The concept that nature imparted a health-giving and curative function to foods is not new. Herbal teas and remedies have been used for centuries and their use continues in many parts of the world. In modern society, we have turned to drugs to treat, mitigate or prevent diseases. Since the discovery of nutrient actions, and because of our involvement with molecular biology and our increasing analytical capabilities at a cellular level, we are beginning to become more knowledgeable about the biochemical structure-function relationships of the myriad of chemicals that occur naturally in foods and their effects on the human body.
Traditionally, substrates present in our daily food are called ‘nutrients’. More specifically, they are classified into ‘macronutrients’ (provision of energy substrates, present in high quantity) and ‘micronutrients’ (non-energy substrates, present in low quantity). Those nutrients which cannot be or are only insufficiently synthesised in the human body are defined as biochemically essential. These considerations are solely grounded on aspects of preventative medicine: avoidance of nutrient deficiencies (e.g. energy/protein malnutrition, hypovitaminosis, osteoporosis), prevention of overnutrition (e.g. obesity, hypervitaminosis), and assurance of metabolite production (e.g. hormones, short chains fatty acids). Obviously, there were no specific links to the therapy of diseases.
In the past decade, evidence was found that various nutrients possess more than the well known ‘nutritive’ effects on body function and metabolism. In-vitro and in-vivo studies showed that nutrients can modify immune response as well as the integrity of organs and tissues. In addition, substrates in our daily food which were formerly classified as not necessary, or even harmful, may have important metabolic roles. Recent epidemiological research has been focused on the importance of the consumption of vegetables, cereals and fruits to diminish the risk for several diseases such as cancer and atherosclerosis as well as to support human well being. This seems strongly linked to the amount of s.c. ‘non-nutritive’ substrates such as polyphenols, flavonoids and phytoestrogens present in these foods. In-vitro studies underlined the quantitative role of these substrates as antioxidants and radical scavengers.
With increasing knowledge about the effects of nutrients at the cellular level, the question was raised whether they could also successfully be used in the therapy of metabolic disorders There are now several reports available that supplementation with specific amino acids, lipids, minerals and vitamins can improve recovery and patient outcome in hypercatabolic and hypermetabolic situations. This new fundamental knowledge initiated a revision of the old nutrient concept. In 1989 the term ‘nutraceutics’ (composed of nutrient and pharmaceutics) was coined by the Foundation for Innovation in Medicine, Art and Educational Foundation for compounds present in foods providing medical or health benefits including the prevention and the treatment of disease. Potential nutraceutics are listed in Table 1. By definition, the term nutraceutics is superimposed on our common classification of macro- and micronutrients and non-nutritive compounds. In Japan, the Ministry of Health and Welfare developed a similar concept: the term ‘functional food’ describes naturally occurring substances ‘for specific health use’.
Several nutrients have recently been suggested to modify the immune response and organ functions under various metabolic stresses. Clinical work in the past 2 decades has revealed that there is a specific role for nucleotides, including polynucleotides such as DNA and RNA. In their review (pp 527-530), Rudolph and Van Buren highlight the possible consequences of no or inadequate intake of nucleotides and focus on the enteral supplementation of RNA in infants and surgery patients. Based on experimental research, the effects of RNA on the immune system and liver and the effects on neurological function are discussed. Moreover, the impact of dietary nucleotides on the health status of the elderly population is discussed.
For many years, supplementation with the basic amino acid arginine has been employed to improve clinical outcome following trauma, cancer and an immune deficiency disease. The mechanism of these effects are not, however, fully understood. Using modern molecular and cell biology technologies, it is now feasible to gain new insights into arginine action. Barbul and colleagues competently summarise current experimental work leading to novel approaches in nutrition therapy (pp 531-538).
The term ‘phytochemical’ refers to every naturally occurring chemical substances present in plants, especially to those phytochemicals that are biologically active. Usually these phytochemicals are present only in small amounts in vegetables, grains, and fruits. The review by Andlauer and colleagues (pp 539-547) gives an overall compilation of recent papers focusing on epidemilogical aspects, bioavailability and chemopreventive actions.
Undoubtedly there are still many questions to be addressed (e.g. bioavailability, dose-response, undesired side effects). Nevertheless, the interdisciplinary concept of nutraceutics will essentially influence our view of nutrition therapy in the forthcoming years. The increasing awareness of pharmacological effects of nutrients in promoting and supporting health will provide new perspectives for nutrient research.