Fruit consumption is associated with improved health outcomes. In particular those who consume more fruit have been observed to have lower rates of Western lifestyle diseases such as cancer, cardiovascular disease and obesity. The reason that fruit is beneficial to the health is not known, but likely relates partly to the nutrient content of the fruit and partly because consumption of fruit tends to be at the expense of other foods that may be less healthy. Apples have been extensively researched for their health effects and the findings from such studies support the contention that they are protective of disease. Apples like most fruits contain sugars, but the sugars content of apples is low, and apples do not cause the stimulation of large quantities of insulin. This likely relates to the water and fibre content of the fruit, as well as the type of sugar present. The water and fibre in apples limits the amount of sugar that can be ingested because the water decreases the concentration of the sugars and the fibre provides bulk which slows ingestion rates. The sugars in apples are also not rapidly absorbed. The pectin may also have other beneficial health effects such as decreasing postprandial glycaemic effects of other foods, lowering cholesterol levels, and stimulating the growth of beneficial gut bacteria.
Apples are also a good source of polyphenols. Polyphenols are plant metabolites that are used for host defence. Plants use polyphenols to protect from environmental damage including ultraviolet light, parasites and pests. When we ingest apples, we consume a range of polyphenols that have been shown to be bioavailable. The main polyphenolic substances found in apples include flavonoids, hydroxycinnamates and chalcones. The flavonoids in apples include quercetin and epicatechin, both of which have been shown to possess beneficial health effects. Epicatechin is also present in green tea and may partly responsible for the benefits of drinking green tea. Quercetin is a common flavonoid in many fruits and vegetables and has been shown to cause anti-cancer effects in human cells. Polyphenols may be beneficial to human health because they have antioxidant effects, and in this respect can reduce inflammatory. Polyphenols also possess anti-microbial, anti-cancer and cardioprotective effects. The polyphenolic and fibre content of apples is concentrated in the skin and so consuming the skin with the rest of the pulp is an important nutritional consideration if health is a concern. Other beneficial substances in apples include the phenolic phloretin, as well as vitamin C and minerals.