Aluminium is a highly reactive metal. They react fast with acidic foods like citrus fruits and vinegar. But manufacturers treat the aluminium vessels before they ship them. This treatment results in the formation of a strong layer over the aluminium pots. The amount of aluminium that gets into the food when you are cooking in treated cookware is very minimal and is well below the levels that cause any toxicity. Therefore, while it is true that pure aluminium is not safe for foods, the aluminium cookware that you have in your home is probably safe.