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Surprising Side Effects of Taking Immunity Supplements, Says Science

Immunity supplements may support the immune system, but there are also some potential downsides to taking these pills.
FACT CHECKED BY Olivia Tarantino

One thing everybody can agree on is that getting sick is the pits. From having a stuffy nose to experiencing a burning fever, dealing with an illness is no fun. And with COVID-19 concerns continuing to be among us, it is only natural for people to be more focused on their immune health than ever before.

The internet is teeming with solutions that will "boost" the immune system. In fact, over 50% of the US population reported the use of supplements, many of them being immune system-focused.

While you will be hard-pressed to find a supplement that prevents a viral or bacterial infection, focusing on certain nutrients may help reduce the severity and duration of symptoms if you do get sick.

Taking immunity supplements comes with the obvious benefit of possibly supporting the immune system. But there are some potential downsides to taking these supplements, too.

If you are popping immunity supplements as part of your daily routine, here are seven side effects you may experience. Read on, and for more on how to eat healthy, consider cutting out The Worst Drinks to Sip On For Your Immunity, Say Dietitians.

You may have a shorter cold duration.

woman getting over a cold

If you are feeling under the weather, taking certain supplements may help you feel better quicker – and who doesn't want that?

For example, zinc supplementation has been linked to a reduction of the duration of a cold by over 2 days. And among travelers, people who did not take elderberry supplements had a longer cold duration compared to those who took elderberry.

Even if taking a supplement can reduce a cold duration by one day, that may be worth exploring. Because who wants to spend their time with a cold?

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You may experience nausea.

Middle aged woman suffering from abdominal pain while sitting on bed at home

Taking certain supplements may make your tummy feel a bit queasy if you are taking large amounts, depending on your choice.

For example, vitamin C, an acidic nutrient, can lead to some unsavory GI outcomes, like nausea, diarrhea, or GI distress.

Taking large amounts of minerals like zinc can have similar effects on digestion, especially when taken on an empty stomach.

READ MORESurprising Side Effects of Taking Vitamin C Supplements, Says Science

You may experience elevated blood sugars.

gummy vitamin

The American Heart Association recommends no more than 25 grams of sugar per day for women and children over the age of 2, and no more than 36 grams of sugar per day for men

Unfortunately, if you are opting for gummy versions of supplements, you may be taking in quite a bit of sugar without even realizing it – which can bump up your blood sugars if you are not careful.

Believe it or not, but adults are now taking more gummy supplements than kids are. And since one gummy vitamin can contain upwards of 3 grams of added sugar per piece, and meeting a "serving" can require people to eat up to eight gummies at a time – which would mean 24 grams of this ingredient!

Your medications may be less effective.

Steroids for physical development of human body as medical's pills.

Sure, supplements are natural. But natural ingredients can potentially interact with medications and make them less effective.

For example, elderberry extracts may interact with drugs designed to suppress the immune system, undermining their efficacy.

And zinc supplements may interfere with the absorption of certain antibiotics, possibly reducing their effectiveness if taken at the same time.

If you are taking prescription medication, it is imperative that you speak with your doctor before you start any supplements to make sure there are no potential interactions.

You may be at risk for developing kidney stones.

Man suffering from back pain and kidney stones

Certain supplements can put a person at risk for developing kidney stones, especially if the quantity is taken in large amounts.

One report highlights 17 supplements that may be linked to increased risk of kidney stones in certain situations.

Vitamin C is one such supplement that can have this effect, thanks to this nutrient's potential to elevate uric acid and oxalates.

You may experience gas and bloat.


Did you know that almost 70% of your immune system is in your gut? Having a healthy microbiota can help keep your gut healthy, and this is why many immune-supporting supplements contain live probiotics – or live bacteria that offer a health benefit to us humans.

And while taking in probiotics consistently may help support a healthy immune system, allowing your body to get used to the new bacteria that is colonizing your gut may result in gas and bloating.

Know that for many people, these symptoms subside within two weeks of starting the probiotic supplements, so hang in there!

You may have too much calcium in your blood.

Woman has a Migraine and headache after wake up in the morning.

Vitamin D is the immune-health darling of the supplement world these days. And while it is true that deficiency of this vitamin is linked to an increased susceptibility to infection, taking in too much of this vitamin can lead to having too much calcium in your blood.

This is because vitamin D helps the body absorb calcium. But too much of this vitamin can kick your body into overdrive and cause hypercalcemia, or high levels of calcium in the blood. High blood levels of calcium can result in you feeling confused, among other symptoms.

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Lauren Manaker MS, RDN, LD, CLEC
Lauren Manaker is an award-winning registered dietitian, book author, and recipe developer who has been in practice for almost 20 years. Read more about Lauren