Discovering Nutrition: Evolution of Nutrition Science

Discovering Nutrition 1.2

Key Points
How did the study of nutrition evolve into a science?
What key historical events contributed to our understanding of nutrition?

Nutrition entered the realm of science with the experiments of Sanctorius (1561–1636). Sanctorius, an Italian physician, published a report in which he weighed the amount of food and drink he consumed every day, then compared that to the weight of his excreta (feces and urine). He noted that his excreta weight was much less then the weight of his food and drink, yet his overall body weight did not change. He concluded that the weight of food and drink retained by the body was slowly lost as water through a process he called “insensible perspiration.” Two centuries later, Lavoisier (1743–1794) conducted more refined experiments on the relationships between food intake and body heat loss, amount of oxygen inhaled, and amount of carbon dioxide exhaled. He concluded that heat produced by the body resulted from the combustion of food in a process that was similar to the process that takes place when substances are burned outside the body. From Lavoisier’s work, we now know that the undetectable loss of food weight originally observed by Sanctorius was due to the loss of carbon dioxide through respiration, not perspiration (Discovering Nutrition 3.1). Lavoisier is often called the father of nutrition because the principles he established regarding respiration and metabolism are still used today. The experiments of Sanctorius and Lavoisier represent early milestones in nutrition that caused major shifts in thinking about the interactions between food and the body.

Another important milestone in the study of nutrition was the recognition that foods are made of specific components—carbohydrate, protein, and fat—that the body uses for energy. The French physiologist Magendie (1783–1855) was the first to distinguish between these three major nutrient categories. Liebig (1803–1873), a German physiologist, later showed that carbohydrate, protein, and fat were indeed the food components “burned” for fuel inside the body. He was also the first to estimate the energy content of foods. Although Liebig misinterpreted how the body uses carbohydrate, protein, and fat, he was correct in proposing that all three components are essential in the diet to maintain health.

In the late nineteenth century, several researchers attempted to reproduce milk in the laboratory using carbohydrate, protein, and fat isolated from cows’ milk and other food sources. When the synthetic milk was fed to laboratory animals, they died. However, the animals survived if natural must be present in food besides carbohydrate, protein, and fat.

Building on the research of Lind and others, the concept that deficiency diseases were caused by the lack of specific chemicals in the diet—and that consuming the chemical would cure the disease—was solidified by Cashmir Funk (1884–1967) and Frederick Hopkins (1861–1947) in their classic papers written in 1912. While Hopkins referred to these food chemicals as accessory factors, it was Funk who proposed the name vitamine—later shortened to vitamin—for these essential nutrients. The discovery and isolation of the vitamins dominated nutrition research in the early part of the twentieth century. Many students are surprised to learn that discovery of the vitamins is fairly recent, beginning with vitamin A in 1909. Vitamin B12 was not discovered until 1946. Even today experts are debating whether the chemical choline is an essential nutrient worthy of vitamin status.

The importance of dietary minerals also became apparent during the past century. The minerals needed in relatively large amounts (e.g., calcium and iron) were more easily studied and the first to be considered essential dietary components. Some trace minerals, however, are needed in very small amounts and were more difficult to study, especially when one considers the limitations of research methods in the early twentieth century. Although research methods used today are much more refined, the exact role of several trace minerals (e.g., boron and nickel) is still uncertain.

The past century was an exciting time for nutrition research, one in which nutrition was firmly establishing as an independent scientific discipline. The early studies have allowed us to view nutrition from a broad perspective in which every food substance we consume ultimately impacts our health and well being. Since the discovery of the vitamins and other essential nutrients, there has been a rapid decline in deficiency diseases among human populations. As we will see in later chapters, attention is now shifting from deficiency diseases to the role of nutrients in chronic diseases such as cancer, osteoporosis, and heart disease. The future of nutrition research will likely reach well beyond our traditional understanding of nutrients and, instead, focus on how substances in food can optimize health even in the absence of disease.

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