Blueberries
The pigment is the working part, and it sits in the skin. Measured in people, at the blood vessel itself.
Glycemic index
53
Low
Fresh. Under fifty-five counts as low on the scale where glucose is a hundred.
How to use it
A handful a day, raw. Through yoghurt, through oats, out of your hand.
The best version
Small and dark, with a dull bloom on them. That bloom is the berry’s own coat and rubs off once it has been handled. Frozen is fine and often better than tired fresh berries that came a long way.
How to prepare it
Do not heat them unless you have to. Let them thaw in your yoghurt rather than in the microwave.
What it does
In healthy people, blueberries improved the working of the vessel wall, measured as flow-mediated dilation, and after a month of eating them daily the 24-hour systolic blood pressure came down as well. Purified anthocyanins did the same as the whole berry, and control drinks containing fibre, minerals or vitamins did nothing.
Watch out
The study used wild blueberries, which carry far more pigment than the fat cultivated berry on the shelf. How much of the ordinary kind you would need for the same effect has not been worked out.
Rodriguez-Mateos A, et al. The Journals of Gerontology Series A, 2019.