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Friday, April 13, 2012

phytic acid, phytase in grains, seeds, nuts etc.

I have always been quite cautious about the amount of phytic acid or phytic acid salts in my diet. That is because my diet does not include any animal products and naturally I have more grains, beans, nuts and seeds, vegetables and fruits compare to many other people.
I have talked about this before but I wanted to put more information in depth after talking to someone about it. he did not believe that soaking brown rice was necessary and it questioned me again about my knowledge.

As we know phytic acid is usually found in many plant tissues, especially the bran part of grains and other seeds. It is found to bind with important minerals, such as calcium, magnesium, iron and zinc, making them unavailable. It also inhibits enzymes needed to digest our foods. Anti- nutritional effects have been observed, including tooth decay, nutrient deficiencies, lack of appetite and digestive problems.

The amount of phytate in these foods is highly variable. It depends on growing conditions, harvesting techniques, processing methods, testing methods and even the age of the food being tested.

As a percentage of dry weight
Sesame seed flour 5.36 5.36
Brazil nuts 1.97 6.34
Almonds 1.35 3.22
Tofu 1.46 2.90
Linseed 2.15 2.78
Oat meal 0.89 2.40
Beans, pinto 2.38 2.38
Soy protein concentrate 1.24 2.17
Soybeans 1.00 2.22
Corn 0.75 2.22
Peanuts 1.05 1.76
Wheat flour 0.25 1.37
Wheat 0.39 1.35
Soy beverage 1.24 1.24
Oats 0.42 1.16
Wheat germ 0.08 1.14
Whole wheat bread 0.43 1.05
Brown rice 0.84 0.99
Polished rice 0.14 0.60
Chickpeas 0.56 0.56
Lentils 0.44 0.50

In milligrams per 100 grams of dry weight
Brazil nuts 1719
Cocoa powder 1684-1796
Brown rice 12509
Oat flakes 1174
Almond 1138 - 1400
Walnut 982
Peanut roasted 952
Peanut ungerminated 821
Lentils 779
Peanut germinated 610
Hazel nuts 648 – 1000
Wild rice flour 634 – 752.5
Yam meal 637
Refried beans 622
Corn tortillas 448
Coconut 357
Corn 367
Entire coconut meat 270
White flour 258
White flour tortillas 123
Polished rice 11.5 - 66
Strawberries 12

*1: Reddy NR and others. Food Phytates, CRC Press, 2001.
*2. Figures collected from various sources. Inhibitory effect of nuts on iron absoprtion. American Journal of Clinical Nutrition 1988 47:270-4; J Anal At Spectrum. 2004 19,1330 –1334; Journal of Agriculture and Food Chemistry 1994, 42:2204-2209.

Like everything else it is not black and white. phytic acid is not a completely evil thing that we need to avoid. the advise is here to reduce the amount as much as possible because now we are eating more of these foods which are not prepared in a traditional way than before and the nutrients we get from our foods have decreased over the years.


Phytase is the enzyme that can help neutralize phytic acid. it can be founded in plant foods that contain phytic acid in variable amount.
In general, us humans do not produce enough phytase, unlike many animals with more than one stomach. However there is a study done suggesting that probiotic lactobacilli, and other species of the endogenous digestive microflora can produce phytase.
Wheat and rye contain high levels of phytase. That is why sourdough bread using wheat and rye are is a good idea. On the other hand corn, millet, oats and brown rice do not contain sufficient phytase to eliminate all the phytic acid they contain.
For these grains with low level of phytase soaking will not eliminate phytates effectively.
Nevertheless, even an eight-hour soak will eliminate some of the phytic acid, reducing the amount in a serving to something like 300 mg or less. Also you can add freshly milled rye grain to give phytase to increase the chance of eliminating the phytate level.

I can not find adequate information on nut preparation. Soaking in salt water does make the nuts more digestible and less likely to cause intestinal discomfort. But I am not sure about the reduction of phytic acid level by soaking them.
Eating nuts in large amounts, especially in an inactivated form, such as in a replacement for grains should be approached carefully.

interestingly potato and yams have a small amount of phytic acids. Cooking does not remove it but it is such small amount, when your diet is nutrient rich, i don't think it is too much of a concern. Sweet potatoes contain no phytate. Another reason to love them!

sometimes I forget that coconut is a nut. You can see from the list that coconut does contain some phytic acids. Fortunately there was a study done that the chelating effect of the phytates in corn, wheat, or soy are not the same as those in coconut.
The mineral-binding effect of the phytates in coconut is essentially nonexistent. Some still suggest soaking of coconut flour but I really don't think it works in a recipe, and the coconut meat from which the flour is made, is naturally soaked in water its entire life (12 months). I don't think it is necessary to repeat the process again.

I didn't write this to scare you into not having any grains, nuts, seeds and beans. They are wonderful foods if prepared in a way to maximise its digestibility and absorbability. Consume them with awareness like any other foods.

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