What You Need to Know About Vitamin Overdose

What You Need to Know About Vitamin Overdose

Every day, many people take vitamins around the world.

Every supplement bottle has guidelines for safe dosing, but people usually take more than the recommended dosage in many cases.

Supplement users are bombarded with information encouraging them to take high doses of vitamins. But the fact is that excess of some nutrients can be dangerous.

Let’s talk about the safety of taking vitamins, the side effects of high doses, and the potential risks involved in vitamin overdose.


What is the difference between fat-soluble and water-soluble vitamins?

Water-soluble vitamins

Water-soluble vitamins are soluble in water. They are readily excreted from the body and are usually not stored in tissues. Therefore, the number of water-soluble vitamins is more than fat-soluble vitamins (2).

Water-soluble vitamins comprise eight B vitamins, plus a vitamin C. The B vitamins include:

  • Thiamine (B1)
  • Riboflavin (B2)
  • Niacin (B3)
  • Pantothenic acid (B5)
  • Pyridoxine (B6)
  • Biotin (B7)
  • Folate (B9)
  • Cobalamin (B12)

Since water-soluble vitamins are not stored in the body but excreted in the form of urine, they may not cause any issues even when taken in high doses.

However, taking extremely high doses of water-soluble vitamins can trigger side effects.

For instance, mega doses of vitamin B6 can cause nerve damage, while overdosing on niacin can cause liver damage (3, 4).


Fat-soluble vitamins

Fat-soluble vitamins do not dissolve in water compared to water-soluble vitamins. And they are easily stored in your tissues (2).

There are four primary fat-soluble vitamins:

  • Vitamin A
  • Vitamin D
  • Vitamin E
  • Vitamin K

Because fat-soluble vitamins can accumulate in the body, these nutrients are more likely to cause some form of toxicity than water-soluble vitamins.

Overdosing vitamin A, D, or E can cause harmful side effects. However, these side effects are rare (5).

On the other hand, one may not experience any side effects from taking high doses of non-synthetic vitamin K. This explains why relevant health authorities have not set an upper intake level (UL) for this nutrient (6).


Potential side effects of water-soluble vitamin overdose

  • Vitamin C. It has relatively low toxicity. However, mega doses of vitamin C can cause disturbances in the gastrointestinal tract, including vomiting, nausea, cramps, and diarrhea. Taking up to 6 grams daily can cause migraines (7, 8).
  • Vitamin B3. Niacin taken in the form of nicotinic acid can cause abdominal pain, high blood pressure, liver damage, and impaired vision, especially when consumed in high doses of one to three grams daily (9).
  • Vitamin B6. Consuming B6 in excess can cause skin lesions, neurological symptoms, nausea, extreme sensitivity to light, and heartburn. Some of these symptoms may occur at intakes of 1 – 6 grams per day (10).
  • Folate (B9). Taking folic acid or folate in excess can affect mental function. It also negatively impacts the immune system and may mask a severe vitamin B12 deficiency (11).

Here’s an important thing to note: these side effects may be experienced by healthy people when they take large doses of these vitamins. However, the side effects may be more severe in individuals with underlying health conditions.

For instance, vitamin C may not cause any side effects in healthy people, but it can trigger fatal heart abnormalities and tissue damage in people suffering from hemochromatosis (12).


Potential side effects of fat-soluble vitamin overdose

  • Vitamin A. Vitamin A toxicity is also known as hypervitaminosis A. One can have it from overeating vitamin A-rich foods, but most cases of hypervitaminosis A are associated with supplement overdose. Symptoms of vitamin A toxicity include nausea, increased intracranial pressure, coma, and in some cases, death (13).
  • Vitamin D. High doses of vitamin D supplements can cause symptoms such as appetite loss, weight loss, and irregular heartbeat. It can also shoot the blood levels of calcium, leading to organ damage (14).
  • Vitamin E. High doses of vitamin E supplements can affect the blood clotting process, leading to hemorrhages and hemorrhagic stroke (15).

While vitamin K may have a low potential for toxicity, it is essential to note that it can interact with antibiotics and warfarin (6).


What is the safest way to take vitamins?

The best way to have your nutrients is by consuming a balanced diet. However, many people may need to supplement with vitamins for various reasons.

Medical conditions, genetic disorders, age, and diet are important factors that can increase the need for some nutrients.

However, the good news is that vitamins are safe to take as long as you use them responsibly.

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