Spinach is indeed considered to be an “alkaline food” as opposed to an acidic food. This is determined by the pH scale which measures overall acidity. This particular type of food is very low in acidity and is therefore acceptable to eat for those who have problems with things like heartburn or acid reflux.
A lot of junk foods along with those which are high in animal protein tend to be very acidic and can therefore worsen acid reflux. Some different examples of alkaline foods include carrots, soybeans, citrus fruits, and of course spinach. It is a good nutritious food to eat overall and a good choice for those who suffer from heartburn.