Phytic acid.

It’s a nutritional whipping boy emphasized by those who adhere to strict Paleo diets. Phytic acid is one of the reasons some nutrition professionals warn against high consumption—or indeed any consumption—of grains and legumes. Also known as inositol hexaphosphate (IP6) phytic acid is the storage form of phosphorus in these plant foods.

Nutritionists and dietitians who warn about the drawbacks of overconsuming foods high in phytic acid aren’t entirely off the mark. Indeed IP6 reduces the bioavailability of key minerals. (IP6 has six reactive phosphate groups available to bind with minerals.) Loren Cordain PhD who has arguably done more than anyone to bring Paleolithic nutrition to the masses cited phytate as a major inhibitor of absorption of zinc calcium and non-heme iron in one of his most celebrated papers Cereal Grains: Humanity’s Double-Edged Sword.

However we can’t ignore the fact that healthy robust and long-lived populations have consumed grains and legumes for centuries. Granted they might have taken care to put these foods through elaborate processes of soaking sprouting or fermenting which reduces the phytate content but these don’t eliminate it entirely. Is it possible there’s actually something beneficial to this compound which we typically think of as best avoided?

Indeed a strong body of evidence supports a beneficial role for IP6 in inhibiting formation of kidney stones and reducing soft tissue calcification. 

Regarding kidney stones and soft tissue calcification what springs to mind first is vitamin K2. Vitamin K2 is often referred to as a “traffic cop” for calcium – directing it into the bones and teeth and keeping it out of arterial walls and other soft tissues. It’s no coincidence that individuals “with chronic kidney disease (CKD) have cardiovascular disease mortality up to 30 times higher than the general population.” But maybe it’s more than just a lack of vitamin K2. Some researchers believe this might be due to elevated phosphorus in the blood and low phosphorus diets are often recommended for those with CKD. Grains and legumes are rich in phosphorus but the bioavailability of this phosphorus is low. Owing to the potential for IP6 to inhibit stone formation and vascular calcification researchers have even called for studies investigating IP6 as an intravenous drug for patients on dialysis. 

Rats fed a purified diet (containing no phytate) are known to develop kidney calcification. When 1% phytate was added to the purified diet there were no significant differences in calcification between the rats fed the phytate-enhanced diet and rats on the standard (phytate-containing) chow. The only group that exhibited calcification was the one fed the purified diet devoid of phytate. Bottom line: it seemed to be the phytate that made the difference. Other studies (also in rats) have come to the same conclusion: IP6 inhibited soft tissue calcification that would otherwise occur in a phytate-deficient diet. 

Kidneys and arteries aren’t the only tissues that can become calcified of course. Calcinosis cutis refers to deposition of calcium in the skin. There may be an autoimmune component to it but it might also result from trauma infection or hyperphosphatemia. If the latter it could be helpful to consume foods with low phosphate bioavailability. And in this case an affected individual wouldn’t even have to consume phytate-rich foods. A rat study showed that IP6 applied topically (as a cream containing 2% IP6) is effective for significantly reducing calcified plaque formation in artificially induced soft tissue calcification. The urinary levels of IP6 in the treated rats “were considerably and significantly higher” than those found of animals treated with a control cream free of IP6 so we can be sure the IP6 was actually absorbed.

People might prefer to avoid phytate-rich foods for reasons other phytic acid. Grains come with a high carbohydrate load and legumes may lead to intestinal gas and bloating. But let’s not banish phytate entirely. Taken as a nutritional supplement it might be the anti-anti-nutrient!