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Vitamin D is extremely important for good health. It plays several roles in keeping the body's cells healthy and functioning properly. Most people don't get enough vitamin D, so supplements are common. However, it is also possible - although rare - for this vitamin to build up and reach toxic levels in the body. This article discusses a number of potential side effects of excessive amounts of this important vitamin.
Vitamin D is involved in calcium absorption, immune function and protects bone, muscle and heart health. It occurs naturally in food and can also be produced by your body when your skin is exposed to sunlight. But apart from fatty fish, there are few foods rich in vitamin D. Also, most of us don't get enough sun exposure to produce enough vitamin D. Thus, deficiency is very common. In fact, it is estimated that around one billion people worldwide do not get enough of this vitamin. Dietary supplements are very common and both vitamin D2 and vitamin D3 can be taken in dietary supplements. Vitamin D3 is produced in response to sun exposure in the skin and is also found in animal products, while vitamin D2 occurs in plants.
Vitamin D3 has been shown to increase blood levels significantly more than D2. Studies have shown that every additional 100 IU of vitamin D3 you consume per day will increase vitamin D levels in your blood by 1 ng/ml (2.5 nmol/l) on average. However, taking extremely high doses of vitamin D3 for long periods of time can lead to excessive accumulation in the body. Vitamin D intoxication occurs when blood levels rise above 150 ng/ml (375 nmol/l). Because the vitamin is stored in body fat and released slowly into the bloodstream, the effects of toxicity can last for months after you stop taking your supplement. Important to know is that toxicity is not common and occurs almost exclusively in people who supplement with the vitamin for a long time without monitoring their blood levels. It's also possible to accidentally consume too much vitamin D by taking supplements that contain much higher amounts than what is listed on the label. However, you cannot reach dangerously high blood levels through diet and sun exposure alone.
If you want to be on the safe side, you can easily test your levels in the blood at BLODKOLLEN .
Achieving adequate levels of vitamin D in your blood can help boost your immunity and protect you against diseases such as osteoporosis and cancer. However, there is no consensus on an optimal range for adequate levels. Although a vitamin D level of 30 ng/ml (75 nmol/l) is usually considered adequate, it is recommended that vitamin D levels should be 40–80 ng/ml (100–200 nmol/l) and says that anything above 100 ng/ml (250 nmol/l) can be harmful.
While an increasing number of people are supplementing with vitamin D, it is rare to find someone with very high blood levels of this vitamin. A new study looked at data from more than 20,000 people over a ten-year period. It found that only 37 people had levels above 100 ng/ml (250 nmol/l). Only one person had true toxicity, at 364 ng/ml (899 nmol/l).
In one case study, a woman had a level of 476 ng/ml (1171 nmol/l) after taking a supplement that gave her 186,900 IU of vitamin D3 per day for two months. The woman was admitted to the hospital after experiencing fatigue, forgetfulness, nausea, vomiting, slurred speech and other symptoms.
Vitamin D helps your body absorb calcium from the food you eat. In fact, this is one of its most important roles. However, if vitamin D intake is too high, the calcium in the blood can reach levels that can cause unpleasant and potentially dangerous symptoms. Symptoms of hypercalcemia, or high blood calcium levels, include:
• vomiting, nausea and stomach ache
• tiredness, dizziness and confusion
• excessive thirst
• frequent need to urinate
The normal range for blood calcium is 8.5–10.2 mg/dl (2.1–2.5 mmol/l). In one study, two men took mislabeled vitamin D supplements, which led to blood calcium levels of 13.2–15 mg/dl (3.3–3.7 mmol/l). Also, it took a year for their levels to return to normal after they stopped taking the supplements.
Many side effects of too much vitamin D are related to excessive calcium in the blood. These also include nausea, vomiting and poor appetite. However, these symptoms do not occur in everyone with elevated calcium levels. One study followed 10 people who had developed excessive calcium levels after they had taken a high-dose vitamin D supplement to correct a deficiency. Four of them experienced nausea and vomiting, and three of them suffered from loss of appetite.
Similar responses to megadoses of vitamin D have been reported in other studies. A woman experienced nausea and weight loss after taking a supplement that was found to contain 78 times more vitamin D than stated on the label. Importantly, these symptoms occurred in response to extremely high doses of vitamin D3, leading to calcium levels greater than 12 mg/dl (3.0 mmol/l).
Stomach pain, constipation and diarrhea are common digestive problems that are often related to food intolerances or irritable bowel syndrome. However, they can also be a sign of elevated calcium levels caused by vitamin D toxicity. These symptoms may occur in those receiving high doses of vitamin D to correct deficiency. As with other symptoms, the response appears to be individualized even when blood levels of vitamin D are similarly elevated. In one case study, a boy developed stomach pain and constipation after taking mislabeled vitamin D supplements, while his brother experienced elevated blood levels without any other symptoms.
In another case study, an 18-month-old child who received 50,000 IU of vitamin D3 for 3 months experienced diarrhea, abdominal pain, and other symptoms. These symptoms resolved after the child stopped taking supplements.
Because vitamin D plays an important role in calcium absorption and bone metabolism, it is important to get enough of the vitamin to maintain strong bones. However, too much vitamin D can be harmful to bone health. Although many symptoms of excessive vitamin D are attributed to high calcium levels in the blood, some researchers suggest that megadoses can lead to low levels of vitamin K2 in the blood.
One of vitamin K2's most important functions is to maintain calcium in the bones and keep it out of the blood. It is thought that very high vitamin D levels can reduce vitamin K2 activity.
To protect against bone loss, avoid taking too many vitamin D supplements and take a vitamin K2 supplement. You can also eat foods rich in vitamin K2, such as dairy and meat products.
Excessive vitamin D intake often leads to kidney damage. In one case study, a man was hospitalized for kidney failure, elevated blood calcium levels, and other symptoms that occurred after he received vitamin D injections prescribed by his doctor.
In fact, most studies have reported moderate to severe kidney damage in people who develop vitamin D toxicity. In a study of 62 people who received excessively high doses of vitamin D injections, every person experienced kidney failure — regardless of whether they had healthy kidneys or existing kidney disease.
Kidney failure is treated with oral or intravenous hydration and medication.
Vitamin D is extremely important for your overall health. Even if you follow a healthy diet, you may need supplements to achieve optimal blood levels. However, it is also possible to have too much of a good thing. Be sure to avoid excessive doses of vitamin D. Generally, 4,000 IU (100 micrograms) or less per day is considered safe as long as your blood levels are monitored. You can check your blood values yourself at BLODKOLLEN .
The Swedish Food Agency recommends (RDI) 20 micrograms of vitamin D per day during the winter for adults, and 5 micrograms of vitamin D during the summer for adults.
