Animal studies are interesting. Many dismiss their relevance to humans because of the differing physiological and biochemical systems of non-human animals. It is true that animals are dissimilar in many ways, and differences between humans and other mammals should not be underestimated with regard nutrition. Cats for example require the amino acid L-taurine in the diet whereas humans do not. Ruminants require salt blocks to remain healthy when they are fed high grain intakes, whereas humans would do well to lower sodium intakes. Rats have a particularly high requirement for the amino acid L-methionine which is significant when assessing the effects of soya protein, a poor source of methionine, for human consumption. Arsenic is an essential element in rats, but its role in human nutrition is uncertain. However, if we ignore such nuances, and instead look at diet as a whole, we see that humans are not too dissimilar from other mammalian animals in terms of their overall nutritional needs.
All animals require good quality unprocessed diet that supply a range of micronutrients suited to their own biochemistry. While small differences can be found the biochemical responses to certain foods, generally omnivorous mammals respond similarly to many dietary components and in this regard they can be useful tools. Rodents have been used extensively for this purpose and as long as the context of the experiment is taken into account, useful data can be obtained from such experiments, and extrapolated to humans (with caution). As a general rule, rodent experiments have not been included as evidence within the writings of this blog because of inherent problems with interpretation, but occasionally certain experiments come along that are both interesting and informative, and therefore worthy of comment. For example, in one recent study1, researchers compared the effects of a transgenic high polyphenol apple with regular Royal Gala apples on the inflammatory response and gut bacteria levels of mice.
The high polyphenol apples were analysed chemically and shown to contain higher concentrations of a number of flavonoids including total anthocyanins, epicatechin, total flavan-3-ol oligomers (procyanidin B2), and quercetin in the form of its glycoside. The changes to the polyphenol content of the apples was due to over-expression of myeloblastis transcription factor 10 which is involved in the production of flavonoids, but not other secondary metabolites. When mice had their diets supplemented with 20 % of the high polyphenol apple pulp and peel, they experienced a 6-fold reductions in a number of inflammatory markers compared to mice who had their diet supplemented with 20 % peel and pulp from regular Gala apples. When the mice had their diets supplemented with 20 % transgenic apple peel, inflammatory marker prostaglandin E2 fell 10-fold compared to mice eating 20 % regular Gala apple peel. The high polyphenol apple diets increased gut bacteria number by 6 % compared to the Gala apples.
These results support other studies showing a distinct anti-inflammatory effect from flavonoids. That the results occurred in mice should always be considered when trying to extrapolate the biochemical effects to humans. However, the anti-inflammatory effects of flavonoids have been demonstrated in humans and so combining the animal data with human data shows a very probably anti-inflammatory effect for flavonoids in mammalian biochemistry. As expected the peel of the apples had stronger anti-inflammatory effects than the pulp, and this relates to the higher concentrations of polyphenols in the peel of most fruits, a factor that relates to the protective effects of flavonoids against environmental stress. The apples used in this study had been genetically engineered to possess higher levels of polyphenols. While interesting from a research perspective, genetically modified food has no place in a healthy high quality diet due to the evidence showing detrimental health outcomes from consuming such foods.
RdB
