Prohibited foods for kidney stones (because they have oxalates)

Oxalates, salts of oxalic acid, are substances present in foods of plant origin which, in high doses, can be harmful to health, since that favor the formation of kidney stones and can hinder kidney function.

It is also known that although oxalates and uric acid are different substancesas both act on kidney function, they can have a synergistic effect, and the presence of one aggravate the problems derived from the other.

It is known that up to 80% of stones are made of calcium oxalate., but only 10-20% of the oxalate present in the urine is of dietary origin, the rest is generated by the body itself. so is there forbidden foods for kidney stones? Although it is popularly said that foods with oxalates are prohibited for kidney stones, in reality it is not necessary to completely eliminate them from the diet. You just don’t have to abuse foods that contain them in significant amounts.

Therefore, when there is a tendency to form oxalate stones, it is important to know what foods have oxalate and how are they producedto adopt some measures to prevent its accumulation in the organism.

Oxalate kidney stones: why they occur

Kidney stones are a frequent pathology: in most underdeveloped countries its incidence is estimated at 5% of the population; in Europe, around 10%; in the US, 12%; and in Saudi Arabia up to 20% of the population suffers from this problem.

The calculations are produced by the presence of abnormal urine (modified in its composition due to metabolic causes), which causes it to have a increased amount of uric acid, calcium and oxalateswhich increases the predisposition to form saline microcrystals that, when agglutinating, generate kidney stones.

It is also known that certain Substances present in the urine (citrates, nephrocalcin, and glycaminoglycans) act as inhibitors of stone formation.

Of those figures in 60%-80% of cases it’s all about calculations for calcium oxalate; so, the incidence of oxalate stones has nearly doubled in the last 50 years and has gone hand in hand with the increase in spending on the shopping cart.

Curiously, the increase by food group has not kept pace with that of dietary oxalates, as most vegetables with oxalates were considered food for “poor people” (spinach, chard…). Therefore, it is not yet known whether there is a direct relationship between oxalic stones and oxalates ingested through the diet.

Kidney stones are linked to genetic conditioning and aspects such as the accumulation of substances in the kidney, such as uric acid.

There are families of stone makers, reinforcing the idea that there is a family predisposition and a matter of transmission of habitssuch as drinking more or less fluids, an important dietary factor in the formation of kidney stones.

For this reason, in addition to moderating the consumption of foods rich in oxalates, it is advisable to follow a diet low in purines, which are rich in uric acid.

Prohibited foods for kidney stones

This table shows the oxalate content per 100 g of food. Source: Justus von Liebig University of Giessen (Germany). Although they are not prohibited foods for the kidney, it is advisable to limit their consumption as much as possible.

Spinach 571 mg Rhubarb 537 mg Cocoa powder 385 mg Beetroot 72.2 mg Green bean 43.7 mg Brown bread 20.9 mg Raspberry 16.4 mg Strawberry 15.8 mg Tea 12.5 mg Blackberry 12.4 mg Plum 11.9 mg Milk chocolate 11.2 mg Red currant 9.9 mg Eggplant 9.5 mg Artichoke fa8.8 mgGrape7.9 mgChol Red Cabbage7.4mgCherry7.2mgWhite Bread6.9mgApricot6.8mgCelery6.8mgCauliflower6.6mgOrange6.2mgPear6.2mgBrussels Sprout6.1mgCarrot6.1mgParsley5.7mgMarmalade5.7mgKale4.9mgWine3.1mg

Diet to avoid oxalate stones

If the above is taken into account, it can be recommended that if you have ever suffered from kidney stones due to the accumulation of oxalates the most appropriate diet should be based above all on the consumption of plant foods. In addition, other considerations must be taken into account:

The consumption of proteins of animal origin, however, does favor the appearance of stonesTherefore, its consumption should be moderated. Meat foods should be minimized (red meats, sausages…).Cooking can reduce oxalates by 10-15%, but it also reduces the vitamin content.When there is a predisposition to suffer oxalic stones, it is recommended not to abuse the foods rich in oxalic acid salts. However, This relationship has not been widely demonstrated.. Besides, oxalic acid salts are hardly soluble in water, so they remain in the food and can form stones. If these salts were highly soluble in water, they would simply be excreted in the urine.Vitamin C is ascorbic acid, and ascorbates, through metabolism, can be transformed into oxalates. This path is only important when large amounts of vitamin C are consumedas happens when following a supplementation 500 mg to 1 g daily, for example, to treat a cold. It is advisable to drink 2.5 to 3 liters of fine water daily (between 400 mg and 1 g of dry residue), preferably at night to avoid accumulate salts in the kidneys. Drinking plenty of fluids helps to expel oxalate stones, although oxalic acid stones are sharp and prickly, making their expulsion quite painful.Does too much calcium cause kidney stones? The excessive expulsion of calcium may be due to an increased consumption of proteins, which need this mineral for their metabolic absorption, which can cause kidney stones, cramps due to calcium deficiency or osteoporosis. But this can happen whether or not there is excess calcium in the body.