15% off with code 15OFF

Free & Fast UK delivery
Free & Fast UK delivery
Recommended by over 100 expert nutritionists
Home Learn Potential Multivitamin Side Effects of Top Supplements


Potential Multivitamin Side Effects of Top Supplements

Table of contents

Do multivitamins have side effects? The answer is a little more complicated than a strict yes or no.

Since humans are all different, what can cause a side effect in one person may not cause a side effect in another.

Also, there are significant differences in supplement amounts and other ingredients when comparing one multivitamin to another.

We analysed 30 best-selling multivitamins on amazon.co.uk to get a more detailed look at what was inside of them. We excluded any products that weren’t actually multivitamins and were duplicates of each other.

What we found was that every one of the multivitamins we examined could have side effects. Every single one contained unnecessary ingredients that are known to cause side effects to at least a small part of the population.

Many contain excessive amounts of vitamins, sometimes over 10,000% of the daily recommended dose. These excessive amounts of vitamins can potentially have side effects.

Yet, these side effects are not inherent to the concept of multivitamins. A multivitamin designed right that doesn’t use cheap manufacturing processes can basically be free of side effects.

Do the Essential Vitamins in Multivitamins have Side Effects?

Many supplements with differing amounts and types of nutrients call themselves multivitamins. We will consider a multivitamin as any supplement that contains more than one essential nutrient.

What we found through our research is that for basically all essential nutrients, there isn’t any known issue with consuming a small amount.

Nutrients like zinc, vitamin C, and iron are essential for your body to survive. If you don’t consume enough of them, you’ll experience medical issues.

For example, if you don’t consume enough vitamin C you’ll develop scurvy, a disease that causes weakness, soreness, and bleeding gums.

Famously, sailors in the 1600s and 1700s had problems with scurvy due to severe vitamin C deficiency. Approximately 2 million sailors died from scurvy between the years 1500 and 1800.

As long as you keep your consumption within a reasonable threshold (i.e. not consuming much more than the daily recommended dosage for several days in a row), there’s no issue with consuming essential nutrients.

Frequency of Excessive Amounts of Nutrients in Multivitamins

When we looked at the thirty best selling multivitamins on amazon.co.uk, we found that it was frequent for multivitamins to contain more than the daily recommended amount.

Here are the most frequent nutrients that we saw were in excess:

most common nutrients above daily recommended dose in 30 best selling uk multivitamins

This is potentially a serious problem. While we know about the essential nutrients that the human body needs. It’s not always clear where the upper limit is. It’s also not always clear as to how an excessive amount of vitamins can affect the human body over the long-term.

A study done by researchers in Britain, Spain, and America found that consuming excessive amounts of vitamin E (which we saw as being above the recommended amount in 12 of 30 supplements) could potentially increase the likeliness of death by 10%.

Taking excessive amounts of vitamin B6 (which we saw as being above the recommended amount in 7 of 30 supplements) over a year or more can lead to nerve damage.

Even for nutrients where there is no known upper limit (like riboflavin), it’s recommended that you don’t consume too much.

By consuming excessive amounts of nutrients, you are only increasing the likelihood of dealing with potential side effects. It’s an unnecessary risk that you can avoid as long you don’t consume improperly balanced multivitamins.

But, when we looked at how many of these 30 supplements contained an excessive amount of a certain supplement, we saw that 21 of them have above the recommended daily amount for at least one nutrient.

number of nutrients above daily recommended amount in 30 best selling uk multivitamins

As you can see, it’s likely that a generic multivitamin contains excess amounts of a certain nutrient. Two of the multivitamins we looked at had excessive amounts of eleven different nutrients.

To be clear, this isn’t always a bad thing. If you consume 200% of the daily recommended dosage of a certain vitamin (like vitamin A), nothing bad will happen to you. Our bodies are quite adaptable.

In fact, it’s likely that you can consume well beyond the recommended dosage of a nutrient.

The specific limits depend on the particular vitamin. For vitamin C, the recommended daily dose is 90 mg. The tolerable upper limit (TUL) of vitamin C is 2,000 mg.

It’s easy to find supplements that contain well over the accepted limit. Just a quick search found this easily available product:

dietary suppliment viamin c powder 5000mg

Also, consider this nutrition label from one of the multivitamins we studied:

multivitamin supplement facts label

It contains excess amounts of several nutrients including 4,167% of the recommended daily dose of thiamin! There is medically no reason you need to consume this much thiamin in one day. In fact, research has shown a link between excessive thiamin and tumor growth.

We’re not saying that consuming one of  . Again, your body is adaptable and will simply remove the excess nutrient.

What can happen is that if you continually consume an excessive amount of a certain nutrient,  .

For example, continually consuming extreme amounts of vitamin C may cause diarrhea or nausea.

Consuming too much iron can result in a condition known as iron overload. This happens when iron gradually builds up in the body because the body’s regulatory system fails to keep iron within healthy limits.

Over time, iron overload can result in medical issues like cancer, arthritis, or liver problems.

Continuous megadoses of vitamin D and/or calcium can cause calcium to build up in your blood (hypercalcemia), resulting in nausea, vomiting, and kidney problems.

Excess folic acid can cause several harmful effects including nausea, loss of appetite, and sleep disturbance.

Side Effects from Over-consuming Vitamins

There are many vitamins and minerals you’ll find in various multivitamins. Instead of listing dozens of essential nutrients and all the side effects that result from overconsumption, we’ve decided to list a select few with some of their side effects:

potential side effects of excess consumption of vitamins

All of the nutrients above are essential. You need them to survive. It’s just that over-consuming them over time can result in the side effects listed above.

What this means is that you need to be careful when selecting a multivitamin. If it contains an excessive amount of a certain nutrient (even if it’s an essential nutrient), you may experience side effects.

Side Effects From Unnecessary Ingredients in Multivitamins

Another way that certain multivitamins can cause side effects is by the unnecessary and excessive ingredients inside them.

Why do multivitamins contain these unnecessary ingredients? Here are some of the reasons:

  • To prevent tablets from sticking to each other or machines in the manufacturing process
  • To bind all of the active nutrients together
  • To sweeten the taste
  • As a coating
  • For color
  • As a preservative

While essential nutrients do not have side effects, common additives do have side effects.

Microcrystalline Cellulose, a common binder, is known to cause gas, bloating, and depression.

Potassium Sorbate, a common preservative, is known to cause diarrhea and nausea.

Xylitol, a common sweetener, is also known to cause diarrhea.

We decided to look at all of the unnecessary ingredients in the same eight best selling multivitamins on Amazon, and here’s what the potential side effects would be:

potential side effects from unnecessary ingredients in 30 best selling uk multivitamins

Again, these are potential side effects. While it’s likely that you won’t experience any of these from consuming a multivitamin, you are increasing your chances of experiencing these symptoms by consuming unnecessary additives.

The crazy thing is that none of the supplements we looked at had any specific warnings about these specific symptoms. They contained a generic warning about side effects, but nothing more.

None of the side effects or information we’ve presented here is a secret or is disputed. It’s all well-known science.

Still, if you decide to consume a common multivitamin, you have to check the additives (which often contain dozens of ingredients that a layperson wouldn’t know about) to see what the potential side effects are.

How Feel Minimises the Chance of Side Effects

We wanted to create a multivitamin without side effects, so we created Feel. It’s a multivitamin that only contains what you need without any of the unnecessary ingredients.

The only ingredients in Feel are the vitamins themselves and an all-natural rice-based agent to keep everything together.

In the spirit of transparency, we suggest that if you are one of the very few people who contain a rice allergy that you don’t consume Feel.

We think Feel is a superior multivitamin. Not only will you not consume unnecessary additives, but you won’t consume excessive amounts of any one particular vitamin.

There’s a lot we don’t know when it comes to the long-term risks of consuming excess vitamins. The research is still ongoing. We think it’s best that you don’t take an unnecessary risk with your health by consuming excessive amounts of vitamins.

We carefully proportioned out all of the ingredients when making Feel to prevent the side effects that can come from excess vitamin consumption.

If you have any questions feel free to reach out to us and our team of experts. Otherwise, we encourage you to give Feel a try.

Subscribe to our newsletter for similar articles
& knowledge on supplements
About the author
Katie Hipwell - Katie is an AfN Registered Nutritionist (RNutr) with a specialism in food and is Head of Nutrition at Feel. Katie has worked in the food supplement industry for 10 years. She has completed a Master's degree in Human Nutrition and an undergraduate degree in BSc Sport and Exercise Nutrition.
Previous post Next post
November 07, 2022

Should You Supplement with Vitamin D This Winter?

November 01, 2022

Is a Vegan Diet Healthy?

October 18, 2022

World Menopause Day 2022