Rhubarb, botanically Rheum rhabarbarum, is actually a vegetable, but like fruit it is used for delicious cakes, compotes, jams and desserts. Characteristic feature of this plant is the strong sour taste. You may have eaten the long, thick stalks raw when you were a child. However, this is not entirely harmless, because the raw stalks of the rhubarb are slightly poisonous due to the oxalic acid they contain.

The ingredient oxalic acid

Rhubarb is high in oxalic acid, which is responsible for the sour taste and furry feeling on the teeth when the raw stalks are eaten. This acid, also known as oxalic acid, is not toxic per se. It is also found in apples, spinach, parsley and other fruits and vegetables. The human body also produces this acid itself during various metabolic processes. In the body, the acid binds to various minerals such as ammonium, calcium and sodium. Since the compounds formed in this way are hardly soluble, the absorption of the minerals through the intestine is made more difficult. The part of the oxalic acid absorbed by the organism is excreted via the kidneys.

effect of the acid

Sensitive people may experience discomfort when Rheum rhabarbarum is eaten raw. In order for serious symptoms of poisoning to actually occur, however, you would have to eat larger quantities of raw rhubarb and especially the leaves. The acid concentration in the leaves is particularly high. However, the leaves are inedible, as are the bitter-tasting flowers. In the human body, the fruit acid can work in different ways:

  • dull feeling of the teeth and damage to the tooth enamel, because the acid already in the mouth combines with calcium, which is deposited on the teeth
  • Formation of kidney and bladder stones by depositing the formed crystals in the kidneys and bladder
  • Iron deficiency, as the acid absorbs iron
  • Heart problems up to cardiac arrest in sensitive people and excessive consumption.
Note: Because the acid attacks teeth, you should wait at least 30 minutes after eating Rheum rhabarbarum before brushing your teeth.

amplification of the effect

Not everyone has to experience discomfort from eating raw rhubarb. Whether symptoms occur and how severe they occur depends on various factors:

  • existing diseases such as rheumatism, gout or kidney damage
  • deficiency symptoms in the organism
  • diet
  • variety of rhubarb
  • time of harvest

If the intestinal flora is already disturbed or if the body is acidic, the effect of oxalic acid can become a problem. This is also the case if too little water is consumed or foods with a high concentration of sodium chloride are eaten.

raw consumption limits

If you eat the stalks of Rheum rhabarbarum raw, it is not necessarily harmful. The effects of eating raw depend on the concentration of oxalic acid, which varies depending on the variety of rhubarb:

  • green varieties with green flesh = highest acid concentration
  • red varieties with green flesh = lower acid concentration
  • red varieties with red flesh = lowest acid concentration

The average acid concentration is 420 milligrams of acid per 100 grams of pulp. As a rule of thumb, the greener the stems, the higher the concentration of oxalic acid. The acidity increases the later the rhubarb stalks are harvested.

Note: The rhubarb season ends on June 24th, as does the asparagus season. Rhubarb must then no longer be harvested, as it then reaches an ever higher concentration of oxalic acid and is poisonous.

Note when eating

Rhubarb is not toxic to healthy people if you keep a few things in mind when eating it:

  • Pay attention to sticks that are as ripe as possible, as they contain the lowest concentration of acid
  • Be sure to peel the stalks before preparing and eating them raw
  • Always drain the cooking water, as the acid goes into the cooking water
  • After consuming rhubarb, use dairy products or citrus fruits for neutralization.

Dairy products are rich in calcium, which counteracts oxalic acid. Citric acid breaks down the acidity of the rhubarb.

Note: Healthy people have no concerns about eating one or two stalks of raw rhubarb in April and May. Tender young stalks of the red variety do not necessarily need to be peeled.

who should give up

You should avoid rhubarb, both raw and cooked, if you already suffer from kidney stones or otherwise

  • kidneys
  • liver
  • Galle
  • rheumatism
  • gout

are ill. Children and pregnant women should be careful when consuming raw rhubarb. The intestinal flora can be disturbed during pregnancy. Rheum rhabarbarum should therefore only be consumed together with dairy products during this time. Boiled rhubarb is more suitable during pregnancy.

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