By William Gamonski
A Squeeze of Nutritional Power
Oranges possess over 60 different flavonoids, making them a nutritious fruit to eat on a daily basis.1 Immensely rich in hesperidin and naringin, oranges are emerging as a weapon for boosting eye health, fighting heart disease, preventing kidney stones, and enhancing immunity.
While oranges are widely available and fairly inexpensive today, they were once considered a prized luxury before the 20th century. The orange (Citrus sinensis) originated in Asia thousands of years ago, with the most common types being bitter and sweet. The latter became popular across Europe in the 15th century before Spanish explorers brought it to Florida and California, currently two of the largest US producers of the citrus fruit. Other major world producers include Brazil, Mexico, and Israel.1
Boosting Eye Health
Glaucoma is a long-term visual neuropathy defined by structural abnormalities in the nerve fibers of eye structures as well as the optic nerve itself. It can result in permanent vision loss if left untreated.2 A wealth of carotenoids, including lutein and beta-cryptoxanthin, along with vitamin C, make oranges well-equipped to protect against this often symptomless disease. In one study, researchers at the University of California revealed that those consuming more than two servings of fresh oranges per week produced an 82% reduction in glaucoma risk compared to those who ingested less than one serving per week.3
A recent study published in the Journal of Neuroscience suggests that vitamin C in oranges might be largely responsible for this powerful protective effect.4 Retinal nerve cells contain GABA receptors, which help modulate their transmission of electrical signals to the brain. Without sufficient amounts of the vitamin, GABA receptors malfunction, causing retinal nerve cells to fire signals at an excessive rate. This constant workload causes nerve cells to “burn out” and induces cell death. Vitamin C rich oranges allow GABA receptors to function properly, thereby protecting against the loss of retinal nerve cells and preserving vision.4
Along with glaucoma, a greater intake of oranges shows promise in defending against age-related macular degeneration, the most common cause of vision loss in individuals over the age of 50.5 Researchers analyzed data from more than 118,400 adults between the ages of 30 to 55 regarding fruit and vegetable intake over an 18-year period. They found that those who ate three or more servings of oranges per week had a 39% lower risk of age-related macular degeneration than those who consumed less than two servings per month.6
Since endothelial dysfunction is perhaps the main underlying cause of heart disease, scientists are continually pursuing new dietary avenues to protect and improve its function. With their antioxidant and anti-inflammatory properties, oranges are beginning to emerge as the ideal candidate for this role. A study published in the American Journal of Clinical Nutrition found that participants with increased risk for cardiovascular disease ingesting about 2 cups of red orange juice daily for one week experienced significant decreases in inflammatory markers that accompanied a 38.5% improvement in endothelial function.7
In a separate study, French researchers observed comparable results between orange juice and hesperidin beverage supplementation on endothelial function and diastolic blood pressure after four weeks in healthy volunteers, suggesting the high concentration of hesperidin in orange juice contributes to its positive effect on blood vessels.8
High levels of homocysteine have been shown to induce endothelial dysfunction and increase the risk for vascular disease.9 Oranges contain a plethora of folate, which enhances homocysteine metabolism. Folate is required for methionine synthase to convert dangerous homocysteine into the amino acid methionine, thus preventing the buildup of homocysteine.9
Oranges also appear to favorably alter lipid metabolism, especially in those with high cholesterol. Brazilian researchers assigned patients with normal and high cholesterol 3 cups of orange juice or a control for 60 days. At the end of the study, LDL cholesterol fell significantly in the high cholesterol group by 19 mg/dL, without affecting HDL cholesterol and triglycerides. The results were attributed to a 27% increase in the transfer of free cholesterol to HDL where it’s transported back to the liver for excretion. No lipid changes were reported for the normal cholesterol group.10
Kidney Stone Prevention
Kidney stones are an increasingly common condition affecting approximately 1 in 11 individuals in the US.11 Kidney stones were once thought to be a painful disorder that rarely impaired long-term kidney function, but recent research suggests otherwise, with stone formers up to 67% more likely to develop chronic kidney disease than non-stone formers.12 Potassium citrate supplements have drawn considerable attention for their ability to inhibit the formation of calcium-oxalate, the most common type of kidney stones. However, its association with gastrointestinal side effects has led researchers to explore other effective alternatives.13 Since citrus fruits are naturally rich in potassium citrate, researchers investigated the potential of citrus fruits, particularly orange juice and lemonade, in preventing the occurrence of kidney stones.
Scientists reported in the Clinical Journal of the American Society of Nephrology that human volunteers with and without a history of kidney stones adhering to a stone prevention diet supplemented with 13.5 ounces of orange juice three times daily with meals for one week increased their citrate levels and urinary pH value, which decreased the risk of calcium oxalate stones, whereas those supplemented with lemonade experienced no such changes.13
Although oranges are often touted as immune boosters because of their vitamin C content, recent findings indicate that pectin fiber might be their true standout for improving immunity. Scientists at the University of Illinois gave mice a low-fat diet rich in soluble fiber pectin or insoluble fiber for six weeks before injecting them with an endotoxin to imitate a bacterial infection. The results showed that the pectin group became less sick and recovered 50% faster than mice in the insoluble group. Pectin fiber was shown to enhance immune function by stimulating the production of the anti-inflammatory molecule interleukin-4.14
Oranges contain a wealth of nutrients, from flavonoids to vitamin C, to pectin fiber. Research has shown that this popular fruit protects against the development of glaucoma and age-related macular degeneration, two of the leading causes of blindness. In addition, oranges improve heart health, block the formation of common calcium-oxalate kidney stones, and enhance immunity, all of which make them one of the healthiest fruits to eat on a regular basis.
While orange fruit contains healthy ingredients, avoid regular consumption of orange juice, even though studies reported in this article report short-term favorable effects on vascular risk markers. The reason is that orange juice concentrates contain fructose that causes sharp after-meal glucose spikes that in the long term can increase the risk of a host of diseases. Feel free to enjoy oranges, but not the concentrated juice.
If you have any questions on the scientific content of this article, please call a Life Extension® Health Advisor at 1-866-864-3027.
- Available at: http://www.whfoods.com/genpage.php?tname=foodspice&dbid=37. Accessed December 27, 2012.
- McKinnon SJ, Goldberg LD, Peeples P, Walt JG, Bramley TJ. Current management of glaucoma and the need for complete therapy. Am J Manag Care. 2008 Feb;14:S20-7.
- Giaconi JA, Yu F, Stone KL, et al. The association of consumption of fruits/vegetables with decreased risk of glaucoma among older African-American women in the study of osteoporotic fractures. Am J Ophthalmol. 2012 Oct;154(4):635-44.
- Calero CI, Vickers E, Cid GM, et al. Allosteric modulation of retinal GABA receptors by ascorbic acid. J Neurosci. 2011 Jun;31(26):9672-82.
- Sayen A, Hubert I, Berrod JP. Age related macular degeneration. Rev Prat. 2011 Feb;61(2):159-64.
- Cho E, Seddon JM, Rosner B, Willett WC, Hankinson SE. Prospective study of intake of fruits, vegetables, vitamins, and carotenoids and risk of age-related maculopathy. Arch Ophthalmol. 2004 Jun;122(6):883-92.
- Buscemi S, Rosafio G, Arcoleo G, et al. Effects of red orange juice intake on endothelial function and inflammatory markers in adult subjects with increased cardiovascular risk. Am J Clin Nutr. 2012 Apr;95(5):1089-95.
- Morand C, Dubray C, Milenkovic D, et al. Hesperidin contributes to the vascular protective effects of orange juice: a randomized crossover study in healthy volunteers. Am J Clin Nutr. 2011 Jan;93(1):73-80.
- Blom HJ, Smulders Yvo. Overview of homocysteine and folate metabolism. With specialreferences to cardiovascular disease and neural tube defects. J Inherit Metab. 2011 Feb;34(1):75-81.
- Cesar TB, Aptekmann NP, Araujo MP, Vinagre CC, Maranhao RC. Orange juice decreases low-density lipoprotein cholesterol in hypercholesterolemic subjects and improves lipid transfer to high-density lipoprotein in normal and hypercholesterolemic subjects. Nutr Res. 2010 Oct;30(10):689-94.
- Scales CD Jr, Smith AC, Hanley JM, Saigal CS. Prevalence of kidney stones in the United States. Eur Urol. 2012 Jul;62(1):160-5.
- Rule AD, Bergstralh EJ, Melton LJ 3rd, Li X, Weaver AL, Lieske JC. Kidney stones and the risk for chronic kidney disease. Clin J Am Soc Nephrol. 2009 Apr;4(4):804-11.
- Odvina CV. Comparative value of orange juice versus lemonade in reducing stone-forming risk. Clin J Am Soc Nephrol. 2006Nov;1(6):1269-74.
- Sherry CL, Kim SS, Dilger RN, et al. Sickness behavior induced by endotoxin can be mitigated by the dietary soluble fiber, pectin, through up-regulation of IL-4 and Th2 polarization. Brain Behav Immun. 2010 May;24(4):631-40.
- Available at: http://nutritiondata.self.com/facts/fruits-and-fruit-juices/1966/2. Accessed January 4, 2013.