Grains, legumes, nuts, and seeds are the major sources of phytic acid in the human diet, with concentrations ranging from 1% to 5% of dry weight across these food groups. Some standouts, like rice bran, wheat bran, and sesame seeds, can reach even higher levels. Whether you’re trying to reduce your intake for mineral absorption reasons or simply want to understand what’s in your food, here’s a detailed breakdown.
Grains and Bran
The outer layers of grains are where phytic acid concentrates, which is why bran and germ have dramatically more than refined flour. Rice bran tops the list at 2.6 to 8.7 g per 100 g of dry weight, followed closely by wheat bran at 2.1 to 7.3 g. Maize (corn) germ comes in at about 6.4 g per 100 g. Wheat germ contains 1.1 to 3.9 g per 100 g.
Whole grains with less processing still carry meaningful amounts, though far less than their bran fractions. Sorghum ranges from 0.6 to 3.4 g per 100 g, rye from 0.5 to 1.5 g, barley and oats from roughly 0.4 to 1.2 g, and millet from 0.2 to 1.7 g. The wide ranges reflect differences in variety, growing conditions, and how the grain is processed before measurement. White rice and refined wheat flour have much lower levels because milling strips away the bran where phytic acid lives.
Seeds and Oilseeds
Seeds as a group rival or exceed grains in phytic acid concentration. Sesame seeds contain 1.4 to 5.4 g per 100 g, and sunflower seed meal runs 3.9 to 4.3 g. Flaxseed (linseed) ranges from 2.2 to 3.7 g per 100 g. Soy concentrates can reach as high as 10.7 g per 100 g, making them among the most phytate-dense foods measured, though whole soybeans are lower at 1.0 to 2.2 g.
If you eat tahini, flaxseed meal, or sunflower butter regularly, these are among your most concentrated sources of phytic acid per serving.
Nuts
Nuts vary enormously. Almonds show one of the widest ranges of any food: 0.4 to 9.4 g per 100 g depending on variety and measurement method. Walnuts range from 0.2 to 6.7 g, cashews from 0.2 to 5.0 g, and peanuts from 0.2 to 4.5 g. The upper end of these ranges puts certain nut varieties on par with bran in phytic acid content.
That said, most people eat nuts in smaller portions than grains, so the total phytic acid from a handful of almonds is typically less than from a bowl of whole grain cereal, even if the concentration per gram is similar.
Legumes
Beans, lentils, and peas contain moderate amounts compared to bran and seeds. Kidney beans range from 0.6 to 2.4 g per 100 g, chickpeas from 0.3 to 1.6 g, lentils from 0.3 to 1.5 g, and peas from 0.2 to 1.2 g. Soybeans sit at the higher end of the legume spectrum at 1.0 to 2.2 g.
Legumes are worth highlighting because many people eat them in large portions and as primary protein sources, particularly in vegetarian and vegan diets. The total phytic acid from a cup of cooked beans can be substantial even though the concentration per gram is lower than wheat bran.
Vegetables and Tubers
Potatoes and other tubers contain lower amounts of phytic acid compared to grains, seeds, and legumes. Potatoes are sometimes noted for having more bioavailable iron precisely because their phytic acid content is modest relative to other crops. Leafy greens contain some oxalates and other compounds that affect mineral absorption, but phytic acid specifically is not a major concern in vegetables. If your diet is heavy on vegetables and light on whole grains and legumes, your phytic acid intake is likely on the lower end.
Why Phytic Acid Affects Mineral Absorption
Phytic acid carries a strong negative electrical charge at the pH inside your gut, which lets it latch onto positively charged minerals like iron, zinc, and calcium and form insoluble complexes. Your body can’t absorb these complexes, so the minerals pass through undigested. The effect is dose-dependent: the more phytic acid relative to a given mineral, the less of that mineral you absorb.
Researchers use molar ratios to gauge this effect. A phytate-to-iron molar ratio above 1 is considered indicative of poor iron bioavailability. For zinc, absorption drops sharply and can result in a negative zinc balance when the phytate-to-zinc ratio reaches 15. For calcium, a ratio above 0.24 begins to impair absorption. When a diet is high in both phytic acid and calcium, the combined effect on zinc absorption is worse than either alone.
This matters most for people who rely heavily on plant foods for their mineral intake, particularly iron and zinc. If you eat meat, fish, or other animal foods regularly, those provide minerals in forms that phytic acid doesn’t block, which buffers the overall impact.
Phytic Acid Isn’t All Bad
The same mineral-binding property that reduces absorption also gives phytic acid some protective effects. It acts as an antioxidant by preventing iron from generating harmful free radicals in the body. Clinical research has linked regular dietary phytic acid intake with reduced risk of kidney stones. In a large prospective study of over 96,000 women, regular intake of dietary phytic acid significantly reduced the risk of calcium kidney stones. Animal studies have shown that rats fed diets containing no phytic acid developed mineral deposits in their kidneys, while those given phytic acid did not.
There’s also evidence that phytic acid may help prevent abnormal calcification in blood vessels and organs, and laboratory studies have explored its potential anti-cancer properties, showing it can enter and affect cancer cells directly. Its ability to bind proteins can be protective too, potentially disrupting harmful proteins involved in diseases like diabetes.
How to Reduce Phytic Acid in Food
Several traditional food preparation techniques break down phytic acid by activating phytase, an enzyme naturally present in many grains and in the microorganisms on their surface. Wheat, rye, barley, and spelt are especially rich in phytase, with activity levels that can exceed 5,000 units per kilogram. Pseudocereals like quinoa, amaranth, and buckwheat also carry phytase-producing microbes.
Fermentation is the most effective method, removing 56% to 96% of phytic acid. This is why sourdough bread has dramatically less phytic acid than regular whole wheat bread: the long fermentation activates grain phytases and the lactic acid bacteria produce their own. Sprouting (germination) progressively breaks down phytic acid over time, from about 4% removal early on to 60% with extended sprouting at warm temperatures. Simple soaking is the least effective approach, though results vary widely. Soaking grains and legumes at room temperature for 24 hours typically reduces phytic acid by 4% to 51%, depending on the food. Soaking pounded maize for just one hour removed 51% of phytic acid in one study, while soaking intact kernels at 25°C for 24 hours removed less than 20%.
The key variables are temperature, time, and how much the grain’s structure has been broken. Warm temperatures (around 30 to 45°C) activate phytase enzymes more effectively than cold soaking. Grinding or pounding the grain before soaking exposes more phytic acid to the enzyme. And acidic conditions, whether from added lemon juice, vinegar, or naturally occurring lactic acid bacteria, create the pH range (4.5 to 6.0) where plant phytases work best.
Combining methods works better than any single technique. Soaking overnight, then sprouting for a day or two, then cooking produces a greater reduction than any one step alone. For bread, choosing sourdough over quick-rise yeast bread is the simplest swap with the biggest impact on phytic acid levels.