The frontiers of nutrition sciences, as represented by the contributions to Volume 7 of the Annual Review of Nutrition, are changing—slightly. The number of reviews in the realm of clinical nutrition has increased, and the number of reviews devoted to epidemiology and public health nutrition has decreased. The number of contributions related to the basic sciences of nutrition has decreased slightly, although the reviews have in one respect become more basic, i.e. five of them deal with modification of the genome by nutrients or metabolites. This latter development illustrates that the field of nutrition is making use of new technologies that enable investigators to probe more deeply into the nature of nutrient interaction with the most fundamental events of cell physiology, namely, gene expression.

An increase in the number of reviews dealing with clinical nutrition also reflects the application of the most modern methods for probing intermediary metabolism in human subjects. Five clinical reviews deal with nutrient effects on metabolism. More specifically one describes the assessment of energy expenditure and fuel utilization in man using whole-body calorimetry and endocrine probes, one deals with the effects of fat-modified diets on cholesterol and lipoprotein metabolism, one considers the metabolic management of obesity, one discusses the nutritional requirements of the elderly, and one recounts the nutrition requirements of low-birth-weight babies. Two reviews deal with either inherited or acquired defects of vitamin metabolism in man for vitamins B6 and B12. Two reviews add important perspectives to our understanding of minerals by discussing the causes and consequences of iron overload and giving a global survey of selenium nutrition.

Dr. Scrimshaw devoted his lead chapter to "The Phenomenon of Famine." He concluded that many of the worst famines have been caused by poor distribution of existing food supplies either because of lack of purchasing power on the part of the poor or because of political interference with normal distribution of food. Economic and social factors that prevent the consumption of food by large numbers of people, even when food supplies are adequate, are the principal causes of famine.

The reviews on basic and experimental nutrition include papers on fatty acid and amino acid transport, the formation of glycogen by a novel pathway, the fate of o-amino acids, and the regulation of intracellular protein catabolism. A review of water homeostasis and five papers on the molecular biology of gene expression are presented. These include reviews on the role of zinc in DNA replication, the role of intracellular vitamin A-binding proteins in mediating the genetic regulatory function of vitamin A, the dietary regulation of gene expression with respect to selected enzymes of lipid and carbohydrate metabolism, the induction of salivary praline-rich proteins by tannins, and nutrient effects on DNA and chromatin structure.

Finally, in the public health and nutrition area, we have a chapter on the evolution of recommended dietary allowances (RDA) and another on nutritional applications of the Health and Nutrition Examination Surveys (HANES).

The heterogeneity of our subject is obvious from the contents of each issue of the Annual Review of Nutrition. This reemphasizes the fact that nutrition science is a field to which investigators from every discipline of biology make contributions. In fact, many investigators who have written for Volume 7 would not regard themselves as nutritionists. They are molecular biologists, physiologists, biochemists, pediatricians, hematologists, internists, animal scientists, epidemiologists, and statisticians. So be it! They all share, however, an interest in the science of nutrients and their relation to health.

Konrad Bloch in a recent paper¹ quotes Auguste Comte, the 19th century mathematician who ranked the sciences in order of precision. In Comte's hierarchy, mathematics stood at the top followed by physics, chemistry, and then biology, with the social sciences at the bottom of the ladder. Comte intended his hierarchy to be a value judgement of his time but, one may ask, have value judgments changed that much in the last century? Thus, continues Bloch, "In physics, classical phenomena are governed by laws, in chemistry, chemical reactions follow rules, and finally, in biology with the unpredictability of Nature, the hypotheses are more likely to be elevated to the state of dogmas, which are periodically modified, if not overturned entirely." The nutritional sciences, with their footing in both biological and social sciences, are particularly vulnerable to the overextrapolation of data to produce dogmas. Nutrition science now deals less with fully reversible single deficiencies and more with complex disorders of multiple etiology such as atherosclerosis, osteoporosis, diabetes, and cancer. These diseases have both genetic and environmental roots. Individual variation, furthermore, may totally change the relative contributions of genetic and environmental factors in the genesis of a single chronic degenerative disease.

Nutrition scientists who study the chronic diseases or models thereof, whether they work in the field of cell biology, experimental nutrition, clinical nutrition or epidemiology, should be cautious in concluding that any variable is the cause of any of these complex chronic diseases. Some of these variables turn out to be only one of many causes. Human variability in response to environmental factors that may affect the progression of one of these diseases is so great that for every human who is responsive to a regimen, there is one who is resistant. Likewise, for every susceptible animal model there is one that is resistant. One must learn to respect the weight of evidence. Dogmas are usually developed when proof is not possible, when circumstantial evidence is all that is available. This is precisely the time for all of us to moderate our hypotheses and reenter the world of physicists and chemists who play by rules, and whose phenomena are governed by laws.

Regarding nutrition science and scientists, the tilt toward dogmas must be scrupulously evaluated in developing research priorities, designing experiments, and writing reports. We must recognize that in this new, exciting, but difficult area of learning the role of nutritional factors in diseases of multiple etiology, the weaknesses as well as the strengths of evidence must be accepted. The conclusions must follow from the evidence. One of the objectives of the Annual Review of Nutrition is to give perspective on these issues.

I would like to thank my associates on the Editorial Committee, the consultants who aided us in assembling the reviews, and the authors of the excellent reviews appearing in Volume 7. Ms. Margot Platt, in Palo Alto, California, deserves our continuing thanks and appreciation for her important work on the production of each volume.

Robert E. Olson, Editor

1.   Bloch, K. 1987. Concepts and approaches to scientific inquiry. Am. J. Clin. Nutr. 45:154-59 (May Suppl.)