Nutrient and Mineral Absorption: Phytic Acid

As well as containing many important nutrients a lot of food also contains anti-nutrients that reduce or prevent the absorption of these nutrients. These anti-nutrients are commonly found in plants as protective and survival measures to encourage successful propagation. For example by making seeds indigestible it allows them to pass through the body unaltered and so fully functioning once they have been excreted.
In order to get the most out of the food that we eat we need to be able to break down these anti-nutrients so that the nutrients are fully available to us. Germinating, soaking and cooking are all common methods used to break down anti-nutrients. It is traditional in many cultures to prepare foods using these methods and it is possible that there was an understanding of the health benefits of such practices. 1
While there are many anti-nutrients and enzyme inhibitors present in plants, phytic acid is one that I feel should be looked at first. This particular anti-nutrient is present in nuts, seeds, pulses and whole grains and research has shown it to prevent the absorption or zinc, iron, calcium, magnesium and copper.

What is Phytic Acid?                                     
Phytic Acid, also known as Phytates, is an anti-nutrient found in grains, legumes, nuts and seeds. Its purpose is to store phosphorous in a plant before germination. It consists of an inositol ring attached to six phosphate molecules (inositol hexaphosphate) (See figure 1). As well as containing phytic acid many plants also contain the enzyme phytase needed to break down the phytic acid. When the conditions for growth are right the enzymes are activated and they release the bound phosphorus for the plant to use. Figure 1: Inositol hexaphosphate (right)

When we eat seeds before the plant has started the germination process the phytic acid will still be present. When consumed phytic acid will prevent the absorption of other minerals such as zinc, calcium, magnesium, copper and iron in the gastrointestinal tract. As shown in figure 2 below, the phytic acid binds to iron (fe3+), zinc (Zn2+), calcium (Ca2+) and protein.Through hydrolyzing (breaking down) these phytate molecules not only will the phosphorous be released but so will the bound minerals. 2 Once the bound minerals are no longer attached to the phytate molecules they are able to be utilised within our bodies.

Figure 2: Breaking Phytic acid attached to zinc, calcium and iron into phosphates, minerals and protein 2

As mentioned already phytase is the enzyme used by plants to release bound phosphorous from the inositol ring and in doing so release any other bound minerals and nutrients. An enzyme is a biological catalyst that is responsible for speeding up the rate at which a reaction occurs. In this case the reaction the enzyme works on is between the phosphorus and the inositol ring. Phytase breaks inositol hexaphosphate (IP-6) to inositol pentaphosphate (IP-5). IP-5 can be further broken into IP-4, and IP-4 into IP-3. The less phosphorous attached to the inositol the fewer minerals will be able to bind to it.2

All enzymes are regulated within both plants and humans by a number of different regulation processes. These processes can be seen to ‘turn on’ or ‘turn off’ an enzyme. The function of this regulation is to prevent enzymes from making reactions take place before they are needed. There are numerous ways in which this is done and in order to understand the importance of phytase it is not necessary to know exactly how this works.

What is important to know is that for phytic acid to break down and for nutrients to become available again we need to encourage phytase to start working. The conditions that are necessary for phytase to work most effectively are: moisture, a slightly acidic environment, warmth and time.How we use this to improve our mineral absorption is discussed in detail later.

Breaking down phytic acid in food
Research carried out
Edward Mellanby carried out numerous studies on phytic acid its rickets producing effects. At the time of his research, which was in the early 1920’s, they had little definative information on phytate other than it had ill effects on calcium and other mineral absorption. As rickets is in an indication of calcium deficiency he used this to determine the effects of different phytate rich foods (grain, lentils etc) on calcium malabsorption. He used this method to analysis the effect of soaking and germinating on the breakdown of phytic acid. It can be seen in the following chart that different grains have different amounts of phytic acid and the extent to which the phytic acid breaks down is also different among them. It is difficult to find studies that provide exact percentages of phytic acid breakdown after soaking, sprouting and cooking but the following table gives information on what has been found.
It can be seen from Table 1 that there is a substantial difference in the breakdown of phytic acid in acidic, warm water compared to normal water at room temperature.

Table 1: Phytic acid content in food

Phytic Acid Content (g/100g dry weight)
Soaking in water (presumably room temp) 12h [% reduction in phytate]8
Soaking in slightly acidic, 45 degree water 12h
[% reduction in phytate] *
Germinated for 72h 8
[% reduction in phytate
0.1 – 1.7 8
0.83 9

0.7 – 0.9 8,9

0.3 – 2.1 8,9
0.9 – 2.1

0.1 – 1. 2 8,9

0.97 9

0.8 – 1.2 8,9
1.01 9

1.1 8

0.83 9

0.3 8 – 0.88 9

1.4 8

1.2 8 – 1.42 9

2.5 8

1.3 – 1.8 8

1.4 8

1.0 8

Sunflower seed
1.1 – 2.1 8,9

Sesame seed (flour after oil extraction
1.7 (5.36) 8

0.5 8

0.01 8

*Values taken from Figure 2 below (Mellanby (1950)


Figure 3: Phytic acid content in grain after soaking in warm acidic water

It is generally agreed that soaking oats in warm water with the addition of an acid (vinegar or lemon juice) and some ground rye or buckwheat will greatly reduce the phytic acid content and also make the oats more digestible 3,2,4 As to the exact temperature and time there are no conclusive answers. However, many studies suggest that the warmer the water and the longer the soaking time the more phytic acid is broken down. Somewhere between 12 – 24 hours is usually recommended.

The reason that ground rye or buckwheat is added to the water is that while most grains, seeds and legumes contain sufficient amounts of phytase to break down their phytic acid some grains such as oats, millet and corn don’t have enough phytase. Combining a grain which is high in the enzyme phytase, such as rye or buckwheat, with a grain that is low can help to overcome this problem. Many different sources agree that adding about 10% ground rye or buckwheat to a phytase low grain’s soaking water can be all that is needed. 4 This is about a tablespoon and a half for every cup of grain. To get the maximum benefit of the added enzymes it is a good idea to freshly grind the whole grains. This ensures that the enzymes are fully alive and ready for action. I keep a container of whole buckwheat grouts beside my coffee mill and each morning when I soak my grains I just add a tablespoon or two of freshly ground buckwheat.

Using this freshly ground, enzyme rich flour is also beneficial to add to grains that have been pre-cooked or that have been processed. This processing may denature some of the phytase in the grain and so by adding a bit of extra enzymes can help the breakdown of the phytic acid. For example roasted buckwheat or processed flours can benefit from the addition of freshly ground buckwheat in their soaking water. 

To remove the phytic acid which is now present in the soaking liquid, the oats can be poured into a sieve and gently rinsed with some water. They can then be cooked in fresh water. 3

Rice (brown)
In the book ‘How to Cure Tooth Decay’ Rami Nagel suggests a special procedure to reduce the phytic acid content in brown rice. It wasn’t possible to find information on why brown rice gets a special procedure but many other sources agree with this method.

Soak the brown rice in warm water (room temperature) for 16 -24 hours. As rice is low in phytase add some freshly ground rye or buckwheat to the mix. Hold onto 10% of the soaking water and pour away the rest. After cooking in fresh water, this process is said to break down up to 50% of the phytic acid in the rice.

Each time you make rice add the 10% soaking liquid which you held onto from the previous rice you made. Then at the end of the soaking hold onto 10% of that liquid. The book suggests that after doing this 4 times up to 96% of the phytic acid can be broken down. 5

The soaking of quinoa is quite straight forward as it contains enough phytase to break down its own phytic acid. Cooking un-soaked quinoa is thought to break down as much as 20% of the phytic acid. Prior soaking for 12- 24 hours in warm, acidic water can increase that to up to a 90% reduction. 3

It seems there has been little research carried out on the reduction of phytic acid in nuts. Many sources suggest that soaking nuts in salted, warm water rather than acidic water is beneficial for the break down. What seems to be agreed is that soaking and then dehydrating on a low heat for a number of hours should eliminate a high percentage of the phytic acid.

Like nuts, seeds may need to be soaked in warm, salted water and then dehydrated to break down the most amount of phytate possible. 9 As so few studies have been carried out on nuts and seeds, it is unclear as to whether it is best to soak in salted or acidic water.
One article suggested that soaking ground nuts and seeds is more beneficial than soaking unground as the surface area is increased. 8
As small seeds such as flax and sesame need to be ground anyway before eating, grinding them and then soaking in water for a 4-8 hours is quite straight forward. 5 As the oils present in flax seed are quite volatile it may be better to store the soaking seeds in the fridge in a closed container. There is little information available on the effects of soaking flax seed. As both flax and sesame are quite high in phytate the soaking process seems necessary.

Beans can be soaked overnight in warm, acidic water and then cooked with kombu. Kombu is a sea vegetable that makes the beans more digestible and increases the amount of minerals available to us when we consume them.

As a seed starts to germinate it will break down its phytic acid stores naturally. How much phytic acid is broken down in this process depends on the seed.

Soaking, sprouting and then cooking beans may be the most beneficial way to eat them. Most beans are thought to show a decrease of 50% phytic acid when soaked, sprouted and cooked.

Mung Beans
Soaking and sprouting mung beans for two to three days is suggested to remove around 50% of the phytic acid present. For most effective phytic acid breakdown the sprouts benefit from being left to soak in a warm environment. 8 There have been no clear studies which indicate the effects of soaking mung beans in acidic water. Our own tests have shown that soaking mung beans in slightly acidic water will not affect their germination. The added advantage of soaking the beans in water and apple cider vinegar is that it may kill E.coli present on the surface of the bean.

How to sprout mung beans:
1. Soak in 60°C water for approximately 12 hours – Ensure that there is more than 4 times the amount of water as beans in the container as they will soak up a lot.
2. Store in a warm environment
3. After twelve hours pour off the water and rinse the mung beans in fresh water
4. Leave to sprout for 2 – 3 days, or until small sprouts have formed
5. Rinse the spouts twice a day ensuring all of the water is drained off after each rinse

Soaking and then cooking lentils has shown to remove up to 76% of their phytic acid. 8 If the lentils were soaked, spouted and then cooked this percentage could increase so that very little phytic acid is left.

A traditional method of food preparation is the souring of ground grains and legumes. Souring can be seen in the making of sourdough bread. The many strains of lactic acid bacteria present in sourdough were analysed in certain studies and they have been shown to encourage the breakdown of phytic acid.10 As rye is particularly high in phytase, making rye sourdough can remove almost all of the phytic acid present. ­­5

Vitamin D
The addition of vitamin D to the diet is thought to conteract the negative impact of phytic acid. Mellanby carried out many studies which suggested that through the proper intake of both calcium and vitamin D the detrimental effect of phytic acid can be greatly reduced.11

Probiotic lactobacilli
Some studies that have been carried out which suggest that probiotic lactobacilli contains the enzyme phytase. This would mean that by consuming these probiotics it may increase our absorption of minerals as the additional phytase in the diet would break down the phytic acid present. 12

There are many steps we can take to help to get the most nutrients possible from the food that we eat. Soaking, sprouting and cooking are three examples that can be effective in the breakdown of anti-nutrients like phytic acid. While there is still much research that needs to be carried out on this subject, it is possible to get an idea of some of the ways that food preperation may help in our nutrient absorption.

[1] Palmer, S. 2011, Nutritional Anomaly — Might Antinutrients Offer Some Benefits? [online] Available at:
[2] Yu, S. et al. 2012, Interactions of phytate and myo-inositol phosphate esters (IP1-5) including IP5 isomers with dietary protein and iron and inhibition of pepsin, [online] Available at:
[3] Nagel, R. 2010, Living with Phytic Acid, [Online] Available at: [Accessed on the 26th December 2012]
[4] Kimball, K. Is Your Flour Wet? Soaked, Sprouted, or Soured: Grains Recipes from Our Kitchens to Yours [ebook] Available at: [Accessed on the 26h December 2012]
[5] Pitchford, P. 2002, Healing with Wholefoods, North Atlantic Books Berkeley: California
[6] Nagel, R. 2011, Cure Tooth Decay Remineralize Cavities and Repair your Teeth Naturally with Good Food, Golden Child Publishing, USA
[8] Schlemmer, U. unknown date, Phytic Acid – its Significance in Human Nutrition and the Mode of Action [online] Available at:
[10] Lopez HW, Ouvry A, Bervas E, Guy C, Messager A, Demigne C, and Remesy C, 2000, ‘Strains of lactic acid bacteria isolated from sour doughs degrade phytic acid and improve calcium and magnesium solubility from whole wheat flour’, [online] Available at:,
[11] Mellanby, E. The Rickets-producing and anti-calcifying action of phytate. Journal of Physiology I949 I09:488-533.
[12] Famularoa G , Simoneb CD, Pandeyc V, Sahuc AR, Minisolad G, 2005, ‘Probiotic lactobacilli: An innovative tool to correct the malabsorption syndrome of vegetarians?’, [online] Available at: