In September 2018 researchers from the Russian Federation published the nutritional profile of grapefruit juice. Grapefruit juice is one of the relatively low-calorie fruit juices – 100 ml of grapefruit juice contains an average of 39 kcal. Like other citrus juices, it is rich in organic acids, the main of which is citric acid (0.8-2 g/100 ml). Potassium, magnesium, vitamin C, as well as flavonoids (mostly narigin) are the most significant nutrients. A glass of grapefruit juice contains, on average, about 10% of the daily requirement of potassium, 6% of magnesium and about 100% of vitamin C. The amount of flavonoids in a glass of grapefruit juice provides up to 60% of the adequate daily intake.
Ivanova NN et al. Grapefruit juice nutritional profile. Vopr Pitan. 2018;87(5):85-94.