medical assistance immediately.
Let your doctor or pharmacist know if you have high calcium and vitamin D levels, malabsorption syndrome, electrolyte imbalance, heart disease, liver disease, or kidney disease before taking vitamin D3.
If you are pregnant or breastfeeding, don't take excessive amounts of vitamin D3 without first consulting your physician.
Let your doctor know all the medications you are taking whether prescription or over-the-counter.
Don't start on a new medication without discussing it with your doctor.
Supplements are not strictly regulated by the government, so there is no guarantee that they are safe or will do what they are supposed to do.
Supplements can act like drugs when taken in high doses. Read all directions and use with care.
Although we do not sell vitamin D, you can compare brands and prices here on PricePlow.
- WebMD; "Cholecalciferol (Vitamin D3) Oral"
- Drugs.com; "Liquid Vitamin D-3"
- Michele Turcotte; Livestrong; "Mental Health Benefits of Vitamin D;" 2013
- The Vitamin D Council; "What Is Vitamin D Deficiency?"
- Drugs.com; "Vitamin D3 Side Effects;"
- Paul Insel, et. al.; "Nutrition;" Fourth Edition; Paul Insel, et.al.; 2201
- University of Maryland Medical Center; Vitamin D;" 2012
- Mark A. Moyad, MD., MPH; Dermatology Nursing; "Vitamin D: A Rapid Review: Vitamin D2 and/or Vitamin D3;" 2009
- Ginde A., et. al. Archives of Internal Medicine; "Demographic Differences and Trends of Vitamin D Insufficiency in the US Population, 1988-2004;" 2009
- Office of Dietary Supplements; "Vitamin D;" 2011
- Halder SK, et. al.; NIH News; "Vitamin D shrinks fibroid tumors in rats;" 2012