Phytate – Phytic acid. Antinutrient or antioxidant?
Phytic acid is the storage form of phosphorus in seeds. The foods that contain high amounts of phytic acid are whole-grains, nuts, seeds, legumes, and beans.
Phytate is the compound when phytic acid is bound to a mineral in seeds. Phytate is also known as inositol hexaphosphate or IP6.
In many cases, phytic acid is referred to as antinutrient. The reason is that it binds with minerals in the body, like zinc, iron, and calcium inhibiting their absorption.
It is said that people who follow a vegan diet, consuming large amounts of foods rich in phytic acid may face mineral deficiencies. Is that true? Should vegans concern about the high amounts of phytate they consume?
On the other hand, phytic acid is a powerful antioxidant that can help in the prevention of many diseases, like cancer.
Why consider of phytic acid in foods?
The estimated daily phytic acid intake of people around the world is about (9):
- 750 mg/day in the US
- 600–800 mg/day in the UK
- 393 mg/day among Canadian children
- 1500 –2,200 mg/day in countries whose diet is based in plants like Nigeria and India.
Foods that contain phytic acid are the plants, especially the whole-grains, nuts, seeds, and legumes.
Phytic acid can bind with minerals like iron, zinc, and manganese inhibiting their absorption. Also, phytic acid can inhibit the digestibility of proteins, carbs, and fats. For these reasons, phytic acid is called antinutrient.
Phytate is mainly concentrated in the hard outer layer of cereal grain, called bran. The rest grain has much fewer phytate (3). On the other hand, bran is a good source of minerals, like iron and zinc. So, the solution isn’t refined grains, as they lack of minerals and vitamins.
As you can see, bran and germ, except from phytic acid, have the majority of protein, healthy fat, fiber, minerals like iron, and vitamin. Endosperm only provides the carbs and calories. Refined floor throws away the bran and it is mainly milled endosperm.
Vegans often consume more iron than omnivores. Yet, they also consume more anti-nutrients, including phytate, and these reduce the amount of iron available to the body. Consuming 5-10 mg of phytic acid can reduce iron absorption by 50%.
Parameters for mineral absorption
Whole foods contain large amounts of phytate, but also, they contain large amounts of minerals like zinc and iron. In the end, what’s the amount of mineral we absorb, as phytic acid inhibits absorption?
The quantities of zinc and phytate in the diet are the primary factors determining zinc absorption (6).
In a scientific article, published in “The American Journal of Clinical Nutrition”, presented the bioavailability of zinc, depending on the total zinc intake and total phytic acid intake (7):
As we observe, zinc absorption decrease on high phytate intake. In contrast, zinc absorption increase on low phytate intake. Above all, we see that higher amounts of zinc intake mean higher amounts of absorbed zinc.
Sure, we should concern about the percentage of absorbed zinc. In the end, the total amount of absorbed zinc is that matters.
So, the first step is to consume large amounts of foods rich in zinc, iron, manganese and other minerals. Secondly, we should concern about the efficiency that these minerals are absorbed, as we’ll see later.
In summary, mineral absorption depends:
- especially on the quantity of ingested mineral
- on age
- on time over which mineral is ingested.
- on phytate content
- vitamin D status
We are what we absorb, not what we eat.
Supplements have similarly absorbability with foods that don’t contain inhibitors of absorption, like phytate (7).
Interestingly, scientific research proved that, in contrast to observations in adults, phytic acid was not significantly related to zinc absorption and phytate reduction shouldn’t play an important role in improving the zinc absorption of young children (5).
Phytic acid-rich foods
Common foods that are rich in phytic acid are cereals, legumes, oilseeds, and nuts. All are important for human nutrition (3).
Table 1: Content of phytic acid in major cereals, legumes, oilseeds, and nuts (3):
|Name||Phytic acid g/100 g(dw)|
As you can see, phytic acid in food can vary greatly depending on the variety or the lab methods that measured it.
Phytic acid in beans
The maximum phytic acid content was measured in soy concentrates. It’s about 10.7% of the dry weight (3).
Beans and legumes contain high amounts of phytic acid, between 0.28 – 2.38% dw (Dry weight).
Likely, we can reduce the amount of phytic acid in beans and legumes with soaking and sprouting, making this healthful food more absorbable. More for soaking and sprouting later.
Phytic acid in nuts
Nuts are also high in phytate. Their value can vary greatly from 0.17 to 9.42. Even different varieties of the same nut can contain a totally different amount of phytic acid. For instance, almonds can contain between 0.35-9.42% dw for different varieties.
In the bibliography, it’s very common to promote GMOs because of their potential to contain far less phytic acid.
There are more sustainable solutions, though:
- Increase the total daily intake of minerals, through a healthy vegan diet
- Soak the beans and nuts
- Mix your diet
- Eat your veggies…they don’t contain high amounts of phytate and
- phytic acid is GOOD for you. DON’T avoid it
Phytic acid in seeds
The phytic acid content varies from 1.0–5.4% (dw) in oilseeds such as soybeans, sesame seeds, sunflower kernels, linseeds and rape seeds (3).
The best practice is to eat seeds and nuts in comparison with foods that don’t contain high amounts of phytate. Such vegan foods are fruits and vegetables.
If you consume high amounts of minerals, like zinc and iron, you will not face mineral imbalances, even if you consume high amounts of phytic acid (11).
Additionally, the body may be able to adjust to the decreased mineral availability by increasing the absorption of the available mineral (11). How efficient is that?
Phytic acid in rice – Brown or white rice is the healthiest?
The major nutrient source for more than one-half of the global population is rice (12).
Approximately 90% of the phytate in rice is concentrated in the bran and only about 4–5% in the rice endosperm (13).
As you can understand, the whole rice is a very different food than the refined rice. Additionally, the best rice you can eat is wild rice. It has much higher amounts of nutrients compared to white rice.
In the whole rice, the mean content of phytic acid is about 3.02 mg/g or 3%.
Unfortunately, rice is a poor source of essential micronutrients (12).
In the following table, we compare the mineral content of the common white rice, with the rare wild rice, and common lentil.
|White rice||Wild rice||Lentils|
|Calcium, Ca mg||9||21||35|
|Iron, Fe mg||0.8||1.96||6.51|
|Magnesium, Mg mg||35||177||47|
|Phosphorus, P mg||108||433||281|
|Potassium, K mg||86||427||677|
|Sodium, Na mg||1||7||6|
|Zinc, Zn mg||1.16||5.96||3.27|
|Copper, Cu mg||0.11||0.524||0.754|
|Manganese, Mn mg||1.1||1.329||1.393|
Data from the US Department of Agriculture.
As you can see, common white rice lacks every mineral compared to lentils. Lentils have more calcium, magnesium, phosphorus, potassium, zinc, copper, iron, and manganese.
If you want to avoid mineral deficiencies, due to phytic acids, consume nutrient-rich foods, like lentils. Practically, you can combine rice with much more nutrient foods, like beans.
Also, try recipes that combine rice with dark leafy vegetables like kale or spinach. This way, you’ll take the calories from rice and the wanted nutrients from veggies.
As we already mentioned, if you consume high amounts of minerals, you will not face mineral imbalances, even if you consume high amounts of phytic acid (11).
Fortunately, studies have proved high-pressure cooking of rice, after soaking, can improve its bioavailability. Pre-soaked rice has better mineral absorption, and improved quality (14).
Phytic acid in oats – Do you need to soak oats?
Oats contain moderate amounts of phytic acid: 0.42 – 1.16 g/100g (dw) (3).
The relatively low amount of phytic acids in oats makes them the perfect ready to eat meal. There is no need for an overnight soaking. Just put some water or almond milk in your dry oats and start to enjoy them.
If you love nuts and seeds with your oat porridge, maybe it’s a good idea to soak them overnight. Rinse them thoroughly before you put them to your oats.
Seeds and nuts contain much greater amounts of phytic acid (0.17-9.42%), so it’s a good practice to improve their bioavailability, with soaking, before their consumption.
How to remove phytic acid from foods?
Legumes, beans, whole-grains, seeds, and nuts are important foods in a healthy balanced diet. Especially vegans consume large amounts of such foods. These foods help us stay healthy, as they are packed with nutrients.
Pre-treatment methods such as soaking, sprouting, cooking, milling, and fermentation can improve the nutritional quality of seeds, nuts, and grains (3). If you concern about excess phytic acid in your diet you can follow these methods to reduce its daily intake.
The simplest way to soak legumes, nuts, and seeds is to put them in water overnight. 12h in water can reduce phytic acid content in legumes, seeds, and nuts. As soaking time increased from 2 to 12h, phytic acid content in chickpea decreased by 47.4 to 55.71 % (3)
Researchers showed that soaking decreased phytate in the grains between 87 and 91% (15).
Phytic acid content is drastically reduced during soaking plus cooking (9).
Soak in warm water
Soak your seeds, nuts, legumes or rice in warm water.
Research has proved that the water of 50 oC can be much more efficient in reducing phytic acid content than water at room temperature (14).
The most effective soaking results for phytate reduction were observed when legumes soaked at 45 °C for 48 h (15). We don’t recommend to soak the legumes for so long, as a great amount of minerals will leach into the water.
Practical, you can put your bowl of legumes and water in the oven. Put the temperature at about 50 oC and let the oven on for 1-2 hours. Turn off the oven and let the legumes soak overnight. The temperature will fall steadily, but you’ll have better results than just letting legumes in temperature water.
Soak in alkaline water
Researchers have found that soaking seeds in an alkaline solution, along with cooking resulted in 30–41% of loss of phytic acid in the seeds (9).
If you want to soak your legumes or nuts to an alkaline solution, instead of plain water, just add one teaspoon of baking soda, sea salt and coral calcium powder to the water.
The downside of this method is that while phytic acid is leaching out to the alkaline water, it can formate insoluble complexes with other nutrients, like protein or minerals (9).
Disadvantages of soaking
Soaking can make nutrients leach in the water.
Scientists have measured the losses of the different nutrients while soaking. They found that:
- Iron can be lost by 50%
- Zinc can be lost by 64%
- Proteins can be lost by 45%
Although protein digestibility and mineral bioavailability were improved, soaking isn’t the perfect solution, as many nutrients leach away.
Prefer to soak overnight legumes and nuts such as almond, which have high phytic acid content, or have higher cooking time.
Milling is the most commonly used method to remove phytic acid from grains (3).
Semi-refined flour is low in antinutrients, like phytate. The bran is partially separated from the rest of the wheat kernel. Low phytate means improved mineral bioaccessibility, hence nutritionally superior flour (8).
Additionally, the nutrient content of semi-refined flour is comparable to whole flour (8).
The disadvantage of milling is that it doesn’t remove only phytic acid from grains, but it can remove some amount of mineral and fibers, as well. Semi-refined floor may be the perfect solution between nutrient content and antioxidant content.
In conclusion, maybe you should prefer the whole flour over a semi-refined one. Phytic acid is both an antinutrient and a powerful antioxidant. If you remove phytic acid, you lose much more. Keep reading…
Sprouting – germination
Soaking is the first step in germination and fermentation process. After soaking, the young plant starts to emerge from the seed. That’s sprouting or germination.
After 4-12h of soaking (depending on the seed, or legume variate), rinse the seeds and let them drain. After rinsing seeds 2-4 times, they start to germinate. Usually, sprouts are ready in 24-48 hours.
Sprouting can remove a great amount of phytic acid in legume or grains. More phytic acid can be removed if sprouts exhibit at a thermal process, like frying. Phytate can be removed at 40–54% (9).
A seed needs a lot of energy when sprouting. During sprouting, phytase enzymes get activated and provide this wanted energy. They hydrolyze the phytic acid into phosphate, the primary energy for seed sprouting. Seeds become more bioavailable, as germination reduces phytic acid content by up to 40% (3).
Improve food quality through sprouting
Additionally, a significant level of increase of total free phenolics (9–27%) was observed during sprouting (9).
Phenolics have been considered powerful antioxidants and proved to be more potent antioxidants than vitamin C, vitamin E, and carotenoids. Researchers have studies phenolics’ effects in the prevention of various oxidative stress associated diseases, such as cancer (17).
Moreover, a thermal treatment, like oil-frying, resulted in the release of more free phenolic compounds (9).
Fermentation is used for centuries as a preservative method of foods. During fermentation, microorganisms digest the food carbs. That process may happen by accident, spoiling your food, or intended, in controlled conditions.
The fermentation of food grains improves the bioavailability of minerals, causing a degradation of phytic acid. That way the amount of soluble iron, zinc, and calcium increases (3).
Fermentation along with germination can reduce the phytic acid content as much as 88% (3).
Through fermentation are made many products, like cheese, beer, wine, yogurt, and sourdough bread.
Traditionally, many fermented foods are made from soybeans. Such foods are tempeh, miso, natto, soy sauce, and many more.
Fermentation and germination did not have significant effects on the solubility of zinc (16). Maybe it is the preferred method to avoid mineral leaching.
Foods with high bioaccessibility
If you worry about your daily mineral intake consider eating large amounts of legumes, grains, and nuts. Don’t avoid them because of the phytic acid, as the total daily mineral intake is most important. Generally, the best sources of bioaccessible minerals seem to be legumes, grains, and nuts (10).
The most significant minerals for body functions are iron, zinc, calcium, and magnesium. The bioaccessibility of minerals varies significantly, depending on the mineral and the type of food.
Concerning the mineral bioaccessibility the best foods for these minerals are (10):
Foods rich in Iron Fe
A relatively high content of iron was found in cashew nuts and green lentils (2.8 and 1.7 mg/100 g).
Foods rich in Zinc Zn
Cashew nuts and buckwheat groats had the highest concentration of zinc. Also, zinc in green lentils (2.1 mg/100 g) is considered highly bioaccessible.
Other foods rich in zinc can you find here.
In general, the best sources of bioaccessible iron and zinc were found to be pulses and nuts (3).
Foods rich in Calcium Ca
Brazil nuts, hazelnuts are rich in calcium.
Also, brazil nuts and shelled pea are foods with high bioaccessibility of calcium (32.6 and 29.1 mg/100 g).
Foods rich in Magnesium Mg
Foods rich in magnesium are brazil nuts, cashews, and hazelnuts.
Most bioaccessible magnesium is in shelled peas and green lentils (43.4 and 33.9 mg/100 g).
Tips for higher mineral absorption
As we saw, the removal or reduction of phytate markedly improves mineral absorption.
Also, consider that:
- Iron can inhibit zinc absorption if given together in a supplement (10). This effect didn’t detect on fortified foods.
- Calcium can also inhibit zinc absorption.
- The amount of protein in a meal can help positively on mineral absorption (4).
- Don’t consume individual proteins, like casein, as they may have the opposite effect (4).
- Amino acids and organic acids (e.g., citrate) can help with zinc absorption (4).
Higher mineral bioaccessibility from onions and garlic
Eat a lot of onions and garlic, as it is evidenced to have a promoting influence on the bioaccessibility of iron and zinc from food grains (18).
Small amounts of onions and garlic were used for the experiments. Only about 0.5g of garlic and 3g of onions were used per 10g of grain. The results were extraordinary. Iron bioaccessibility increased up to 73%, while zinc bioaccessibility increased up to 159% (18).
Scientists promote onion and garlic consumption, as a part of improving the bioavailability of trace minerals (18).
Additionally, vitamin C improves non-heme iron absorption, while vitamin D improves calcium, phosphorus, and magnesium absorption. Also, as carotenoids are fat-soluble, it’s better to be eaten with some healthy fats, as fat will enhance carotenoids’ bioavailability (19).
The best legume recipe
With that in mind, the best legume recipe is when:
- use sprouted legumes.
- add onion and garlic through cooking.
- add a tiny amount of healthy fats. A tablespoon of extra virgin olive oil, as a dressing, for instance.
- add fresh lemon juice, as lemon is rich in vitamin C.
Combining these steps, you’ll skyrocket the mineral bioavailability of the legumes.
Benefits of phytic acid for health
Sprouted legumes and grains could be suitable for the dietary management of certain chronic diseases (9).
May consider phytic acid more as antioxidant than an antinutrient?
Phytic acid as antioxidant
When phytic acid binds minerals in the gut, it prevents the formation of free radicals, thus making it a powerful antioxidant.
Also, it seems to bind heavy metals helping to prevent their accumulation in the body.
Phytic acid has such an antioxidant impact, that it is used as a preservative in foods.
Sprouting, onions, garlic, fat, and vitamin C for super bioavailability.
Phytic acid and cancer
Phytic acid may decrease iron-mediated colon cancer risk and protect against other inflammatory bowel diseases (1,2).
Phytic acid has both preventive and therapeutic effects against various cancers including that of the colon. It also can inhibit cancer cell adhesion and migration (20).
Also, phytic acid can lower serum cholesterol and triglycerides (1).
Scientists don’t hesitate to tell that phytic acid “holds great promise in our strategies for the prevention and treatment of cancer” (21).
An extraordinary anti-cancer action of phytic acid has been demonstrated both in lab studies and in clinical trials (22).
Phytic acid along with inositol enhances the anticancer effect of conventional chemotherapy, controls cancer metastases, and improves the quality of life (21).
Moreover, the vitamin D status in the body seems to influence how much phytate is actually retained. The more vitamin D, the more phytate retained. Vitamin D is a key factor in body functions.
Should avoid phytic acid?
You can decide on your own. We propose:
- Embrace phytic acid, as it’s a powerful antioxidant, with anti-cancer effects.
- Consume foods rich in minerals, in order to avoid mineral deficiency.
- Whenever possible, follow phytate reducing technics, like soaking or sprouting.
- NCBI – Pubmeb.gov – Phytic acid in health and disease.
- NCBI – Pubmeb.gov – Antioxidant functions of phytic acid.
- NCBI – PMC – Reduction of phytic acid and enhancement of bioavailable micronutrients in food grains
- NCBI – Dietary factors influencing zinc absorption.
- NCBI – Zinc Absorption Is Not Related to Dietary Phytate Intake in Infants and Young Children Based on Modeling Combined Data from Multiple Studies
- NCBI – PMC – A Mathematical Model of Zinc Absorption in Humans As a Function of Dietary Zinc and Phytate
- NCBI – Pubmeb.gov – Zinc bioavailability and homeostasis.
- NCBI – PMC – Nutrients, antinutrients & bioaccessible mineral content (invitro) of pearl millet as influenced by milling
- NCBI – PMC – Effect of certain indigenous processing methods on the bioactive compounds of ten different wild type legume grains
- NCBI – Pubmeb.gov – Evaluation of the content and bioaccessibility of iron, zinc, calcium, and magnesium from groats, rice, leguminous grains and nuts.
- NCBI – Pubmeb.gov – Effects of fiber, phytic acid, and oxalic acid in the diet on mineral bioavailability.
- NCBI – PMC – Manipulating the Phytic Acid Content of Rice Grain Toward Improving Micronutrient Bioavailability
- Wiley online library – Rice antioxidants: phenolic acids, flavonoids, anthocyanins, proanthocyanidins, tocopherols, tocotrienols, γ‐oryzanol, and phytic acid
- NCBI – PMC – Effect of soaking and single/two-cycle high-pressure treatment on water absorption, color, morphology and cooked texture of brown rice
- ReasearchGate – Effect of soaking process on nutrient bio-accessibility and phytic acid content of brown rice cultivar
- NCBI – Pubmeb.gov – Effects of soaking, germination and fermentation on phytic acid, total and in vitro soluble zinc in brown rice.
- NCBI – PMC – Plant Phenolics: Extraction, Analysis and Their Antioxidant and Anticancer Properties
- NCBI – Pubmeb.gov – Higher bioaccessibility of iron and zinc from food grains in the presence of garlic and onion.
- Sage Journals – Bioavailability of micronutrients obtained from supplements and food: A survey and case study of the polyphenols
- NCBI – Pubmeb.gov – The effect of inositol hexaphosphate on the expression of selected metalloproteinases and their tissue inhibitors in IL-1β-stimulated colon cancer cells.
- NCBI – Pubmeb.gov – Cancer inhibition by inositol hexaphosphate (IP6) and inositol: from laboratory to clinic.
- NCBI – Pubmeb.gov – IP6: a novel anti-cancer agent.