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Can Vitamins Be Too Much of a Good Thing?

A 2017 consumer survey found that 76 percent of Americans take dietary supplements and vitamins, up from 64 percent in 2008. But taking too many – especially if you aren’t sure you have a vitamin deficiency — can result in vitamin toxicity. And some vitamins are more dangerous than others because not all vitamins are absorbed by the body in the same way.

Vitamin deficiencies can be serious, causing diseases such as osteoporosis and anemia. A vitamin D deficiency can worsen complications from COVID-19. But doctors are seeing an uptick in patients who are developing toxicity from taking more vitamin supplements than needed.

Fat-Soluble vs. Water-Soluble Vitamins: What’s the Difference?

Vitamins are divided into two types: fat soluble and water soluble.

The fat-soluble vitamins – such as vitamins A and D – are absorbed by the gut and delivered through the blood to different areas of the body where they are needed. The excess is then stored in your liver and other fatty tissues. These vitamins can stay in your system for up to six months, accumulating and potentially reaching toxic levels.

The water-soluble vitamins — such as vitamin C — travel in your bloodstream and replace any deficiencies. Your body absorbs what it needs and eliminates any excess through urine.

Signs of Elevated Vitamin Intake:

  • Vitamin A (fat-soluble): Too much can cause hypervitaminosis A, symptoms of which may include blurry vision, bone pain, decreased appetite, liver disease, high calcium levels and osteoporosis.

  • Vitamin D (fat-soluble): High levels can lead to hypervitaminosis D, which can cause over-calcification of the bones and soft tissues such as the heart and kidneys. Other symptoms are diarrhea, kidney stones, dehydration, constipation, fatigue, muscle weakness and decreased appetite.

  • Vitamin B3, or niacin (water-soluble): In normal levels, this vitamin prevents pellagra, a disease marked by skin inflammation, diarrhea, dementia and mouth sores. But too much of this vitamin can cause liver damage, increased blood sugar and lower blood platelets.

  • Vitamin B6 (water-soluble): This vitamin can prevent anemia and peripheral neuropathy, but doses of more than 100 mg aday can cause nerve damage.

  • Vitamin C (water-soluble): Toxic levels of this vitamin can cause stomach pain, diarrhea and flatulence.

Well-Balanced Diet Provides Nutrients

Wondering if you can overdose on vitamin intake from diet alone? The good news is that eating a balanced diet rich in fruits, vegetables, whole grains and proteins will provide your body with adequate levels of every major vitamin. It’s highly unlikely your diet will result in vitamin toxicity unless you’re eating lots of fortified foods or protein shakes with added vitamins.

Over-the-counter multivitamins generally follow the FDA’s recommended daily allowances for vitamins and minerals, unlike vitamin-specific supplements, which often contain higher doses.

Bloodwork Reveals Deficiencies

To prevent vitamin toxicity, patients should visit their primary care doctor to determine if they truly have a deficiency to correct and which supplements may safely benefit them.

A blood test will measure your vitamin levels and ensure you don’t have any underlying deficiencies. Patients with a history of bariatric surgeries, irritable bowel disease (IBS), pancreatic issues and other GI tract illnesses need to pay particular attention to vitamin deficiencies.

When choosing vitamins at the store, first consult the fact sheets with the recommended daily guidelines for dietary supplements from the National Institutes of Health. Recommendations can differ based on factors such as age and gender.

If you’re healthy and eating a well-balanced diet, the body will absorb the nutrients it needs. 


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