Sufficient blood levels of vitamin D may help defend against many symptoms and chronic conditions, including heart disease, cancer, diabetes, bone fractures and depression, just to name a new of the positive vitamin D side effects. It’s no surprise then that so many people now supplement with vitamin D, especially considering that vitamin D deficiency is so common, affecting between 50 percent to 90 percent of adults worldwide.
But can too much vitamin D hurt you? How much vitamin D is too much? While you’re much more likely to be negatively impacted by vitamin D deficiency than a vitamin D overdose, it’s still possible to develop negative vitamin D side effects if you supplement with high doses consistently. Some examples of potential vitamin D side effects include developing high blood calcium levels, exhaustion, abdominal pain and other digestive issues.
Positive Vitamin D Side Effects
Vitamin D is a fat-soluble vitamin. We get the vast majority of it from our skin absorbing sunlight, and it has many roles when it comes to protecting health. Vitamin D benefits, aka positive vitamin D side effects, include:
- Helping with absorption of minerals like calcium
- Aiding in bone health and preventing weak, brittle bones
- Boosting immune function and preventing infectious diseases
- Supporting growth and development in infants/children
- Helping with hormonal balance, including sex hormones like testosterone
- Stabilizing moods and helping with depression
- Supporting cognitive health and helping reduce the risk for memory loss
What is the difference between vitamin D and vitamin D3? There are two forms of vitamin D supplements: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). The type of vitamin D our bodies naturally make from sunlight exposure is called cholecalciferol/D3. Vitamin D3 supplements are derived from animal products that contain cholesterol and are believed to be better utilized by our bodies compared to vitamin D2.
Negative Vitamin D Side Effects
Vitamin D causes your liver to produce a chemical called 25(OH)D. When 25(OH)D levels become elevated, calcium can accumulate in your bloodstream. In order to prevent this from happening, most health authorities recommend taking no more than 4,000 international units daily for an extended period of time, even though some research has indicated that 10,000 IU per day of vitamin D typically causes no adverse reactions.
If you’re getting too much vitamin D from supplements, since sunlight is very unlikely to cause a problem, negative vitamin D side effects might develop that include:
- High blood calcium levels and possibly kidney stones
- Abdominal pain and digestive issues like nausea, constipation, diarrhea or loss of appetite
- Increased thirst, dry mouth and possibly kidney stones
Side Effects of Too Much Vitamin D
Vitamin D is a fat-soluble vitamin. This means it’s stored in body fat and can remain in your body for a long time.
If you choose to take vitamin D supplements, be sure to stick to a dosage that is within the recommended range. Do not take more unless you’re monitored by a health care provider and instructed to take more, perhaps because a blood test has revealed you’re deficient. “Vitamin D toxicity” (when you’ve taken too much vitamin D) can potentially develop if someone takes more than 300,000 IU in a 24-hour period or more than 10,000 IU of vitamin D per day for months.
In order to prevent side effects of vitamin D you should avoid taking very high doses of vitamin D in supplement form, such as 10,000 IU per day for more than several weeks in a row. While supplements are necessary and beneficial in many cases, it’s ideal to get the vitamin D you need directly from sunlight, particularly from exposing your bare skin to the sun for 10–20 minutes most days of the week.
You can also safely increase your vitamin D level by eating vitamin D-rich foods, such as fish, eggs and raw milk.
Side Effects of Low Vitamin D
Low vitamin D is also called vitamin D deficiency. Believe it or not, an estimated 1 billion people worldwide are affected by vitamin D deficiency, and many more are suspected to be at least marginally low in this essential vitamin. Side effects of low vitamin D can include:
- Osteoporosis or bone fractures
- Higher risk for cardiovascular disease
- High blood pressure
- Higher risk for certain types of cancer
- Autoimmune diseases
- Higher risk for diabetes
- Chronic pain
- Susceptibility to infectious diseases
Why is vitamin D deficiency so common? The main reason is many people today don’t spend enough time in the sun, due to factors like working indoors or wearing sunblock, and also don’t eat enough foods that supply vitamin D (like fish). You’re at an increased risk for having low vitamin D levels if:
- You have dark skin
- You’re an older adult over 70 (since the production of vitamin D from the skin decreases with age). Infants, children, and older adults are all at risk for low vitamin D
- You spend little time outdoors or always wear sunscreen when exposed to sunlight
- You’re a shift worker, health care worker or another “indoor worker,” which means you get little outdoor time and sunlight exposure
- You’re overweight or obese (since vitamin D can accumulate in body fat)
- You are a nursing home resident or hospitalized patient
- You have a health condition such as celiac disease, Crohn’s disease or cystic fibrosis that interferes with absorption and processing of vitamin D in the intestines, kidneys or liver
- Breast-fed infants are also at risk for vitamin D deficiency, which is why supplementing is recommended
How to Prevent and Treat Adverse Vitamin D Side Effects
How much vitamin D should I take daily?
According to the USDA and National Institutes of Health, the standard vitamin D dosage recommendation in order to prevent deficiency is:
- Between 600 to 800 IU per day for adults, depending on age.
- Adults over 70 should supplement with more, at least 800 IU per day, while younger adults need at least 600 IU daily.
- Children younger than 5 should get up to 35 units per pound/day.
- Children ages 5–10 should get about 400 IU daily.
- Pregnant women/breastfeeding women need between 600–800 IU per day, but up to 5,000 units/day can be taken safely.
Some research suggests that a higher dose than the current RDA for vitamin D, around 2,ooo to 5,000 IU per day, may be more beneficial for certain people, especially since deficiency in vitamin D is so common. Vitamin D 5,0000 IU benefits can include improved immune function, improved moods and better sleep.
How can you achieve high vitamin D levels without supplements?
Including vitamin D-rich foods in your diet and enough sunlight exposure are two natural ways to boost your levels. Sunshine and vitamin D-foods do not cause vitamin D toxicity because your body regulates how much vitamin D is made/absorbed by these natural sources.
The top sources of vitamin D include:
- Sunlight on your skin (aim for at least 10 minutes per day if possible)
- Cod liver oil (take about one tablespoon daily)
- Wild-caught salmon
- Tuna fish
- Fortified milk
- Beef liver
- Pastured eggs
- Fortified cereal
In order to avoid vitamin D supplement side effects it’s important to follow dosage recommendations. When it doubt, ask your doctor about the right dose of vitamin D for you to take.
Some people are more likely to experience side effects of too much vitamin D — therefore taking supplements is not always recommended, especially in high doses. Vitamin D supplements should not be taken by anyone who takes these prescription drugs, unless a health care provider recommends otherwise:
- Epilepsy drugs, such as phenobarbital and phenytoin
- The weight loss medication Orlistat
- Corticosteroids, such as prednisone
- Diabetes medicines
- Blood pressure drugs
- Seizure medicines, such as phenobarbital and Dilantin (phenytoin)
- Calcium supplements and antacids
If you have any of the health conditions listed below, you should not supplement with vitamin D without being monitored by your doctor:
- Inflammatory bowel disease
- Cystic fibrosis
- Kidney disease
- Liver disease
- Primary hyperthyroidism
- Granulomatous tuberculosis
- Metastatic bone disease
- Williams syndrome
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