Grains, legumes, nuts, and seeds contain a mineral inhibitor known as phytic acid which binds to the minerals in those foods and keeps your body from absorbing them. The packaging label on your food might have a high content of iron, calcium, zinc, or magnesium, but if your food is a high phytic acid food, you will fail to gain much from the minerals in the food items. What is great about phytic acid, however, is that food science gives us straightforward methods to reduce it in food.
Soaking and fermentation methods are some of the most powerful strategies for reducing phytic acid in your food. If you prepare your meals intentionally, you may improve your absorption of minerals by anywhere from 50% to 400%, depending on the food itself. Generally speaking, using sourdough baking techniques will be extremely effective for nearly all whole grains. You can improve your beans and nuts as well, but you will not likely reduce phytic acid levels to zero.
For warm cereal like a whole wheat porridge, you can soak the porridge in warm water, approximately body temperature, over night to reduce the phytic acid. Use the quantity of water required by your recipe, bring it to a
For baking bread, your best technique to reduce phytic acid is to use sourdough fermentation. Sourdough techniques use multiple rise times, each of which reduces phytic acid further. The lactic acid bacteria in your sourdough starters do as well. But even if you are not ready to commit to sourdough baking, a yeast bread left to rise before baking will fairly effectively break down the phytic acid in the whole grain flour.
In regards to beans, many cooks soak them for some hours before cooking. To reduce phytic acid soak the beans overnight (or better yet, for about 18 hours) in very warm water. We recommend starting with a temperature of approximately 120 degrees and keep the beans in a warm place. Of course, the water cools down in that time but as the beans soak up the water, add more warm water to your bowl of beans. When the beans are soaked and ready to be cooked, strain the soaking water and add new water to the beans, in line with your recipe. Cook your beans as you would do normally following a recipe for soaked beans (should your recipe not specify "soaked beans," you will want to reduce your cook time).
You may wish to soak nuts and seeds (e.g. almonds and walnuts) to reduce the levels of phytic acid, though the soaking will be more effective if the nuts and seeds are broken into pieces. By breaking the nuts, you increase the surface area of the item and the soaking is more effective. Soak the nuts or seeds for twelve to eighteen hours, much like you would do the beans. Pour off the soaking water and then allow the nuts to dehydrate on a clean cookie sheet until they are crispy. You can dry them in a warm spot like a low-temperature oven or food dehydrator.
Techniques always tend to have special cases and there are some here too: Soy, corn, and oats most notably do not respond well to the soaking techniques above. These excepted foods are low in an enzyme called "phytase" that breaks down the phytic acid. The difficulty of breaking down phytic acid in soy is made clear in the figure at right. Scientists soaked, boiled, and then steamed soybeans with very little change in the phytic acid content. Fermenting the beans made a much bigger difference. Soy must be made into tempeh or miso, fermented soy products, to see appreciable change in the phytic acid content. Oatmeal and corn can be fermented as well, but they will improve with the addition of a grain high in the enzyme such as fresh wheat or rye. Cornbread is a great example: Use whole wheat flour combined with cornmeal to leverage the enzymes in the wheat for the benefit of the corn.
These foods, plant-based foods packed with minerals, can be exceptionally healthy, especially if you prepare them using methods that reduce their phytic acid content. Adopt these strategies in your own kitchen to improve your health.