Cow milk and human development and well-being

Abstract

Fifty years ago animal foods were considered complete foods and important for human health. In most developed countries substantial dairy cattle and milk production industries existed which made major contributions to human welfare including the provision of cow milk to infants and young children. Then, over the last forty years, hypotheses have been developed largely by the medical profession and associated fields of research on the unfavourable roles of dietary cholesterol (DC), animal fats and serum cholesterol (SC) in coronary heart diseases (CHD). These postulates resulted in new and strange equalities such as DC+animal fat=SC=CHD. These hypotheses were followed by simplistic dietary recommendations with warnings against animal fats. These warnings have been heeded by the medical profession in many developed countries and under medical authority large sections of the public have made dietary changes and the per capita consumption of milk has fallen. More recently other risk factors have been found for CHD, and knowledge of their relative importance has increased. Understanding has grown over the question of versatility, optima and interactions between nutrients. Other new factors in this field include: the minor effect of DC on SC, the U-shaped effect of SC on total mortality in men with no effect in women less than 50 years of age, positive effects of other milk constituents on SC, different effects of high density C (HDL-C) and low density C (LDL-C) and of saturated, monounsaturated and polyunsaturated fatty acids (SFA, MUFA, PUFA) on CHD risk, the harmful effects of trans-FA, the meaninglessness of the P/S ratio, the medical and non-medical side effects of lowering SC and the high heritability of SC. These new recoveries have not been given the publicity accorded to the original hypotheses. It is the aim of this paper to seek a balanced review of the subject in the light of new scientific evidence. Further the broader implications of the topic for society, human development and well-being are also considered. Thus there are two main theses in this paper. One is to review the hypotheses of the relationship between cow milk and human coronary heart disease. These hypotheses are examined and their original historic deficiencies are discussed. This is followed by the new and emerging scientific evidence to support, question or refute these original hypotheses. The second major thesis in this paper deals with the impact which these hypotheses have had upon the pattern of human nutrition which are reflected in many important economic, social and other nutritional issues, all of which merit attention. It is considered inadequate to base general recommendations in the field of human health and well-being solely or mainly upon postulations about the relationship between milk and CHD without taking into account the larger and more complex issues. In addition to the general field of human health, the consequences of these hypotheses include the responses of the dairy production and processing industries. For example, if the hypotheses are reliable, tested and to become basic components of human nutrition, then the milk production industry has to reshape its system to produce a product more suited to the changes in consumption. If however, the assumptions are not substantiated permanently the such a re-tooling of milk production is futile. Milk production represents a major component in global food production and the implications of change are enormous. Issues to be considered include the efficiency of dairy cow in converting plant material, inedible to humans, to a human food of high nutritional value, the economic and nutritional contribution of dairy cattle production systems to beef production, the strong genetic correlations between the fat content, the protein content and the yield of milk per cow, the slowness of achieving changes in milk composition in bovine species with low reproductive rates and long generation intervals, and interactions between nutrients. Further, there are other broader issues including the incidence of other human conditions and diseases besides CHD, which can be affected by the presence or absence of milk in the diet, the genetic differences between individuals and human races, the need to address the hunger of the world's human population and further economic, social and psychological factors. Many questions need research to find sustainable breeding goals and milk production systems which are related to the reality of how milk contributes to human development and welfare. The paper concludes by considering the negative impact which the questionable hypotheses have had upon an important component of food production, namely dairy cattle farming which historically has contributed enormously to human development and welfare. The author considers there is a vacuum of knowledge here which cannot be filled simply by expertise in the medical field alone. The issue is a prime candidate for interdisciplinary research.