Evidence: Reasonable Possible Benefits: Reasonable Safety: Reasonable
TABLE OF CONTENTS
What is horsetail?
Equisetum arvense, also known as Horsetail, is an adaptogenic herb with a long history of use as a traditional medicine. This herb is often used as a supplement for its diuretic effects but can also have various other beneficial effects. This article is about the main benefits of horsetail, its potential side effects, the best time to take it, and more.
Possible benefits
All of the potential benefits mentioned below are dose-dependent. As with other adaptogenic herbs, there is a sweet-spot dose that allows you to get most of the benefits without causing meaningful side effects or tolerance buildup in the body. We will discuss the best dosing protocol later in this article.
Minor benefits
Increased urination – Horsetail acts as a strong diuretic (water pill), which means it can increase urination. This can be helpful for people with high blood pressure caused by excess sodium as horsetail can help your kidneys release more sodium into the urine.
Lowered blood pressure – This benefit is secondary to horsetail’s diuretic effects and is helpful mainly to people with excess sodium levels.
Antioxidant properties – This herb contains a variety of antioxidants and can be helpful for reducing oxidative stress in the body.
Improved cholesterol levels – Animal and test tube studies show reductions in LDL and total cholesterol and possible increases in HDL cholesterol levels. Human studies are needed to confirm that this benefit applies to humans as well.
Reduced inflammation – While more studies are needed to confirm this effect, this herb appears to have anti-inflammatory properties.
Possible side effects
The side effects below are dose-dependent. The risk for them increases (often linearly but sometimes exponentially) as you increase the dose. Some of the side effects only apply to very high doses.
Vitamin B1 deficiency – Horsetail contains a compound called thiaminase that can deplete the body of vitamin B1 (thiamine). If you are going to take horsetail, make sure you’re getting enough thiamine as well.
Potassium or sodium deficiency – Since horsetail is a diuretic, it causes the body to flush out water, sodium, and potassium through the urine. This can be problematic when you don’t get enough of one of these. Most people do get enough water and salt but potassium is relatively easy to become deficient in, especially when one takes diuretics.
Initial adverse reaction – When you start taking horsetail, things can get worse before they get better. This herb can temporarily worsen some aspects of your health and even make you sick for a few days after you start taking it. That can be unpleasant, but it is usually a sign that the supplement is working and creating a hormetic response that allows the body to adapt and become more resilient in the long term.
Allergic reaction – Some people are allergic to this herb and may experience an allergic reaction after they start taking it. Unlike the “initial adverse reaction,” allergic reactions typically don’t disappear until one stops taking the herb.
Nausea – This side effect is most common when people take the herb on an empty stomach.
Diarrhea – You can usually prevent diarrhea or stomach discomfort by taking this herb with a meal.
Toxicity – As an adaptogen, horsetail acts as a mild stressor on the body. That is usually a great thing as it allows your body to adapt to specific forms of stress and become more resilient. However, stressing the body too much can be counter-productive and cause multiple side effects, including toxicity. While acute toxicity is extremely rare, taking high amounts of this herb could lead to chronic toxicity and cause health problems over time. To prevent chronic toxicity or the buildup of tolerance, staying below 900 mg in a day is best unless you have a great reason to take more.
Contamination – If growing or storing conditions are not adequately controlled, horsetail can be contaminated with bacteria, molds, and other potentially harmful microorganisms. Some growers also use pesticides and herbicides that can be unsafe. Another issue is that herbal supplements can get contaminated with other supplements and chemicals during the manufacturing process. Choose the brand you get herbs and herbal supplements from wisely. It is often best to use websites like Amazon, where thousands of users have reviewed and rated the products. You are less likely to buy something of lower quality there.
Who should not take horsetail?
You should probably avoid taking horsetail if you:
experience a severe adverse reaction after taking the herb (though a mild adverse reaction is usually a great thing as it is a sign that the supplement is working and causing a hormetic response that allows the body to adapt and become more resilient)
are pregnant or breastfeeding (while it can be safe to take this adaptogen during pregnancy or breastfeeding, it acts as a mild stressor and can put some unnecessary risk to the child)
are on a tight supplement budget (there are more cost-effective supplements on the market for most people)
Who will benefit the most?
You should consider taking the supplement if you:
have excess sodium in the body
have a high budget for supplements and are willing to experiment with a variety of them (assuming you don’t fall into any of the categories that should avoid this herb, horsetail appears safe and is unlikely to do more harm than good for most people)
How much horsetail should you take?
Because horsetail is an adaptogenic herb, it acts as a mild hormetic stressor on the body, which allows your body to adapt and become more resilient to certain kinds of stressors in the long term.
A higher dose does not necessarily lead to more pronounced benefits. Instead, there appears to be an inverted U-shaped dose-response pattern. In other words, you want to find a sweet-spot dose that allows you to get the benefits of horsetail without putting too much pressure on the body or quickly causing the body to develop tolerance to the herb.
The sweet-spot dose typically ranges anywhere between 300-900 mg of dry herb daily. If you buy an x:1 extract, divide the dry herb powder dosage by x.
The higher end of this range usually provides slightly more benefits in the short term. If you plan to take this herb for a longer time (multiple months or years), the lower end is probably a better way to go since you would develop tolerance faster if you were to take higher doses.
Additionally, very high doses can put too much pressure on your system and cause health problems if you take the supplement for a prolonged period.
While this herb could theoretically cause acute toxicity, you’d need to take an extremely high dose that would be way beyond what even the most potent supplements contain.
Like most other adaptogens, it is best to cycle horsetail and take about two days off weekly to reset your tolerance. That will allow you to keep getting the benefits in the long term.
Keep in mind that the effects of this herb are cumulative. Therefore, you must take it for at least 2-4 weeks to notice most of the benefits. But again, cycling the herb and not taking it at least twice a week is necessary to prevent tolerance in the long term.
Best time to take horsetail
You can take this herb with or without food. Each of these options has its benefits. The main bioactive compounds in the herb should absorb well either way.
If you experience nausea or stomach discomfort when you take this herb, taking it with food should prevent these unpleasant effects or at least make them less intense.
If you take this herb on an empty stomach, the short-term effects will kick in faster, and they will be more pronounced but will not last as long.
Whether you take this herb in the morning or the evening typically does not make much difference. Both options are fine so feel free to experiment.
Interactions
Vitamin B1 Horsetail contains a compound called thiaminase that can deplete the body of vitamin B1 (thiamine). If you are going to take horsetail, make sure you’re getting enough thiamine as well.
Potassium Since horsetail is a diuretic, it causes the body to flush out water, salt, and potassium through the urine. This can be problematic when you don’t get enough of one of these. Most people do get enough water and salt but potassium is relatively easy to become deficient in, especially when one takes diuretics.
Where to buy horsetail?
In most countries, Amazon is the best option for ordering horsetail and other herbs and herbal supplements. They offer some very affordable products backed by many positive reviews. Also, you can choose from a wide range of brands without having to search through other markets on the Internet.
Some brands display the dosage per serving instead of per pill or capsule. Therefore, you may accidentally buy something less potent than you intended. Do not fall for this marketing trick.
FAQ
As with most other herbs and herbal supplements, it is best to cycle horsetail and take a break from it for about two days per week to reset your tolerance back to baseline. That will keep your body sensitive to the herb and allow you to keep getting the benefits in the long term.
When you take a standardized extract, you know exactly how potent it is and how much you need to take to get the desired outcome. Herbal extracts also tend to be cheaper than unextracted powders in many cases. However, many of the potentially beneficial compounds get lost during the extraction process. Therefore, if you know how potent the unextracted powder is, it is almost always a better option.
All of these options are fine. The two most important things to consider are the price and dosing. Powders are almost always the cheapest form. However, you may need a highly accurate scale to dose them correctly (preferably 0.001g). You can get one for as little as $20 from Amazon. Dosing the powders also takes time which can add up over months or years. The disadvantage of capsules is that they are often made of bovine gelatine, which rarely comes from ethical sources.
Yes, you can. This herb should not impact your sleep in any negative way. Whether you take it in the morning or the evening typically doesn’t make much difference. Both options are fine so feel free to experiment.
This herb should not become harmful once it exceeds the expiration date, but it can lose potency over time. Keep this herb or herbal supplement in a cold, dark, and dry place and it should remain just as potent for many months or even years.
As an adaptogen, horsetail acts as a mild stressor on the body. That is usually a great thing as it allows your body to adapt to specific forms of stress and become more resilient. However, putting too much pressure on the body can be counter-productive and cause multiple side effects, including toxicity. While acute toxicity is extremely rare, taking very high amounts of this herb could lead to chronic toxicity and cause health problems over time. High doses can also make you develop tolerance much faster than lower doses so they may be less effective in the long term.
While you could safely take higher doses, there is usually no point in taking more than 900 mg of dry herb daily. This amount should give you most of the benefits without meaningful side effects. Paradoxically, taking a higher dose would likely lead to fewer benefits as the body would quickly become accustomed to the herb.
Unfortunately, there is not much information about the half-life of horsetail in the body. However, most of the effects of this herb are cumulative, so they mostly happen in the long term rather than acutely. Therefore, the half-life of this herb isn’t very relevant in practice.
The effects of this herb are cumulative. Therefore, you must take it for at least 2-4 weeks to notice most of the benefits. But again, cycling the herb and not taking it at least twice a week is necessary to prevent tolerance in the long term.
Yes, horsetail is vegan-friendly. If you buy this herb in a capsulated form, beware that the capsules often contain animal-based gelatin. Instead, find a brand that puts its products into cellulose capsules.
No, it does not. The herb does not interfere with fasting in any significant way.
References
Most of the information in this guide is based on scientific research that can be found and verified in the PubMed medical library. We highly encourage you to use the library to verify anything you read in this article. We excluded from consideration studies that are either confounded or have a high conflict of interest.
