.C&EN ANNUAL REVIEW OF DEVELOPMENTS /K
CHARLES GLEN KING' Scientific Director of The Nutrition Foundation, inc., and Professor of Chemistry, Columbia University, New York, Ν. Υ· FOODS
AMD
NUTRITION
Better Health in Balanced Diets Principle of b a l a n c e a p p e a r s m o r e c l e a r l y in r e g a r d to trace m i n e r a l elements as essential catalysts in controlling b o t h a n i m a l a n d p l a n t m e t a b o l i s m a n d in the constant interplay ^between vitamins, a m i n o acids, a n d the combustion o f either sugars or fats as e n e r g y sources
X HE year has fceen marked by great advances i n (1) understanding fat metabolisira, as regulated by a series of specific enzymes, vitamins, and amino acids, and (2) b y an increased empha sis upon the urgent need to maintain a balance oF ail nutrients required for normal health, The above principle of balance ap p e a r e d more dearly than ever before i n regard t o the trace mineral elements as essential catalysts in controlling both animal and plant metabolism, and in the constant interplay between vita mins, amino acicls, and the combustion of either sugars or fats as sources of energy. In the areas of nutrition that relate most cogently t o public health, there has been n o letup in the emphasis upon the degenerative diseases associated with the upper age brackets. A long range approach is required in develop ing preventive measures against such diseases a s hardening of the arteries, cerebral hemorrhages, arthritis, dia betes, fatty livers, early senility, and the neurologic disturbances that have a physiologic basis. Minerai Elements Special attention is focused on the role of molybdenum as an "active center" in respiratory enzyme systems. These precise chemical advances have been accompanied by a greater appreci ation of the value of molybdenum as a plant nutrient over wide areas of the earth and as a n element that must be kept in balance in animal nutrition as well. The relation of molybdenum to SO
specific enzyme systems and to the other mineral elements with which it is associated in physiological b a l a n c e copper, iron, cobalt, and phosphate— will probably receive vigorous attention in the immediate future. Zinc reached a position of much greater emphasis in plant nutrition. The area being brought under irriga tion in the Columbia River project in eastern Washington represents about 1 million acres of land that requires extra zinc for highest yields of 13 major crops. In California and adjacent areas, there is acreage in nearly every county where added amounts of trace mineral elements are a practical re quirement—zinc, molybdenum, boron, manganese, and copper. In Australia, also, enormous areas have been identi fied where additions of trace mineral elements make a large difference in agricultural productivity. Despite the clear evidence that boron plays an important role in plant physiology, there is still no evidence of a function for the element in animals. There is further clear-cut evidence that the claim for manganese as a protective nutrient against brucellosis infections (contagious abortion) in cattle, has no basis in fact. Tests re ported during the year should have a wholesome effect in correcting mis statements that have had wide pub licity. Zinc deficiency was observed in mice that had not received the quantity furnished normally in colostrum. Despite the extensive balance studies C H E M I C A L
and other experimental approaches toward a satisfactory estimation of the ideal calcium intake for human adults, there is still a considerable diversity of opinion among experienced and competent investigators. Animal ex perimentation, however, has given more decisive evidence and most of the data from this approach favor high levels of intake. A life span concept in such an area of human investigation is difficult to establish, when there is uncertainty in regard to the ap plicability of experimental animal data to the human situation. Preliminary reports on iodate as a satisfactory source of iodine when in corporated in salt have been favorable. The iodate is of practical importance in large areas over the world, be cause the standard formulas for pure table salt are based upon the use of iodides. These are not satisfactory for use in crude salt. No evidence has appeared to show a hazard in regard to possible toxic effects from iodates. Vitamins Vitamin Br> (pyridoxine, pyridoxal, and pyridoxamine) reached much greater prominence as a human nu trient. A clear-cut human requirement for the nutrient has been established, and there is a lively interest in the benefits that might be achieved by increasing the content of the nutrient in our food supply. Among infant food manufacturers, the item is one of considerable practical interest already, and there is likely to be an increasing regard for this nutrient in maternal diets. Many common foodstuffs, including meats, fruits, vegetables, and whole cereals; can furnish adequate sources, but in view of the lesser stability of the aldehyde and amine forms during processing storage, the nutrient is likely to receive more critical attention. A basis for interpreting the quanti tative interplay between required in takes of vitamin C, folacin, vitamin B 1 2 , AND
ENGINEERING
NEWS
THE CHEMICAL AND CHEMICAL PROCESS INDUSTRIES,
GROSS PATTERN OF FATTY
ACID
OXIDATION
C H 3 C H 2 C H 2 C H 2 C H 2 C H 2 CH 2 COOH
ACTIVE
ACETATE
ATP = Energy
CH3CCH2COOH^_ II
^
ο ACETO A C E T A T E
• — ^ C I T R A T EΛ OXALACETÂTE KETOGLUTARATE ,
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CYTOCHROMES
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ELECTRON TRANSPORT AND PHOSPHORYLATION
KREBS TRICARBOXY ACID CYCLE
H20
;
The "Energy Transformer"
An important advance during the year was a better understanding of fat metabolism as regulated by a series of specific enzymes, vitamins, and amino acids
tyrosine, niacin, vitamin B 6 , tryptophan, methionine, and choline has been clarified to some extent. The conversion of tryptophan to niacin and its derivatives is contingent upon an adequate intake of vitamin BG and its role as a coenzyme. The interplay between vitamin C and folacin appears to be in part due to the role of the former in the reactions by which folic acid is converted to its active coenzyme form, folinic acid. Both vitamins appear to participate in regulating the normal metabolism of tyrosine. The interplay between vitamin B 1 2 , folacin, and choline appears to involve both sulfhydryl group reactions and monocarbon units that contribute to methyl group synthesis and hence to transmethylation reactions. Glucuronic acid was found to be rapidly metabolized when injected as a lactone into the albino rat or guinea pig. The acid is formed readily from glucose, and in albino rats appeared to be a normal intermediate in the transition from glucose to vitamin C—as demonstrated by the use of C 1 4 in each of the metabolites. Preliminary evidence pointed toward a role for vitamin B 1 2 in the conversion to linoleic and linolenic acids into more highly unsaturated fatty acids. No other area of vitamin research—or VOLUME
3 2,
NO.
1
*
»
perhaps even in the field of biochemistry—has been so active a n d productive of basic information during the year as the study of pantothenic acid. T h e coenzyme role of pantothenic acid has been established for an extensive series of major reactions. These control both the synthesis and degradations of fatty acids, and hence control their combustion and their conversion to other lipid materials. The acetate group is fundamental in nearly all of the reactions but in a further series of reactions the alpha keto acids are controlled as well. The latter type of reaction, especially for pyruvate and alpha keto glutaric acid, has furnished a link that was long missing, to account for the conversion of carbohydrates to fats when they a r e not burned directly to carbon dioxide. T h e new reaction systems also link the fats with the tricarboxylic acid respiratory system, generally referred to as the Krebs Cycle. Investigation of carotenoids to find whether they might have an essential nutritive or physiological role in addition to their conversion to vitamin A gave entirely negative results. Another item of interest in relation to vitamin A was the discovery that X-disease in livestock is caused by ingestion of highly chlorinated aromatic hvdrocarbons. The mechanism of
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inducing toxicity appeared to involve disturbance of vitamin A metabolism. Studies of vitamin Ε deficiency in calves confirmed an earlier finding that the vitamin is necessary for protecting the musculature and that chronic de ficiency resulted in death of many of the animals from heart failure. How ever, there has been no satisfactory evidence to support the extravagant claims promulgated for the use of vitamin Ε in clinical heart disease or muscular dystrophy. Two Childhood Diseases Controlled
Further evidence during the year strongly supported reports that celiac disease can be cured by avoidance of protein ( gluten ) fractions in wheat and rye. A metabolic peculiarity apparently accounts for the occasional incidence of this disease. The recent high incidence of retrolental fibroplasia (early blindness) among small premature infants was thought for a time to represent a nu tritional problem or possibly might in volve unidentified infections. However, the evidence is strong and independ ently confirmed that the primary causa tive factor (during incubator handling) has been occasional use of too high concentrations of oxygen. Of interest in infant feeding was the finding that human colostrum and, in 21
.C&EN AHNUAL REVIEW OF DEVELOPMENTS
Special Dietary Foods
Studies of obesity continue to occupy much of the effort of researchers. The mouse on the right, shown beside a control from the same litter, grew obese following a single dose of gold thioglucose given by scientists at the National Institutes of Health
lesser degree, normal human milk, contains a nutrient that may be domi nant in establishing a favorable in testinal flora in t h e infant. Amino Acids
T h e biochemical study of amino acids reached another landmark in establish ing the complete structural sequence of amino acids in protein hormones. Excess Fat
Advances during the year have par tially clarified the relationships of ex cess caloric intake to risks of injury to health. The changes may b e ass«™iated basically with either excess caloric intake or nutrient deficiencies. A notable advance in this area was the observation that methionine, fur nished chiefly by animal protein foods, tends to exert a protective effect against excessive deposits of cholesterol in arterial plaques ( atherosclerosis ) . The nutritive requirement for either choline or methionine is to a considerable de gree modified b y an intake of the other, since both contribute methyl groups into the body pool. Further evidence supports t h e view that high concentrations of cholesterol in the blood are commonly a result of excessive caloric intake and con sequent excessive formation of cho lesterol. Under normal conditions, the cholesterol content of foods is not high enough to be significant, com pared to the quantities formed and disposed of. Hence, there is good reason to maintain a well balanced diet, including t h e use of animal pro tein foods even when there is need to work toward low blood cholesterol values. Diseases associated with fatty fivers continue to be most prominent among 22
patients where there is a background of both obesity and an excessive intake of alcohol. In most of these cases, t h e diet has been poor in quality, in addi tion to being excessive in caloric con tent. Technological
Advances
O n e of the most exciting develop ments during the year was the finding that coumariii, long used as an artificial flavoring material, carries risk of tox icity. An alert food laboratory m a d e the discovery during a series of screen ing tests and by vigorous action, in cooperation with food and chemical manufacturers and government agen cies, clarified the picture and estab lished corrective measures with re markable promptness. An interesting by-product of this discovery was the careful rechecking of vanillin for possible toxicity, with a resulting finding that high levels of intake were not injurious despite the similarity in structure and physical properties. A substantial report was published concerning the prospect that chlorella production might reach a stage of practical usefulness, to supplement other food and feed resources. Al though applications in this field appear to be somewhat remote, the informa tion reported is such that there is likely to be continued laboratory and pilot plant study. T h e Cinderella of t h e food industry during the year appears to have been soluble coffee. Technological advances by which the flavor and b o u q u e t of good quality coffee can b e retained in a stable and technologically satisfactory product, is an event of economic im portance as well as an encouragement to pleasant living. C H E M I C A L
Special dietary foods have h a d sub stantial acceptance. It is difficult to predict how far this group of com modities will develop as a sizeable part of the food industry. However, the total volume and n u m b e r of prod ucts is indicative that this field will receive vigorous attention. Foods with out added salt have h a d extensive acceptance a n d there is a lively pros pect tb.at specialty products will have a favorable a n d legitimate acceptance by older folk» Cereals, including break fast foods, b r e a d , and toast have al ready entered this area of specialty markets. Obviously there is going to be a period of tension and uncertainty in regard t o how far the public and those with a special interest in public health will go, in encouraging the use of foods and beverages in which arti ficial sweeteners represent the point of appeal. Frozen Foods Frozen foods have continued to grow in volume a n d undoubtedly represent one oE the areas of food production that will find acceptance into wider world markets about as fast as techno logic circumstances will permit. The industry has undertaken an extensive study of the nutritive values in frozen foods. The resultant data should fur nish a n impetus toward wide use, es pecially in institutional feeding. Dehydrated Foods
The enthusiasm with which nutri tion scientists have sponsored the use of nonfat milk solids is completely sound from a physiological point of view. There are also aspects to the problem t h a t are encouraging for the dairy industry. However, the struggle to gain increased economic support for trie use of these products repre sents a difficult period of adjustment. There is general acceptance of the viewpoint t h a t nonfat constituents of milk merit higher economic return than they h a v e had in t h e past. The competition from other fatty foods in partial substitution for the public's use of milk fat presents a problem which will require diligent attention on be half of educators, farmers, and the dairy industry for a long time. In the long run, b o t h the public and the in dustry should gain from these adjust ments. The» use of ascorbic acid as an anti oxidant, without toxicity and with some positive nutritive value, has entered a relatively novel area of application in the treatment of meats, where it has a favorable effect on color and tenuerization i n storage. AND
Ε Ν G I Ν EE RI N G
NEWS
