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Surprising Side Effects of Drinking Grapefruit Juice, Say Dietitians

RET’s Laura McDermott, MS, RDN, CD, spoke with Eat This, Not That about the surprising effects of drinking grapefruit juice, read on below!


There’s something so unbelievably refreshing about freshly squeezed grapefruit juice, especially if you’re enjoying a fun brunch with friends on a hot summer day. Grapefruit juice also makes an amazing mixer for a refreshing cocktail or mocktail at happy hour.

But what are the health benefits of this delicious drink? And are there any potential side effects to drinking it? To learn more, we talked with some expert dietitians about what happens when you drink grapefruit juice. Read on, and for more healthy drinking tips, check out Surprising Effects of Drinking Cranberry Juice.

It will provide plenty of important nutrients.

One of the best outcomes of drinking grapefruit juice is that you can get a boost of helpful nutrients.

“Grapefruit juice contains flavones and flavonoids, which are part of a group called phytonutrients. Phytonutrients are important to our health because they have antioxidant properties, which means that they protect your cells from oxidative damage which can lead to disease,” says Laura McDermott, MS, RDN, CD, a registered dietitian with RET Physical Therapy Group.

McDermott cautions to not go overboard with this jewel-toned juice. “As with anything though, we are looking to keep grapefruit juice in moderation and we want a variety of foods to provide phytonutrients to ensure diversity in them as well as diversity in vitamins and minerals,” she adds.

It may interact with certain medications.

According to McDermott, those on certain medications may want to limit their consumption of grapefruit juice.

“The dark side of grapefruit juice is the potential drug interactions. Grapefruit juice has been known to have drug interactions with more than 85 drugs,” she says.

Experts believe that “grapefruit juice can block an enzyme called CYP3A4 that is in charge of the metabolism of many medications in the small intestine. If this enzyme is not working properly, the drug may be absorbed in larger doses and can stay in the body longer—resulting in more of the medication than desired,” McDermott explains.

It may raise your blood sugar.

Drinking fruit juice of any kind can alter your blood sugar levels, so depending on what your blood sugar needs are, this may end up being a positive or negative outcome for you.

“It can raise your blood sugar (depending on quantity), which can be not great for people with diabetes who don’t know they have it and are walking around with chronically high levels. Conversely, for people with low blood sugar levels, drinking half a cup of juice can help normalize their blood sugar. It really just depends on the circumstance,” says Dana Ellis Hunnes, PhD, MPH, RD, a registered dietitian and author of Recipe for Survival.

It might boost your immunity.

Lastly, drinking grapefruit juice may potentially help boost your immunity, as long as it’s paired with a healthy diet.

“Grapefruit is filled with vitamins A and C, which carry antioxidant features that fight inflammation and infectious diseases,” says Nataly Komova, RD, a registered dietitian and fitness expert at Just CBD. “It also has minerals, including zinc, iron, and copper, that increase immunity and promote the skin’s integrity, thus blocking infections,” she adds.

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