Components of Soy – Phytic Acid and Purine

Recently, there were concerns that soy might burden health because it contains phytic acid and purine. These are unfounded, as many studies have proven that soy consumption is safe and beneficial to health.

Soy and phytic acid

Soy contains moderate amounts of phytic acid, a natural organic acid present in the hulls of grains and seeds. Its unique structure enables it to bind easily to elements like calcium, iron, magnesium, phosphorus, and, in particular, zinc in the gastrointestinal tract. Hence, some people think that long-term consumption of soy products will cause a deficiency of trace elements in the human body and suggest that those with zinc deficiency avoid soy products such as soy milk.

In actuality, soy is rich in iron and calcium that are easily absorbed by the human body. It is also rich in FOS, which can promote absorption of calcium and magnesium, thereby making up for the metallic elements bound to phytic acid. In addition, fermented soy (such as preserved bean curd, preserved soybeans, and natto) can also alleviate the phytic acid problem. During fermentation, microorganisms break down the phytic acid in soy so that minerals present in soy like calcium, iron, and zinc can be more easily absorbed by the human body.

Hence, phytic acid in soy will not have a major effect on mineral absorption when individuals consume moderate or suitable amounts of soy products as part of a balanced diet. In fact, phytic acid benefits health with its anticancer effects. To reduce the amount of phytic acid, soak soybeans before removing their skin.

Soy and purine

Gout commonly affects men over 40 years old and menopausal women. It is a disorder of purine metabolism. Purine is an organic compound that occurs naturally in the human body. It is the main component of DNA and RNA and is essential for providing energy, regulating metabolism, and forming coenzymes.

Aging body cells or excessive consumption of purine-rich foods such as organ meats and seafood can lead to excessive amounts of purine in the body. Uric acid is produced when the body breaks down purines. If the body cannot remove excess uric acid in time or the uric acid excretion mechanism degenerates, there will be high levels of uric acid in the blood. This can cause painful uric acid crystals to form in joints, tissues, and kidneys, causing the immune system to mount an attack against these crystals because they do not belong there. This immune reaction causes inflammation and induces gout.

A myth is circulating that gout patients should avoid soybeans and soy products, especially soy milk, because they are rich in purine, which is highly hydrophilic and increases greatly after soybeans are ground into soy milk. That is not true. The amount of purine in soy is moderate; it is lower than purine-rich foods (e.g., organ meats) but higher than foods low in purine (e.g., fruits and vegetables).

Most purines are removed along with excess water during the manufacturing process of many soy products. Five hundred grams of soybeans can produce 2,500 ml of soy milk. Hence the amount of purines in 500 ml of soy milk is insignificant. A study by Japanese researchers concluded that tofu is a safe source of protein for gout patients due to its small and transient effect on plasma urate levels. A 12-year study involving more than 45,000 men found that higher levels of meat and seafood consumption are associated with an increased risk of gout, whereas moderate intake of purine-rich vegetables is not associated with an increased risk of gout.

In addition, estrogens help inhibit the formation of uric acid. Soy isoflavones can restore balance to men experiencing irregularities in uric acid elimination due to interference from male hormones and replenish estrogens in menopausal women, thereby reducing gout incidence. Compared to fish, meat, seafood, and freshwater delicacies, soy and soy products are relatively safer and more ideal sources of protein.

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