Grapefruit: Good or evil?

Grapefruit is an interesting fruit. People on weight loss diets have been eating it for decades It’s not available year-round, not everybody likes it and some people can’t have it. Is grapefruit good or evil?

What is grapefruit?

The citrus fruit commonly known as grapefruit (Citrus paradisi), is a natural hybrid between pomelo and orange (1).

Nutrients in grapefruit

Grapefruit and its juice contains various nutrients, including vitamin A, C and fibre (2). See the table below for the nutritional composition of grapefruit and grapefruit juice (3).

As other citrus fruits, grapefruit is rich in flavonoids, which have numerous health benefits (more on this later), including naringin and naringenin (2, 4).

Pros

If you have ever heard about or done the grapefruit diet, you know the fruit has been associated with weight loss for decades. There is some evidence in humans that grapefruit can help obese patients with metabolic syndrome lose weight. In addition, some of the flavonoids in grapefruit might lower total cholesterol and LDL-cholesterol levels, resulting in decreased cardiovascular and diabetes risk (1).

The flavonoids in citrus fruit in general have antioxidant and anti-inflammatory properties. In particular, naringenin, which is present in grapefruit, inhibits enzymes and proteins that are involved in the generation of lipoprotein (4).

The Nurses Health Study, a large cohort study conducted in the US decades ago, found that higher intake of grapefruit was associated with lower inflammatory markers (5).

Scientists have also determined associations between the intake of certain fruits, including grapefruit, with a reduced risk of type 2 diabetes. However, they observed the opposite effect with intake of fruit juice (6).

Cons

The biggest drawback of grapefruit is its known interaction with many drugs. These include anticancer agents, anti-infective agents, statins, cardiovascular agents, central nervous system agents, gastrointestinal agents, immunosuppressants and urinary tract agents (7).

This interaction can potentially leading to detrimental effects such as rhabdomyolysis (a serious condition where muscle cells are damaged and their contents enter the bloodstream), respiratory depression, gastrointestinal bleeding and kidney toxicity (7).

When statins are taken with grapefruit, the patient might experience symptoms ranging from mild discomfort to rhabdomyolysis (7, 9). As a side note, rhabdo is also experienced also by athletes participating in intense sports such as Crossfit and mixed martial arts. However, the risk of rhabdomyolysis in statin users is very low, and grapefruit intake only increases this risk by a small margin (9).

How does this work? In brief, certain components in grapefruit (furanocoumarin derivatives) inhibit the activity of the enzyme known as CYP3A4. This enzyme normally decreases the absorption of certain drugs; therefore, when CYP3A4 is inhibited, more drug is absorbed (2, 7, 8, 9). Note that other citrus fruits (Seville oranges, limes and pomelos) also produce this effect (7).

The action of grapefruit intake on drug concentration depends on frequency of intake (7, 8), timing (7, 9) and individual characteristics of the patient (7).

The population at greater risk of detrimental side effects are elderly patients, due to their higher use of drugs and compromised drug metabolism (2).