While beneficial in regular doses, taking too much of a vitamin or supplement can be toxic.
Around three-quarters of Americans take dietary supplements and vitamins every day to boost their overall health or correct an imbalance. But there can be too much of a good thing.
While vitamins are touted as good for you, the body isn’t designed to handle excessive vitamin intake.
Humans have evolved to require only small amounts, naturally found in a wide variety of foods, to support cell and organ function, and the body isn’t able to quickly eliminate excess vitamins, allowing some to build to dangerous levels.
Supplement overdoses can lead to serious complications, including liver and kidney damage, hardening of soft tissues, bleeding, and nerve damage.
However, because it can take weeks or even months for signs of toxicity from some vitamins to cause symptoms, you may be causing damage without even realizing it.
The risk of overdose depends on the base recommendation. For instance, the recommended amount of vitamin A for adult men is 900 micrograms.
However, taking too much – about three to four times the recommendation – can lead to minor symptoms like a headache or severe complications like brain damage.
Iron is essential for producing hemoglobin, which carries oxygen in red blood cells, but taking over 20mg can be toxic
Iron
Recommended daily dose for adults: 8 milligrams (mg) for men; 18 mg for women
Iron plays a key role in the production of hemoglobin, the protein in red blood cells that carries oxygen throughout the body, but too much, around 20mg or higher, can be toxic.
Symptoms of iron toxicity may start out minor and be blamed on something common like the stomach flu and include nausea, vomiting, abdominal pain.
However, severe iron poisoning can lead to severe complications like liver damage and heart failure.
The harm becomes even more severe when a person takes too much over a long period of time. Gradually, iron accumulates in the organs, causing potentially fatal damage to the brain and liver.
Iron supplement overdose over an extended period of time mimics a natural iron balance disorder called iron overload. This is caused by the body’s regulatory system failing to keep iron levels within healthy limits.
Over time, an excess of iron can increase one’s risk of arthritis, colon cancer, liver problems, diabetes, and heart failure.
Calcium
Recommended daily dose for adults 51 and up: 1,000 to 1,200 mg
Adequate calcium is crucial to shoring up the bones and keeping skeletal muscles working properly. Calcium supplements are often recommended to seniors who are at increased risk of deficiency and osteoporosis.
Brittle bones make severe breaks and fractures more likely, especially in the hips, spine, risk, and forearm. They’re likely to be painful and require surgery to repair.
However, it’s important to strike the right balance. Taking more than 1,200 mg can lead to hypercalcemia, in which too much calcium is circulating in the blood.
It can cause a wide range of symptoms from seemingly innocuous nausea and constipation, to more concerning effects like dehydration, confusion and disorientation, muscle and bone pain, high blood pressure, kidney damage, and even coma.
Severe cases of vitamin D overdose can lead to kidney failure and abnormal heart rhythm, as well as an unsteady gait, confusion, fatigue, constipation, nausea, bone pain, and muscle weakness
Vitamin D
Recommended daily dose for adults: 600 International Units (IU)
Vitamin D is often thoughts of as the sunshine vitamin as people can get it from about 15 minutes of being in the sunlight.
For those who prefer the shade, however, doctors recommend 600 international units (IU). Taking extremely high doses – around 4,000 IU – over a long period of time can cause vitamin D toxicity.
Severe cases can lead to kidney failure and abnormal heart rhythm, as well as an unsteady gait, confusion, fatigue, constipation, nausea, bone pain, and muscle weakness.
Cases of vitamin D toxicity are rare, with roughly 4,500 cases in the US every year.
While sunlight is an excellent source of vitamin D, spending too much time outdoors will not cause vitamin D toxicity.
Vitamin D toxicity doesn’t occur suddenly and you may be experiencing it without even realizing.
Instead, it occurs when a person takes large doses of supplements over months or years.
Vitamin A
Recommended daily dose for adults: 900 microgram retinol activity equivalents (mg RAE) for men, 700 mcg RAE for women
Vitamin A is crucial for vision, immunity and growth.
But exceeding 3,000 mcg RAE of vitamin A can, over time, cause significant organ damage.
Vitamin A toxicity leads to hypervitaminosis A. Taking a lot over a short amount of time has been known to cause nausea, dizziness, blurred vision, loss of appetite, and headache.
Chronic over-use causes the liver to malfunction and become enlarged until it fails. High vitamin A levels may also cause weakened bones, increasing the risk of fractures.
Pregnant women who take too much vitamin A also risk birth defects in their babies, such as a cleft palate or cleft lip, congenital heart defects, brain malformations, and thyroid problems.
Pregnant women are generally advised not to exceed 770 mcg RAE per day, which can come from cod liver oil, egg yolks, whole milk, cheese, and beef liver.
Too much magnesium can cause diarrhea, low blood pressure, breathing difficulty, irregular heart rhythm, kidney damage, and coma.
Magnesium
Recommended daily dose for adults: between 310 to 410 mg
Magnesium is essential for maintaining bone density, muscle function, and heart health.
The powerful mineral can also improve sleep quality and heart health by regulating the heart’s rhythm. It has also been shown to help reduce stress levels.
Too much magnesium, though, can cause diarrhea, low blood pressure, breathing difficulty, irregular heart rhythm, kidney damage, and coma.
In severe cases or if the kidneys aren’t working well, dialysis might be needed to remove the excess magnesium from the body.
Hypermagnesemia is rare because the kidneys remove excess magnesium. But complications can occur in people with kidney problems who take magnesium-containing medications like laxatives or antacids.
People with kidney disease, heart disease, or digestive issues are at higher risk and should avoid magnesium supplements.
Folic acid
Recommended daily dose for adults: 400 mcg
Recommended daily dose for pregnant women: at least 600 mcg
Folic acid helps prevent birth defects in a baby’s brain and spine
Folic acid is commonly taken by pregnant women or women trying to conceive as it helps prevent birth defects in a baby’s brain and spine.
The mineral plays a crucial role in producing red blood cells in utero and supports the development of the baby’s neural tube into their brain and spinal cord.
Folic acid also works alongside other vitamins such as B12 to control high levels of an amino acid called homocysteine, which has been associated with an increased risk of heart disease, stroke, and other health problems.
In high amounts, however, folic acid can obscure a deficiency of B12, which can lead to severe nerve damage.
When taken in large quantities, folic acid can correct low red blood cell counts, but it does not address potential nerve damage that has gone undiagnosed.
Too much folic acid can also irritate the digestive system, causing bloating, gas, and nausea.