This section is from the book "Meals Medicinal", by W. T. Fernie. Also available from Amazon: Meals Medicinal: With "Herbal Simples" Curative Foods From the Cook in Place of Drugs From the Chemist.
The Hazel Nut is wild, and the Filbert is got from the same tree when cultivated. Formerly the Hazel was a very abundant, indigenous tree throughout England. Filberts are superior nuts for dessert, being free from oil, and therefore seldom disagreeing. In 1897 a number of physicians in various parts of Europe made experiments for deciding as to the nutritive, and medicinal properties of all kinds of Nuts, and published their conclusions, favouring the use thereof in both capacities under certain conditions. One fact advanced was that Nuts contain a special kind of salt, particularly adapted for softening, and lubricating the muscular coats of arteries. Some of these physicians asserted that elderly persons would be benefited by a more liberal Nut diet; but Nut-meats must be thoroughly masticated, or finely pounded, so that no hard, insoluble pieces may reach the intestinal canal. Nuts are practically devoid of such carbohydrates as starch, and sugar, except cellulose, whilst rich in proteid, and fat; they may therefore be given with advantage in almost every case of diabetes.
The fatty matter predominates in their composition, and by reason of this fat various Nut-butters have been prepared, which are actually quite as nutritive as ordinary butter, and more economical; nevertheless, they are not readily digested in the stomach, partly because their fat is often rancid, and partly because their structural cellulose is so firm, and close, and compact.
"The sweetest nut hath sourest rind; Such a nut is Rosalind." - As yon like it.
For persons whose teeth are defective, Nuts may be ground in a small nut-mill, as made for the purpose. Grated nuts are an excellent addition to stewed fruits; they are much in favour with vegetarians. Roasted Hazel Nuts (first removing the skin thereof by rubbing them when hot) are excellent with bread and butter. The Hazel Nut (Coryllus avellana) contains an abundant supply of vegetable oil, and is therefore of service (to persons who can digest it) for keeping up the bodily warmth in cold weather. Nut sandwiches are popular in New York, made with brown bread, buttered, and cut in very thin slices, which are then sprinkled with chopped Nuts.