The intriguing jak fruit is extremely nutritious and medicinal. Jak (Artocarpus reterophyllus) comes in two varieties in Sri Lanka. They are soft or 'vala' and hard or 'waraka'. The latter is more popular than the soft. The bark of the jak tree is used mainly for medicinal purposes including sprains and fractures.
Tender jak which is known as 'polos', can be made into a delicious curry and, in the diet of ancient Lankan royalty this was a dish that was rarely absent. Nursing mothers are given 'polos' and boiled jak to increase milk. 'Polos' curry also helps those recovering from diarrhoea, because 'vala' or the soft ripe jak is a laxative which can be eaten as it is. It helps clear the bowels and assists in digestion. It also helps relieve bronchitis when kept in bees honey and given to the patient each morning. 'Waraka' or the hard jak variety is beneficial to diabetic patients.
The leaves are dried, powdered and made into a coffee-like drink to be given to diabetics. According to an ancient recipe the ripe jak leaves are pounded and fried in gingili (sesame) oil and given to the diabetic patient each day. It is hard to imagine that such a simple recipe can be a cure for diabetes but the fact that it has been mentioned often in ancient books is proof of its efficacy.