Vitamin D plays a role in keeping the body’s cells healthy and functioning properly. Most of us don’t get enough vitamin D, so supplementation is essential and common. However, too much vitamin D can build up and become toxic to the body. This article will discuss 6 potential side effects of too much vitamin D.
1. Deficiency and toxicity
Vitamin D is involved in calcium absorption, immune function, and protecting bone, muscle, and heart health. It occurs naturally in foods and can also be produced by the body when the skin is exposed to sunlight. Most people don’t get enough sun exposure to produce enough vitamin D. Therefore, vitamin D deficiency is relatively common. In fact, an estimated 1 billion people worldwide are deficient in vitamin D.
Both vitamin D2 and vitamin D3 can be taken in supplement form. Vitamin D3 is produced in response to sunlight and is found in animal products, while vitamin D2 is usually found in plants. Vitamin D3 can increase blood levels significantly more than D2. Studies have shown that 100 IU of supplemental vitamin D3 you consume each day will increase your blood vitamin D levels by 1 ng/ml (2.5 mmol/l), on average. However, taking high doses of vitamin D3 over a long period of time can lead to an excessive buildup in the body, resulting in vitamin D3 excess. Vitamin D toxicity occurs when blood levels rise above 150 ng/ml (375 mmol/l). Since the vitamin is stored in body fat and released slowly into the blood, the effects of toxicity can last for several months after you stop taking the supplement. Importantly, toxicity is uncommon and almost exclusively occurs in people who take high doses of supplements long-term without monitoring their blood levels. You can also accidentally consume too much vitamin D by taking much higher amounts than the label recommends. Here are six major side effects of too much vitamin D.
Vitamin D3 can be taken in supplement form.
2. High Blood Levels
If you have adequate levels of vitamin D in your blood, it can help boost your immunity and protect you from diseases like osteoporosis and cancer. However, there is no optimal range for what is appropriate.
Although a vitamin D level of 30 ng/ml (75mmol/l) is generally considered adequate, and the recommended daily intake of vitamin D is 40-80ml (100-200mmol/l). Vitamin D levels above 100 ng/ml (250mmol/l) can be harmful.
More and more people are taking vitamin D supplements. But it is rare to find people with very high blood levels. A recent study looked at data from more than 20,000 people over a 10-year period. The study found that only 37 people had levels above 100 ng/ml (250mmol/l). Only one person experienced true toxicity, at 364 ng/ml (899 mmol/l).
In one case study, a woman had a level of 476 ng/ml (1,171 nmol/l) after supplementing with 186,900 IU of vitamin D3 daily for two months. This is a whopping 47 times the generally recommended safe upper limit of 4,000 IU per day. The woman was admitted to the hospital after experiencing fatigue, forgetfulness, nausea, vomiting, slurred speech, and other symptoms.
While only extremely large doses can cause rapid toxicity, even staunch advocates of these supplements recommend a daily upper limit of 10,000 IU.
3. Elevated Blood Calcium Levels
Vitamin D helps your body absorb calcium from the foods you eat. In fact, this is one of its most important roles. However, if too much vitamin D is present, blood calcium can reach levels that cause unpleasant and potentially dangerous symptoms. Signs of too much vitamin D in the blood, or high blood calcium levels, include:
- Digestive upset, such as vomiting, nausea, and stomach pain
- Fatigue, dizziness, and confusion
- Thirst
- Frequent urination
The normal range for blood calcium is 8.5–10.2 mg/dl (2.1–22.5 mmol/l). In one case study, an elderly man with dementia who took 50,000 IU of vitamin D daily for 6 months was repeatedly hospitalized with symptoms related to high calcium levels. In another case, two men who took improperly labeled vitamin D supplements developed blood calcium levels of 13.2–15 mg/dl (3.3–3.7 mmol/l). Furthermore, it took a year for their levels to normalize after they stopped taking the supplements.
Excess vitamin D causes fatigue, dizziness, memory loss
4. Nausea, vomiting and poor appetite
Many side effects of vitamin D overdose are associated with increased blood calcium levels. These include nausea, vomiting and poor appetite. However, these symptoms do not occur in everyone with high calcium levels.
One study followed 10 people who developed excessive calcium levels after taking high doses of vitamin D to correct a deficiency. Four of them experienced nausea and vomiting and three of them lost their appetite. Similar reactions to vitamin D have been reported in other studies. One woman experienced nausea and weight loss after taking a supplement that was found to contain 78 times more vitamin D than the labeled amount.
Importantly, these symptoms occurred when taking extremely high doses of vitamin D3, resulting in calcium levels greater than 12 mg/dl (3.0 mmol/l).
5. Stomach pain, constipation, or diarrhea
Stomach pain, constipation, and diarrhea are gastrointestinal side effects often associated with food intolerances or irritable bowel syndrome. However, they can also be signs of high calcium levels due to vitamin D toxicity.
These symptoms can occur in people who take high doses of vitamin D supplements to correct a deficiency. As with other symptoms, the response seems 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 an improperly administered vitamin D supplement, while his brother developed high blood pressure without any other symptoms.
In another case study, an 18-month-old child given 50,000 IU of vitamin D3 for 3 months developed diarrhea, stomach pain, and other symptoms. These symptoms stopped after the child stopped taking the supplement
6. Osteoporosis
Because vitamin D plays an important role in calcium absorption and bone metabolism, getting enough is important for maintaining strong bones. However, too much vitamin D can be detrimental to bone health. Although many of the symptoms of excessive vitamin D are thought to be due to high blood calcium levels, some researchers believe that high doses of vitamin D can lead to low blood levels of vitamin K2. One of the most important functions of vitamin K2 is to keep calcium in the bones and out of the blood. It is believed that very high levels of vitamin D can reduce the activity of vitamin K2. To protect against osteoporosis, avoid excessive vitamin D supplementation and supplement with vitamin K2. You can also eat foods rich in vitamin K2, such as dairy and meat from grass-fed animals.
7. Kidney Failure
Consuming too much vitamin D regularly can lead to kidney damage. In one case study, a man hospitalized for kidney failure developed elevated blood calcium levels and other symptoms after he received vitamin D injections as prescribed by his doctor. Indeed, most studies have reported moderate to severe kidney injury in people with vitamin D toxicity. In one study, 62 people who received excessive doses of vitamin D showed signs of kidney failure, whether they had healthy kidneys or existing kidney disease. Kidney failure is treated with oral or intravenous hydration and medications.
Vitamin D is extremely important for overall health. Even if you follow a healthy diet, you may still need to supplement to achieve optimal levels. Be sure to avoid overdose on vitamin D. Generally, 4,000 IU or less per day is considered safe, as long as your blood is monitored.
Also, be sure to buy supplements from reputable manufacturers to reduce the risk of overdose due to improper labeling. If you have taken vitamin D supplements and experience any of the symptoms listed in this article, consult a healthcare professional as soon as possible.
