Sure, it's low in calories, but does it actually do anything for you
Grapefruit is one of those foods that perennially shows up on lists of low-calorie and low-sugar fruits, but how many calories are in a grapefruit, really? Well, it turns out that grapefruit is, in fact, as low-calorie as we've all been lead to believe. According to the US Department of Agriculture's Agricultural Research Service, a whole, single red or pink grapefruit that's 3¾ inches across has only 103 calories. That's fewer calories than a large, raw banana. But there has to be more to grapefruit nutrition than the number of calories in a single fruit. So what are some other health benefits of grapefruit besides being low in calories (if you even consider the number of calories a "health benefit")?
Grapefruits are packed with nutrients, including vitamins C and A, according to the USDA. It's also a good source of dietary fiber, which is what helps keep you regular. Plus, if you're one of those people who forgets to drink water during the day and is constantly dehydrated, you might want to consider eating more grapefruit. It's got a super high water content—about 90 percent of total weight, depending on what type and size of fruit you get.
The sugar in grapefruit is where things get a little tricky. A whole grapefruit has almost 17 grams of sugar, which is relatively high as far as fruits are concerned. For some context, a cup of raw watermelon has about ten grams of sugar.
But the relatively high sugar content of grapefruit doesn't mean that the fruit is suddenly unhealthy. After all, it's natural sugar, not added, and there's even been some studies that have found that eating a grapefruit a day can actually help improve high blood pressure (though other studies add that more research is needed to confirm the full scope of benefits of grapefruit, even though the prospects look good).
If you are looking to get these same—or, at minimum, similar—health benefits from grapefruit juice, go for the freshly squeezed stuff, since a lot of commercially available grapefruit juice has sugar added or is watered down. Really, you're going to maximize the benefits of raw grapefruit if you just eat a raw grapefruit.