Carbohydrates, proteins and fats are essential nutrients to all animals. Yet dietary variation between species, populations and individuals can vary dramatically.
In an international collaborative study, researchers from Australia, Denmark and Finland investigated how individuals of the same population differ in their ability to survive on various diets.
The researchers utilised a genetic reference panel consisting of roughly 200 closely related fruit fly strains (Drosophila melanogaster). The flies were fed six different diets containing high concentrations respectively of protein, sugar, starch, coconut oil or lard, or a combination of sugar and lard.
The strains used in the study have had their genomes fully mapped, which made it possible to link the differences seen in the experiments to specific genetic variation.
The study, published in the journal Nature Communications, found that small genetic differences affected the flies' ability to use the energy of various nutrients.
"Unexpectedly, we found that the fruit fly strains differed considerably, for example, in their ability to survive on a high-sugar diet. What makes this particularly surprising is the fact that the food consumed by fruit flies in nature contains a lot of sugars," said Essi Havula, a post-doctoral researcher at the University of Helsinki and the lead author of the study.
"The genes that regulate metabolism have been conserved well in evolution, which is why we can learn a lot about human metabolism through studies carried out with fruit flies," Havula adds.
In genetic analyses, the researchers identified a number of genes that contributed to the ability of flies to tolerate sugar. Most of these genes are found also in humans and have been suggested in previous genome-wide association studies to play a role in obesity and Type-2 diabetes.
In addition, the researchers demonstrated that the JNK pathway, one of the most important stress-signalling pathways, regulated sugar metabolism and storage-fat synthesis in the case of high-sugar diets in the study.
"It appears that dietary sugar causes stress to the cells, giving the JNK pathway an important role in how effectively flies tolerate and process sugar," Havula said.
According to the researchers, most of the findings can be applied to humans as well, even though further research is still needed. Havula pointed out that the study provides concrete evidence on how the same dietary recommendations do not necessarily suit everyone.
One option is to develop nutrition in a more personalised direction with the help of nutrigenomics, they suggested.