Humans also produce it, but in very small quantities (e.g. one study has measured a 30-times less quantity than in rats), which are also variable from human to human, so some people are more susceptible than others to the deficiencies caused by the phytic acid from seeds and nuts.

An alternative to adding phytase to any food with seeds (this includes all cereals and legumes) or nuts is to soak them for some hours in water, before cooking, as it was already done in the traditional methods of cooking for many of them. Then they can be washed and the phytic acid can be eliminated with the water.

The soaking is much more effective if the water is acidulated, e.g. with lemon juice or vinegar.

The white flour has much less phytic acid than whole grain floor, therefore it is healthier to eat white flour for starch and proteins and eat other kinds of vegetables to get minerals and vitamins.

In my opinion all the propaganda about whole grains is very wrong. Whole grains are better than eating only white floor or white rice, but they are much worse than eating white floor or white rice together with a large number of different vegetables, or even than eating white floor or rice together with one multivitamin/multimineral pill (because in the latter case the minerals will be better absorbed than when eating whole grain floor or whole grains that have not been soaked).

The phytic acid is used in all seeds and nuts as a storage means for phosphorus, so a plant that would be modified to not make it would not have viable seeds, so it could be reproduced only by cloning. That works for many fruit trees, but it would not work for cereals and legumes.