They’re staple ingredients in our favourite homemade soups or casseroles, but celery and spinach should be avoided if you’re planning on reheating a batch.
The nitrate contents of the vegetables which give them some goodness may be
problematic if you heat them for a second time, as it can cause the release of these cancer-causing toxins.
Avoid the risk: Either eat all the food straightaway or pick out the celery or spinach before reheating the dish.
Jo adds: “Celery also contain psoralens which can cause sensitivity to sunlight if eaten raw, but that’s a pretty low risk in this country as our sunlight is poor.”