After many years of research, fish lipids have been recognized as essential in animal and human nutrition. The strongest evidence comes from studies of omega-3 fatty acids, which now are marketed in pure form as food supplements. However, fish lipids occurring in fatty tissues and in various organs in fish contain a very complex mixture of different fatty acids in many molecular forms, and most nutritionists recommend getting the full complexity of fish lipids by including fish in the diet, instead of taking omega-3 supplements. But there are almost no studies that substantiate this advice, as we know too little about the nutritional effects of lipids other than the omega-3 fatty acids. Some studies have started to look for such effects by applying so-called lipidomics; i.e., getting a ‘map’ of all the lipid structures, similar to genomics, by which the full gene chart is being uncovered.
This is a strong tool, and it is also possible to get a picture of all proteins in a given tissue, which is then called proteomics, or when only peptides are considered, peptidomics. The hope is that such analyses can be used to identify specific nutritional effects of proteins and peptides, giving further evidence to the advice that eating fish is better than getting only some of its components from food supplements. Studies are under way to determine if fish peptides have specific nutritional effects using the same rationale as when fish lipids were recognized for their health effects.
Recently, I attended a scientific conference where the use of fish peptides in nutrition was presented. Two different areas were approached: sports nutrition and sarcopenia in hospitalized patients who were unable to use their muscles over a certain time. In both cases, the use of peptides, i.e. partly hydrolyzed proteins, in the diet showed pronounced positive effects. Most such studies concern dairy peptides, but studies of fish peptides have started to emerge. However, none of the presentations were able to give full details of the amino acid composition of the peptide preparations used, nor were their sources presented. A molecular weight distribution could sometimes be seen, but the total mixture was too complex to make it possible to pick an individual peptide, or even a group of peptides, and demonstrate a specific nutritional effect.
The situation is more or less similar in studies that aim to demonstrate a narrower metabolic effect, such as inhibiting the angiotensin converting enzyme (ACE inhibitors). We see many such studies, as well as studies on fish peptides acting as antioxidants or having other, less specific effects. It is probably not worthwhile to search for a ‘silver bullet’ among the fish peptides that would have such specific effects as the omega-3 fatty acids. Nature works best when several essential components are acting together. The different species used for aquatic food may contain different mixtures and thus act differently in human nutrition. However, this is rarely studied. It must be our responsibility as aquatic food product technologists to supply well-characterized sources for nutritional studies, and we should study how processing and storage may affect the composition of the original sources. It is my hope that we can publish results of such studies in our journal, thus helping nutritionists and other scientists to work with well-characterized sources in their research.