MSM side effects and warnings: What's really behind them?

MSM is being used more and more often as a dietary supplement. At the same time, you can find lots of different statements online about possible side effects and experiences. But what is scientifically proven, and what belongs in the realm of myth?

We take a closer look and separate study results from personal experience reports and unproven claims. That way, you get a clear overview of what you should know about MSM.

Important: This article does not replace medical advice. If you have persistent or severe symptoms after taking it, getting them checked by a doctor is the right way to go.

Table of Contents

1. What is MSM and what does it do in the body?
2. Which side effects are actually documented?
3. Where do the warnings online come from?
4. What users report
5. Who should be careful with MSM
6. If you want to try MSM: Here's how to go about it
7. Briefly mentioned: MSM and a racing heart or blood pressure
8. My personal assessment
9. Conclusion
10. Common questions about MSM side effects
11. Sources

What is MSM and what does it do in the body?

MSM, short for methylsulfonylmethane, is an organic sulfur compound that occurs naturally in small amounts in some foods, such as fruit and vegetables. Chemically speaking, MSM is the oxidized breakdown product of dimethyl sulfoxide (DMSO), a related but distinct substance with a different safety profile.1

As a dietary supplement, MSM is usually sold in capsule or powder form. There are no authorized health claims for MSM, meaning no reviewed and approved statements about any specific effect. That's why in this article we deliberately make no statements about what MSM is used for, and instead look exclusively at what has been documented about its tolerability and possible side effects.

Which side effects are actually documented?

In the controlled studies on MSM available so far, the most commonly reported effects were mild digestive complaints and headaches, but overall these were rare and mostly no differently distributed than in the respective placebo group.

In a randomized controlled pilot study with 50 women and men aged 40 to 76 with knee osteoarthritis, one group took 6 grams of MSM daily for 12 weeks, the other a placebo.(2) No notable changes in blood pressure, blood count or bleeding tendency were seen. (2) However, people who were already taking blood thinners were excluded from participating, so the study cannot say anything about this group.

A review by researchers at the University of Memphis, which summarizes various studies and reports on the safety of MSM, describes MSM at the doses examined there as well tolerated by most people, with few and predominantly mild side effects.(1) In addition, experience reports mention other complaints, such as skin reactions or sleep problems, and sometimes inner restlessness. These reports have not yet been systematically studied, so they can neither be confirmed nor ruled out.

How often individual complaints occur cannot be reliably quantified from the available studies. The numbers of participants are small, the studies mostly last between 12 and 16 weeks, and research so far has been conducted almost exclusively in older people with knee osteoarthritis. Data on long-term use and on other groups, such as young, healthy adults, are almost entirely lacking. Why some people develop complaints and others don't cannot be conclusively answered from the studies.

Where do the warnings online come from?

A large share of the MSM warnings online goes back to two things: confusion with the related substance DMSO, and individual, often unverified experience reports.

MSM is formed as the oxidized breakdown product of dimethyl sulfoxide (DMSO) (1), a solvent that is used medically, among other things for external application, and that comes with its own warnings. MSM itself is chemically a distinct substance, but warnings about DMSO are sometimes transferred to MSM online without distinction.

The term "sulfur allergy" is also often used very loosely online, sometimes for drug intolerances, sometimes for reactions to sulfur-containing food additives. There is no scientific investigation of this term specifically related to MSM.

On top of that come experience reports from forums and social networks. They often describe individual cases, usually without precise information on the product, dose or other influencing factors, which makes it hard to derive a reliable statement about MSM as a whole. Another part of the uncertainty is created by advertising itself: some providers promise more with MSM than the research supports, and disappointed expectations are then sometimes passed on as a "warning." Occasional circulating claims of poor tolerability with alcohol, or of increased blood pressure and altered liver values, also cannot be confirmed based on the sources we reviewed. If you want to know more about sulfur and MSM in the body in general, this article might interest you: MSM: The effect of sulfur in your body.

What users report

In experience reports on MSM, digestive complaints and headaches come up most often, which roughly matches what is also described in studies.

However, individual reports say little about MSM as an active substance. There is no control group to compare against, to see whether a complaint is actually related to taking it or would have occurred without MSM as well. Expectations can also influence perception: anyone who has read about side effects beforehand often pays closer attention to physical signals; this is called the nocebo effect. Other life circumstances or coexisting illnesses also cannot be factored out of a single experience report.

Who should be careful with MSM

For some groups, particular caution makes sense before trying MSM.

• Pregnancy and breastfeeding: There are not enough human data on this. The German Federal Office of Consumer Protection and Food Safety (BVL) therefore recommends not taking MSM products during this time without consulting a doctor first. (3)
  
  
• Children and adolescents: Here too, the BVL advises against taking it without consulting a doctor first. (3)
  
  
• Coumarin anticoagulants (certain blood thinners): For this group of active substances, the BVL explicitly gives a precautionary recommendation. (3) For other blood thinners or before surgery there are hardly any data so far; here too, it makes sense to check with your doctor or pharmacy.
  
  
• Pre-existing conditions and regular medication: For example, with liver or kidney disease, checking with your doctor beforehand is the safer way to go.

For context: In 2013, the BVL determined that dietary supplements with MSM imported from other EU countries may only be marketed in Germany with a daily amount of up to 50 milligrams. (3) This is an administrative market-access rule for imported products and says nothing about the safety of higher amounts that are regularly permitted in Germany.

If you want to try MSM: Here's how to go about it

A few simple steps help you avoid typical pitfalls when taking it.

• Follow the dosage on the product: The stated daily dose is not exceeded.
  
  
• Starting gradually as a practical option: Some people start with a lower amount and only increase it after a few days. Whether this reduces complaints has not been scientifically tested, but it is a possible practical approach.
  
  
• Drink enough: A general tip when taking dietary supplements, but without specific evidence for MSM.
  
  
• Pause if you have complaints: If they persist or get worse, getting checked by a doctor is the next step.
  
  
• Look for transparency when buying: Complete information on ingredients, origin and any additives used makes an informed decision easier.
  

Briefly mentioned: MSM and a racing heart or blood pressure

There are no controlled studies so far on a racing heart in connection with MSM, only isolated experience reports without a control group. The data on blood pressure changes are also thin: the knee osteoarthritis study described above found no notable changes here, though people on blood-thinner therapy were excluded.(2) If you have a persistent racing heart or unusual blood pressure, the rule in any case is: get it checked by a doctor.

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My personal assessment

What struck me while researching this article: compared with many other nutrients, the research on MSM is narrow, but within this narrow base it is surprisingly consistent. Again and again the same mild complaints, mainly in the digestive tract and headaches.

Still, I would never conclude from this that MSM is automatically unproblematic for every person. A small study with 50 participants over 12 weeks is something different from proof of safety over years or with every pre-existing condition. That's why I'm trying to give an honest interim assessment here: what has actually been studied and what remains open. If you're unsure whether MSM fits your current situation, talking to your doctor is in any case more helpful than a forum post.

Conclusion

In the studies available so far, MSM was mostly well tolerated; reported side effects were usually mild and mainly concerned digestion and headaches. At the same time, the data are thin: the studies are small, short and were conducted almost exclusively in older people with knee osteoarthritis. If you searched for "MSM warning," here is the most honest answer: research findings and experience reports are two different things and deserve different weight in your decision.

A practical first step if you want to try MSM: before taking it for the first time, briefly note which of the typical complaints you already get occasionally anyway. That makes it easier later to tell what has actually been added. If you belong to one of the groups mentioned above for whom particular caution applies, a short conversation with your doctor or at the pharmacy is the most sensible first step.

Common questions about MSM side effects

Is MSM dangerous?

The studies available so far, which are admittedly small and short, give no indication of serious side effects at the doses examined. For certain groups, such as during pregnancy and breastfeeding or with regular medication use, special recommendations apply, which is why consulting a doctor makes sense here.

What side effects does MSM have?

The most frequently mentioned in studies and experience reports are digestive complaints such as bloating or soft stools, as well as headaches. Less often, tiredness or concentration problems are also reported. How often these complaints occur individually cannot be reliably quantified from the small studies so far.

Can MSM cause headaches?

Headaches are among the most frequently mentioned complaints in connection with MSM. A clear mechanism for this has not yet been studied. If the headaches persist, getting checked by a doctor makes sense to rule out other causes.

Can I take MSM during pregnancy?

There are not enough human data for pregnancy and breastfeeding. The BVL therefore recommends not taking MSM products during this time without consulting a doctor first. It's best to discuss this question directly with your gynecologist.

What should I do if I have complaints after taking it?

If you have complaints after taking it, it makes sense to pause MSM first and observe whether the complaints improve. If they persist or get worse, getting checked by a doctor is the next step. It's best to note down since when you've had which complaints; that makes the conversation at the practice easier.

Related reading: MSM: The effect of sulfur in your body, Frankincense and MSM

Sources

1. Butawan M, Benjamin RL, Bloomer RJ. Methylsulfonylmethane: Applications and Safety of a Novel Dietary Supplement. Nutrients. 2017;9(3):290. doi: 10.3390/nu9030290. PMID: 28300758. Review summarizing areas of application and safety data on MSM from various studies and reports.
2. Kim LS, Axelrod LJ, Howard P, Buratovich N, Waters RF. Efficacy of methylsulfonylmethane (MSM) in osteoarthritis pain of the knee: a pilot clinical trial. Osteoarthritis Cartilage. 2006;14(3):286-294. doi: 10.1016/j.joca.2005.10.003. PMID: 16309928. Randomized controlled pilot study with 50 participants with knee osteoarthritis over 12 weeks, used here exclusively for the side-effect data.
3. Bundesamt für Verbraucherschutz und Lebensmittelsicherheit (BVL). Bekanntmachung einer Allgemeinverfügung gemäß § 54 LFGB für Nahrungsergänzungsmittel mit Zusatz von Methylsulfonylmethan (BVL 13/01/022). November 25, 2013. Official German authority regulation on maximum amounts and on population groups for whom particular caution is recommended.