Surprising Side Effects of Eating Grapes, Say Dietitians

Did you know that grapes are one of the most popular fruits in America, right after strawberries and bananas? It's not all that surprising, though. Grapes taste as sweet as candy, make a convenient portable snack since you don't need utensils, and are just plain fun to eat. Not to mention, they're packed with a wide range of beneficial nutrients, so you can generally feel good about eating them.

According to registered dietitian Shirlene Reid, MA, LD, RD grapes—like any other fruit—are healthy, as long as they're consumed in moderation. The only thing you really need to watch out for is the high sugar content, which can add up quickly if you're devouring them in large handfuls. In fact, one 1/2-cup serving (about 16 grapes) delivers about 7.5 grams of sugar. If you'd like, it may be helpful to portion out that serving size in a plastic bag so you don't get carried away.

But have you ever wondered how eating grapes might affect your body? Experts say there are both pros and cons to eating them, so here are a few common health benefits, as well as one potential side effect. Read more, and then don't miss What Happens To Your Body When You Drink Pomegranate Juice.

Your brain will thank you.

woman picking grapes
woman picking grapes

Looking to keep your brain in tip-top condition as you age? Then consider packing some grapes in your work lunch bag.

"Grapes improve memory and focus," says Danielle McAvoy, RD with Strong Home Gym. "The antioxidant compounds in grapes help minimize oxidative stress in the brain, which can protect your brain from cognitive decline and memory loss as you age."

Grapes can also improve blood flow to the brain, thus improving your daily focus, notes registered dietitian Melissa Mitri, RD. Studies have shown that resveratrol, a specific antioxidant found mainly in the skin of grapes, helps reduce your risk of Alzheimer's by lowering inflammation in the brain and also getting rid of the amyloid-beta peptide, which has been linked to the progression of this disease when it accumulates.

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Inflammation may go down in your body.

Chronic inflammation has been linked to cancer, heart disease, asthma, type 2 diabetes, and rheumatoid arthritis, among other conditions. Fortunately, grapes are brimming with antioxidants like vitamin C, vitamin K, polyphenols, catechins, and anthocyanins—all of which can help reduce inflammation, says Jesse Feder, RD a registered dietitian and personal trainer with Strength Warehouse.

"Additionally, grapes—especially red ones—are known to be rich in resveratrol," adds Feder. And as we mentioned in the previous slide, resveratrol is known to help protect against inflammation. Specifically, resveratrol provides a protective lining for blood vessels to prevent injury, thereby warding off heart inflammation.

Your blood pressure may improve.

When high blood pressure is left unchecked, it can increase your risk for the two leading causes of death in America: heart disease and stroke. But the good news is that there are plenty of diet-related ways to help manage and prevent high blood pressure.

For one, McAvoy and Mitri suggest snacking on some grapes, which can help balance blood pressure because they're high in potassium (one cup of grapes has 176 milligrams) and low in sodium (less than two grams in one cup).

A 2016 study in Nutrients suggested that potassium helps lower blood pressure by helping to dilate veins and arteries while also flushing out excess sodium. Snacking on foods, like grapes, that are lower in sodium can be helpful as well because according to the CDC, too much sodium can raise blood pressure.

You might get a better night's sleep.

grapes
grapes

Grapes are a great evening snack because they can help you drift off and catch some quality Zs, says McAvoy. Why? Because this fruit contains a small amount of melatonin, the hormone that helps regulates your body's sleep-wake cycle.

Try eating grapes an hour or two before bedtime. And remember, be mindful of your portion size or you might accidentally overload on sugar, which can interfere with the quality of your sleep.

RELATED: Surprising Side Effects of Eating Apples, According to Science

You could get an upset stomach (if you overdo it).

If you've ever lost track of how many grapes you've eaten—which, let's face it, is all too easy to do—you may have experienced a tummy ache. According to Reid, this usually happens because of the high amounts of fructose in grapes (about 12.3 grams per cup).

"Fructose is a natural sugar found in fruits that can cause gas when consumed in high amounts," says Reid. "So, when you eat too many, you may get a stomachache due to the gas. Tannins in grapes, which are found in the skin and seeds, may also play a role in an upset stomach because these naturally occurring polyphenols can cause nausea and diarrhea if eaten in high amounts."

Mitri adds that some people who are particularly sensitive to these compounds in grapes may experience bloating, constipation, or diarrhea after eating too many.

An original version of this story was published in April 2022. It has since been updated to include more information.