Grapefruit Nutrition Calculator — Calories, Vitamin C & Lycopene per Serving

Pink and red grapefruit (FDC 174673) deliver 42 calories per 100g with 0.77g protein, 0.14g fat, 10.66g total carbohydrates, and 6.89g natural sugars. A typical half grapefruit (~128g) provides about 54 calories — making it one of the lowest-calorie citrus fruits per serving. White grapefruit (FDC 174677) is even lower at 33 kcal per 100g with 8.41g carbs ^[1].

The most dramatic difference between pink/red and white varieties is vitamin A: pink grapefruit provides 58mcg RAE per 100g (6% DV) while white grapefruit has effectively 0mcg. This 58x difference comes from the carotenoid pigments — lycopene and beta-carotene — that create the pink-red flesh color. These pigments are entirely absent from white grapefruit ^[1][2].

Both varieties deliver nearly identical vitamin C: 31.2mg (35% DV) for pink and 33.3mg (37% DV) for white per 100g. One half grapefruit provides roughly 40-43mg vitamin C (44-48% DV), covering nearly half the daily value from a single fruit. Potassium is also comparable at 135mg (pink) vs 148mg (white) per 100g ^[1].

Pink and red grapefruit contain approximately 1,135mcg lycopene per 100g (USDA), making it one of only three major fruit sources of this red-pigmented carotenoid alongside tomatoes (~2,573mcg) and watermelon (~4,532mcg). White grapefruit contains zero lycopene — the color literally is the nutrient ^[1][2].

Grapefruit also contains naringin, the bitter-tasting flavanone glycoside responsible for grapefruit's characteristic bitter flavor. Naringin concentrations range from 100-500mg per liter of juice depending on variety and processing. Research has studied naringin's interaction with drug-metabolizing enzymes, specifically CYP3A4 — a relevant consideration for anyone tracking supplement-food interactions in their journal ^[2][3].

Beta-carotene at approximately 686mcg per 100g (pink/red) converts partially to vitamin A, accounting for the 58mcg RAE value. Combined with the lycopene content, pink grapefruit offers a unique carotenoid profile among citrus — oranges have neither significant lycopene nor the same beta-carotene density ^[1][2].

Fresh pink grapefruit juice (FDC 167774) has 39 calories per 100ml — close to the whole fruit's 42 kcal. But the fiber content drops from 1.6g to 0.1g per 100g — a 16x reduction. One cup of juice (247g) delivers 96 calories and 22.5g sugar with only 0.2g fiber, while one cup of sections (230g) has 97 calories and 15.8g sugar with 3.7g fiber ^[1].

Juice actually provides more vitamin C per 100g (38mg vs 31.2mg) because the juicing process extracts vitamin C efficiently from cell compartments. However, the potassium advantage of juice (162mg vs 135mg per 100g) doesn't offset the fiber and sugar density trade-off for most tracking purposes ^[1].

For nutrition logging: a 247ml cup of grapefruit juice has roughly the same calories as one whole medium grapefruit (256g edible portion), but with 28% more sugar (22.5g vs 17.6g) and 94% less fiber (0.25g vs 4.1g). The practical difference matters most for people tracking sugar intake or fiber goals ^[1].

Per 100g of edible fruit, grapefruit (42 kcal pink) sits below oranges (47 kcal) and tangerines (53 kcal) in calorie density but above lemon (29 kcal). The vitamin C ranking reverses: lemon provides 53mg, orange 53.2mg, and grapefruit 31.2mg — grapefruit is actually the lowest vitamin C citrus per 100g among major varieties ^[1].

Where grapefruit distinguishes itself is lycopene content (1,135mcg — oranges have zero), lower sugar (6.89g vs orange's 9.35g), and a larger portion size (a half grapefruit at 128g delivers more total nutrients than a medium tangerine at 88g simply because you eat more of it) ^[1][2].

Fiber at 1.6g per 100g is moderate for citrus — comparable to orange (2.4g) when accounting for the pith, which many grapefruit eaters remove more thoroughly than orange pith. Eating grapefruit segments with the membrane intact captures more fiber than scooping with a spoon ^[1].

Grapefruit's bitter taste comes from naringin, a flavanone that concentrations are highest in the peel, pith, and segment membranes. The edible flesh contains lower but still significant amounts. Research has documented that naringin and related furanocoumarins in grapefruit can inhibit CYP3A4 enzymes, which affects how the body processes certain compounds ^[2][3].

This enzyme interaction is well-documented in research literature and is the reason many information labels note grapefruit as a consideration when tracking dietary intake alongside certain supplements. The effect is specific to grapefruit among common citrus — oranges, lemons, limes, and tangerines do not contain significant furanocoumarins ^[2][3].

For nutrition journaling purposes, the relevant data point is that grapefruit contains unique bioactive compounds beyond standard vitamins and minerals. The naringin content is not captured in USDA nutrient panels but is tracked extensively in food science research at approximately 17-76mg per 100g of juice depending on variety ^[2][3].