Dr Cordain’s Response:
Attached is the most recent comprehensive review of phytate in foods to date (Schlemmer U, Frølich W, Prieto RM, Grases F. Phytate in foods and significance for humans: food sources, intake, processing, bioavailability, protective role and analysis. Mol Nutr Food Res. 2009 Sep;53 Suppl 2:S330-75). This article lists the (phytate/phytic acid) content in cereals, legumes, seeds and nuts. Note that phytic acid and phytate are not synonymous terms – rather phytate is the salt of phytic acid (myo-inositol-1,2,3,4,5,6- hexakis dihydrogen phosphate) and contains other minerals including calcium and magnesium. In the scientific literature these two terms are often times used interchangeably which is inappropriate – hence reported concentrations of phytic acid may frequently include the total phytate content or vice versa. The bottom line is that there is great variability in reported values – making it difficult to precisely compare foods groups.
In the table in the attached article, nuts appear to be high in phytate, but these results require confirmation by reporting specific methods utilized for phytic acid analysis. Hence the jury is still out when it comes to precise concentrations of phytic acid in nuts.
The greatest known adverse health effects of phytic acid is that it binds divalent minerals (iron, zinc, calcium, magnesium, manganese etc.) making them unavailable for absorption or poorly absorbed in the gut. Vegetarian diets high in phytic acid from legumes, whole grains, nuts and seeds) frequently result in mineral deficiencies and impairment of health. In a typical modern day “Paleo” diet (contain some nuts), these mineral shortcomings are of little concern because meat and seafood (including shellfish) are rich sources of iron and zinc, whereas fresh fruit and vegetables are excellent sources of magnesium and manganese. Only when nuts and seeds become the dominant daily caloric source would potential mineral deficiencies appear.
Phytate probably breaches the gut barrier and enters circulation in small concentrations, however few or no adverse effects upon health have been documented to date. Rather the opposite is true, and phytate may be protective against certain cancers and may have therapeutic antioxidant effects.
Nuts are one of the most common allergenic foods and therefore may contain antinutrients which interact with the immune system of certain people. The lectin content of nuts has been poorly studied, so we simply have no information how nuts may affect the immune system of certain people. Most people can eat modest amounts of nuts and have no ill effects. Unless, you have chronic allergies or are an autoimmune disease, nuts are highly nutritious foods and good sources of healthful monounsaturated fats.
Loren Cordain, Ph.D., Professor