Juicy Citrus

The Sweet (and Tangy) Truth

by Evangeline Yvonne Samples, MS, RDN, LD

ThinkstockPhotos-482452958

Citrus fruits include familiar items such as oranges, lemons, limes, tangerines, grapefruit and kumquats.(1)  However, several other varieties are available to grocery shoppers. For example, the pummelo, or shaddock, is a native of Malaysia. It has a green rind with dark pink flesh. Japanese cuisine includes the yuzu, a citrus fruit native to East Asia. Finally, the tangelo is a cross between a grapefruit, orange and tangerine. The “ugli fruit” is one type of Jamaican tangelo.(2)

People throughout the world consume a variety of citrus fruits. For instance, Filipino cooks use lime wedges, called calamansi, to add flavor to meat dishes. Oranges and lemons are popular in Southeast Asian cuisine. Citrus is also plentiful in the United States. Florida is a major producer of oranges, and the Florida Keys are known for their key limes.(3) 

Healthful Properties 
Citrus fruits are excellent sources of nutrients and phytochemicals. On average, one raw navel orange provides 82.7 milligrams of vitamin C, 48 dietary folate equivalents (DFE), and 3.1 grams of fiber for a mere 69 calories.(4) These fruits are also a good source of carotenoids (a class of phytochemicals). In particular, the Cara Cara sweet orange is high in the carotenoids lycopene and phytoene. The tangerine, a type of mandarin orange, is high in β-cryptoxanthin and phytoene. The phytochemicals are present at greater levels in the whole fruits than in the juice.(5) 

According to many studies, citrus fruits promote health in different ways. As a health coach, one must frequently separate fact from fiction. For example, clients might ask whether eating grapefruit will help them lose weight.

Weighty Matters
The evidence about the relationship of citrus fruits to body weight is mixed. Eating fruit was associated with a loss of 0.49 pound during a four-year period. However, the study examined fruit consumption in general, rather than specific categories of fruit, such as citrus.(6) In another study of 18,146 middle-aged and older female participants from the Women’s Health Study, researchers observed an inverse relationship between intakes of citrus fruits and the risk of becoming overweight or obese.(7) In addition, a review of the effects of grapefruit did not suggest that the fruit helps with weight loss. Nonetheless, consuming grapefruit resulted in a significant decrease in systolic blood pressure of 2.43 mmHg.(8) Such a benefit is one of several positive effects that the antioxidants from citrus fruit have on cardiovascular health. 

The Cardio Connection
Dietary antioxidant intakes and the resulting plasma antioxidant levels appear to influence cardiovascular disease. Oxygen free radicals are molecules that contain one oxygen atom and one or more unpaired electrons. The unpaired electrons make the free radicals highly unstable and reactive. To stabilize itself, the free radical then steals electrons from other molecules, turning those molecules into free radicals. The new free radicals then look for stable molecules from which to take electrons. When there are many free radicals and few antioxidants, the result is oxidative stress. This stress triggers a chronic inflammatory process in blood vessels, causing the onset of cardiovascular disease.(9) 

Researchers have extensively studied the relationships between citrus intake, oxidative stress and cardiovascular disease. In one study, rabbits received diets to raise their blood cholesterol levels. The control group received only the hypercholesterolemic diet. The first intervention group received one gram per day of dried lime peel powder. The second intervention group received five milliliters (one teaspoon) of lime juice per day. Rabbits fed either the lime peel or lime juice had a higher total antioxidant capacity than did the control group. Furthermore, researchers observed decreased presence of fatty streaks (the first visible sign of atherosclerosis) in the groups that received either lime peel or lime juice.(10) Additionally, as little as 10 microliters of fresh lime juice or 20 microliters of lime peel extract inhibited the oxidation of LDL cholesterol.(11) 

In a recent review, men with low plasma levels of carotene and vitamin C were four times more likely to die from ischemic heart disease than those with normal plasma levels. Vitamin C deficiency was also associated with a higher risk of myocardial infarction (heart attack). In contrast, taking vitamin C supplements had no effect on cardiovascular risk.(9)

Cancer Prevention
Several studies suggest that consuming citrus fruits may prevent some types of cancer. Phytochemicals and fiber from these fruits appear to prevent colon cancer by stopping cancer cells from dividing and by inducing apoptosis, or programmed cell death. Researchers observed an inverse association between intake of citrus fruit and the risk of non-Hodgkin lymphoma.(12) Citrus fruits also may protect against cancers in the digestive and upper respiratory tracts, including oral, pharyngeal, and laryngeal cancers; stomach cancer; and colorectal cancer.(13,14) An intake of four or more servings per week appeared to be beneficial. 

Antimicrobial Activity
Furthermore, citrus fruits seem to have antimicrobial activity. Staphylococcus aureus (S. aureus) is a type of bacteria that causes a wide range of diseases. S. aureus produces the toxin alpha-Hemolysin that leads to tissue injury. Diosmetin, a phytochemical found in citrus fruits, diminishes the production of alpha-Hemolysin in  S. aureus cultures. From these results, the researchers suggest that Diosmetin has the potential to be a new medication for the treatment of S. aureus infections.(15)

In addition, lime juice may help to fight malaria. When used with antimalarial treatments, lime juice enhanced parasite clearance in patients with uncomplicated malaria. Furthermore, the lime juice had no side effects.(16) 

Conclusion
Citrus fruits are rich in nutrients and phytochemicals, but low in calories. These fruits may aid in weight control, cardiovascular health and cancer prevention. As a health coach, one might advise clients to prepare a salad with grapefruit segments. A fresh orange is a great addition to breakfast or lunch. Lemons and limes can flavor main dishes, or can be added to water to make a refreshing, albeit slightly tart beverage. One can also use citrus zest in pancake batter, cookie dough or hot cereal. AF

Evangeline Yvonne Samples, MS, RDN, LD, is currently an adjunct professor of nutrition at Pierpont Community & Technical College, a part of Fairmont State University in West Virginia. Samples is a Registered Dietitian and Nutritionist, and holds a Master of Science in Dietetics from Marshall University. She is a contributing writer for American Fitness and you can follow her on Tumblr at wvhootowl2014.tumblr.com.

REFERENCES
1. LABENSKY, S.R. AND HAUSE, A.M. ON COOKING: A TEXTBOOK OF CULINARY FUNDAMENTALS (2ND ED.). UPPER SADDLE RIVER: PRENTICE HALL, 1999.

2. MOORE, M. “CITRUS APPEAL: SQUEEZE IN FLAVOR AND NUTRITION.” FOOD & NUTRITION, 4, NO. 1 (JAN/FEB 2015): 22-23.

3. KITTLER, P.G. AND SUCHER, K.P. FOOD AND CULTURE (5TH ED.). BELMONT: THOMSON WADSWORTH, 2008.

4. UNITED STATES DEPARTMENT OF AGRICULTURE NATIONAL NUTRIENT DATABASE FOR STANDARD REFERENCE. RELEASE 27. ORANGES, RAW, NAVELS. 
NDB.NAL.USDA.GOV/NDB/FOODS/SHOW/2332?MANU=&FGCD= (ACCESSED JUN 16, 2015).

5. RODRIGO, M.J., ET AL. “CAROTENOID BIOACCESSIBILITY IN PULP AND FRESH JUICE FROM CAROTENOID-RICH SWEET ORANGES AND MANDARINS.” FOOD & FUNCTION (MAY 2015). EPUB AHEAD OF PRINT. DOI: 10.1039/C5FO00258C.

6. MOZAFFARIAN, D., ET AL. “CHANGES IN DIET AND LIFESTYLE AND LONG-TERM WEIGHT GAIN IN WOMEN AND MEN.” THE NEW ENGLAND JOURNAL OF MEDICINE, 364, NO. 25 (JUN 2011): 2392-404.

7. RAUTIAINEN, S., ET AL. “HIGHER INTAKE OF FRUIT, BUT NOT VEGETABLES OR FIBER, AT BASELINE IS ASSOCIATED WITH LOWER RISK OF BECOMING OVERWEIGHT OR OBESE IN MIDDLE-AGED AND OLDER WOMEN OF NORMAL BMI AT BASELINE.” THE JOURNAL OF NUTRITION, 145, NO. 5 (2015): 960-68. DOI: 10.3945/JN.114.199158.

8. ONAKPOYA, I., ET AL. “THE EFECT OF GRAPEFRUITS (CITRUS PARADISI) ON BODY WEIGHT AND CARDIOVASCULAR RISK FACTORS: A SYSTEMATIC REVIEW AND META-ANALYSIS OF RANDOMIZED CLINICAL TRIALS.” CRITICAL REVIEWS IN FOOD SCIENCE AND NUTRITION (APR 2015): EPUB AHEAD OF PRINT. PMID: 25880021.

9. WANG, Y., CHUN, O.K. AND SONG, W.O. “PLASMA AND DIETARY ANTIOXIDANT STATUS AS CARDIOVASCUAR DISEASE RISK FACTORS: A REVIEW OF HUMAN STUDIES.” NUTRIENTS, 5, NO. 8 (JUL 2013): 2969-3004. DOI: 10.3390/NU5082969.

10. BOSHTAM, M., ET AL. “IMPACTS OF FRESH LIME JUICE AND PEEL ON ATHEROSCLEROSIS PROGRESSION IN AN ANIMAL MODEL.” ARYA ATHEROSCLEROSIS, 9, NO. 6 (NOV 2013): 357-62.

11. BOSHTAM, M., ET AL. “ANTIOXIDANT EFFECTS OF CITRUS AURANTIFOLIA (CHRISTM) JUICE AND PEEL EXTRACT ON LDL OXIDATION.” JOURNAL OF RESEARCH IN MEDICAL SCIENCES, 16, NO. 7 (JUL 2011): 951-55.

12. CHIU, B.C., ET AL. “DIETARY INTAKE OF FRUIT AND VEGETABLES AND RISK OF NON-HODGKIN LYMPHOMA.” CANCER CAUSES & CONTROL, 22, NO. 8 (AUG 2011): 1183-95.
13. KAUR, J. AND KAUR, G. “AN INSIGHT INTO THE ROLE OF CITRUS BIOACTIVES IN MODULATION OF COLON CANCER.” JOURNAL OF FUNCTIONAL FOODS, 13 (MAR 2015): 239-61.

14. FOSCHI, R., ET AL. “CITRUS FRUIT AND CANCER RISK IN A NETWORK OF CASE-CONTROL STUDIES.” CANCER CAUSES & CONTROL, 21, NO. 2 (FEB 2010): 237-42. DOI: 10.1007/S10552-009-9454-4.

15. LIU, S., ET AL. “DIOSMETIN INHIBITS THE EXPRESSION OF ALPHA-HEMOLYSIN IN STAPHYLOCOCCUS AUREUS.” ANTONIE VAN LEEUWENHOEK (MAY 2015). EPUB AHEAD OF PRINT. PMID: 26021482.

16. ADEGOKE, S.A., ET AL. “EFFECTS OF LIME JUICE ON MALARIA PARASITE CLEARANCE.” PHYTOTHERAPY RESEARCH, 10 (OCT 2011): 1547-50. DOI: 10.1002/PTR.3418.
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