Orange
The fruit itself, not the carton. What was measured comes from hesperidin, and that is in the flesh as well.
How to use it
As fruit, in segments. Do not pick the white pith off: that is where most of the hesperidin and the fibre sit.
The best version
Heavy for its size, with a thin skin. Eating oranges are for eating and juicing oranges are for juicing, and you taste that straight away.
How to prepare it
Peel it and eat it. If you do juice it, drink it straight away, because vitamin C leaves a glass that stands around.
What it does
In 24 moderately overweight middle-aged men, diastolic pressure fell after four weeks of 500 mL of orange juice a day. A control drink with hesperidin alone did the same, and a control drink without it did nothing. Blood flow in the small vessels improved in the hours after drinking.
Watch out
That was juice, half a litre a day, for four weeks. It is a serious amount of sugar with no fibre, which is why the fruit is listed here rather than the carton.
Morand C, et al. The American Journal of Clinical Nutrition, 2010.