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Does an Apple a Day Keep the Doctor Away: The Core of the Issue
October 24, 2008
Past pre-school, every American knows the old adage, “An apple a day keeps the doctor away.” This adage sticks with us to this day, yet the extent to which it is true is not widely known. How do apples really keep us healthy? Why doesn’t the expression involve oranges, blueberries, or better yet, the highly-touted cranberry? Can apple juice or apple sauce suffice? Is it because apples are America’s fruit (i.e. “As American as apple pie”) or is there something truly special about the revered apple?
State of US Health
The health of the United States population as a whole is worsening every year as we continue to lose the battle of the bulge and as chronic diseases cripple our nation. According to the World Health organization, in 2004, 66.3% of the adult population had BMIs qualifying them as overweight (Ogden, et al., 2006). Furthermore, diabetes rates reached 12.7% of adults over 50 in 2002 (CDC, 2003). Overall, 31% of all deaths in 2002 were due to causes related to obesity and diabetes (WHO, 2002). One explanation for these poor health statistics may be that 76.4% of US adults in 2003 reported eating less than the recommended five fruits and vegetables per day (CDC, 2004). As the health measures all appear to be inversely proportional to fruit and vegetable intake, one wonders whether this relationship has a scientific basis.
The Apple of Our Eyes: Popular Knowledge
Many believe apple consumption will help alleviate these negative
health outcomes. The US Apple Association makes various claims about the health benefits of eating apples. These claims include: reducing the risk of cancer, the risk of coronary heart disease, cholesterol, asthma, and hypertension (USAA, n.d.). The association’s website even states, “Apple juice was one of the earliest prescribed antidepressants” ( NY Apple Country, n.d.). (USAA, n.d.). Clearly, the US Apple Association disseminates this knowledge in order to increase apple sales and may be presenting some of this information as only applicable to apples, while the claims presented may also be generalized to include other fruits and/or vegetables. However, these beliefs of apples’ potential are not limited to the apple-distributing community. In fact, West Virginia’s Clay County holds the “An Apple a Day Keeps the Doctor Away” festival every year “that focuses on the history and nutritional importance of the Golden Delicious apple while encouraging daily consumption of this fruit for nutritional benefits and lifestyle adaptation” (AMS, 2007).
Definitions of Terms
Before we get into the scientific basis to the benefits of apples, here are some useful definitions:
-Phtyochemical: Also called phytonutrient. any of various bioactive chemical compounds found in plants, as antioxidants, considered to be beneficial to human health.
-Antioxidant: an enzyme or other organic substance, as vitamin E or beta carotene, that is capable of counteracting the damaging effects of oxidation in animal tissues.
-Flavonoid: Any of a large group of water-soluble plant pigments, including the anthocyanins, that are beneficial to health. Also called bioflavonoid.
All definitions courtesy of www.dictionary.com.
Getting to the Core: Literature Review
Given the wide belief in the “Apple a day…” adage, researchers investigated multiple facets of this claim. One such researcher proposes that “one of the mechanisms by which the consumption of apples (and other fruits and vegetables) is beneficial to health is because of the anti-viral properties of the phytoestrogens that they contain” (Martin, et al., 2007). Though there are two classes of phytoestrogens—flavonoids and non-flavonoids—the flavonoids are most active in fruits such as apples.
The main phytoestrogen found in apples is quercetin, but the small amount of genistein also plays a critical role. In analyzing several studies, Martin, et al. determined that apples help prevent viruses by inhibiting virus entry, signaling pathways, viral protein synthesis, and stages of the viral cycle, as well as limiting host tissue damage. By inhibiting certain kinases, phosphorylation is prevented, thereby, stopping the “virus-induced events important for viral entry and infection” (Martin, et al., 2007). Once phosphorylation is stunted, the signals that put the virus’s path in motion are cut off, and the virus cannot synthesize its proteins within the host (Martin, et al., 2007).
Another meta-analysis, by Boyer and Liu in 2004, also comments on the functions of phytochemicals, but instead of viruses, discusses the phytochemical role in preventing chronic diseases. Due to the popularity of apples in this country, apples comprise 22% of all flavonoids consumed in the US (Boyer and Liu, 2004). Also vital to an apple’s health benefit are its antioxidants which help to prevent stress on the body, thereby reducing the risk of chronic conditions.
Specifically focusing on cancer, Boyer and Liu cited several studies in which apple intake was associated with reduced risk in lung cancer. While reduced risk of lung cancer was found with diets rich in fruits and vegetables in general, “apples were the only specific foods that were inversely related to lung cancer risk” (Boyer and Liu, 2004). One of the studies included in their analysis questioned whether intake of the flavonoids found in tea could produce similar results, but no association was found between tea flavonoids and cancer risk reduction (Boyer and Liu, 2004).
In the cardiovascular disease section of their analysis, Boyer and Liu reference studies conducted in Finland. In the Finnish study, “women ingesting the highest amounts of flavonoids had a 35% reduction in risk of cardiovascular events” (Boyer and Liu, 2004). When considering apples alone with no other sources of flavonoids, apple intake accounted for a 13-22% decrease in risk (Boyer and Liu, 2004). These studies not only strongly suggest the protective factor of apples against heart disease, but also highlight the fact that apples in particular are responsible for the decrease in risk and not just fruits and vegetables in general.
Boyer and Liu’s analysis also addresses the source of the flavonoids in apples. Their research found that “apple peels contain … two to three times more flavonoids in the peels when compared to the flesh” (Boyer and Liu, 2004). Also, “the antioxidant activity of these peels was also much greater, ranging from two to six times greater in the peels when compared to the flesh, depending on the variety of the apple.”
Along the same lines as this research, Liu conducted another analysis in which he questioned whether eating the whole fruit was necessary for its health benefits or if taking a supplement containing the same antioxidants was sufficient. However, he found that simply taking the supplements did not produce the same results, perhaps because “the isolated pure compound either loses its bioactivity or may not behave the same way as the compound in whole foods” (Liu, 2003).
Long before science had the capabilities to prove that “an apple a day keeps the doctor away,” people have believed in the powerful health benefits of apples. Now that technology developed to a point where scientists could test the claim, more and more evidence has been found to support the hypothesis. Apple intake is associated with reduced risks of cancer, cardiovascular disease, and viruses among many other health benefits. Furthermore, these benefits have been linked specifically to apples and not just to fruits and vegetables on the whole or dietary supplements of apples’ active ingredients.
However, what most of the analyses seemed to ignore is the fact that the incorporation of fruits and vegetables into an individual’s diet usually supplants other foods. Therefore, it’s possible that the substitution of food higher in fat and calories with low calorie, zero fat fruits and vegetables is a protective factor in its own right. Perhaps if these fattier foods were taken out of the diet without the addition of fruits and vegetables, similar health benefits would be seen.
In any regard, one would be hard pressed to find research in which fruits and vegetables hurt one’s health, and thus, it would be wise to consume a diet rich in fruits and vegetables regardless of how the association between improved health and increase fruit and vegetable intake is reached. All in all, according to the literature, an apple a day might actually keep the doctor away—but don’t forget the peel!
AMS, Fruit and Vegetable Program Specialty Crop Block Grant Program Fiscal Year 2007 Awards. AMS, 1-30. Retrieved Oct. 7, 2008, from http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=STELPRDC5069113.
antioxidant. (n.d.). Dictionary.com Unabridged (v 1.1). Retrieved October 08, 2008, from Dictionary.com website: http://dictionary.reference.com/browse/antioxidant
Apple and Stethescope. (n.d.). Retrieved Oct. 7, 2008, from http://www.istockphoto.com/file_closeup/food-and-drink/fruits-and-vegetables/5415608-stethoscope-and-apple-on-a-white-background.php?id=5415608.
Apples. (n.d.). Retrieved Oct. 7, 2008, from appleslapbook.tumblr.com/.
Boyer, J., & Liu, R. (2004). Apple phytochemicals and their health benefits. Nutrition Journal, 3, 3-5. Retrieved Oct. 3, 2008, from the PubMed database.
Death and DALY estimates by cause, 2002. Oct. 7, 2008, from the World Health Organization database.
Eat More Rainbows. (n.d.). Retrieved Oct. 7, 2008, from blog.attuningwithyoursoul.com/.../3720896.html.
flavonoid. (n.d.). The American Heritage® Dictionary of the English Language, Fourth Edition. Retrieved October 08, 2008, from Dictionary.com website: http://dictionary.reference.com/browse/flavonoid
Ham, S. (2004). Behavioural Risk Factor Surveillance System. Centers for Disease Control and Prevention. Retrieved Oct. 6, 2008, from http://www.who.int/infobase/reportviewer.aspx?rptcode=ALL&uncode=840&dm=16&surveycode=100976a2.
Ham, S. (2003). National Health Interview Survey. Centers for Disease Control and Prevention. Retrieved Oct. 6, 2008, from http://www.who.int/infobase/reportviewer.aspx?rptcode=ALL&uncode=840&dm=2&surveycode=101259a2.
Lui, R. (2003). Health benefits of fruit and vegetables are from additive combinations of phytochemicals. The American Journal of Clinical Nutrition, 78(3), 517S-520S. Retrieved Oct. 3, 2008, from http://www.ajcn.org/cgi/content/full/78/3/517S.
Market. (n.d.). Retrieved Oct. 7, 2008, from www.agr.state.nc.us/.../apples/recipes.htm.
Martin, J., Crotty, S., Warren, P., & Nelson, P. (2007). Does an apple a day keep the doctor away because a phytoestrogen a day keeps the virus at bay? A review of the anti-viral properties of phytoestrogens. Phytochemistry, 68(3), 266-274. Retrieved Oct. 8, 2003, from http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TH7-4MM2644-2&_user=86629&_coverDate=02%2F28%2F2007&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_version=1&_urlVersion=0&_userid=86629&md5=c76a7e4f5d2f152cfc1a00c3943a67bd.
NY Apple Country Cancer Findings. (n.d.). Retrieved Oct. 7, 2008, from http://www.nyapplecountry.com/cancer.htm.
Ogden, C., Carroll, M., Curtin, L., Mcdowell, M., Tabak, C., & Flegal, K. (2006). Prevalence of overweight and obesity in the United States, 1999-2004. JAMA, 295(13), 1549-1555. Retrieved Oct. 7, 2008, from the WHO Global InfoBase database.
Phytochemical. (n.d.). Dictionary.com Unabridged (v 1.1). Retrieved October 08, 2008, from Dictionary.com website: http://dictionary.reference.com/browse/phytochemical
Southwest Airlines Careers. (n.d.). Retrieved Oct. 7, 2008, from http://southwest.com/careers/freedom_health.html.
US Apple: Consumers - An Apple A Day: Apple Nutrition Facts. (n.d.). Retrieved Oct. 4, 2008, from http://www.usapple.org/consumers/dailyapple/nutrition.cfm.
US Apple: Consumers - Apple Bits: Juicy Apple Stories. (n.d.). Retrieved Oct. 4, 2008, from http://www.usapple.org/consumers/applebits/stories.cfm.
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