anti-nutrients: what you need to know about phytic acid

You may have heard the recent news about nuts - that they're actually lower in calories than originally thought! In a new study in the American Journal of Clinical Nutrition, almonds were found to contain 129 calories per 28 gram serving as opposed to the current calorie value of 170. Now that healthy nuts like almonds are lower in calories, some of my patients have been asking if they can incorporate more into their diet. As a recovering peanut butter addict, I wish I could in good conscience tell them yes, but I cannot. I found I've been explaining frequently to patients that while nuts (and some grains and legumes) are healthy in moderation, they contain a compound called phytic acid that causes issues when consumed in excess. Allow me to tell you about this sneaky little antinutrient. 

Phytic acid is the storage form of phosphorous that plants use to grow once they sprout. It is found in the hull of grains, nuts, and seeds. While ruminant animals (cows, sheep, goats) can digest phytic acid, humans cannot. This is significant for two reasons:

once the seed sprouts, phytic acid is degraded to phosphorous which the plant uses to grow.

1) because it is not digested, phytic acid binds to minerals (especially iron, zinc, and calcium) and prevents us from absorbing them. Over time this can lead to deficiencies in these minerals, causing serious health conditions. 

2) It interferes with enzymes that help us digest our food including pepsin and trypsin (required to breakdown protein in the stomach and small intestine, respectively) and amylase (required to break down starch). When your food does not get digested properly, it backs up into your intestines and causes all sorts of havoc on your organs and lymphatic system.

Now that I've caused you to be thoroughly terrified of phytic acid, let me tell you that the average human can tolerate low levels of phytic acid (400-800mg a day), and that by sprouting your grains and legumes you can reduce the phytic acid level by up to 50 percent. Soaking and roasting nuts will also significantly reduce the amount of phytic acid. 

I do really like phytic acid's chemical structure though. so pretty. 

Bottom line: even though nuts may have fewer calories that previously thought, it is a good idea to stick to one to two 1 oz servings a day due to the phytic acid content (as well as high levels of omega 6 fatty acids... we'll save that for another discussion). It is especially important for people with iron deficiency anemia, vegans, and vegetarians to watch their levels of phytic acid intake and consider sprouting or soaking beans, grains, and legumes prior to consumption.