What is Phytate?
Phytate is the storage form of phosphorus for plants. In humans it generally passes straight through us, but it can have positive and negative effects on us as it passes through.
It can be visualised from above as a massive hexagonal molecule with a lot of phosphate groups on the outside. However, in 3 dimensions it looks more like a spider. Chemically it is known as inositol hexaphosphate and given the abbreviation IP6. Both the inositol and phosphate that make up phytate, are substances that our body needs to function properly. Phosphate is vital for all functions in the body as it provides us with energy. Inositol helps us control how our cells work. However, most phytate is not absorbed from our gut, and luckily for us, we can get phosphate from elsewhere and inositol can be produced from glucose.
Where is phytate found?
Phytate is found primarily in nuts, seeds, beans and grains. It is found particularly in the skins and bran layer. The amount of phytate present in plants is dependent on factors such as the type of soil and the amount of fertiliser used. There can be wide variability in levels of phytate found. As such it is best to look at foods and their phytate values in the context of your whole diet. Don't get hung up on whether you are having too much or too little of a particular phytate containing food.
The list below gives some idea of the levels of phytate measured in a range of foods(1).
|FOOD||% dry weight - max-min||FOOD||mg per 100g of food (dry weight)|
|Sesame seed flour||5.36||5.36||Brazil nuts||1719|
|Brazil nuts||1.97||6.34||Cocoa powder||1684-1796|
|Linseed||2.15||2.78||Almond||1138 - 1400|
|Beans, pinto||2.38||2.38||Peanut roasted||952|
|Soy protein concentrate||1.24||2.17||Peanut ungerminated||821|
|Peanuts||1.05||1.76||Hazel nuts||648 – 1000|
|Wheat flour||0.25||1.37||Wild rice flour||634 – 752.5|
|Soy beverage||1.24||1.24||Refried beans||622|
|Whole wheat bread||0.43||1.05||Corn||367|
|Brown rice||0.84||0.99||Entire coconut meat||270|
|Polished rice||0.14||0.6||White flour||258|
|Chickpeas||0.56||0.56||White flour tortillas||123|
|Lentils||0.44||0.5||Polished rice||11.5 - 66|
As you can see, figures in the two tables don't neccessarily place foods in the same order with respect to one another, for example brown rice. However, the measurements do show that processed grains tend to have less phytate than unprocessed grains.
Phytate affects nutrient absorption
Phytate can easily bind to vitamins and minerals in the gut, preventing their absorption, and potentially putting you at risk of deficiency. Vitamins such as niacin, and minerals such as zinc and iron, and to a lesser extent calcium and magnesium, are affected.
However, if you consume these vitamins and minerals at times when you are not consuming phytate rich foods then you should end up absorbing more of these valuable vitamins and minerals. In practice deficiency has only been noted in societies eating just one type of food, such as a staple grain product in which phytate is present. In these societies all food is consumed with phytate and so the risk of deficiency is much greater.
In many cases the food containing the phytate is also a good source of the vitamin or mineral that is bound by phytate. An example is nuts which contain good amounts of magnesium, but which also have plenty of phytate.
However phytates are not alone in binding to valuable nutrients in our gut. Other plant chemicals such as polyphenols and soluble fibre can also bind to minerals. One thing all these plant chemicals have in common, is that they can also do us a lot of good.
Phytates the health benefits
Phytates act as anti-oxidants and there is evidence that it can help reduce risk of a number of diseases.
The use of phytate to treat a similar degenerative brain condition in mice, has yielded promising results(2).
Tests using phytate with cancerous cells taken from human colons have shown good results in reducing the proliferation of these cells(3).
A epidemiological study with post-menopausal women from Majorca showed improved bone density in those consuming more phytate(4). Helping us absorb calcium and magnesium may be one way in which this works. Of course it could actually be that phytate containing foods also contain other substances that help maintain bone density.
Other health benefits
It seems that phytate can also help us control our blood sugar levels, may help in cases of type 2 diabetes and has a number of anti-cancer effects in addition to those identified above(5).
I think the message from these studies is that we should not panic about the fact that phytate can reduce mineral absorption. Reduced absorption in itself does not mean we should avoid or even reduce our phytate intake. By avoiding foods rich in phytate there is a clear danger that we could lose more than we stand to gain.
How can I reduce the impact of phytate?
Many foods that contain phytate, particularly nut and seeds, are full of goodness. This has led many people to find ways of minimising the effects of phytate in nuts and seeds while still consuming foods that contain them. The main methods are:
Fermentation is used for foods such as soya beans. Fermented soya beans are found in natto, tempeh and pickled tofu. Fermentation is probably one of the most effective ways of reducing phytic acid. It certainly works well in rice(6).
You've probably heard of bean sprouts. However it is also possible to sprout nuts, seeds and grains. Many vegans and followers of the paleo diet engage in this practice.
The act of sprouting of a seed releases many plant enzymes. These enzymes break down indigestible nutrients into digestible nutrients. Toxins that were present to prevent the seed being devoured by predators, are also often broken down at this stage also.
Cooking helps reduce levels of phytate. Heat breaks down the structure of phytate. However, it is considered far more effective to treat seeds, nuts and grains with acid, such as vinegar or lemon juice, or soak them before cooking, to have a significant impact.
Soaking and adding acid
Soaking beans, seeds, nuts and grains is effective in reducing phytate levels. Also the addition of an acid, such as vinegar or lemon juice can also help to reduce phytate levels further. This is due to the ability of phytase (see below), the enzyme that breaks phytate down, to work more efficiently at low pH.
Use phytase supplements
Phytase is the enzyme that breaks down phytate. You can either use a supplement that provides phytase directly or consume a probiotic bacterium (Bifidobacterium pseudocatenulatum) that itself produces phytase.
Phytase is present in the guts of ruminent animals, e.g. cattle, goats, sheep and deer. However, there is not much phytase present in the human gut, or indeed in pigs, which often get phytase supplements added to their feed. Phytase supplements differ in their effectiveness depending on 1) whether they can survive attack from our own stomach enzyme (pepsin), and 2) the strength of their phytate splitting activity(7).
Phytase enzymes are not widely available outside of the animal feed sector.
Bacteria that produce phytase
It is probably a better approach to use bacteria that make their own phytase, than take phytase directly. There is a probiotic strain of bacteria called bifidobacterium pseudocatenatulum that has been used successfully in some studies(8).
Phytates are unlikely to harm you as long as you have sufficient minerals in your diet. I eat a lot of nuts and seeds as snacks, and drink cocoa regularly. Both of these are high in phytate.
Should I cut down? I don't think so. I will continue as I am doing unless I see evidence that I am deficient in iron or zinc. There are major health benefits in many foods that contain phytate (nuts, seeds and cocoa) and I feel for most people these benefits will outweigh any reduction in magnesium, iron and zinc absorption.
You may want to cut down on the amount of wholemeal grains you eat, but there are other reasons for doing this as well as increasing mineral absorption.
1) http://www.westonaprice.org/food-features/living-with-phytic-acid Original source: Reddy NR and others. Food Phytates, 1st edition, CRC Press, 2001.
2) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3021000/ - Alzheimer's effect
3) http://www.spandidos-publications.com/or/23/3/787 - Colon cancer effect
4) http://www.ncbi.nlm.nih.gov/pubmed/21794821 - Increases bone density
6) http://www.sciencedirect.com/science/article/pii/S0308814608002513 Ferment brown rice for better nutrient absorption
7) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1375699/ Phytase possibly not that effective in humans
8) http://www.ncbi.nlm.nih.gov/pubmed/19674804 Bacterial source of phytase