Apple Health Research

The health benefits of apples and apple products were first recorded as early as medieval times, giving rise to the old English saying “Ate an apfel avore gwain to bed Makes the doctor beg his bread” and its more recent variation, “An apple a day keeps the doctor away.” Apples’ healthy attributes have received considerable renewed interest recently, following the publication of several studies linking apple nutrients to an impressive range of health benefits.

While apples do not naturally contain high amounts of well-known nutrients (e.g., vitamin C, folic acid), they are an excellent source of dietary fiber, while apples and apple juice are a regular source of potassium. Apples also have significant amounts of a wide array of important phytonutrients that research has found to have extremely important health benefits.

Following are summaries of health benefits studies that have been conducted to date on apples and apple products. Key findings are noted in bold.




Weight Loss

Weight Loss: Researchers from the State University of Rio de Janeiro studying the impact of fruit intake on weight loss found that overweight women who ate just 300 grams of apples or pears – that’s the equivalent of three small fruits a day – lost more weight on a low-calorie diet than women who didn’t add fruit to their diet. In addition, the fruit eaters ate fewer calories overall, boosting their weight loss efforts. Researchers suggested several theories as to why apple and pear consumption may promote weight loss. First, fruits like apples and pears are “low energy-density” foods – that is, they have a relatively low calorie count compared to other non-fruit foods. Second, research has shown that eating a high-fiber diet (calorie intake being equal) promotes postmeal “satiety”, leaving subjects feeling fuller for longer. And finally, research has also established that eating a high-fiber diet decreases total calorie intake, thus contributing to weight loss. (Source: Nutrition, 2003, 19: 253-256)


Brain Health

Cognitive function, memory and learning: Researchers at the University of Massachusetts at Lowell report that nutrients in apples and apple juice may improve memory and learning, and may protect against oxidative damage that contributes to age-related brain disorders such as Alzheimer’s disease. Dr. Thomas Shea and colleagues assessed whether consuming apple juice might protect against oxidative damage that results from normal metabolism, dietary insufficiencies or genetic deficiencies. They found that adding apple juice to the diet protected “normal” mice from oxidative stress imposed by a deficient diet, and even improved their performance slightly on memory and learning maze tests. In fact, the apple juice diet also protected the genetically-deficient mice from both their genetic predisposition and the deficient diet, allowing them to perform at the same level as normal mice on the complete diet. While researchers did not study what components in apples were responsible for the neuroprotective effects demonstrated, they ruled out sugar and energy content, and suggested that the antioxidant potential of apples and apple juice was responsible. This study validated earlier in vitro findings. (Source: Journal on Nutrition Health and Aging, 2004, 8: 92-97)


Cancer

Prostate Cancer: Researchers at Rochester, Minn.’s Mayo Clinic report that quercetin, a plant-based nutrient found most abundantly in apples, may provide a new method for preventing or treating prostate cancer. Researchers found that quercetin inhibits reduced or prevented the growth of human prostate cancer cells by blocking activity of androgen hormones, in an in vitro (laboratory) study. Previous studies had linked androgens to prostate cancer’s growth and development. This is the first known study to link apples with a major men’s health issue. (Source: Carcinogenesis, 2001, 22: 409-414)

Colon and Liver Cancer: Researchers at Cornell University report that phytonutrients in apples inhibited the growth of colon cancer and liver cancer cells in vitro. While the beneficial phytonutrients were most strongly concentrated in the apple skin, the apple flesh also contained significant levels of phytonutrients. According to the Cornell researchers, 100 grams of unpeeled fresh apple – about two-thirds of a medium-sized apple – provides the total antioxidant activity of 1,500 milligrams of vitamin C. (Source: Nature, 2000, 405: 903-904)

Lung Cancer: Researchers at the University of Hawaii found that increased consumption of quercetin was associated with a reduced risk of lung cancer in this population-based, case-control study involving 600 lung cancer patients and 600 cancer-free persons. Researchers investigating a possible relationship between the consumption of flavonoids and lung cancer risk found a statistically significant inverse association between lung cancer risk and intake of the flavonoid quercetin, found primarily in apples and onions, and the flavonoid naringin, found in white grapefruit. No association was found for important food sources of other flavonoids. This study validated similar findings published in 1997 (see the American Journal of Epidemiology study referenced below). (Source: Journal of the National Cancer Institute, 2000, 92: 154-160)

Cancer and Lung Cancer: Epidemiologists from Finland’s National Public Health Institute report that consumption of a flavonoid-rich diet – and particularly flavonoid-rich apples – was associated with a reduced risk of developing cancer. Their study of 9,959 cancer-free Finnish men and women, begun in 1965, revealed that people who regularly consumed the most flavonoid-rich foods – apples, onions, fruits, juices, vegetables and jams – during the 24-year study period were about 20 percent less likely to develop cancer. Researchers found that lung cancer was 46 percent lower among those whose diets contained the highest amount of flavonoids, particularly from apples. Of the major dietary flavonoid sources, apples showed the greatest inverse association with lung cancer incidence. (Source: American Journal of Epidemiology, 1997, 146: 223-230)


Lung Health

Asthma: Australian researchers studying the relationship between diet and asthma report that, among the fruits and vegetables they studied, eating apples and pears appears to provide the best protection against asthma. The cross-sectional Australian study involved 1,607 young adults aged 20-44 American Journal of Clinical Nutrition Of all the fruits and vegetables evaluated, study participants who ate apples and pears had the lowest risk of asthma. The researchers noted that more study is needed to determine whether changes in diet could be used to prevent asthma or lessen its severity. (cite: American Journal of Clinical Nutrition September 2003; 78; 414-21)

Asthma: Researchers from London’s King’s College and the University of Southampton report that people who ate at least two apples per week had a 22-32 percent lower risk of developing asthma than people who ate fewer apples. Their conclusions were based on a population-based case-control study of 1,471 adults in the United Kingdom that sought to examine how dietary antioxidants might affect asthma risk and severity. (Source: American Journal of Respiratory and Critical Care Medicine, November 2001, volume 164, number 10: 1823-1828)

Lung Function: Researchers from the University of Nottingham in the United Kingdom report that apple eaters have better lung function and lower risk of respiratory disease such as asthma than non-apple eaters, based on a nine-year population study of 2,633 adults. This study’s findings are similar to previous findings (see the Journal of the National Cancer Institute and Thorax studies referenced below.) (Source: American Thoracic Society, unpublished findings presented at the society’s Annual Meeting, May 2001, poster 618)

COPD: Researchers from the University of Groningen in the Netherlands report that eating fruits and vegetables, and in particular an apple a day, may reduce smokers’ risk of developed chronic obstructive pulmonary disease (COPD), based on their case-control study of long-term heavy smokers. This is the first known study to suggest smokers could benefit from increased apple consumption. (Source: American Thoracic Society, unpublished findings presented at the society’s Annual Meeting, May 2001, poster 617)

Lung function: British researchers report that apple eaters had better lung function than non-apple eaters, as measured by forced expiratory volume. Investigating an hypothesized association between diet and lung function, researchers at London’s St. George’s Hospital found a strong positive association between lung function and the number of apples eaten each week after analyzing dietary records and health outcomes of a study group of 2,512 men studied for five years. Although it had been suggested by other researchers that vitamin C from fresh fruit was responsible for improving lung function, this research found to the contrary. Researchers postulated the healthful effect may be due to antioxidants in apples (e.g., flavonoids like quercetin.) (Source: Thorax, 2000, 55:102-108)


Heart Health

Fiber and coronary heart disease: U.S. researchers report that for every 10 grams of fiber consumed per day the risk of developing heart disease may decrease 14 percent, and the risk of dying from heart disease may decrease 27 percent. Fiber from fruits appeared to be slightly more protective than cereal fiber, lowering the risk of coronary disease death by 30 percent. {Apples are one of the best fruit sources of fiber; one medium-tennis ball-sized apple (154 grams) contains 5 grams of fiber.) Findings were based on researchers' pooled analysis of data from 10 recent prospective cohort studies in the United States and Europe involving 91,058 men and 2345,186 women that measured the amount of fiber in participants’ diets over a period of 6-10 years. Findings challenge the potential long-term health costs of low-/no-carbohydrate diets that discourage consumption of high-fiber carbohydrates in the process. (Source: Arch Int Med, vol. 164, no. 4, Feb. 23, 2004; 370-376)

LDL Oxidation: Researchers at the University of California-Davis report that daily consumption of apples and apple juice may help reduce the damage caused by the “bad” type of cholesterol and protect against heart disease, based on the first human study of its kind. Researchers demonstrated that apples and apple juice may help to slow the oxidation process that is involved in the build-up of plaque that leads to heart disease. Clinical study participants added only two apples, or 12 ounces of apple juice, to their diet. This study validated earlier in vitro findings (see the Life Sciences study referenced below.) (Source: Journal of Medicinal Food, 2000, 3: 159-165)

LDL Oxidation: Researchers at the University of California-Davis reported that phytonutrients in apples and apple juice prevent oxidation in vitro of the “bad” (LDL) cholesterol, and thus may help protect against cardiovascular disease. They also confirmed that important phytonutrients from apples are also found in apple juice. While both foods varied in the levels of phytonutrient concentrations, both inhibited oxidation of LDL cholesterol, which can lead to unwanted build-up of harmful plaque in arteries. (Source: Life Sciences, 1999, 64: 1913-1920)

Coronary Mortality: Finnish epidemiologists concluded that high consumption of flavonoids from apples and onions was directly associated with the lowest risk for coronary mortality. This conclusion was based on their analysis of diet and health outcomes of a study of 5,133 Finnish men and women aged 30-69 who were initially free of heart disease when the study began in 1967. (Source: British Medical Journal, 1996, 312: 478-481)


Stroke

Thrombotic Stroke: Finnish researchers report that persons who ate the most apples had the lowest risk of thrombotic stroke, possibly due to the phytonutrients found in the apples. This conclusion was based on evaluation of dietary records and health outcomes of 9,208 men followed for 28 years. Unlike findings from other epidemiological studies, the researchers attributed this positive association to phytonutrients other than quercetin found in apples (e.g., catechins), demonstrating apples’ broad phytonutrient content. (Source: European Journal of Clinical Nutrition, 2000, 54: 415-417)


Other Studies

Chronic Disease Risk: Finnish researchers report that components found in apples may keep the doctor away by reducing the risk of many chronic diseases, including heart disease, cancer, stroke, type 2 diabetes and asthma. Conclusions drawn by researchers at the National Public Health Institute in Helsinki, Finland, were based on ongoing research of 10,054 Finnish men and women that began in 1966. They sought to study the potential association between intake of flavonoids and reduced risk of several chronic diseases. (Source: American Journal of Clinical Nutrition, 2002; 76: 560-8)


Updated March 2004