What is cola de caballo?

What is cola de caballo?

Cola de caballo is a tall, reed-like plant. In English it is called giant horsetail. Its botanical name is Equisetum giganteum.

It grows in wet ground from Mexico down through South America. The hollow green stems are cut, dried and brewed as a tea. Market stalls and herbal shops across Latin America still sell it by the bundle.

It was used mainly to make a person pass more urine. It was also taken for the kidneys and bladder, and applied to skin, hair and nails.

Here is the honest verdict. Human research on this species is almost absent. Long use in tradition is not proof that it works, and it is not proof that it is safe.

One small trial of a close relative, Equisetum arvense, found a real but short-lived diuretic (urine-increasing) effect. That is the strongest human evidence the horsetail family has. It does not cover hair, nails, bone or kidney stones.

How does cola de caballo work?

Why might it make you pass more urine?

No one has shown clearly how cola de caballo acts in the human body. The usual explanation is a mild diuretic effect, meaning it makes you urinate more.

In animal studies, horsetail extracts raised urine output. In one small human trial, an Equisetum arvense extract did the same. That trial used a different species, so the result may not carry over.

The flavonoids and potassium salts in the plant are the usual suspects for this effect. That link is proposed, not proven.

In laboratory tests, horsetail extracts slow the growth of some bacteria. They also lower some markers of inflammation in cell studies. Whether either happens inside a person is not established.

The stems are rich in silica, a mineral also found in sand. Tradition took this as the reason for stronger hair and nails. The idea that silica from a tea reaches hair, nails or bone has not been shown in people.

What forms does cola de caballo come in?

How is it sold?

- Loose dried stems, sold in bundles or bags. - Tea bags, often blended with other herbs. - Capsules and tablets of dried extract.

- Liquid tinctures and fluid extracts. - Hair rinses, shampoos and nail creams. - Sitz baths and skin washes made from the tea.

Quality varies a lot. Loose herb from a market may be another Equisetum species.

One of them, marsh horsetail, is poisonous. A labelled product from a regulated maker is the safer buy.

Where it comes from:

What did tradition claim?

Horsetails have been used in the Americas since before European contact. Colonial-era Spanish and Portuguese herbals recorded the plant and borrowed its uses.

Healers in Mexico, Peru, Chile, Argentina and Brazil used it as a urine-promoting tea. It carried names such as cavalinha, carricillo and cola de caballo.

It was also traditionally washed over wounds and sore gums. Women were given it after childbirth for bleeding. Hair rinses for shine and strength were common.

These records describe what people did. They do not tell us whether it helped.

What does cola de caballo help with?

• Mild fluid retention (puffiness from held water): This is the best-supported use, and the support is still thin. Tradition drank the tea to shed held water. One small Brazilian trial of the related Equisetum arvense raised urine output in healthy men over four days. No trial has tested Equisetum giganteum this way. Swelling in the legs can be a sign of heart or kidney trouble, which needs a doctor, not a tea.
• Urinary discomfort and 'flushing' the bladder: Tradition used it to wash out the bladder during stinging or frequent urination. There is no human trial showing it treats a urinary infection. Laboratory tests show some action against bacteria, which is not the same as working in a person. A urinary infection can reach the kidneys, so it needs proper medical care.
• Preventing kidney stones: Tradition treated it as a stone-clearing tea. Animal and test-tube work hints at an effect on crystal formation. No human trial supports this use. Drinking more fluid is the step with real evidence behind it.
• Brittle hair and nails: The claim rests on the plant's silica content. A few small studies used silicon supplements, not this plant, and the results were weak. There is no good trial of cola de caballo for hair or nails, taken by mouth or used as a rinse.
• Bone strength: Tradition linked the gritty stems to strong bones. Some animal work suggests horsetail extracts affect bone cells. There is no reliable human trial. Do not use it in place of treatment for thin bones.
• Minor wounds and mouth sores: Washes and gargles were a common folk use. Evidence is limited to laboratory tests and a few small studies on other horsetail species. Deep, dirty or spreading wounds need medical care.
• Heavy bleeding: Tradition gave it after childbirth and for heavy periods. No human evidence supports this. Heavy or unexplained bleeding needs a doctor, and this plant should not be used while pregnant or soon after birth without medical advice.

What are the side effects of cola de caballo?

• Passing urine more often
• Thirst and dehydration
• Low potassium, which can cause muscle cramps and weakness
• Headache
• Stomach upset or nausea
• Skin rash or allergic reaction
• Thiamine (vitamin B1) depletion with long or heavy use
• Worsening of existing heart or kidney problems
• Poisoning if the product is really marsh horsetail (Equisetum palustre)

Good to know:

Most people who drink the tea briefly have no trouble beyond extra trips to the toilet.

The serious risks come from three places. One is heavy loss of fluid and potassium. Another is vitamin B1 loss with long use.

The third is picking or buying the wrong species.

Stop and seek advice if you feel weak, dizzy or notice an odd heartbeat.

How much cola de caballo should you take?

• Recommended daily: This is general label information, not advice for you. Labels on European-style horsetail products often list about 1 to 2 grams of dried stem per cup of tea, two or three times a day. Capsule products often list a few hundred milligrams of dried extract daily. These figures come mostly from Equisetum arvense. There is no agreed dose for Equisetum giganteum. Talk to a doctor or pharmacist before using it, especially if you take any regular medicine.
• Best time of day: Earlier in the day suits most people. It can make you pass more urine, so an evening cup may wake you at night. Timing does not change how well it works.
• With or without food: It is usually taken as a tea, with or without food. Taking it with food may ease stomach upset. Drink enough water while using it, since it makes you lose fluid.
• Time to effect: If it increases urine output, that usually shows within a few hours. In the one small trial of a related species, the effect appeared on the first day. For hair, nails, bone or stones, no timeline can be given. Nothing has been shown to happen at all. It may do nothing for you.
• How long to take it: Short use is the norm. Most herbal guidance caps horsetail at a few weeks at a time. The reason is the thiaminase in the plant, which can break down thiamine (vitamin B1). Long or heavy use has been linked to thiamine deficiency in animals. There is no safety data for months of daily use in people.