Forty-two percent of the American population doesn't get enough vitamin D, reports the director of wellness at Mercy Medical Center, Stephanie Wheeler. This nutrient, crucial for bone health, immune function and controlling inflammation in the body, is found in foods and also synthesized by the body from exposure to sunlight. If you're deficient, taking a vitamin D supplement can help.
Fifty-thousand IU per week is well above official recommendations proposed to avoid health risks. However, it's often prescribed in this dosage to correct vitamin D deficiencies. But should you take this amount if you don't have a deficiency? Recent research shows that it might not be harmful and could actually be helpful for the general population.
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A weekly dosage of 50,000 IU of vitamin D is almost double the tolerable upper intake level. It may or may not pose health risks.
Tolerable Upper Intake Level
The tolerable upper intake level, or UL, is the maximum amount of a nutrient that is safe for the general population to get each day on a regular basis. Above this amount, the health risks increase; the greater the excess intake, the greater the health risks, according to the National Institutes of Health (NIH).
The National Academy of Medicine (NAM) has set the UL for vitamin D at 4,000 IU, or 100 mcg, per day for all adults. Taking 50,000 IU of vitamin D each week, divided among seven days, would give you 7,143 IU each day, which is nearly double the UL.
How Much You Need
The NAM developed the recommended daily allowance, or RDA, based on the needs of the general population. This is the amount it has determined will prevent deficiencies and the negative health effects caused by getting too little vitamin D in 97.5 percent of people.
The RDA for vitamin D for men and women, ages 19 to 70, is 600 IU daily. If you take 7,143 IU each day, that's nearly 12 times or 1,200 percent of the RDA.
Conflicting Vitamin D Recommendations
Not everyone agrees with the National Academy's proposed RDA and UL. Some reputable sources believe that people need well more than the RDA, and in fact more than the UL. For example, the Vitamin D Council, a California-based nonprofit, recommends adults take 5,000 IU daily or 8.3 times the RDA. People with overweight and obesity may require as much as up to 8,000 IU per day, or more than 13 times the RDA.
According to the Endocrine Society, the current official guidelines are based specifically on bone health but do not take into account vitamin D levels needed to prevent other conditions that may result from vitamin D deficiency. Specifically, NAM set the benchmark for deficiency at a blood level of 20 ng/ml of 25-hydroxyvitamin D, the main circulating form of vitamin D in the body. However, the Endocrine Society classifies blood levels below 29 ng/ml as insufficient and recommends a better target is 30 ng/ml or higher.
Director of the General Clinical Research Unit and Bone Health Care Clinic at Boston University Medical Center, Michael F. Holick, M.D., Ph.D., told Endocrine News, a publication of the Endocrine Society, that he believes blood levels between 40 and 60 ng/ml are an even better goal and that blood levels up to 100 ng/ml are perfectly safe.
Scientific Support: Increased Vitamin D
Research shows proponents of increased vitamin D intakes may be onto something. A 2017 study in Dermato-Endocrinology evaluated the effects of daily intakes up to 15,000 IU and blood levels up to 120 ng/ml on calcium regulation, kidney, liver and immune function. Using data collected from 3,882 participants between 2013 and 2015, the researchers found that even at blood levels of 120 ng/ml there was no negative effect on calcium regulation and no incidence of toxicity.
In a 2016 study in the North American Journal of Medical Sciences, participants took 50,000 to 100,000 IU of vitamin D per week without a significant change in blood calcium levels. Serum vitamin D levels also rarely exceeded 100 ng/ml, and there were no signs of toxicity.
A Simple Miscalculation?
According to a statistical analysis published in Nutrients in 2014, the NAM actually miscalculated its estimation of the RDA for vitamin D. In reviewing the 10 studies used by the NAM to determine the RDA, the researchers discovered that although the NAM calculated that 600 IU is the amount needed to reach serum 25-hydroxyvitamin D (25(OH)D) levels of 20 ng/ml, those calculations were critically underestimated.
In fact, the studies showed that 8,895 IU might be required to meet the target blood level of 20 ng/ml. The authors conclude that the NAM's miscalculation poses serious risks for bone health and disease and injury prevention in the general population.
Vitamin D Side Effects
There are health risks for taking too much vitamin D, but perhaps not at the levels previously suspected. Taking a 50,000 IU vitamin D supplement weekly is not likely to get you to that level. But it's a good idea to know what these possible dangers are and at what intake and blood level the mainstream medical community says you are at risk.
Read more: Symptoms of a Vitamin D Deficiency in Adults
Vitamin D Toxicity
Vitamin D is a fat-soluble vitamin, meaning any excess is stored in your fat cells. This differs from water-soluble vitamins, like the B vitamins, which get carried out in urine and need to be replaced each day. Excess fat-soluble vitamin intake can lead to a buildup of the nutrient in your body, which, over time, can be toxic, according to the NIH. Excess vitamin D side effects include:
- Weight loss
- Frequent urination
- Heart arrhythmia
More seriously, excess intake can increase blood levels of calcium, which can cause vascular and tissue calcification. This can damage the heart, blood vessels and kidneys.
Long-term intakes of 10,000 to 40,000 IU daily and consistent blood levels of 200 ng/ml or greater are considered to be potentially toxic. According to the NIH, intakes below 10,000 IU daily aren't likely to cause toxicity symptoms.
Other Potential Negative Effects
But toxicity may not be the only thing to worry about. Even at lower intakes, as low as 30 to 48 ng/ml, the NIH reports potential risks including increased all-cause mortality, greater risk of some cancers, such as of the pancreas, increased risk of cardiovascular events, and a higher incidence of falls and fractures among older adults.
What Should You Do?
These conflicting recommendations and data pose a dilemma for the consumer. A daily intake of 7,000 IU is highly unlikely to cause vitamin D toxicity and very unlikely to cause other problems. However, there's no way to be sure.
If you think you may be deficient in vitamin D, see your doctor for a blood test. Get her expert advice on the right blood level. If testing shows you are below this level, then follow your doctor's recommendation for how much vitamin D to take each day.
Food, Sunlight and Supplements
There's no risk of toxicity from vitamin D in foods or excess exposure to sunlight. It is only caused by taking excessive amounts of vitamin D pills over a period of time. If you don't have a deficiency requiring medical treatment, you may be able to hedge your bets by getting more D from natural sources.
Safe Sun Exposure
When you spend time outdoors, ultraviolet B radiation (UVB) penetrates the skin, which converts it to a substance called cutaneous 7-dehydrocholesterol, then to previtamin D3 and finally to vitamin D3. Many factors affect how easily your body creates the vitamin: the season, the time of day, the length of the days where you live, the amount of melanin your skin produces, smog and cloud cover and sunscreen among them. Therefore it's not a good idea to rely on getting everything you need from sun exposure.
Furthermore, organizations like the Skin Cancer Foundation and the American Academy of Dermatology caution that there is no such thing as safe sun exposure. According to Anne Marie McNeill, MD, PhD, and Erin Wesner, not using sunscreen increases your risk of squamous cell carcinoma, melanoma and premature skin aging.
It doesn't take a lot of sun exposure for your skin to make vitamin D. About 10 to 15 minutes on the legs, arms, abdomen and back is more than enough. However, McNeill says even that amount of sun exposure can cause dangerous DNA damage, and she recommends protecting your skin with SPF 15 or higher whenever you venture outdoors.
Vitamin D in Your Diet
- Swordfish: 566 IU per 3 ounces
- Sockeye salmon: 447 IU per 3 ounces
- Tuna in canned water: 154 IU per 3 ounces
- Beef liver: 42 IU per 3 ounces
- One large whole egg: 41 IU
- Sardines canned in oil: 46 IU in two sardines
Other commercially prepared foods are often fortified with vitamin D. Some examples include:
- Orange juice: 137 IU per cup
- Milk: 115 to 124 IU per cup
- Yogurt: 80 IU per 6 ounces
Regularly including these foods in your diet can often help you get all the vitamin D you need without sun exposure or a supplement.
Vitamin D Deficiency
Not getting adequate vitamin D can also have serious consequences. In its role as a hormone, vitamin D aids the regulation of more than 200 genes in the body. Some of the jobs vitamin D is responsible for include preventing the multiplication of abnormal cells in breast and colon tissue and helping to regulate blood pressure in the kidney and blood sugar in the pancreas.
Additionally, Erin Michos, M.D., M.H.S., reports that there is a strong connection between vitamin D deficiency and an increase in risk of heart attack, congestive heart failure, peripheral arterial disease (PAD), stroke, high blood pressure and diabetes.
Read more: 9 Ways to Help Avoid Vitamin D Deficiency
For certain people, getting more than the established RDA may be especially important, according to MedlinePlus. These include older adults whose kidneys aren't as good at converting vitamin D to its active form, people with darker skin colors, people with digestive disorders such as Crohn's or celiac disease, people with obesity, those with chronic kidney or liver disease and people with lymphomas. These people should be sure to have their blood levels tested regularly and to adhere to their doctor's recommendations for diet and supplementation.
- Mercy Medical Center: 42 Percent of Americans Are Vitamin D Deficient. Are You Among Them?
- National Institutes of Health: Tolerable Upper Intake Level
- Vitamin D Council: How Much Vitamin D Is Needed to Achieve Optimal Levels?
- Endocrine Society: Just Right: How Much Vitamin D Is Enough?
- Dermato-Endocrinology: Evaluation of Vitamin D3 Intakes up to 15,000 International Units/Day and Serum 25-Hydroxyvitamin D Concentrations up to 300 Nmol/L on Calcium Metabolism in a Community Setting
- Nutrients: A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D
- American Academy of Dermatology: Vitamin D
- Skin Cancer Foundation: Skin Cancer and Vitamin D
- Johns Hopkins Medicine: Vitamin D and the Heart
- MedlinePlus: Vitamin D Deficiency
- American Journal of Pharmacy Benefits: Vitamin D Deficiency Treatment Patterns in Academic Urban Medical Center
- National Institutes of Health: Vitamin D
- North American Journal of Medical Sciences: Safety of 50,000-100,000 Units of Vitamin D3/Week in Vitamin D-Deficient, Hypercholesterolemic Patients With Reversible Statin Intolerance