Corn & phytates: To soak or not to soak?

Corn contains phytic acid that makes it difficult to absorb iron, zinc, magnesium, and calcium in the corn. In fact, iron is particularly poorly absorbed in corn. There are simple kitchen preparation techniques you can use to reduce the phytic acid in your grains, legumes, nuts, and seeds. You will find such discussions peppered around this website. You can also purchase the downloadable phytic acid 50-page paper that goes into a good bit of detail and includes graphic displays of research like that below.

Corn is an interesting grain because it is more difficult to reduce its phytic acid content. Notice in the graph below that phytic acid is reduced readily in wheat, rye, and barley but not so in oats and corn. (Read more about oatmeal and phytic acid at the Rebuild blog.)

Corn products from masa such as corn tortillas, corn
tortilla chips, and tamales is made from a corn dough that has been
nixtamalized.  The corn is soaked
in lime to improve the bioavailability of niacin.  This preparation process reduces the level of phytic acid by
only about 20% (Bressani et al. 2004). 

What then can you do to reduce the phytic acid further in corn?

You can make the masa/nixtamal yourself using a masa recipe (cornmeal soaked in a lime solution) or you can purchase it at a Mexican market. Once you have the masa you could soak it again to reduce the phytates further, but it is unclear how effective that would be. With limited kitchen time, your best strategy is one of these two:

(1) Add a vitamin C-rich food to your meal.

(2) Eat the corn with a small amount of meat to improve your mineral absorption.

(3) Use a complementary grain technique much like I recommend in this article on soaked grains at the Rebuild website. (I should add that recipes like cornbread and corn muffins that include cornmeal with whole wheat flour have the complementary flour built in since wheat is high in the enzyme that breaks down phytic acid.)

(4) Don’t worry about it if it’s not a big part of your diet. 

Read more about Kitchen Techniques to Reduce Phytic Acid in Your Food in the phytic acid paper, available for purchase.

Citation:

Bressani, R., Turcios, J.C., ColmenaresdeRuiz, A.S., and
dePalomo, P.P., 2004.  “Effect of
Processing Conditions on Phytic Acid, Calcium, Iron, and Zinc Contents of
Lime-Cooked Maize.”  Journal of
Agricultural and Food Chemistry 52(5): 1157 – 1162.

This post is part of Real Food Wednesday.

More posts like this one:

1. Grains and phytic acid: Soak, sprout, ferment?
2. Phytic acid / phytates in whole wheat
3. Soaking grains for nutrition?