Today the opinion that oxalates - harmless substances that contain many plants - may promote the formation of kidney stones.
Therefore, many nutritionists recommend avoiding foods that contain oxalates.
But is this really so?
Should we, for fear of the formation of kidney stones, avoid useful and nutritious foods such as spinach, parsley, raspberries, and even cocoa?
What are oxalates
Oxalates are natural substances found in plants, animals and humans. In chemical terms, belong to the group of organic acids.
Our body always has them in certain quantities because our cells routinely convert other nutrients (eg, vitamin C) in oxalates.
Oxalates in our body can come from the outside - from certain foods containing them, to varying degrees.
Among the fruits, vegetables and various other fruits are major sources of oxalate:
* Black and green tea
From all parts of the plant are almost always the most oxalate in the leaves, while the stem or stalk considerably less.
Mainly oxalate containing plant foods, while foods of animal origin contain negligible amounts of these substances.
It is assumed that oxalate plants are used to get rid of excess calcium. However, according to some researchers have also used the plant oxalates to protect against infections and parasites.
And oxalate stones - Myth or Reality?
Oxalic acid has the ability to form a strong bond with various minerals such as sodium, potassium, magnesium and calcium. When this happens, the resulting compounds are generally referred to as oxalate salts.
Salts of sodium and potassium oxalate are soluble in water and is excreted in the urine, but the calcium oxalate is practically insoluble.
That's why calcium oxalate, when present in high enough levels, tends to merge into crystals in the kidney or urinary tract.
It is believed that these crystals can contribute to kidney stones, which then interfere with the functioning of the kidney channel.
According to surveys, as many as eighty percent of kidney stones in adults is caused by calcium oxalate.
However, there is no scientific evidence that the intake of oxalate from the diet to blame for the formation of kidney stones.
Unfortunately, many nutritionists now recommend strongly reduce intake of foods containing oxalates in order not to create scale.
However, studies show that the intake of oxalate in people who already have the scale is not of any importance, since the scale is already created.
For people who have problems with stones, studies show that the intake of oxalate or no impact on their health.
Therefore, there is no need to restrict the intake of beneficial and healthy ingredients like green tea, cocoa, spinach and grapes for fear of the formation of kidney stones.
When you still need to limit the intake of oxalate
Despite the levels of oxalate in the body that we take very small, there are a few relatively rare medical conditions that require strict oxalate restriction.
These are hypercalcemia (elevated levels of calcium in the blood) and Primary Hyperoxaluria (increased production of oxalate in the body).
In such cases, you should oxalate intake limited to 50 milligrams a day.
But as far as - 50 mg of oxalate per day?
For example, one cup of raw spinach contains about 200 milligrams of oxalate. Therefore, patients with this rare diagnosis allowed a quarter cup of spinach a day.