Ask Mr. Wizard

Adding Magnesium Salts in Beer


Anonymous professional brewer — via email asks,

I recently was told by another brewer I should not be adding magnesium to my brew water because of its laxative effects. Is this true? I’ve never heard of this being an issue. Also, how much magnesium does a person need to consume for that effect to kick in?


According to the article “Can You Take Too Much Magnesium” published on the Medical News Today website, the National Institutes of Health recommends 310–320 mg as the daily magnesium allowance for adult women and 400–420 mg as the daily magnesium allowance for adult men. Although typical diets may naturally contain sufficient magnesium to satisfy daily recommendations, some people take dietary supplements for a variety of reasons including magnesium deficiencies associated with the modern diet.

The NIH recommendation for all people older than 9 is to limit magnesium supplements to 350 mg per day (this is above magnesium ingested from food and beverages). I don’t offer medical advice because I am a brewer, so please read up on magnesium if you want to know more about how it’s used by the body and why there is a recommended daily allowance.

It is well known that magnesium has a laxative effect on people when ionic magnesium, for example from salts like magnesium chloride and magnesium sulfate, is ingested above about 350 mg/day. And higher consumption rates above 350 mg/day usually leads to diarrhea. That’s why my friend does not want to add magnesium to brewing water. The related questions are: 1) how much magnesium is normally present in beer and 2) how much magnesium needs to be added to water to affect beer flavor?

Commercially brewed beers typically contain between about 40–150 ppm (mg/L) of magnesium. It’s hard to know how much of this magnesium is from the brewing water, but levels in water are typically below 40 ppm, meaning that the balance originates from other brewing ingredients, primarily malt. That’s a good thing because yeast do require magnesium for certain enzymatic reactions, and water devoid of magnesium need not be a concern.

The easiest way to understand how magnesium influences beer flavor is to buy Epsom salt without any aromatherapy additives.

The reason I am a fan of magnesium in brewing water is that it adds to the flavor of beer. At low levels, magnesium is hard to pick up, but is known to make water more refreshing. That may be why Dasani water adds a magnesium salt to its water. But when the concentration in water is increased to 20–40 ppm, magnesium adds a distinctive bitter-metallic flavor that can be detected in the finished beer. Why do all beers not taste like magnesium given the concentration in malt? It’s likely the form; magnesium in malt is largely bound or associated with proteins, nucleic acids, and bran. Plant physiology aside, magnesium added to brewing water affects beer flavor.

The easiest way to understand how magnesium influences beer flavor is to buy Epsom salt (magnesium sulfate heptahydrate) without any aromatherapy additives. Make up a solution in water and add a few drops to a beer for tasting. If you like what a bit of magnesium adds to your pint of beer, this salt may be a water treatment you should try in your next brew.

Back to the original concern, how much magnesium-spiked beer can the average beer lover consume without having gastric issues? Referencing the NIH recommendations, the maximum intake from supplements is 350 mg/L. If we consider magnesium added to brewing water as a supplement and set our level in brewing water at 35 mg/L, which is on the high side, a beer drinker would hit this maximum intake after consuming 10 liters, or (28) 12-ounce bottles of beer.

Like I stated earlier, I don’t provide medical advice. But I will wager a guess that most people will have problems much worse than a touch of the runs after consuming 28 beers in a day. Therefore, I suggest that adding a touch of magnesium to brewing water is not likely to cause gastrointestinal problems for the typical beer lover, even if your nickname is Joe Six-Pack. That’s my answer and I am sticking to it!

Response by Ashton Lewis.