What is Oxidative Stress and Inflammation?

Oxidative stress refers to the imbalance of the body’s defence systems, like damage, from free radicals in our environment. Inflammation often occurs from oxidative stress, and it is a response of the immune system that sometimes results in redness and swelling. Food allergies or an infection, like the cold or flu, are among the causes of short-term inflammation. Long-term, or chronic, oxidative stress or inflammation are thought to play a significant role in the onset and progression of several diseases including cardiovascular disease.

Reducing Oxidative Stress and Inflammation

Nutrients in grapefruit have been associated with reducing oxidative stress and inflammation:

Vitamin C: Vitamin C supports antioxidant activities in the body which in turn may help lessen oxidative stress and inflammation.¹ For example, vitamin C deactivates free radicals in the skin providing photo protection against sunburn and premature aging.² Vitamin C also helps regenerate vitamin E into its antioxidant form providing further protection against damage.¹

An 150ml glass of 100% grapefruit juice or ½ of a medium fresh grapefruit (120g) are excellent sources of vitamin C, providing 47% (juice) and 53% (fruit) of the reference intake (RI).*

Flavonoids: Plant compounds called flavonoids, such as naringin found in grapefruit and hesperidin found in oranges, may help maintain cell health. Some research indicates these flavonoids found in orange juice may be able to reduce inflammation and support health of blood vessel cells.^3,4

The flavonoid naringin is the primary flavonoid found in grapefruit⁵ and is concentrated in the peel of the grapefruit. Commercial grapefruit juice can have higher amounts of absorbable flavonoids compared to fresh-squeezed grapefruit juice because of the increased pressure during processing which releases these compounds from the peel.

Carotenoids: Carotenoids are colourful plant pigments that affect oxidative stress and inflammatory pathways, thus can inhibit the production of inflammation in our cells.⁶ Ultraviolet sunlight is a source of oxidative stress which can contribute to age-related eye diseases including cataracts and Age-related Macular Degeneration (AMD). Several studies have observed reduced risk of AMD with increased intake of carotenoids.⁷ Carotenoids have also been shown to protect against sunburn^8,9 and premature aging.¹⁰ Since carotenoids are stored under the skin, regular consumption of grapefruit juice may increase carotenoid levels in the skin. Grapefruit and 100% grapefruit juice contain a number of carotenoids including beta-carotene, lutein, zeaxanthin and lycopene (in coloured fruit varieties), which may help manage inflammation.

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Detailed Nutritional Information

In vitro and animal studies support a role for naringin in increasing the activity of various antioxidant enzymes, including catalase, superoxide dismutase and glutathione peroxidase.¹¹ Extracts from red grapefruit have been shown to have antioxidant activity and free radical scavenging activity in in vitro model systems¹² while grapefruit peel, seeds and juice have been shown to have antioxidant and anti-inflammatory activities.¹³

Epidemiological and clinical data suggest that grapefruit or grapefruit juice may be associated with favourable effects on antioxidant and anti-inflammatory biomarkers. A cross-sectional analysis of National Health and Nutrition Examination Survey (NHANES) 2003-2008 data found that compared to non-consumers, grapefruit consumers had significantly lower blood levels of C-reactive protein, a systemic marker of inflammation.¹⁴

In clinical studies, individuals with high blood cholesterol who consumed 100 or 200 ml/day of a pummelo-grapefruit hybrid juice for 30 days showed a significant increase in serum, albumin, and fibrinogen antioxidant capacity.¹⁵ Although regular consumption of 340 ml/day of 100% grapefruit juice for 6 months by middle-aged, healthy postmenopausal women was found to be beneficial on arterial stiffness, there was no significant effect on various oxidative stress or inflammatory biomarkers.¹⁶ Daily consumption of red grapefruit for 6 weeks by overweight or obese men and women reduced urinary F2-isoprostanes, a marker for oxidative stress, but had no impact on other markers of oxidative stress or inflammation, including plasma high-sensitivity C-reactive protein or soluble vascular cellular adhesion molecule (VCAM).¹⁷ A systematic review supports that 100% fruit juices, such as grapefruit juice, can have positive impacts on antioxidant status and lipid profiles in adults.¹⁸

*Reference Intake: Based on a 2000 calorie diet. Information is not intended for labelling food in packaged form. Nutrient values may vary based on variety of citrus fruit and place of origin. Check with your citrus vendor for additional information.

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