Yesterday, my mum messaged me to ask a question that had just occurred to her:
“Are red greens healthier than green greens?”
She’d just bought a red cabbage instead of green to go with her dinner and was wondering if there was any nutritional difference between them or whether it was all about the colours. As someone who knows a little bit about plants, I was her first port of call but, as someone who has absolutely no expertise in nutrition, I also knew I was out of my depth.
The chemical difference that makes some vegetables redder or more purple than others is a class of pigments called anthocyanins. If you spot a plant which isn’t plain green, it’s probably got a load of extra anthocyanins in it, doing the heavy lifting to make it colourful, but do they make your veggies healthier?
Anthocyanins have been shown to work as antioxidants in the lab and this is why their presence is so celebrated by marketers of health foods like blueberries and beetroot. Antioxidants may be beneficial to your health more generally but, unfortunately, anthocyanins don’t seem to have any real effects when tested within the human body. We just don’t absorb them very well by comparison to other antioxidants like vitamin C, which can be up to 3000 times more active!
So my frantic googling (remember: not an expert nutritionist!) seems to suggest that my mum will be no healthier for eating red greens than green ones. Oh, well. At least she’ll have a pretty meal…
It did get me thinking of another question though:
“Are red greens greener than green greens?”
Or, to put it differently:
“Are vegetables with more anthocyanins more environmentally friendly than vegetables with less?”
One of the main reasons plants invest their valuable resources in to making anthocyanins is because they’re a good defence against the worst effects of drought, cold weather, and high levels of ultra-violet light. They may also help to defend against fungi and insects.
Does this mean that red vegetables require fewer agricultural treatments to keep them safe from these same threats? Needing less insecticides and fungicides to be sprayed on a farm would certainly count as a ‘greener’ form of agriculture but I can’t find any records that suggest this is happening. Most likely, red and green cabbages are treated with exactly the same care and attention when they’re growing so there’s probably not much of a difference here.
There’s not likely to be any difference in the other big environmental impacts of your veggies either. Red and green vegetables will probably be packaged in much the same way as one another and be travelling similar distances from the farm to your table. That only leaves one big category left for anthocyanins to reduce an environmental impact: food waste.
In the UK, 9.5 million tonnes of food are wasted every year. That’s a huge environmental impact when you consider all the emissions that went into making it, transporting it, and then disposing of it!
There’s some evidence that anthocyanins can lengthen shelf-lives of vegetables, potentially reducing food waste. When scientists enhanced the levels of anthocyanins in tomatoes they were studying, they managed to double the length of time those tomatoes could be stored after harvest! I’ve not been able to find any studies of shelf-lives for naturally occurring levels of anthocyanins though so it’s hard to say for sure if there’s any real benefit in your average supermarket shop. Your best bet to reduce food waste, as always, is to only buy what you need and then eat as much of it as is actually edible!
So, after all that, it’s hard to be sure whether red greens are greener than green greens, but at least it seems unlikely that green greens would be greener than red greens, which is almost as satisfying a thing to say. Plants are complex and amazing organisms and, even when I can’t my answers, it’s always fun to learn more about them.
If any actual experts on red greens want to weigh in on this, do let me know. In the meantime, I’m off to buy some veg!