Vitamin D Deficiency, Treatment, Risk, Benefits and Side Effects

Vitamin D Deficiency

Vitamin D has many benefits to health. Musculoskeletal problems are more common in those with vitamin D deficiency/insufficiency. This includes osteoporosis, an increased risk of fractures, an increase risk of falls and reduced muscle function.

Osteoporosis affects a large percentage of nursing home residents. Osteoporosis is a bone disease associated with low bone mass and an increased risk of fracture. Ten million Americans are afflicted with osteoporosis while 34 million are afflicted with osteopenia. It is estimated that 70 to 85 percent of individuals who live in a nursing home have osteoporosis.

Osteoporosis is associated with inadequate calcium intake, but vitamin D helps with calcium absorption. Long-term vitamin D deficiency increases the risk of osteoporosis2. Vitamin D may prevent osteoporosis in older adults who are non-ambulatory, those on chronic steroids and for post-menopausal women.

Vitamin D supplementation has the potential to increase bone density. In one study there was an increase in the density of lumbar spine and the femoral neck bone with vitamin D supplementation of 50,000 international units twice a week for five weeks in those who were vitamin D deficient.

Vitamin D and calcium together reduce fractures in institutionalized older adults, but vitamin D alone is not effective in reducing the risk of falls or fractures. Those over the age of 65 with low vitamin D levels are at increased risk for hip fractures and reduced muscle mass and strength.

Vitamin D has the potential to reduce the risk of falls. It potentially does this through the improvement of muscle function. Low levels of vitamin D in the blood are linked to the poorest muscle function and higher levels are linked to better muscle function. Those with a low baseline level of serum 25-hydroxyvitamin D concentration (between 10-20 ng/ml) are likely to benefit the most in regards to muscle strength when supplemented with vitamin D.

When vitamin D supplementation is consumed in doses of 700 to 1000 international units per day the risk of falls are reduced. When 500,000 units of cholecalciferol were given once annually the risk of falls was actually increased.

Hat Causes Vitamin D Overdose?

Vitamin D overdose happens most often when someone gets plenty of sun exposure, enjoys foods that contain high amounts of Vitamin D, and exceeds the recommended dosage with Vitamin D supplements. If you’re taking a quality multivitamin and getting enough sunshine, you may not need to take additional vitamins at all. Doubling up on supplements of any kind may lead to problems, particularly with vitamins that are stored in the body. In healthy adults, taking more than 40,000 IU of Vitamin D can cause toxicity after several months.

Vitamin D is one of the fat-soluble vitamins, along with Vitamin A, E and K. This means it will dissolve in fat but not water. Once your body absorbs Vitamin D, it stores it in your liver and your fatty tissues. Fat-soluble vitamins can be stored in your body for up to six months.

Although there’s no established threshold for Vitamin D overdose, the upper intake level is generally agreed to be about 4,000 IU per day for most people, from pre-teens to adults. If you’re taking liquid Vitamin D supplements, be sure the dropper is clearly marked so you can get the proper dosage and avoid unwanted Vitamin D side effects.

Vitamin D overdose causes something called hypercalcemia, or too much calcium in the blood. If hypercalcemia is not treated, it results in excess deposits of calcium in soft tissues and organs such as the kidneys, liver, stomach, lungs and heart, causing pain and even organ damage.

Taking excessive amounts of Vitamin D can result in side effects commonly beginning with a loss of appetite, nausea and vomiting. These are often followed by itching, weakness, insomnia, nervousness, general depression, excessive urination, excessive thirst, and in extreme cases, renal failure. Other symptoms of Vitamin D overdose include abnormal bone growth, diarrhea, irritability, weight loss, and severe depression.

Treating Vitamin D toxicity starts with restricting Vitamin D supplements and limiting calcium intake. Exposure to sunlight for prolonged periods doesn’t normally cause Vitamin D overdose, so it isn’t much of a factor in overcoming Vitamin D side effects.


A link between vitamin D and cancer has been established. Vitamin D may help in the prevention of colon, breast and prostate cancer. Precancerous lesions of the intestine and breast are linked to a deficiency of the vitamin D receptor in animals.

Many cancers have been linked to poor vitamin D status. Colorectal cancer risk is increased in those with poor vitamin D status. One analysis showed that those who consume 1000 international units per day of vitamin D have a reduced risk of colorectal cancer. Another analysis showed that vitamin D intake is inversely related to the risk of colorectal cancer. Despite the positive data on vitamin D, the research is inconsistent and the National Cancer Institute does not advise for or against the use of vitamin D supplements to lower the risk of colorectal or any other type of cancer.

Some studies show serum 25-hydroxyvitamin D concentration is associated with a reduced risk of breast cancer but findings do not reach statistical significance. More research is needed to determine the role of vitamin D on breast cancer risk.

There is some evidence that vitamin D may be harmful. One large prospective study suggested that vitamin D does not decrease the risk of prostate cancer and higher circulating vitamin D levels may be associated with an elevated risk of aggressive disease. Other research suggests that those with the highest level of vitamin D may be at an increased risk for pancreatic cancer.

Despite some research suggesting that vitamin D reduces the risk of some cancers, current evidence does not recommend large doses of vitamin D in the prevention of cancer. A large analysis of over 16,000 people suggested that total cancer mortality is not related to baseline vitamin D status. Overall research does not support role of vitamin D in the prevention of cancer. More research is needed to determine the exact link between cancer and vitamin D.

Immune system

Vitamin D has effects on the immune system. Vitamin D may reduce the risk of autoimmune diseases in animals. Diseases that may be affected by vitamin D status include: diabetes mellitus type 1, multiple sclerosis and inflammatory bowel disease.

Vitamin D supplementation in early infancy reduces the risk of type 1 diabetes. One study suggested that those with a serum 25-hydroxyvitamin D concentration below 20 ng/mL had about a twofold increased rate for the future development of multiple sclerosis. Currently only animal, in vitro and epidemiological studies suggest a link between diabetes/multiple sclerosis and vitamin D. Before a firm conclusion can be reached, randomized controlled trails need to occur.

Higher levels of vitamin D are associated with a lower risk of Crohn’s disease. The impaired regulation of vitamin D is related to the development of autoimmune processes (including inflammatory bowel disease) in animals. The administration of vitamin D may improve these symptoms.

Vitamin D may help fight both bacterial and viral infections. Vitamin D levels are linked to tuberculosis. Vitamin D deficiency may be more common in those with tuberculosis. Vitamin D may have a role in the treatment of tuberculosis, but more research is needed before this link is definitely established.

Vitamin D levels may have a beneficial effect on respiratory tract viral infections, but this relationship is not strongly established. Multiple studies have not found a link between vitamin D status and the prevention of viral respiratory infections. A more recent analysis suggested that vitamin D supplementation may reduce the risk of viral upper respiratory tract infections and tuberculosis.

Vitamin D and the Heart

Many genes in the cardiovascular system are regulated by vitamin D. Vitamin D deficiency has been linked to heart attack, stroke, high blood pressure, diabetes, peripheral vascular disease and heart failure. There is a paucity of studies that look at vitamin D and cardiovascular disease. Observational research suggests that there is a link between cardiovascular disease and vitamin D status. More research is needed to determine the role of vitamin D supplementation in cardiovascular disease.

The renin-angiotensin system is regulated in part with the help of vitamin D. There is an inverse relationship between incident hypertension and serum 25-hydroxyvitamin D concentration. More research is needed to confirm a causative relationship between vitamin D levels and blood pressure.

In a review study, five out of seven studies showed an inverse relationship between the serum 25-hydroxyvitamin D level and cardiovascular disease. The prevalence of coronary heart disease is higher in those with a low serum 25-hydroxyvitamin D concentration than those with higher levels. Supplementation with vitamin D did not result in any beneficial effect on risk factors for cardiovascular disease and no benefit was appreciated after increasing the serum 25-hydroxyvitamin D concentration from 23 ng/mL to over 40 ng/mL.

Vitamin D and Other Diseases

Diabetes is linked to vitamin D. The link between vitamin D and diabetes mellitus type 1 was discussed above. Low vitamin D levels are associated with type 2 diabetes. Higher levels of vitamin D intake are associated with a lower risk of type 2 diabetes. Despite these correlations, interventional studies with vitamin D have not demonstrated that vitamin D supplementation reduces the risk of diabetes.

Vitamin D is important for brain development, so it may be linked to psychopathology. Low levels of serum 25-hydroxyvitamin D have been shown to be present in those with Alzheimer’s disease and depression. These studies do not demonstrate that low levels of vitamin D are the cause of these conditions.

Low levels of vitamin D may increase the risk of death. Even though there is an association between vitamin D and all cause mortality, it is unclear if this increased risk of death is strictly related to the vitamin D deficiency or simply overall poor health status. Some studies suggest that cancer patients have a reduced risk of mortality with a higher vitamin D level, but other studies showed no association between cancer death rates and serum 25-hydroxyvitamin D concentration.

A recent analysis showed that higher vitamin D levels. are associated with reduced all-cause mortality, but no association between vitamin D levels and stroke or ischemic heart disease was established. Those with severe chronic renal failure are at increased risk for death with low levels of serum 25-hydroxyvitamin D concentration and treatment with vitamin D improves survival.

How Do You Get Enough Vitamin D?

There are 3 ways for you to get vitamin D:

  • 1) Your skin makes vitamin D through sunlight
  • 2) You can get vitamin D from food
  • 3.) You can take a vitamin D supplement

Let’s start with the sun on your skin.

As a general rule, exposure of the face, hands, arms, and legs to sunlight 2 to 3 times a week may produce enough vitamin D to stay healthy. Exposure should be about 1/4 of the amount of time it takes for you to get a mild sunburn. Depending on your skin color, this can mean from 5 to 30 minutes of sun exposure between 10 am and 3pm.

It is the ultraviolet B radiation in sunlight that helps your skin make vitamin D. Complete cloud cover reduces this radiation by about 50%. Shade, including the shade from severe pollution, reduces this ultraviolet B radiation about 60%.

How about food?

Surprisingly, there are not too many foods that are naturally high in vitamin D. The following list includes the foods highest in vitamin D:

  • Vitamin D Measured in IUs:
  • Cod liver oil, 1 tbsp, 1,360
  • Swordfish, cooked, 3 oz., 566
  • Sockeye Salmon, cooked 3, oz., 447
  • Mackerel, canned, 3 oz., 214
  • Sardines, canned, 3 oz., 197
  • Tuna Fish, canned in water, drained, 3 oz., 154
  • Orange juice Vitamin D-fortified, 1 cup, 137
  • Milk, Vitamin D-fortified, 1 cup, nonfat, reduced fat, & whole, 115-124

The abbreviation IU stands for “international unit” and is what you will find on food and supplement labels.

The third source of vitamin D is from supplements.

In general, there are two different forms of vitamin D on the market: ergocalciferol (also known as vitamin D2) and cholecalciferol (also known as D3). I will discuss their effectiveness in the following section.

IS Cod Liver Oil The Solution?

Cod liver oil certainly appears to be the most promising of the foods rich in vitamin D but there are several factors to consider before choosing this as your vitamin D program:

  • Vitamin D is not absorbed well without complementary vitamins
  • Cod liver oils vary significantly in the amount of vitamin D they provide
  • Several tablespoons a day may be necessary to maintain recommended blood levels of vitamin

Complementary Vitamins

The Vitamin D Council warns that a variety of vitamins and minerals are needed to help the body use vitamin D properly. These include:

  • Magnesium
  • Zinc
  • Vitamin K2
  • Boron
  • Genestein
  • A tiny amount of vitamin A

Magnesium is the most important of these complementary factors but is rarely included with cod liver oil. Taking cod liver oil (or increasing vitamin D through supplements) could actually worsen an underlying magnesium deficiency…which is already common throughout North America.

Brands of Cod Liver Oil

Most brands of cod liver oil go through a process that removes all of the natural vitamins including vitamin D…although some manufacturers add vitamins to the final product. Cod liver oil that is unheated, fermented and produced with a filtering process that retains the natural vitamins is widely recommended. But most popular brands provide only 400 IUs of vitamin D per teaspoon (the equivalent of 1,200 IUs per tablespoon) which is well below recommended levels. During the winter months in northern regions (north of Boston, Rome and Beijing) several tablespoons would be required each day to maintain adequate blood levels-and additional magnesium would be required to facilitate absorption.

Many brands of cod liver oil have the benefit of providing EPA and DHA acids (which are valuable for the brain and nervous system) but few provide the higher dosage recommended by a growing number of vitamin D experts. Although manufacturers argue that their oils provide more absorbable nutrients because of the high vitamin A content…this is widely disputed as vitamin A deficiency is rare in developed countries. Indeed, too much vitamin A may prove toxic and is particularly dangerous during pregnancy.

A good bone building supplement is an excellent complement to a diet of foods rich in vitamin D. A higher quality supplement will not only provide additional vitamin D3 but also the magnesium and vitamin K needed to facilitate absorption. Although cod liver oil is one of the foods rich in vitamin D…it may not provide as much absorbable vitamin D as expected while providing a false reassurance that intake is adequate.

How Much Vitamin D Do You Need?

Well, if you can get enough sun on your skin as described above, you really do not have to worry about getting more vitamin D from food and supplements.

On the other hand, food and supplements can provide a healthy dose of vitamin D if you have any (or a combination) of the following risk factors for low vitamin D:

  • You do not spend enough time outdoors, especially in the sun.
  • You live in a northern latitude, especially north of the Philadelphia-San Francisco line. For example, in Boston, there is not enough sunlight to make vitamin D in your skin for about 4 months of the year. If you go further north to Edmonton, Canada, your skin cannot make vitamin D for 5 months of the year.
  • You have been following your dermatologist’s suggestion of liberally using sunscreen to protect yourself from the sun’s radiation.
  • You have darker skin. Skin pigment reduces the skin’s ability to absorb the ultraviolet radiation in the sun. In a bathing suit, a light-skinned person spending 10-12 minutes under peak July sun in Boston can make 10,000 to 20,000 international units of vitamin D. It will take an Asian Indian person, who has darker skin, about 30 minutes to make as much vitamin D. It will take an African American with very dark skin about 120 minutes to make the same amount of vitamin D.
  • You are obese. Fat cells hoard vitamin D. This reduces the circulating vitamin in your blood.
  • Your have a medical condition such as Crohn’s disease, celiac disease, and cystic fibrosis that impairs your gut’s absorption of vitamin D.
  • You are a strict vegetarian.
  • Your kidneys are impaired so they cannot activate the vitamin D you have.
  • You are older than 65. This means your skin makes less vitamin D, your gut may not absorb nutrients as efficiently, and your kidneys may not activate vitamin D as effectively. Even in sunny South Florida, as many as 40% of older people have low vitamin D levels.

If you have any of these risk factors, how many international units of vitamin D should you aim for a day?

This depends on whom you talk to. In recent years, various scientific authorities came up with different amounts of vitamin D that they consider good for your daily intake through food and supplements.

To spare you the confusing numbers and arguments, here is the bottom line.

If you are an adult, aim for 600 to 2000 IUs of vitamin D a day from your food and supplements.

And if you get vitamin D from supplements, keep in mind that unit for unit, cholecalciferol (vitamin D3) is better used by your body than ergocalciferol (vitamin D2).

In general, vitamin D3 is about 3 times more powerful than vitamin D2.

Where Does Vitamin D Go?

The type of Vitamin D that’s formed when sunlight contacts the skin is known as vitamin D3, or cholecalciferol. The body manufactures it when ultraviolet rays in sunlight reacts with the cholesterol naturally found under the skin. In the liver Vitamin D3 is then “activated,” or converted to a more active form of Vitamin D, then delivered to where the body needs it most.

Some of this Vitamin D stays in the liver and kidneys, helping calcium re-absorption from the blood. Another portion of the Vitamin D is sent to the intestines to aid absorption of calcium from food. It also goes to the bones to help them retain calcium.

While it’s important to have enough Vitamin D in your diet, it is possible to take in too much vitamin D. This can happen when someone gets plenty of sun exposure, eats lots of foods high in Vitamin D, and takes a Vitamin D supplement. If this sounds like you, talk to your healthcare professional about whether or not you need a Vitamin D supplement as part of your diet.

When it comes to Vitamin D and its many benefits, the thing to keep in mind is that deficiency is the most common problem. In this age of desk jockeys, couch potatoes and night owls, the odds of getting too much of the “sunshine vitamin” are pretty low.

Who Is At Risk of Vitamin D Side Effects?

People with certain medical conditions like hyperparathyroidism are more sensitive to Vitamin D and are more prone to develop hypercalcemia if they get too much Vitamin D.

Maternal hypercalcemia during pregnancy can increase sensitivity for the unborn child. This could lead to tragic consequences such as mental retardation and facial deformities for the baby. Pregnant or breastfeeding women should consult a healthcare professional before taking a Vitamin D supplement.

For liquid Vitamin D meant for babies, the FDA recommends that the dosage dropper holds no more than 400 IU. Babies up to one year old should have no more than 1,000 IU per day. In November 2010, the Institute of Medicine (IOM) increased the daily upper limit to 2,500 IU for children 1 to 3 years old. For ages 4 to 8 years, the maximum dose is 3,000 IU per day.

If you’re a healthy adult and you’re taking large doses of Vitamin D, you could be flirting with some serious side effects. Published cases of toxicity involving hypercalcemia all involve an intake of more than 40,000 IU per day. If your own Vitamin D consumption falls under this limit, then your outcome is likely to be sunny.