Fruit and vegetables contain phytochemicals, which are substances such as carotenoids, flavonoids and phenolic acids. Scientists have identified thousands of them, but many more are still to be discovered. They are responsible for many of the benefits of fruits and vegetables, as they are anti-oxidants, which are molecules that help to protect you against the effects of free radicals.
Reactive oxygen species
Free radicals, such as reactive oxygen or nitrogen species (for simplicity we will call all of them “ROS”), are a normal by-product of your metabolism. They can cause cell injury and death, and your body has therefore a defence system of anti-oxidants to keep them under control.
Oxidative stress occurs when there are more ROS than your defences can handle, and leads to damage of your DNA, lipids and proteins. As this accumulates over the years, it results in ageing and increases your risk of chronic illnesses such as cardiovascular disease and cancer. An effective anti-oxidant system can therefore slow down aging and help to prevent chronic disease.
As there are many different ROS, your body needs many different anti-oxidants. Your body can make some of them itself, but others have to come from your diet, and vegetables and fruits are a good source.
ROS are not totally bad though, as they are important for cell growth and inflammatory reactions. Destroying all of them is thus harmful; your body just has to be able to regulate them. The advantage of getting your anti-oxidants from your diet is that your body is able to pick and choose what it needs, and to let go what it has already in abundance.
Health effects of apples
Epidemiological studies have shown that people who eat apples on a regular basis suffer less from lung cancer, cardiovascular disease, asthma and type II diabetes. Eating apples has also been linked to weight loss.
Laboratory studies have shown that the total anti-oxidant activity of 100 g apple with peel corresponds to 1500 mg vitamin C. As 100 g apple contains only 5.7 mg vitamin C, most of this anti-oxidant activity must come from a variety of phytochemicals. Researchers believe that these substances complement and stimulate each other, so that together they achieve much better results than the individual substances could ever do. This explains why it is so important to eat whole-, unprocessed foods.
Most of the anti-oxidants are in the peel. Consequently, apple juice is less good for you than the whole fruit, even though it is still a good source of anti-oxidants.
Apples lower your cholesterol levels by reducing its absorption, and research has shown that this due to the combined effects of fibres and phytochemicals.
In the lab, studies on cell cultures have demonstrated that apple can decrease the proliferation of cancer cells. Again, this was more pronounced when apples with peels were used. Different varieties of apples had different effects on cancer cells, suggesting that the unique combination of phytochemicals of each variety is important.
Researchers have noticed that different varieties of apples contain different kinds and amounts of phytochemicals. For example, Rome Beauty apples have a high phenolic content, while Jonagold contain plenty of quercetin. In general, there are more phytochemicals in sun ripened fruit than in fruit that has grown in the shade. Storage on the other hand, does not have much effect.
Do not waste the peels
As mentioned earlier, most of the phytochemicals are situated in the peel. By processing apples to make juice or puddings, we lose much of the health benefits of apples, unless, of course, we could keep the peels. Research has shown that blanching them for 10 seconds and then air- or freeze-drying them conserves most of the phytochemicals. The treated peels could then be used in food, or turned into a powder to promote health.
How could we use apple peels in food? If you have any ideas, please let us know.
Boyer J and Lu RH. Apple phytochemicals and their health benefits. Nutr J. 2004; 12: 3-5.
Lu RH. Potential synergy of phytochemicals in cancer prevention: mechanism of action. J Nutr. 2004; 134 (12 Suppl): 3479S-3485S.
Wolfe KL and Lu RH. Apple peels as a value-added food ingredient. J Agric Food Chem. 2003; 51(6):1676-1683.