It is the middle of winter in Wisconsin and the sun doesn’t get too high in the sky or stay out for very long these days. Most of us have heard the buzz about vitamin D deficiency and suspect that at 43.07° N, we may be among those who are at risk. Yet there seems to be a lot of mixed information circulating out there and many people seem to hold some misconceptions and misunderstandings regarding “the sunshine vitamin.” As scientists continue to discover a greater and greater connection between adequate amounts of vitamin D and health, I would like to take this opportunity to share with you information on vitamin D to help you work it into your daily health regime.

What is vitamin D?
Vitamin D is not really a vitamin at all. It was discovered at the same time as vitamin A, B and C and was originally thought to be a vitamin. Vitamin D, however, is a type of prohormone. A prohormone is any substance that can be converted into a hormone in the body. Hormones work as chemical messengers to carry information from one cell, or group of cells, to another. Vitamin D is one of the oldest prohormones, having been produced by life forms for over 750 million years.

Why is Vitamin D important?
Beginning in the womb and continuing throughout our lifespans, vitamin D is critically important for the development, growth and maintenance of a healthy body. Vitamin D’s metabolic product—calcitriol—is a secosteroid hormone (the key to unlock binding sites on the human genome). There are more than 2,700 binding sites for calcitriol on the human genome. These binding sites are near genes involved in virtually every known major disease of humans.

  • It is crucial for the absorption and metabolism of calcium and phosphorous, which have various functions, especially the maintenance of healthy bones.
  • It is an immune system regulator. It may be an important way to arm the immune system against disorders like the common cold, according to scientists from the University of Colorado–Denver School of Medicine, Massachusetts General Hospital and Children’s Hospital Boston.
  • It may reduce the risk of developing multiple sclerosis. Studies have indicated that Multiple Sclerosis is much less common the nearer you get to the tropics, where there is much more sunlight, according to Dennis Bourdette, chairman of the Department of Neurology and director of the Multiple Sclerosis and Neuroimmunology Center at Oregon Health and Science University.
  • Vitamin D deficiency plays an important role in the development of both type 1 and type 2 diabetes. Vitamin D supplementation can increase insulin sensitivity and decrease inflammation according to a recent study conducted by Laboratory for Experimental Medicine and Endocrinology in Belgium.
  • Vitamin D is probably linked to maintaining a healthy body weight, according to research carried out at the Medical College of Georgia.
  • Vitamin D may have a key role in helping the brain to keep working well in later life, according to a study of 3000 European men between the ages of 40 and 79.
  • It can reduce the severity and frequency of asthma symptoms, and also the likelihood of hospitalizations due to asthma, researchers from Harvard Medical School found after monitoring 616 children in Costa Rica.
  • It has been shown to reduce the risk of developing rheumatoid arthritis in women.
  • A form of vitamin D could be one of our body’s main protections against damage from low levels of radiation, say radiological experts from the New York City Department of Health and Mental Hygiene.
  • Various studies have shown that people with adequate levels of vitamin D have a significantly lower risk of developing cancer, compared to people with lower levels. Vitamin D deficiency was found to be prevalent in cancer patients regardless of nutritional status, in a study carried out by Cancer Treatment Centers of America.
  • High vitamin D doses can help people recover from tuberculosis more rapidly, researchers reported in September 2012 in the Proceeding of the National Academy of Sciences (PNAS).
  • An additional study published in September 2012 suggested that low levels of vitamin D may increase the risk of heart attack and early death.
  • Some researchers believe that some depression, insomnia and sleep apnea are due in part to vitamin D deficiency and that correcting the deficiency can reverse mood and sleep irregularities. This could be due to the fact that one of the many roles of vitamin D is to regulate the pineal gland’s secretion of melatonin. Melatonin is the master hormone that regulates circadian rhythms and controls the cascade of other hormones and chemicals needed for falling asleep and waking up. With the help of vitamin D, melatonin is released into the blood during periods of darkness or episodes of reduced sunshine.  Adequate levels of vitamin D also influence activity of the neurotransmitter serotonin—thought to be a contributor to feelings of well-being and happiness. This explains why many people enjoy restful sleep during a night that follows spending time in the sun.

How do we get vitamin D?
From phytoplankton and zooplankton to humans—most living creatures exposed to sunlight are capable of producing vitamin D. The human body was designed to receive the vitamin D it needs by producing it in response to sunlight exposure—specifically, the UVB band of the sun’s ultraviolet spectrum. When the sun’s UVB rays hit the skin, a reaction takes place that enables skin cells to manufacture vitamin D.

In the winter time, it’s impossible for us here in Madison (in fact anywhere north of Atlanta, GA) to produce vitamin D from the sun. This is because the sun never gets high enough in the sky for the vitamin D producing UVB rays to penetrate the atmosphere. While we may be able to stock up on this important nutrient during the summer months, we are just plain out of luck right now.

Food sources of vitamin D include fatty fish, such as salmon and mackerel, beef liver, egg yolks and fortified cereals, dairy products and orange juice.

How much is enough vitamin D?
Many doctors still consider a result of 30 ng/mL (75 nmol/L) to be sufficient, even though recent studies indicate otherwise. While experts still do not agree on what exactly constitutes an “optimal” level of vitamin D in the blood, recent research suggests 40 ng/ml or more are necessary to provide protection against diabetes, heart disease, and cancer.

How do you know if have a vitamin D deficiency?
If you do not receive UVB exposure either from the sun or a tanning bed, and you don’t supplement with adequate amounts of vitamin D3, odds are you are vitamin D deficient. Vitamin D is fat soluble, which means it can be stored up in the body during summer months for later use. Many people these days, however, intentionally avoid the sun—or use sunscreen—blocking the beneficial wavelengths that produce vitamin D in their skin. While over-exposure to the sun’s short UVB rays can burn the skin and long UVA rays will age the skin, far more lives have been lost due health complications tied to vitamin D deficiency than from over exposure to sunshine. Experts say going outside for 10 minutes in the midday sun—in shorts and a tank top with no sunscreen—will give you enough radiation to produce about 10,000 international units (IU) of vitamin D. This is usually well before most people burn.

Some symptoms associated with vitamin deficiency include obesity, cognitive impairment, depression, and muscle weakness. Other early deficiency signs include profuse sweating, heightened anxiety, fatigue, reduced appetite, mild depression, muscle cramps and sore joints. But as all these symptoms can arise from numerous other causes and are not necessarily due to vitamin D deficiency. The only way to know for sure if you are vitamin D deficient is to have your blood levels tested. Your health care provider can order a test to determine if you have a vitamin D deficiency. Most medical insurances cover this test if your doctor feels it is indicated. While some doctors order a 1,25-dihydroxyvitamin D test, this is the wrong test as it cannot determine vitamin D deficiency. Ask your doctor to order the 25-hydroxy vitamin D test. This is the most accurate way to measure how much vitamin D is in your body. It is also a good idea to ask for the exact number value of the test results, or a hard copy. Results that are conveyed by use of the words “normal,” “within range,” or similar wording can be misleading.

If you don’t have insurance or your insurance will not pay for your vitamin D test, you may wish to purchase an in-home test kit and test your levels yourself. A simple home test kit can be ordered online for about $65 dollars. Besides low-cost, additional benefits to using an in-home test are that you are in control of when, and how often, you test as well as what you do with the results. Resources for obtaining an in-home vitamin D test kit are given at the end of this article.

Supplementing with vitamin D
There are several forms of vitamin D: supplemental vitamin D, pharmaceutical vitamin D, and those that exist in the body—what are called vitamin D’s metabolites.
Vitamin D3 is real vitamin D. It is the same substance as what is produced in human skin in response to sun exposure. Supplemental vitamin D3 is derived from either lanolin or cod liver oil extract and is the form of vitamin D that most effectively treats vitamin D deficiency. We have this supplement available in multiple forms for your convenience in the wellness department. We have vegan D3 at the Co-op that originates from algae. Whether you choose softgels, tablets, sublingual or liquid drops is a matter of personal preference. All of these varieties will effectively deliver the nutrient into your system.

Vitamin D2 is derived from fungal sources by activating ergosterol with ultraviolet light. It is not naturally present in the human body and may have actions within the body different to those of vitamin D3. Although many doctors are still prescribing vitamin D2, vitamin D3 is the preferred form for treating deficiency and is what the majority of the experts recommend.

There are also prescription forms of vitamin D, such as synthetic calcitriol and vitamin D analogs. Vitamin D analogs are synthetic compounds based upon variations of the naturally-occurring vitamin D metabolites. High dose calcitriol use has been known to increase risk of hypercalcemia. Vitamin D analogs are seen as a way to achieve the beneficial effects of calcitriol without this risk. Pharmaceutical vitamin D should never be used to treat vitamin D deficiency according to the Vitamin D Council.

What is the recommended dosage of vitamin D supplements?
Vitamin D is measured in International Units and is potent in small quantities—one IU is equal to only 0.000025 milligrams (mg). Conversely, 40 IU is equal to one microgram (mcg or µg).

The government’s official dietary recommendations are 200 IUs a day up to age 50, 400 IUs to age 70, and 600 IUs over 70. These recommendations, however, are considered by many experts far too low to maintain healthful vitamin D levels. According to the American Association of Clinical Endocrinologists, 1000-2000 IU of Vitamin D daily is required to maintain a 25(OH)D level at 30 ng/ml or above. They advocate for supplementation in the winter of about 2,000 IUs per day and a 10–20 minute dose of daily sunshine in the summer. As always, consult with your healthcare practitioner.

Can too much vitamin D be harmful?
Vitamin D is one of the safest substances known to man and vitamin D toxicity is extremely rare. In fact, people are at far greater risk of vitamin D deficiency than they are of vitamin D toxicity. Yet it is important to understand that while adequate levels of vitamin D are helpful in the prevention of many serious health conditions, having too much vitamin D in your system can be potentially hazardous.

How do you get too much vitamin D?
Consuming foods fortified with vitamin D are unlikely to cause toxicity due to the fact that they just don’t contain that much vitamin D. It is also impossible to get an overdose of vitamin D from sun exposure. This is because the body has a built in mechanism for preventing toxicity with vitamin D produced in the skin, so there is no risk of vitamin D toxicity due to UVB exposure—whether from the sun or a tanning bed.

However, since vitamin D supplements bypass this built-in protection, high doses consumed over a period of time could eventually lead to levels that are toxic. This condition of having too much vitamin D in your blood is called “hypervitaminosis D.” However, studies conducted on D3 supplementation of adults showed no toxicity with oral supplements below 30,000 IU/day, and a 25(OH)D blood level of 200 ng/ml.
The main consequence of vitamin D toxicity is a buildup of calcium in your blood, called hypercalcemia. This can cause over-calcification of bones, soft tissues, heart and kidneys, damaging the kidney and producing kidney stones. Hypertension can also result from excessive vitamin D.  Other symptoms of vitamin D toxicity include poor appetite, nausea and vomiting. Muscle weakness, frequent urination and kidney problems also may occur.

Treatment includes the stopping of excessive vitamin D intake. Your doctor may also prescribe intravenous fluids and medications, such as corticosteroids or bisphosphonates.

Hypervitaminosis D symptoms appear only after several months of excessive dosing. In almost every case, a low calcium diet combined with corticosteroid drugs will allow for a full recovery within a month.

Signs of Toxicity
Vitamin D facilitates the balance of calcium in the body. Too much vitamin D interferes with the mechanisms for calcium reabsorption in the kidneys. Excess calcium is excreted in the urine. This is called “hypercalciuria.” This is followed by high blood calcium—hypercalcemia. Toxic levels of vitamin D may present with the following symptoms: nausea, vomiting, poor appetite, constipation (possibly alternating with diarrhea), weakness, weight loss, tingling sensations in the mouth, confusion, heart rhythm abnormalities.

The immediate symptoms of vitamin D overdose are abdominal cramps, nausea and vomiting.

Over the course of my life, I have lived in a several different climates. I have endured long, gloomy rainy seasons in Seattle and enjoyed warm trade winds in Hawaii, skied through snowy blizzards in Switzerland and sought shelter through fierce hurricanes in Florida. One thing I learned about myself is that I definitely prefer places where there is a generous amount of sunshine. Lucky for me, we are blessed here in Madison with sunshine and a beautiful, frozen, rural landscape. But  until we can get back out there in the sun next summer for safe amounts of glorious sunshine, I for one am going to protect my health by getting my sunshine in a bottle. If you want to too, please come see us at the Health and Wellness department at the Co-op. We will help you find a vitamin D supplement that is right for you.