• Helping the body absorb vital nutrients
• Providing the calcium necessary to prevent brittle bones, osteoporosis and arthritis
• Reducing inflammation
• Regulating blood pressure and improving cardiovascular strength by providing a protective lining for the blood vessels
• Reducing stress, anxiety and depression
• Improving muscle strength and skin health
• Promoting healthy blood sugar levels
Vitamin D deficiency is dangerous. One clinical trial found that an average 42 percent of Americans are D-deficient, which can lead to a variety of health problems.
But like most things, more is not always better, and too much vitamin D can be dangerous for your health. Fortunately, overdosing on vitamin D is rare, but it is possible if you’re taking supplements. While the vitamin is also known as the “sunshine” vitamin, it’s impossible to overdose from too much sun exposure or a high vitamin D diet. When levels of D reach a potentially toxic amount, your body stops allowing vitamin D production based on sunlight, and foods fortified with vitamin D don’t contain high enough amounts to become toxic.
Overdosing on D
Most people take a D supplement without any issues, simply by following the dosage recommended by their doctor, the RDA (recommended daily allowance) or the vitamin manufacturer. But taking a high dose for a long period of time can lead to toxicity.
Vitamin D is fat soluble. Unlike water soluble supplements, your body cannot eliminate what is no longer needed, and dangerous levels can accumulate quickly. After a large, longtime intake of D, your liver starts to produce a chemical called 25(OH)D. High levels of this compound cause high levels of calcium to develop in your blood, a condition known as hypercalcemia.
Specific and nonspecific symptoms of hypercalcemia include:
• Poor appetite
• Marked thirst and dehydration
• Passing urine often
• Constipation or diarrhea
• Stomach pain
• Confusion
• Muscle pain or weakness
• Abnormal heart rhythm
• Nausea and/or vomiting
• Weight loss
How Much to Take
So how much is enough? It’s hard to say. Even the experts can’t agree on a proper dosage of vitamin D. The 2010 recommended daily allowance (RDA) for people 1 through 70 years of age, as well as pregnant or breastfeeding women, is 600 IU. This recommendation tripled from 200 IU. The new recommended amount for those 71 years of age and older is 800 IU, which is up from 600 IU.
The Institute of Medicine also increased what they call the upper-level intake -- or the limit boundary at which they believe vitamin D becomes unsafe. That dose is 4,000 IU a day for adults, 3,000 IU day for children ages 4 through 8, 2,500 IU a day for kids ages 1 through 3, 1,500 IU a day for infants ages 6 through 12 months, and 1,000 IU a day for infants ages 0 through 6 months.
But many experts cite recent studies that have found healthy adults can take more than 10,000 IU of vitamin D a day. According to Dr. John Jacob Cannell, executive director of The Vitamin D Council, your skin manufactures approximately 10,000 IU of vitamin D after 30 minutes of full-body sun exposure, which in his opinion, suggests that 10,000 IU of vitamin D is not toxic.
Michael F. Holick, Ph.D., M.D., is considered the top doc when it comes to vitamin D. Dr. Holick is Professor of Medicine, Physiology and Biophysics at Boston University Medical Center, as well as Director of BU Medical Center’s Bone Health Care Clinic, and Director of its Heliotherapy, Light, and Skin Research Center. He also authored the top-selling book The Vitamin D Solution.
“My take is that the IOM at least recognized that the last recommendations were woefully inadequate and have recommended for both children and adults to increase their vitamin D intake by 200 percent.
“This is a step in the right direction, but they still need to go further. There is no downside to increasing vitamin D intake. The recent study in Japanese children demonstrating in a randomized placebo-controlled trial that taking 1,200 IU of vitamin D a day from December through March during the past year reduced their risk of developing influenza A infection by almost 50 percent is just one reason why physicians should continue to recommend that children receive at least 1,000 IU of vitamin D a day and adults receive 2,000 to 3,000 IU of vitamin D a day.”
Testing for an Overdose
If you were a firm believer in the “if a little is good, more is better” school of thought, and you believe you’ve taken far too much vitamin D, what should you do?
First, stop taking the supplements and see if you have any of the symptoms listed above. If you have no symptoms, in all likelihood, you don’t have a toxic overload of D. If you think you have symptoms, your doctor will test your blood for 25 (OH)D to determine if levels are too high.
Your doctor also may check for elevated levels of calcium in your urine and blood serum. While a vitamin D overload is uncommon, even among those who take supplements, people with health problems such as liver or kidney disease or those taking thiazide-type diuretics, are at increased risk.
New Study Finds Too Much Vitamin D as Dangerous as Too Little
A new 2015 study by the University of Copenhagen found, for the first time, a link between high levels of vitamin D and death from heart attack or stroke.
Researchers led by Dr. Peter Schwarz studied vitamin D levels of 247,574 people and analyzed their mortality rate over seven years. “We have looked at what caused the death of patients, and when numbers are 40 ng/mL (3,600 IU), it appears that there is an increased risk of dying from a stroke or a coronary,” Schwarz says. “In other words, levels of vitamin D should not be too low, but neither should they be too high.
Some experts believe more studies need to be conducted. The Vitamin D Council issued the following statement regarding the study: “This study proposes interesting findings that should not be ignored; however, they should be interpreted carefully. First of all, as with any observational study, this study does not prove causation. Also, vitamin D levels were only measured once over the span of seven years. Levels could have easily fluctuated over this long duration.”