Lemon
The acid that finishes a dish and keeps water drinkable. What gets said about kidney stones holds up less well than you would think.
Glycemic index
None. You do not eat enough of it to take in any carbohydrate worth measuring.
How to use it
Squeezed over fish, vegetables, pulses and salads. In water, warm or cold, if you otherwise drink too little.
The best version
Unwaxed if you use the zest, because the wax and the preservative sit exactly there. Heavy for its size, with a supple skin.
How to prepare it
Roll it hard across the worktop before you cut it and it gives more juice. The zest carries the scent and goes in last.
Combine with
Lentils or black beans
Vitamin C in the same meal lifts the absorption of iron from plants. Squeezing it over your plate costs nothing and does something.
What it does
The honest gain is that you drink more. In 21 people who form kidney stones, lemonade was compared with potassium citrate: urinary citrate and pH improved only on the drug, but the people on lemonade kept their urine output higher, and with stones that is the first thing that counts.
Watch out
Lemon water is therefore not a replacement for potassium citrate if your doctor prescribed it. And the acid eats at your enamel: drink it through a straw or rinse with water afterwards, and do not brush straight away.