Last week was quite exciting – my pêches de vigne finally arrived from the South Island. These beautiful and rare peaches are grown in New Zealand as "Black Boy peaches", which is a somewhat less appealing name when compared with the French 'vineyard peach'. I've never seen them sold commercially in Australia, although I'm sure they are there.
The pêche de vigne is not a modern hybrid, rather, it is a natural mutation of a white-fleshed peach, selected and propagated in France several centuries ago. They have a very short, late season, so you have to be quick to get hold of them. How this uncommon fruit made its way from France to New Zealand, yet almost nowhere else in the world, is somewhat of a mystery (to me at least) - I'm very glad it did though.
Fruit with red-coloured flesh used to be more prevalent in the past, although producers are now realising that the 'health appeal' of these fruits (and vegetables) is increasingly profitable. In the USA, there is the lovely Hidden Rose apple, and just recently in New Zealand the Zespri Red kiwifruit is being trialled, prior to potential commercial release.
So what are the 'health benefits' that make these jewel-coloured fruits so appealing to consumers? To put it succinctly, it's the perceived positive effects of anthocyanin consumption. Anthocyanins, a small group of pigments in the diverse flavonoid family, are responsible for the red-blue-purple colouration in a huge number of plant species worldwide.
Most frequently occurring in nature are the glycosides of cyanidin, delphinidin, malvidin, pelargonidin, peonidin and petunidin. Peonidin, for example, gives purplish-red hues to flowers such as the peony, from which it takes its name, and also roses. Initially it was believed that the antioxidant properties of anthocyanins were responsible for observed health promoting effects, however, we have come to realise that the story is a lot more complex than that. It is now appreciated that anthocyanins likely influence a wide array of cell signalling, anti-inflammatory, and gene expression pathways.
What's really interesting is that a fairly significant paradox exists: after ingestion of foods or supplements rich in these pigments, anthocyanins and their predicted metabolites appear to be only sparingly present in human plasma. How could these molecules confer health benefits, if they are apparently so poorly bioavailable? As is often the case, the answer is likely to be that we are only just beginning to understand the complexity of how these molecules may function in a living person (or animal!) Here's an example of this.
A study by Esposito et al. (2105) using lean and obese mice with healthy and disrupted gut microbiota revealed that cyanidin-type anthocyanins were much more sensitive to gut microbial degradation than delphinidins. When the gut microbiota were disrupted (by administration of antibiotics), administration of anthocyanins to the animals failed to curb body weight gain or improve glucose metabolism.
But without antibiotic pretreatment (when gut microbiota was intact), the resulting anthocyanin metabolites (especially delphinidin-derived) were clearly protective against obesity and associated insulin resistance. A recent hypothesis is, therefore, that anthocyanin metabolites may not be exerting direct influence on human tissues, but may indirectly be attenuating inflammation and exerting antioxidant effects on the gut microbiota, effectively lowering intestinal and systemic inflammation and consequently improving metabolism.
There's a clearly lot more research to do. We know almost nothing about whether or how anthocyanins might be of benefit to dogs and cats, or alternatively whether they might be harmful. What we can probably say is that it's not a sensible idea to purchase anthocyanin-rich supplements like this for your dog or cat, because there is just too much we don't know at this stage.
Giving your dog a few berries is unlikely to be risky, however these concentrated supplements may be. Luciano (2014) reported a case of acute kidney injury in a person that consumed tart cherry concentrate on a daily basis. More is not always better!
It will be exciting to learn more about this class of molecules, and the way they work, in the future. For now, I suggest that you enjoy the array of beautiful red and purple-coloured fruits that are available at the moment - they are doubtlessly good for your health for many reasons, and perhaps just as importantly, they're delicious.
Read the full paper by Esposito et al. here: https://www.ncbi.nlm.nih.gov/pubmed/26066489