the composition of foods: its evolution and ‘new look’
TRANSCRIPT
R E F E R E N C E S
Badenoch, J., and Callender, S . T. E. (1960). Lancet i, 192. Black, D. A. K., Fourman, L. R. P., and Trinder, P. (1946). Lancet i , 574. Frazef, A. C . (1949). Brit. Med. J . 2, 769. Grasbeck, R., Kantero, I., and Siurala, M. (1959). Lancet i, 234. Hardt, L., and Rivers, A. (1923). Arch. intern. Med. 31, 171. Hodgkinson, A., and Pyrah, L. N. (1958). Brit. J. Surg. 46, 10. Malrn, 0. J. (1958). Scand. J . Clin. andLab. Invest. (supplement). Rubner, M. (1879)Z. Biol. 15, 115. Taylor, W. H. (1955). Clin Sci. 14, 723.
The Composition of Foods ITS EVOLUTION AND ‘NEW LOOK’ *
BY ELSIE M. WIDDOWSON, D.Sc. Medical Research Council Department of Experimental Merlicine, University of Cambridge
HE STORY OF “The Composition of Foods’’ goes back to 1925 when T Dr. McCance was a medical stu-
dent at King’s College Hospital, Lon- don. Dr. R. D. Lawrence was at that time trying to design diets for diabetics from food tables that were then in existence. The carbohydrate in these older food tables had not been deter- mined directly but was calculated ‘by difference’, that is, it was taken to be all that was left after deducting the protein, fat, water and ash. This is how Atwater and Bryant (1906) had arrived at it in their classical work “The Chemical Composition of American Food Materials”. Plimmer (1921) in his “Analyses and Energy Value of Foods” determined sugar directly, but he assessed starch “by difference”. These tables, moreover, gave figut es only for raw foods, and Dr. Lawrence realised that any food containing sol- uble sugar would contain less carbo- hydrate after it had been boiled in water than when it was raw. Dr. McCance suggested to Dr. Lawrence that, since information about carbo-
Based on a talk given at the Annual General 7th May, 1960.
hydrate in foods was so incomplete, he (McCance) should make some analyses of fruit and vegetables, which were then the main source of carbohydrate in diabetic diets. He looked up the literature and soon discovered that a great deal of the carbohydrate in vegetables was present as pentosans and cellulose which are not available as carbohydrate to man. He therefore started to make systematic analyses of fruits and vegetables commonly eaten in Britain; he determined the “available carbohydrate” by boiling the food with 5 per cent. hydrochloric acid to convert starch and sucrose to reducing sugar, which he then estimated by a standard method. He also worked out a method for the determination of pentosans and applied this to many of the foods. Since man eats most of his vegetables cooked, determinations were made on cooked foods in preference to raw. The results of this work, and a comprehen- sive review of knowledge about avail- able and unavailable carbohydrates in foods, were published under the title of “The carbohydrate content of foods”
Meeting of the British Dietetic Association o n
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(McCance and Lawrence, 1929). Before it was published the manu-
script of this work was submitted to Professor E. P. Cathcart in Glasgow. Professor Cathcart was interested in the whole subject of nutrition, and he at Once said that, from the point of view of general nutrition, protein and fat were more important than carbohydrate; he thought it was a great pity that these constituents had not been determined as well as carbohydrate. Dr. McCance told Professor Cathcart that he was willing to analyse foods for protein and fat, and also for minerals, if he could be provided with some assistance. The result of this was that Mr. F-I. L. Shipp joined Dr. McCance at King’s College Hospital in 1930, and a detailed study of the composition of meat and fish began. Continuing the idea that it was important to know the composition of cooked food, Dr. McCance and Mr. Shipp included in their work an in- vestigation of the losses of various constituents from meat and fish when they are cooked in various ways. The results of this study were published under the title of “The chemistry of flesh foods and their losses on cooking” (McCance and Shipp, 1933).
Mr. Shipp left Dr. McCance in 1933, and was replaced by Mr. L. R. B. Shackleton; the plan being that fruits and vegetables should now be analysed for protein, fat and minerals. Just at this time, however, I was about to begin the first Diploma Course in Dietetics at King’s College of House- hold and Social Science, and I was sent to King’s College Hospital for my training in a general hospital kitchen. There I saw a white-coated gentleman come down to the kitchen every now and again and put food into the oven or the steamer, and after a while re- appear and take it out again. I naturally inquired what was going on, and was told that this was Dr. McCance and he was doing “Research” on cooking. I had already had several years bio- chemical experience, so one dsy I plucked up my courage and spoke to
him and he invited me to visit his laboratory. There I learned about the previous studies, and about the one thst was just commencing. It so hap- pened that I knew something about the determination of carbohydrate in fruit, for I had recently finished an investigation of the carbohydrate con- tent of developing apples. 1 told Dr. McCance that his previous values for carbohydrate in fruit were undoubtedly all too low, for much of the carbohyd- rate in fruit is present as fructose, which is partially destroyed by boiling with acid. He at once asked me whether I would join himself and Shackleton in the new analyses of fruits and vegetables and repeat the determination of carbo- hydrate by more accurate methods. 1 began this work at the same time as the Dietetics Diploma course. We eventually analysed all common fruits, vegetables and nuts for water, nitrogen, fat (where present), minerals, and all the separate “available” carbohydrate fractions, starch and dextrin, sucrose, glucose and fructose. Vegetables that are generally eaten cooked were analy- sed after cooking, and asain a study was made of the losses of soluble con- stituents on cooking. The results were published in a repwt entitled “The nutritive value of fruits, vegetables and nuts” (McCence, Widdowson and Shackleton, 1936). The stocks of these three publications were all destroyed in a fire started by enemy action during the war, and they are now out of print.
Long before this I had finished the Dietetics Diploma Course. I did my diet kitchen trainins at Bart’s under Miss Abrahams, and while I was there I realised how much we needed com- prehensive tables of the composition of British foods. The thought came to me one day that, since meat and fish and fruit and vegetables hsd now been extensively analysed, there only re- mained cereal foods, dairy products, and items such as beverages, preserves and sweets; if these were also analysed we should have all the material available for making a practical set of food tables.
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I put this idea to Dr. McCance and we accordingly embarked on an analysis of these other foods, and that is how the first edition of “The Chemical Composition of Foods” came to be born. The tables evolved through a series of happy coincidences. They have been used for many purposes other than the calculation of special diets, but it was the needs of dietitians which were responsible for their conception. They were not published until 1940, after we had moved to Cambridge, although most of the work represented in them had been done in London.
In making these tables we departed from food table tradition in several ways. First, the composition of cooked foods was often given, and a section was included on the composition of cooked dishes containing several in- gredients. Miss C. M. Verdon-Roe, a dietitian, also trained by Miss Abra- hams, was responsible for that part of the work. The dishes were prepared and cooked according to recipes that were given, the losses in weight at all stages measured, and the composition of the final dish calculated from the known composition of all the ingredi- ents. The second way in which we departed from tradition was this. In order to obtain representative figures for the composition of foods it is clearly necessary to analyse more than one sample. Earlier workers had gener- ally analysed several samples separately and then calculated the average repre- sentative figure. We reduced the amount of work involved by collecting together a number of different samples of each food and mixing them together before we started the analysis. Thus we got no information about the variation in composition between different samples, but it was the representative figure that was generally wanted, and even after cutting the work down in this way the tables included about 10,000 separate determinations, every one of them made in duplicate.
The shortage of some foods during the war and afterwards, and the intro-
duction of foodstuffs which had not been much used in times of plenty, made it seem desirable to revise the food tables, and a second edition was published in 1946. The original analyti- cal figures were not altered except in a few instances but the values for calories were all recalculated since there had been an error in the method of calcula- tion originally used. The tables were extended to include the composition of economical cooked dishes such as were commonly being prepared at that time, besides the composition of such foods as 85 per cent. extraction National flour and the bread made from it, Household milk and dried eggs.
About six years ago the time seemed to have come for us to begin the preparation of a third edition. The first two editions had no figures for vita- mins, for methods in those days did not seem to be precise enough to warrant any attempt to include them. Tech- niques had improved, however, and in the early 1950’s we decided to include them in the third edition of the tables. We had Dr. W. I. M. Holman with us at that time and he undertook the responsibility of reading and abstracting every paper published in the literature during the past 15 - 20 years on the vitamin content of foods. This involved studying well over 1,000 papers. There was so much information, particularly about certain foods such as milk, that we decided it was unnecessary for us to set out to analyse every food for every vitamin, so we agreed to depart from our own tradition and to use published values for the vitamins in foods. With Dr. Holman’s special knowledge about methods of vitamin assay he was able to select the published papers which gave results more likely to be reliable than others, and he wrote summaries of all these papers on punched cards. He got thus far, and then he left us to go to a job in South Africa. We were fortun- ate in finding a chemist, Miss I . M. Barrett, who came to us when Dr. Molman left, took over all his records from him, and she spent about a year
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going through these abstracts, recording the values once again on other cards, which were indexed under ‘foods’, and finally she and I went through all her summaries together, and between us we decided upon the figure for each food which we thought most nearly represen- ted the amount of the vitamin in that foodstuff.
For some foods and some vitamins there was much more information than for others. It is well known that pub- lished values for vitamins in foodstuffs are more variable than those for other constituents, and for many foods the range of published values is very wide. This variability is partly caused by real differences. For example, in the case of fruit and vegetables, the vitamins are affected by soil and climate, degree of maturity and methods of storing and processing. In the case of meat they are affected by the food given to the animal and by the proportion of fat in the sample. Part of the variability, however, is due to differences in the techniques used to determine the vitamins. In assessing the representative figure for a vitamin in a food we gave special consideration to the best analyses of British foods, and to workers who had analysed large numbers of samples. We gave preference to the more recently published values, particularly when these were based on what we con- sidered to be more accurate methods of analysis. Thus, our representative value is not the arithmetical mean of all the figures we could find. It some- times corresponded very closely to the arithmetical mean, but that was not how it was chosen. When we had decided upon the representative value we com- pared it with the figures given by other compilers. Our chosen values generally agreed with one or other of these, but where they did not, and there was no clue as to the source of the other compiler’s figures, we retained the values we had selected. Then we drew up tables of the vitamin content of food- stuffs arranged in groups as in the other part of the tables and we submit-
ted them to experts in the various fields for criticism and advice. The final tables may have mistakes - 1 am sure they will have - but we have done our best.
The vitamin tables are divided into two sections. The first gives figures for the vitamin A potency, carotene, vita- min D, thiamine, riboflavin, nicotinic acid and ascorbic acid in 280 foods and the second, a shorter section, gives figures for pantothenic acid, vitamin B g , biotin, folic acid, vitamin B I 2 and tocopherols. The published figures for the amounts of these vitamins present in foods are sometimes conflicting, and many are based on only one analysis. In several instances the methods of estimation have ngt been proved to be applicable to all foods. The figures, therefore, may need revision and we have only included them because we have had so many requests that we should do so. We give information about the effect of cooking on the various vitamins in foods where such infoimation is available, but for many foods only the raw material has been analysed. The vitamin section also includes complete references to the 970 publications which have been consulted.
Another way in which we have ex- tended the tables in the new edition is by including figures for amino-acids. Dr. B. P. Hughes was responsible for this part of the work, and again the tables are largely a compilation of other workers’ values, though some of the figures are the result of his own analyses. These tables are considerably shorter than those for calorific constitu- ents and minerals or those for vitamins because it has been possible to condense the information in them. There are two reasons for this. First, the amino-acid composition of the proteins in many foods of similar type is for all practical purposes the same. By expressing the amino-acids in terms of nitrogen rather than in terms of food it is possible to eliminate variations due to non-protein components, particularly fat and mois- ture, and to give single series of values for all meat, all fish and all milk pro-
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ducts. It has also been possible to condense the cereal section in a similar way. Secondly, in the average diet in the United Kingdom 55 per cent. of the protein is derived from meat, milk products and eggs, 35 per cent. from cereals, and of the remaining 10 per cent the potato contributes about half. Individual diets do, of course, differ considerably, but since in the average diet the main sources of dietary protein are meat, fish, milk products, eggs and cereals, and since it is within these groups that the greatest uniformity in amino-acid content is found, it has been possible to give the amino-acid com- position of 90 per cent. of the dietary sources of protein in a few short tables. The compsition of the protein in the foods providing the remaining 10 per cent differ much more widely, so in- dividual values are given for those foods which have been analysed, and this includes nuts, for which there is a considerable amount of information available.
Before we finally decided to present our tables in this simplified way composite samples of the diet eaten over a week by an adult and by a child of two were made up. These two mixed diets were analysed by Dr. Hughes for amino-acids and their amino-acid com- position was also calculated from the tables we had made. The results agreed closely.
With the assistance of Mr. D. A. T. Southgate we have also extended the section of the tables giving the ptotein, fat and carbohydrate and mineral constituents, for we realised that this was in many ways incomplete. We first wrote to the Secretary of the British Dietetic Association, telling her that we were preparing a new edition of the Chemical Composition of Foods, and asking her if she would send us a list of the names of the chief dietitians at all the big hospitals, for we would like to write to them and ask for criticisms of the old edition and suggestions for the new one. She sent us 34 names, to all of whom we wrote. We sent a short
questionnaire, containing the following questions :- 1.
2.
3.
4.
5.
Do you use the figures given per 100 grams and per ounce, or do you think one of these sections might be omitted? Are the columns arranged in the order that you ,find most useful, or would you prefer to have them set out in some diferent way, e.g. calories in the jirst column, or carbohydrate before protein and.fat? What foods have you found not to be given in the tables and which you would like to have included? What vitamins do you fhitzk would be most useful to include in the tables, particularly which members of the B-complex? Do you ever require figures for vitamin E? Anything else? We received 32 redies and I would
like to take this oppoitunity of thanking all who helped us in this way. Nearly all asked that both the 100 gram and the ounce section be retained and this we have done. With regard to the arrangement of the columns all agreed that everybody had become so accus- tomed to having them in the order in which they were that it would only be confusing to change them, so again they have not been altered.
Question 3, ‘What foods have you come across that are not included in the tables and that you would like to have analysed’, provided us with plenty of food for thought. Altogether, 233 different foods were mentioned, but figures for some foods were obviously needed more than for others because they were mentioned by several people. We have used this list of foods as the basis of the additions, but we could not include them all, and some of the requests were for foods already given in the second edition of the tables!
In all we have added about 100 new foods, which we have analysed for protein, fat, carbohydrate and minerals, just as we did before. Many of these new foods are proprietary preparations
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which have come on the market since the second edition of the tables was published or have become much more popular than they were before the war. Canned and dried soups are examples of these. It was impracticable to analyse every variety of canned soup, so we called at grocers’ shops in various towns and found out which types of canned soup were sold in the largest quantities. Those are the ones we have included. We have also analysed a variety of soft drinks, for example lemon squash, lime juice cordial, Lucoz- ade, and also a further variety of cheeses. Alcoholic drinks, which were never adequately covered in the previous editions, now have a whole page to themselves. The section on sweets, too, has been extended to include such things as peppermints, Mars Bars, Bounty Bar, fruit gums and Liquorice All-sorts. The whole of the section on cooked dishes has been revised by Mrs. M. W. Gar- diner and Mrs. A. M. Denny of Queen Elizabeth College. Where they did not think our original recipe was a good one they have cooked the dish again on at least two occasions, using a different recipe from the original one, and making all the measurements and weighings to enable us to calculate the composition of the cooked dish. Some entirely fresh recipes are now included and we have taken out all the economical war-time ones.
Bread is such an important pait of the diet, and white flour is now enriched with calcium, iron and B-vitamins, that we have made a special study of these foods. The method of collecting the samples of bread has already been described by Coppock, Knight and Vaughan (1958). Twenty-five white loaves from different parts of England, Scotland and Wales were obtained on three separate occasions. They were sent to the British Baking Industries Research Station, where they were air dried and their moisture content deter- mined. They were then allocated into three samples representing large, small and batch loaves, and in all, nine mixed
samples of white bread were analysed for nitrogen, fat, carbohydrate and minerals, and the B-vitamins in them were determined at the Cereals Research Station. Brown bread, Hovis bread and Allinson’s wholemeal bread were col- lected and sampled on two separate occasions in a similar way.
A number of prsprietary foods were represented in previous editions. We wrote to all the manufacturers con- cerned, sending them the figures for their praducls which were given in the second edition and which had been approved beforz they were originally published; we asked whether there had been any chsrlge in th: method of manufacture which necessitated a re- analysis of the product. Almost all of the manufacturers replied that some- thing had been chmged, so we bought more sarnp:es, re-analysed the product and again submitted the figures to the manufacturers. We have similarly sub- mitted our figures for all the proprietary foods now analysed for the first time, and all the figures for proprietary foods which are givzn in th: tables have been approved by the manufacturers.
It has b x n decid-d to change the title of the report from the original “Chemicsl Composition of Foods” to “The Compxition of Foods”. This is because the determination of some of the vitamins was made by micro- biological and not by chemical methods; th.: tables have been given a new num- ber (297) in the Medical Research Council Spxial Repxt Series.
All the figures have bezn checked and rechecked many t i m s over. There are about 25,030 separate values in the tables, and with this large number it is almost impxsibl: not to let mistakes slip thraugh here and there. We apAogise for any en-srs and omissions, but I quoted onze b- fxe in another conne:tion and I quote it again, “The man who makes no mistakes does not usually make anythin?”. He certainly do:s not make food tables.
References ox page 20 19
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R E F E R E N C E S
Atwater, W. O., and Bryant, A. P. (1906). U.S. Dept. of Agriculture Bull. NO. 28. Coppock, J. B. M., Knight, R. A. and Vaughan, M. C. (1958). Nutrition, 12, 63. McCance, R. A., and Lawrence, R. D. (1929). Spec. Rep. Ser. med. Res. Coun. Land., No. 135.
McCance, R. A., and Shipp, H. L. (1933). Spec. Rep. Ser. med. Res. Coun., Lond., No. 187. H.M. H.M. Stationery Office.
Stationerv Office. -~...
McCance, R.>A,, Widdowson, E. M., and Shackleton, L. R. B. (1936). Spec. Rep. Ser. med. Res.
Plimmer, R. H. A. (1921). “Analyses and energy values of foods”. London: H.M. Stationery Office Coun., Lond., No. 213. H.M. Statlonery Office.
Diet in Chronic Chest Disease BY R. B. PRIDIE, M.B.,”
Registrar, Chest Clinic, Hammersmith Hospital
AND ROSAMUND HARRISON Chief Dietitian, Hammersmith Hospital
WENTY-FIVE YEARS AGO this title would inevitably have been the T prelude to a discussion of how to
“feed up” the tuberculous patient. In 1961 however, a very different state of affairs exists. The treatment of tuber- culosis now is almost entirely a question of the proper management of chemo- therapy whilst the patient continues with his ordinary routine of life.
I t used to be taught that the failure of the chronic tuberculous patient to put on weight was due, in some way, to loss of pulmonary tissue. In support of this argument instances of the patients with bilateral artificial pneumothorax were cited. Almost from the day that the second artificial pneumothorax was instituted, these patients ceased to gain weight and many began to lose it. Numerous theories were put forward to explain this phenomenon and it was often suggested that the cause was anoxia, which prevented the proper metabolism of the nutrients derived from food. No convincing evidence was ever produced to support this theory.
Tuberculosis is the classical “wasting disease”; but nowadays only a very
small proportion of the more advanced and more chronic sufferers are, in fact, underweight. The vast majority of tuberculous patients are ordinary well- nourished individuals who have been diagnosed as the result of a chance X-ray or after only very minimal symptoms. This is especially applicable to the younger sufferers - they look like the buxom prima donnas who play Mimi rather than resembling the role which Puccini created. This change has come in the last fifteen years, largely due to the introduction of effective treatment which eliminates gross lung destruction and chronic disease in young people. Earlier diagnosis with mass X-rays has also played a part.
However, the under-nourished advan- ced case does still exist. With them there is indeed a need to give a diet both with a high calorific value and a high protein content, This is not always easy because the patients frequently have diminished appetites. Many of this group of patients are in the lower income range as well as being on a fairly low intellectual level. The associa- tion of advanced tuberculous disease in
“Present address: University College Hospital, London, W.C. 1.
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