Is oxalic acid in food bad?

Foods high in oxalic acid are often discouraged because they increase the risk of kidney stone formation and mineral deficiencies. However, since oxalic acid is found in almost all foods of plant origin, especially in vegetables and aromatic herbs, a low oxalic acid diet is neither easy to implement nor very healthy.

Oxalic acid in food

There is no doubt that pure oxalic acid is toxic in very high concentrations. In most foods, however, the substance is present in low doses. At least 600 mg of oxalic acid per kg of body weight would have to be ingested to die. For a 70 kg person, it means that they should consume between 70 and 140 kilos of spinach in a day.

On the other hand, the oxalic acid values ​​in a food are very difficult to determine because they depend on factors such as the variety, the part of the plant examined, the growing conditions, the time of harvest, and even the measurement technology. . Analyzes have shown that the oxalic acid content of a sample of spinach can vary between 500 and 1,000 mg per 100 g.

Kidney stones and iron deficiency

In United States an average of 70 to 150 mg of oxalic acid is consumed per day. In vegetarians the intake is higher, but it is not a problem. Most nutritionists agree that only people with nutritional deficiencies, kidney disease, or a tendency to form stones should be careful about how much oxalic acid they eat.

For example, if you are iron deficient, you should not eat a meal rich in oxalic acid at the same time you take an iron supplement. People with kidney stones (so-called calcium oxalate stones) should not eat large amounts of spinach or Swiss chard every day, as oxalic acid, under certain circumstances, can promote the formation of new stones.

However, most urologists only prescribe a strict low-oxalate diet (less than 50 mg per day) for patients with very high urinary oxalate levels.

Healthy people excrete oxalic acid, which binds minerals such as calcium, in the urine. Calcium oxalate stones are not due to excess in the diet, but rather to a metabolic bias. Oxalic acid alone is not enough to develop kidney stones.

Some studies indicate that the alteration of the intestinal microbiota may favor a hyperabsorption of oxalic acid because there is a deficiency of certain bacteria that decompose the acid.

Fruits and vegetables protect against kidney stones

In fact, the consumption of fruits and vegetables can prevent the formation of calcium oxalate stones in most people, according to a study from the University of California School of Medicine. Another study also concludes that a diet high in fruit and vegetables is the best way to prevent kidney stones, along with a good calcium intake, low salt intake, and low animal protein. This benefit is explained by the content of vegetables in water, vitamins and organic acids.

Fiber and phytic acid from whole grains, legumes, nuts and seeds also help in this regard. According to researchers from Norfolk and Norwich Universities, phytic acidstrongly inhibits the formation of calcium oxalate crystals.

How to Reduce Oxalic Acid

If you want to consciously reduce the oxalic acid content of your food, you can pay attention to the following:

Discard the cooking water after cooking vegetables that are high in oxalic acid, such as spinach. This can reduce the oxalic acid content by up to 87 percent. If steamed, the reduction is 53 percent.Baking alone can reduce oxalic acid levels by up to 15%. Blanching reduces oxalic acid in spinach, but not in other vegetables.Legumes are usually prepared by soaking overnight. This measure alone significantly reduces oxalic acid.Fermentation also reduces the oxalic acid content.

Other measures to reduce the risk

If you drink a lot of water every day, oxalate crystals cannot form. Drink a minimum of 1.5 liters of water a day if you are at increased risk of kidney stones. If you make sure you drink enough water before you go to bed, crystals cannot form and accumulate overnight.It is best to follow an alkaline diet, since acidifying foods and drinks (meat, sugar, alcohol, caffeine) acidify the urine, which favors the formation of kidney stones.Take citrates (for example, magnesium citrate), which lead to deacidification and thus reduce the risk of kidney stones.Take vitamin B6 or a vitamin B complexas it can reduce the risk of kidney stones.

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