They are ...
...
Apples (one 125g serving) contain more nutrients per gram than most foods out there.
They are a source of Vitamin C, Vitamin K, and Folate. These flavonoids have strong antioxidant properties with many health benefits.
One cup of fresh, chopped apple contain 10% of daily recommended levels of vitamin-C. Vitamin-C is a moderately powerful antioxidant, which may help the human body develop resistance against infectious agents and attack the harmful oxygen free radicals.
Apples are also an source of Vitamin K; 125 g of apple provide 3% of the RDA. Vitamin K, a great antioxidant, is required for blood clotting and building healthy bones.
Antioxidants such as the ones found in apples are said to be essential for boosting immunity. Some of these may play an important role in helping improve your immune system to fight off flu and other viruses.
Eat and be healthy.
...