Apples - do they really keep the doctor away?

Is there any truth to the old saying, "An apple a day keeps the doctor away"? Well in fact there is.

The new wave of food chemistry which is influencing health-thinking is largely about so-called phytochemicals. For apples, whereas they were previously thought of as contributing mainly dietary fibre, water and physical structure to food intake, with little in the way of micronutrients, they are now seen to be of much greater potential health significance.

Apples contain antioxidant vitamins, but they only make up a small proportion of the antioxidants in apples. Apples, especially apple skins, are also high in the antioxidant phytochemicals such as flavonoids and polyphenols (including epicatechins, quercetins and chlorogenic). Research has indicated that phytochemicals found in apples could be responsible for the prevention of heart disease and certain cancers.

Vitamin C only accounts for less than 10% of the antioxidant capacity of apples. The balance is derived from the phenolic antioxidants. Cornell researchers found that eating 100g of fresh red delicious apples with skins provided the total antioxidant activity equal to 1,500 milligrams of vitamin C (Eberhardt et al. 2000). Oxidation is a natural process in the body that can lead to cell and tissue damage, and may also lead to more serious problems such as cancer, cardiovascular disease and cataracts. Antioxidants are substances which delay or prevent deterioration caused by oxygen.

Phytochemicals found in apples are not only potent antioxidants, they can also help prevent inflammation and blood clotting (important for preventing heart disease), and prevent the proliferation and spread of cancer cells.

A study conducted at the UC Davis School of Medicine in California (Published in the Journal of Medicinal Food, Winter 2001) showed that eating 2 apples or 2 small glasses of 100% apple juice daily for 6 weeks (without changing anything else in their diets), helped reduce the oxidation of 'bad cholesterol' or LDL. When LDL becomes oxidised, it is more likely to form plaques along the walls of blood vessels and cause atherosclerosis - a process that can lead to the development of heart disease. The study participants consumed several varieties of apples like Fuji, Golden delicious, Granny Smith and Red Delicious.

Apples are also an excellent source of pectin, a soluble fibre found in most fruits and vegetables. A number of studies have shown that pectin helps reduce cholesterol.

Another study reported that participants who ate the most apples had the least risk from thrombotic stroke (Knekt et al., 2000).

The antioxidants in apples, especially in the skin, are also thought to be helpful in cancer prevention, by decreasing oxidative damage to DNA and preventing uncontrolled cell division.

It has been reported by the US National Cancer Institute that the flavonoids found in apples may reduce the incidence of lung cancer by as much as 50%. A study in Finland showed that the likelihood of developing lung cancer among those who ate the most apples fell by 57% relative to those who ate the least amount of apples (Knekt et al. 1996).

Using colon cancer cells treated with red delicious apple extract, the scientists at Cornell University found that cell proliferation was inhibited. Colon cancer cells treated with 50milligrams of apple extract from the skins were inhibited by 43%; by contrast, the apple flesh extract inhibited colon cancer to a lesser extent (by 29%) (Eberhardt et al. 2000).

The anti-cancer effect was strongest in extracts made from unpeeled apples, probably because the skin contains more antioxidant phytochemicals than the flesh.

Apples may also be helpful in improving lung function. A British study reported that men who eat at least five apples a week experience better lung function (Butland et al. 2000).

Consumption of apples (and other antioxidant rich foods) was recently reported to be associated with less skin wrinkling in a sun-exposed site. This study was conducted at Monash University by our editors (Professor Mark Wahlqvist, Dr A Kouris-Blazos) and a PhD student (Martalena Purba) (Purba et al. 2001). This study is the first study to show a relationship between diet and skin wrinkling and the possible benefit of apples in skin health (which could be attributable to the antioxidant activity of compounds present in apples). Click here to read more about this study.

According to Cornell University researchers grapes, pears and peaches exhibit higher antioxidant activity than apples; bananas are similar; oranges and grapefruits are lower. Among vegetables, garlic shows the highest antioxidant activity followed by broccoli and tomatoes, all of which are higher than apples. Other vegetables, such as spinach, carrots, onions and green pepper show some antioxidant activity, but not as much as apples.

Eating your apple with the skin on ensures that you get all of the phytochemicals the apple has to offer.

Also, eat a variety of different apples because the amount of phytochemicals in the apple flesh and in the skin varies from variety to variety, year to year, season to season and from growing region to growing region.

For example, according to Cornell University researchers apple varieties such as Northern Spy, Liberty, Crispin, Delicious and Fuji have be shown to have high antioxidant activity; Idared, Jonagold, Gala, Freedom, and McIntosh apples medium activity, while Empire, Ginger Gold, NY674 and Golden Delicious apples were relatively low. The difference in antioxidant activity among apple varieties is due to the varying composition and concentration of specific phenolic compounds.

Find out about different apple varieties and what time of the year they are picked in Australia at the Wild About Fruit web site.

Although intact fresh apples are preferable, apple juice is also good (especially if you can't eat in tact apples for some reason). Ideally the apple juice should be 100% unfiltered and contain the entire apple and skin, such as "Wild about Fruit", where the juice is extracted from the entire fruit, retaining the flavonoids and nutrients.

So yes, an apple a day can keep the doctor away. Not only do apples taste great, they are also very good for your health. Apples are a convenient, fast snack to have on hand. They need no preparation or packaging, throw one in your bag to take to work, or put one in the kids' lunch boxes as a snack.

Butland BK, Fehilyb AM, Elwood PC. Diet, lung function, and lung function decline in a cohort of 2512 middle aged men. Thorax 2000; 55:102-108 ( February ).

Eberhardt M.V, Chang Yong Lee, Rui Hai Liu. Antioxidant activity of fresh apples. Nature, 22 June 2000, Vol. 405, pp. 903-904.

Interview with Dr Normal Swan - The Health Report, ABC Radio.

Knekt P, Jarvinen R, Seppanen R, Hellovaara M, Teppo L, Pukkala E, Aromaa A. Dietary flavonoids and the risk of lung cancer and other malignant neoplasms. Am J Epidemiol 1997 Aug 1;146(3):223-30.

Knekt P, Isotupa S, Rissanen H, Heliövaara M, Järvinen R, Häkkinen S, Aromaa A, Reunanen
A. Quercetin intake and the incidence of cerebrovascular disease. European Journal of Clinical Nutrition, May 2000, vol. 54, no. 5 pp. 415-417.

Purba M, Kouris-Blazos A, Wattanapenpaiboon N, Lukito W, Rothenberg E, Steen B, Wahlqvist ML. Skin Wrinkling: Can food make a difference. Am Coll Nutr, 2001: 20 (1); 71-80. On-line abstract and for citation and International health reuter.

Last Updated: November 1, 2001.