Another apple to keep your eye on - one of several native fruits in Sri Lanka, the wood apple has amazing nutritional value and can used eaten to treat various ailments. Inside the hard shell is a soft, fibrous pulp which contains several vitamins, and organic compounds like calcium, fibre, phosphorous, protein, and iron. In Asia, the fruit is eaten to treat everything from constipation and indigestion, to ulcers and diarrhea. It is also known to boost the immune system, prevent cancer, fight infections and bacteria, reduce inflammation and increase milk production for nursing mothers.