Now scientists say the iron in spinach doesn't absorb into humans very well and we've all been warned that red meet contains cholesterol that clogs arteries and causes heart attacks.
In the meantime we've been advised to eat certain foods and avoid others, but the advice has changed over the years. The seven basic food groups of proteins, carbohydrates, dairy, green vegetables, fruits, red and yellow vegetables and fats were changed to the food pyramid, which has also been modified.
The newest suggestion seems to be the Paleo Diet, which is supposed to be what cave men ate; lots of fruits, vegetables and meat, including the red kind, and no grains or dairy products at all.
And then there are all the diets that are supposed to help people loose weight.
It seems to me that except for special diets required for medical reasons, the best thing to do is follow the ancient advice from Aristotle, "moderation in all things."