Foods That Fight Cancer™
Grapefruit – an 18th century hybrid of the pummelo and sweet orange - is grown mainly in the Americas. Its name derives from the fruit's appearance as it grows: grape-like clusters on trees. Grapefruit may not be a miracle fat-burner as some claim, but as part of an overall healthy diet, its low calorie density can help promote healthy weight. And this tasty fruit is packed with vitamins and phytochemicals.
What's in Grapefruit?
One-half of a medium grapefruit - red, pink and white - provides at least half of most adults’ daily vitamin C needs.
Grapefruit contains these phytochemicals:
- Naringenin and other flavonoids
- Limonin and other limonoids
- Beta-carotene and lycopene (pink and red varieties)
Grapefruit can interfere with the activity of some medicines, both prescription and non-prescription.
For more information, see FAQ section.
The Cancer Research
Grapefruit are rich sources of vitamin C and the pink and red varieties contain carotenoids (including lycopene and beta-carotene) and dietary fiber. Dietary fiber can act in several ways to lower cancer risk, including helping with weight control. (Excess body fat increases the risk of 12 cancer types, and dietary fiber can increase the feeling of fullness.)
Current Evidence: AICR/WCRF Expert Report and its Updates (CUP)
After a systematic review of the global scientific literature, AICR/WCRF analyzed how fruit and grapefruit's nutrients affect the risk of developing cancer. This comprehensive review of decades of research concluded that there is strong – probable - evidence that:
- foods containing dietary fiber DECREASE the risk of colorectal cancer
- a diet high in fruits along with non-starchy vegetables DECREASE the risk of lips, mouth, tongue and other aerodigestive cancers
Evidence categorized as "probable" means there is strong research showing a causal relationship to cancer – either decreasing or increasing the risk. The research must include quality human studies that meet specific criteria and biological explanations for the findings. A probable judgement is strong enough to justify recommendations.
Source: AICR/WCRF. Diet, Nutrition, Physical Activity and Cancer: A Global Perspective, 2018.
”Grapefruit's vitamin C and unique phytochemicals offer potential for acting through several paths to reduce cancer risk.”
- Karen Collins, MS, RDN, CDN
Open Areas of Investigation: Laboratory Research
In animal and cell studies, grapefruit powder, limonin and naringenin decrease growth and increase self-destruction of colon, mouth, skin, lung, breast and stomach cancers. Lab studies suggest these compounds act in a variety of ways: They decrease inflammation and increase enzymes that deactivate carcinogens. In lab studies, naringenin inhibits enzymes that activate carcinogens and the aromatase enzyme that stimulates estrogen production.
Vitamin C protects DNA from damage by trapping free radicals and inhibiting formation of carcinogens. It also helps other compounds maintain their antioxidant power. Carotenoids are also antioxidants. They reduce inflammation, improve immune function and decrease cancer cell growth.
Open Areas of Investigation: Human Studies
Evidence shows that diets high in fruits decrease risk of certain cancers (see chart) but most human studies look at overall fruit consumption. Some studies also investigated overall citrus intake, which includes oranges and lemons. Studies show a lower risk of several cancers in people who eat more fruit or citrus fruit, compared with people who eat the least. Research is ongoing as to grapefruit and citrus fruits specifically.
After some lab studies suggested phytochemicals in grapefruit affect estrogen metabolism, researchers investigated a grapefruit-breast cancer connection. One 2007 study linked frequent grapefruit consumption with greater risk of postmenopausal breast cancer. However, two other large population studies did not find any increase in estrogen levels or breast cancer risk linked to grapefruit. (See Frequently Asked Questions for more.)
In the Kitchen
- You can choose from red, pink and white grapefruit. These have similar flavor and vitamin C levels but only the red and pink varieties contain beta-carotene and lycopene.
- Choose firm grapefruit that has a little spring when you give it a very gentle squeeze.
- Select heavier grapefruits. For equal-sized fruits, the heavier ones are juicier than lighter weight grapefruit.
- Avoid grapefruit with brown or soft spots because their flavor may be bitter.
- The outside skin should be intact, but slight discoloration doesn’t affect flavor.
- If using within a week, store grapefruit at room temperature so it stays at its juiciest. Otherwise it will stay fresh for two to three weeks in the refrigerator. Return to room temperature before serving for best flavor.
- Rinse well under cool water before cutting. This lowers risk of surface bacteria or dirt being transferred from the skin to the inside flesh.
- Most Americans are familiar with scooping out sections from the grapefruit. If you peel it and eat the sections like an orange, you get more fiber because you eat the membrane surrounding each section.
- Grapefruit sections add a delicious tang to green salads; grapefruit and avocado is a classic salad.
- Make salsa out of diced grapefruit, chopped bell peppers and cilantro.
- Sprinkle a grapefruit half with a touch of brown sugar and broil just until bubbly.
Caution: Phytochemicals in grapefruit decrease the enzymes that breakdown several prescription drugs, raising drug levels in the body. This can be dangerous, so check with your healthcare provider about eating grapefruit or drinking grapefruit juice if you take any prescription medicines.
Fennel and Red Grapefruit Salad with Asiago Cheese
- 1 large fennel bulb
- 1 large red grapefruit
- 1 oz. Asiago cheese
- 4 tsp. extra virgin olive oil, preferably mild and fruity
- Freshly ground black pepper, to taste
Trim fennel by slicing across top just where bulb starts to swell, cutting off any stalks and fronds. Cut off a slice from tough bottom. With your fingers pull away any tough or bruised outer layers. Halve bulb vertically, making 2 pieces. Cut each half vertically into five 1/2-inch wedges. Trim away most of hard core from each wedge, leaving just enough to hold layers together.
Cut top and bottom off grapefruit, cutting deep enough to expose flesh. Standing grapefruit on its flat bottom on work surface, work a knife down the side, following curved shape of fruit to slice the peel and white pith in a strip. Keep rotating grapefruit until all peel is removed. Holding peeled fruit over bowl, work knife in along membrane on both sides of every section, releasing flesh into bowl. Squeeze juice from membrane into bowl.
To assemble salad, on each of four salad plates, arrange 5 fennel wedges in an arc. Fan out 4 grapefruit wedges below fennel, slightly overlapping them. Holding chunk of cheese over each plate, use vegetable peeler to shave a few thin slices over salad, using one-quarter ounce of cheese for each serving. Drizzle 1 teaspoon oil over each salad. Season with a pinch of pepper. Serve salad immediately.
Makes 4 servings.
Per serving: 110 calories, 7 g total fat (2 g saturated fat), 11 g carbohydrate, 3 g protein, 3 g dietary fiber, 115 mg sodium.
Below are answers to some of the most frequently asked questions we get asked.
I've heard that I should avoid drinking grapefruit juice or eating the fruit if I'm on medication. True?
Grapefruit can interfere with the activity of some medicines, both prescription and non-prescription. Phytochemicals in grapefruit decrease the enzymes that break down several prescription drugs, raising drug levels in the body and increasing the chances of side effects from it. This can be dangerous, so check with your healthcare provider about eating grapefruit or drinking grapefruit juice if you take any prescription medicines.
The Food and Drug Administration has more information on medicines that may not mix with grapefruit.
Is it true that women should avoid grapefruit because of a possible link to breast cancer?
A 2009 population study (Spencer et al., Cancer Causes Control) did not find any link between grapefruit consumption and breast cancer risk or estrogen levels. The study included about 114,000 women. A 2007 population study (Monroe et al. Br J Cancer) with about 50,000 women, had found an association with breast cancer risk but the researchers emphasized that more studies were needed to confirm their finding.
Grapefruit is a good source of vitamin C and several antioxidant phytochemicals. One of them, naringenin, has been shown to inhibit growth of breast cancer and other cancer cells in laboratory studies. So for now, unless a woman's doctor tells her otherwise or if she is taking medications that necessitate avoidance of grapefruit, she can reasonably include grapefruit as one fruit among the recommended wide variety of healthy fruits.
Does drinking grapefruit juice help promote weight loss?
Claims that grapefruit or grapefruit juice can somehow burn body fat are not true. Even the one study widely circulated on the Internet, in which people consuming grapefruit or grapefruit juice before each meal lost more weight than people who ate no grapefruit, does not prove that the grapefruit was responsible.
Grapefruit juice, like grapefruit, is an excellent source of vitamin C and antioxidants, so if drinking a small glass of it before a meal helps you get used to smaller portions of food at your meals, that's great. But keep in mind that it's not a fat-burner and not to be consumed in endless amounts. The 96 calories per cup will add up if you overdo. And, of course, make sure you are working on ways you can continue long-term to keep calorie consumption in balance with what you burn up in activity.
- Fujioka, K., et al., The effects of grapefruit on weight and insulin resistance: relationship to the metabolic syndrome. Journal of medicinal food, 2006. 9(1): p. 49-54.
- Silver, H.J., M.S. Dietrich, and K.D. Niswender, Effects of grapefruit, grapefruit juice and water preloads on energy balance, weight loss, body composition, and cardiometabolic risk in free-living obese adults. Nutrition & metabolism, 2011. 8(1): p. 8.
- U.S. Department of Agriculture, A.R.S., Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2. 2010.
- Wolfe, K.L., et al., Cellular antioxidant activity of common fruits. Journal of agricultural and food chemistry, 2008. 56(18): p. 8418-26.
- Vanamala, J., et al., Suppression of colon carcinogenesis by bioactive compounds in grapefruit. Carcinogenesis, 2006. 27(6): p. 1257-65.
- Roy, A. and S. Saraf, Limonoids: overview of significant bioactive triterpenes distributed in plants kingdom. Biological & pharmaceutical bulletin, 2006. 29(2): p. 191-201.
- Chidambara Murthy, K.N., et al., Citrus limonin and its glucoside inhibit colon adenocarcinoma cell proliferation through apoptosis. Journal of agricultural and food chemistry, 2011. 59(6): p. 2314-23.
- Miller, E.G., et al., Inhibition of oral carcinogenesis by citrus flavonoids. Nutrition and cancer, 2008. 60(1): p. 69-74.
- Leonardi, T., et al., Apigenin and naringenin suppress colon carcinogenesis through the aberrant crypt stage in azoxymethane-treated rats. Experimental biology and medicine, 2010. 235(6): p. 710-7.
- Moon, Y.J., X. Wang, and M.E. Morris, Dietary flavonoids: effects on xenobiotic and carcinogen metabolism. Toxicology in vitro : an international journal published in association with BIBRA, 2006. 20(2): p. 187-210.
- World Cancer Research Fund / American Institute for Cancer Research, Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective, 2007: Washington, DC. p. 82-113.
- Monroe, K.R., et al., Prospective study of grapefruit intake and risk of breast cancer in postmenopausal women: the Multiethnic Cohort Study. British journal of cancer, 2007. 97(3): p. 440-5.
- Spencer, E.A., et al., Prospective study of the association between grapefruit intake and risk of breast cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC). Cancer causes & control : CCC, 2009. 20(6): p. 803-9.
- Kim, E.H., et al., A prospective study of grapefruit and grapefruit juice intake and breast cancer risk. British journal of cancer, 2008. 98(1): p. 240-1.