F. A. Cajorie, Yale University, New Haven, Conn.
Mr. President and members of the Northern Nut Growers' Association: It was with great pleasure that I accepted the invitation of your Association to be present at this convention and give a discussion of nuts and nut production, from the point of view of their nutritive or food value. During the last few years our knowledge of nutrition and the parts that individual foods may play in the diet has been greatly increased and in the light of the new discoveries, it is interesting and valuable to view the place that nuts hold.
As you are well aware, nuts have been used as foods by the peoples of the world. In many places nut products have made up a very appreciable part of the diet. Chestnut flour is extensively used in Southern Europe. Among the peasants of Tuscany, chestnut flour forms a considerable part of the total diet. In this region, also ground acorns are made into bread with cereal flours and in this form is a common food. The hazel or filbert nut is also seen in the form of flour on the shores of the Black Sea. Races living in the tropics have utilized the many varieties of nuts indigenous to tropical climes such as the coconut, Brazil nuts, Java almond, Paradise nut, candle nut and African cream nut. In the Orient, the lichi, ginko and water chestnut, and in Italy and India the varieties of the pine nut are used to considerable extent.
In America, with the exception of a few localities and among a limited class of people, nuts have never made up a staple part of our dietaries, rather they have been used as tasty supplements to otherwise complete menus. That they are prized as adjuncts and are sought after is strikingly shown when we see in our markets not only the products of our native American nut trees, the hickory, walnut, butternut, chestnut, pecan, beechnut and pinion, but the Brazil nut, filbert, English walnut, peanut, coconut, all of which are derived from foreign countries or from trees originally imported to America from other lands.
Analysis of nuts have shown them to be of two types, one rich in fats and protein, the nitrogen containing component of our foods and the other relatively rich in carbohydrates, or starches. With the exception of the chestnut, and the coconut, most of our more common nuts belong to this first class, and chemists have pointed out that in these nuts we have a concentration of protein and fat seen in no other class of foodstuffs. For example, the protein-fat rich nuts have a percentage of protein varying between 15 and 30% and a fat content of 50-70%; compare this with other foods that we think of as being concentrated; eggs, 12% protein and 10% fat; cheese 28% protein, 37% fat; round steak, 20% protein, 14% fat; and bread, 10% protein. This nutritive concentration in nuts places them in a unique position among our natural food products. Our cereals, meats, fruit and vegetables all contain more or less water or refuse that reduces their concentration, while in nuts we find a compact form of almost pure food.
We are dependent on foods for the source of energy that is necessary to perform our work and maintain our body temperature much in the same way that a steam engine is dependent on the fuel supplied it to perform the mechanical tasks assigned to it, and this fuel value of foods in turn, depends on the amount of protein, carbohydrate and fat, particularly the latter, that are present in the foods. At once we see, in our concentrated nuts, a tremendous source of energy, provided that we can digest these nuts and make this energy available.
Despite the fact, as revealed by chemical analysis, that in nuts we have a source of protein and fat in a concentration rarely seen in foods, there have been relatively few experiments to actually determine the digestibility. Prof Jaffa at the California Experiment Station was the first to make a comprehensive investigation along these lines. He made extensive digestion tests on men using most of the more common American nuts. His results, as reported in a bulletin of the U. S. Department of Agriculture, indicated that nuts when they made up a substantial portion of the diet, were well digested by those who ate them and gave no intestinal disturbance or discomfort.
Nuts have had a reputation for indigestibility that was wide spread, not only among people in general, but also among physicians and dieticians, and even Prof Jaffa's clear cut experiments failed to dispell this idea of indigestibility that had been empirically assigned to nuts. A few years ago, a rather extensive series of digestion experiments were inaugurated at Yale University in an effort to settle this question of the indigestibility of nuts and also to test out some of the commercial nut products to find what effect roasting, boiling, and other processes that nuts are subjected to, had to do with the digestibility. Through the courtesy of Dr Kellogg of Battle Creek, it was possible to follow up these experiments with a series here at Battle Creek. It is the result of these tests that I wish to speak of today. One word regarding the method which is the conventional one for such experiments. The amount of food eaten by the individual or animal is weighed at each meal and the composition determined by chemical analysis. The intestinal output is collected, weighed and analysed. From the difference in any substance such as protein in the food and the protein which appears in the body refuse, the amount digested and absorbed or utilized by the body is easily determined. For example; if 10gms. of nitrogen were eaten in the food and one gm appears in the feces, we say that the coefficient of digestibility of that nitrogen is 90%, that is 9 of the 10 gms. eaten were absorbed by the body. The average of a great many such tests on mixed diets has the following standard coefficient: protein 93%, fat 95%, and carbohydrates 98%.
Our digestion experiments show the following results: for protein digestion of nuts, almond 89%, peanut 84%, pine nut 89%, Eng. walnut, 83%, Brazil 88%, and coconut 88%. In all cases the carbohydrate coefficients are 98 or 99%, and in the case of the carbohydrate rich chestnut, normal digestion took place after the nut was heated so as to rupture the starch granules. In all of these cases the nut made up a substantial part of each meal and was eaten in large amounts. The experimental subject, experienced no digestive troubles or discomforture whatsoever except in the case of the English walnut, which evidently contains some irritating substance that causes diarrhea. Except for the pecan which gave rather low utilization, the protein of nuts was digested to a high degree that compares most favorably with our ordinary foodstuffs.
How then explain the undoubted discomforture that many people experience after eating nuts? I believe that the explanation rests on the fact that our common American way of eating nuts, is not the rational way. We would not consider topping off a heavy meal with eggs, meats or cereals or to eat these in large quantities between meals realizing that we are exposing ourselves to possible digestive discomfort. No more then, can we expect to so eat nuts which are even more concentrated or "heavy" than meat or eggs without occasional discomfort. Unpleasant results from so eating does not condemn the nuts as indigestible, rather it condemns our mode of using that nut. Further, we must recognize that the nut is a hard, compact substance and that unless completely masticated, is not readily penetrated by the digestive juices of the alimentary canal. This was very well brought out in our experiment with dogs. The dog bolts his food and where there were large fragments of the nut in the food, they appeared almost unchanged in the feces, while if the nut is ground fine before feeding, it was readily digested. Comparisons of nut butters and nut pastes with the whole nut also brought out this point. The completely commuted nut butters showed consistently higher degrees of digestion than the whole nut.
With the exception of the starch rich chestnut, the heating of the nut did not seem to effect the digestibility whether this heat was boiling, steaming or roasting. The raw nut apparently is as well digested as the heated products. No differences were found between nut butters whether the process involved steaming or roasting of the nut. I am not speaking of the enhancing of the flavor that heating may bring about, but only of the digestibility.
Dr. Longworthy and his co-workers in the Dept. of Agriculture have investigated in recent years the digestibility of many vegetable oils, among them nut oils, and have found as high a percent of utilization with these as with butter and our other common animal food fats.
I believe that we are fully justified in the conclusion that nuts and nut products, if rationally used in our diets, are as digestible and fully as valuable from a nutritional point of view as our other foodstuffs.
While we can now definitely speak of the high digestibility of nuts, it is necessary to consider other phases of the part played by foods in nutrition. The fact that a food after being taken into the body can be broken up by the digestive juices of the alimentary tract, and the products absorbed, as we have found, to be the case with the nuts, is not the end of the story of the function of that food.
About fifteen years ago, it was discovered that during the progress of digestion, the protein materials are reduced by the digestive juices of our stomachs and intestines to smaller chemical compounds, and that it is these smaller fragments of the protein molecule that are absorbed into the blood and are used to build up our muscles and tissues. These fragments or "building stones" as they have been fancifully called, are all of a distant class of chemical compounds known to chemists as amino acids. Eighteen of these acids have been found as the products of protein digestion.
We may conceive of our bodies as being continually supplied with a mass of these 18 building stones from which it selects the kind and number that it needs to repair the everyday wear and tear of the tissues and in the case of the growing child builds new structures.
Since the date of this important discovery regarding the fate of indigested protein, it has been found that with few exceptions, the body is not able to manufacture these amino acids or to change one kind into another, and must depend on the protein eaten, for a supply of the various kinds that go to make up the body protein. Further it has been found, that many of our commonly used food proteins do not contain all 18 of these amino acids components. In some foods one, two, and sometimes more are lacking, or if present are in very small amounts. If our diet contained only proteins of an inferior grade, we can picture our body requiring building stones of various kinds to maintain the structure of the body and unable to obtain them due to the poor quality of the food, protein. Nutritional failure would be the result. The proteins then must be of the right quality as well as present in the proper quantities, to prevent mal-nutrition. Bearing in mind these facts, it is necessary in studying a food such as our nuts, to determine the kind of protein the individual nut contains as well as to know whether or not it can be digested by the body.
During the past few years, it has been found that we must have in our foods a certain amount of substances whose chemical nature is at present unknown and to which the name of vitamines has been given. It is not my purpose to discuss with you the many phases of vitamines and their relation to nutrition, but I only wish to impress upon you the fact that it is of the utmost importance for a dietary to contain these substances; fully as important as that the protein, fat, carbohydrate, and inorganic salt content shall be satisfactory. Lack of these vitamines brings on various evidences of mal-nutrition. One vitamine which is found in animal fats and the leaves of plants and is soluble in, and associated with fats, is, for that reason, called fat soluble vitamine. Another called the water soluble vitamine is widely distributed in cereal seeds, vegetables, and legumes. The third, the so-called antiscorbutic vitamine because of its action as preventative and cure for scurvy, is found in certain fruits and vegetables.
We then ask the next question: Are nuts adequate as far as their proteins contain these essential amino acids, and do nuts contain vitamines? That is, is their biological value as satisfactory as their digestibility?
Dr. Hoobler of Detroit, in a study of the diets of lactating mothers and wet nurses, a year or so ago, compared the value of proteins from animal and vegetable sources for the elaboration of milk. He found that a mixture of the almond, English walnut, peanut and pecan, furnished proteins that were equal to the animal food tried, and far superior to other vegetable proteins. Here then is evidence that nuts provide the necessary building stones to form milk that food par excellence for the newly born individual. Drs. Mendel and Osborn, experimenting on white rats have shown that the principle proteins of the Brazil nut will maintain animals through the growing period. Bureau of Chemistry workers and others have found similar results with the coconut and the peanut. I have now, experiments underway at New Haven, on the biological value of the filbert, English walnut, pine nut, almond, and pecan. While these tests are yet incompleted, it can at least be said that to date there is no evidence that the proteins of these nuts are in any way less satisfactory than those of the peanut or Brazil nut that have been thoroughly tested out.
As to the vitamine content, abundant quantities of water soluble vitamine have been found in the peanut and the coconut. Experiments that we have in progress as well as a series conducted here at Battle Creek under Dr. Kellogg's direction give promise to increase this list of vitamine containing nuts to include at least many of our common nuts. Along with our vegetable oils in general, coconut oil and peanut oil contain insufficient quantities of the fat soluble vitamine to maintain growth in young animals. Whether the other nut oils will prove more efficacious in this respect, is now under investigation. As far as I am aware, the antiscorbutic properties of nuts have not been studied.
With the population of the world on a steady increase, it continually becomes necessary for mankind to seek out new sources of food, and utilize products that formerly had received little attention as possible foods. Conditions that disturb normal food production and distribution, such for example as were brought about by the world war, produce serious food shortages in the world, and emphasize how close is the margin that determines whether the peoples of the world have adequate quantities of food or whether they are faced by shortages, and, in many cases, by starvation. In this continual development of our food resources, nuts stand out prominently as offering possibilities which are very great. Not only do they represent a very concentrated form of food which is highly digestible, but they possess a number of characteristic and highly pleasing flavors that recommends them for use in all manner of culinary procedures. The variety of uses to which nuts can be put in the kitchen is amply demonstrated right here in Dr. Kellogg's sanitarium and I feel sure that even he has not exhausted the possibilities of nuts in the dietary. The forms of nut products on the market are steadily increasing. The nut butters, nut pastes, nut margarines, meat substitutes, and so forth, all point to the variety of ways that nuts can be handled as foods.
The tremendous increase in the use of nut oils in the form of the oil itself and as nut margarines within the last few years is a striking example of the utilization on a large scale of relatively new food products. The press cake which remains as a by-product of this oil industry finds ready use as concentrates for cattle feeds. Many of our ideas in the feeding of our domestic animals are undergoing development along with the idea of human nutrition. Just recently, investigators at the Wisconsin Experiment Station, reported that the well known "home grown ration" for dairy cows that consist of cereals, silage and hay, is not a large milk producing diet. Their recommendation is to supplement this ration with protein concentrates. Nut meals recommend themselves most highly as protein concentrates. It certainly is safe to say that the day when the fruits of our nut bearing trees will be allowed to fall ungathered from the trees, is at an end.
There are many problems that still call for an answer by the chemist and dietitian. The nutritive value of the individual nuts should be firmly established in all its phases. The causes that have made the use of certain nuts unprofitable commercially, should be studied with the view of correcting these stumbling blocks. For example, the freeing of the horse-chestnut from its poisonous saponins and enable us to use this starch rich nut as food is well within the range of possibility as indicated by experiments conducted in Austria during the war. Why do nut oils tend to become rancid easily and can this tendency be remedied? Is the freeing of the acorn and its tannin and other objectionable substances a practical consideration? What is the irritating principle of the English walnut?
All these problems and many others wait solution. Research on nuts is in progress in many places. It involves time consuming experiments that are often times expensive. As a result, progress is slow, the amount of research being limited by the financial factor. The value of the pecan nut crop alone of the year 1918, was over 91 million dollars and the value of the imports and exports of nuts and nut products during the same year amounted to over 51 million dollars. If one one-hundredth of one per cent of this sum should be devoted by those interested in the development of our nut industry in this country for the study of the nutritional and chemical properties of nuts, I feel sure that they would be amply repaid for their investment.
President Reed: I believe this will complete our program for tonight. We have quite a full program for tomorrow morning. Mr. C. A. Reed, nut culturist of the U. S. Department of Agriculture, is with us and was to have been on the program tonight, but he has been busy all day and was hardly ready for tonight's program, as he has been busy getting the exhibit in order, and he will be on the program tomorrow morning, and three or four others, among them Dr Kellogg, I believe, so that there will be quite a full morning's program, and we will be glad to have all of you come who can. We meet in the parlor of the Annex at ten o'clock tomorrow morning. If any one desires to join the Association and will speak to the secretary, he will give yow the necessary information.