The Problem With Phytates
Phytates are found mainly in grains, legumes, seeds and nuts where - as either phytates or phytic acid - they are the principal plant storage form of phosphorus. Whilst phosphorous from grains is made available to ruminants because the microorganisms present in the rumen produce the digestive enzyme phytase which liberates the mineral, it is not generally bioavailable to humans who lack this enzyme.
The importance of phosphorous
Phosphorus is one of the key elements in the body and it plays an important role in the structure of DNA and RNA, in energy production as adenosine triphosphate (ATP), in the structure of all cell membranes and as calcium phosphate in the hardening of bones and teeth.
The vast majority of the phosphorous in humans is present in the hard tissues with the remainder in the fluids of the body and only about 1% in circulation.
Whilst too much phosphate can cause diarrhoea, calcification of organs and interfere with the body's ability to use other essential minerals, a lack of phosphate can cause muscle and nerve dysfunction and disruption of muscle and blood cells due to a lack of ATP and this may have implications for fatigue sufferers.
Dietary sources of phytic acid
The table below shows the average percentage dry weight of various phytate-containing foods.
|
|
|
FOOD
|
AVERAGE % DRY WEIGHT |
|
Sesame seeds flour
|
5.3
|
|
Brazil nuts
|
4 |
|
Almonds
|
2.2 |
|
Tofu
|
2.3
|
|
Linseeds
|
2.5 |
|
Pinto and soy beans
|
2.4 |
|
Oat Meal
|
1.8 |
|
Corn
|
1.5 |
|
Peanuts
|
1.4 |
|
Wholegrain/brown rice
|
0.9 |
|
Wheat flour/wheat bran/wholewheat
|
0.8 |
|
Oats
|
0.8 |
|
Chickpeas and lentils
|
0.5 |
|
White rice
|
0.4 |
|
The good news about phytates
In humans phytates pass through the digestive system unaltered and, as such, can act as a source of dietary fibre. It is the phytates that are thought to help prevent colon and other cancers. They are also considered a phytonutrient with an antioxidant effect and their ability to bind minerals may actually reduce oxidative stress within the digestive tract itself.
There is also some laboratory evidence to suggest that phytates may protect against Parkinson's disease and this may be because the phytates bind the minerals - especially iron - that the tumours need to grow, although this obviously has implications for the non-cancerous cells also. This mineral binding ability can also be used to therapeutic effect to bind toxic metals such as uranium or nickel in both soils and humans.
The bad news about phytates
However, the problem with phytate-containing foods is that the phytic acid dramatically decreases the amount of iron absorbed from the diet by a factor or fifteen-fold according to one study conducted in Goteborg, Sweden. This can have long-term implications for the development of clinical or sub-clinical anaemia and the fatigue that accompanies it.
Various studies have also shown that supplementing vitamin C significantly counters this inhibition. In fact, the authors of the Goteborg phytate study suggested that if the phytate content of the diet is high, the vitamin C intake should also be high and that "The most feasible way to improve iron nutrition in populations where the traditional diet has a high phytate content would probably be to increase the ascorbic acid (vitamin C) content."
Not only do phytates prevent iron uptake, they also have a strong binding affinity for other essential minerals such as calcium, magnesium and zinc. When bound by phytic acid, minerals become insoluble and unavailable for uptake in the intestines. Consuming phytate-rich foods can therefore contribute to multiple mineral deficiencies over time. Phytic acid also binds vitamin B3 (niacin) and this can result in the vitamin deficiency condition known as pellagra.
Dietary recommendations
In light of this understanding about the effects of phytates in foods, you may want to consider the following dietary recommendations:
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Grains were introduced relatively recently in evolutionary terms (10,000 years ago) and they have formed no part of the diet throughout most of man's history. The indigenous peoples of the world to this day do not eat grains and enjoy a better health record than the developed world. Avoiding grains in favour of a Stone age diet where possible seems advisable.
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Whilst eating refined grains reduces the dietary phytate content, it also reduces the iron and other nutrients available and so is not recommended.
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Cooking phytate-containing foods reduces the amount of phytic acid, as does soaking in an acid medium, sprouting seeds and grains, lactic acid fermentation, yeasting breads and fermenting soybeans to make tempeh. That is to say, many traditional and time-honoured ways of producing and treating foods.
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The bioavailability of the phosphorus from phytates can be increased by supplementing digestive enzymes containing phytase.
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Supplementing vitamin C increases iron uptake and probably the uptake of many minerals by helping to make them more soluble and by increasing absorption in the intestine.
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Supplementing probiotic bacteria helps to liberate the phosphorous and other minerals bound by the phytates and make them more absorbable.
Further resources
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