Is it possible to take too many vitamins?

Imagine this: It’s Saturday afternoon. You watch as your friend pulls out her pill organizer to prepare for the week ahead. It has morning, midday and evening slots for each day of the week that she carefully fills with pills.

You take a closer look and you realize the pill bottles aren’t prescription medications but vitamins, dozens of them. You wonder if she needs to take all those vitamins and if it’s possible to take too many?

This scenario is more common than you think. From time to time, I encounter a patient who has a long list of vitamins they’re taking. The main question I have for them is: Do you really need to take them?

Sometimes people take vitamins out of habit, and they aren’t aware if they’re helping. They could be doing harm.

Which vitamins can you take too much of?

Any supplement you take in too large a dose can cause side effects. You should only take the doses recommended on the product label or by your health care provider.

Vitamins A, D, E and K are fat-soluble vitamins. That means they’re stored in your liver and fatty tissue. If you take too much of them, you could experience vitamin toxicity, which could affect different organs.

Vitamin K can interfere with blood-thinning medications. The amount you take should be kept stable to avoid possible consequences that could occur with quick increases.

Some water-soluble vitamins, if taken in very large doses, consistently can cause problems. The following can happen if you take three to 10 times above the recommended limit:

• Vitamin C - nausea, diarrhea, vomiting or headaches
• Vitamin B3 - stomach pain, high blood pressure, vision problems and liver damage
• Vitamin B6 - skin lesions, heartburn or neurological problems
• Vitamin B9 (folic acid) - neurological problems, may weaken the immune system and can mask a severe B12 deficiency

What’s the difference between water-soluble and fat-soluble vitamins?

Water-soluble vitamins dissolve in water. If you take too many, your body will excrete the excess in your urine. That’s why they don’t typically accumulate in your body. Examples are vitamin C and vitamin B12.

Fat-soluble vitamins are stored in fat. Taking too many fat-soluble vitamins can lead to toxicity. Examples are vitamins A, D, E and K.

Which vitamins shouldn’t be taken together?

Taking certain supplements together could reduce how well they’re absorbed into your body as well as increase your risk of side effects or harmful reactions.

When vitamins and minerals are combined in a multivitamin supplement, that’s OK. If you’re taking a combination of vitamins and minerals at the direction of your physician to address a specific health issue, you should discuss the timing of when you take the supplements to make sure they’re absorbed effectively.

For vitamins:

• Excess vitamin C may interfere with how vitamin B12 is absorbed. The vitamins should be taken at least two hours apart.
• Vitamin E may decrease the effects of vitamin K when taken together.

For vitamins and minerals, these should not be taken together:

• Calcium and magnesium
• Calcium and iron
• Zinc and copper
• Calcium and iron

Herbal supplements can sometimes interfere with medications, so talk to your health care provider before taking them. Natural doesn’t necessarily mean safe.

However, eating herbs as food in cooking, such as basil or oregano, is safe. I encourage my patients to use herbs and spices in their meals. They’re an excellent source of antioxidants, nutrients that protect cells from damage.

Which two vitamins pose the greatest risk of toxicity?

• Vitamin A - taken in excessive doses may cause liver damage, weaker bones and cause birth defects. Smokers and former smokers may be at increased risk of lung cancer if they take a lot of vitamin A.
• Vitamin D - excessively high doses can cause cognitive issues, heart problems, kidney failure and, in severe cases, possibly death.

How do we know if we need a vitamin or mineral?

It’s best to get your vitamins and minerals from a varied diet. Your body is well designed to break down food and absorb its nutrients. But in some situations, supplements are necessary.

Vitamin or mineral supplements might be helpful if you’re:

• Pregnant or breastfeeding
• Over 50 and need certain nutrients because of decreased absorption of the nutrients
• On a restricted diet such as veganism or have medical or genetic condition and an increased need for certain nutrients

Your health care provider can help you decide if you need a supplement.

Choosing a vitamin that’s been third-party tested, such as by the United states Pharmacopeia (USP), is optimal to make sure you’re getting what’s advertised on the label.