Five Questions about magnesium with Jeroen de Baaij What is true about the health claims of influencers on social media?

10 October 2023

Influencers online are raving about the alleged effects of magnesium. They claim it makes you burst with energy and helps with various ailments, such as fatigue and brain fog. But are these claims well-founded, or are they mainly fueled by sellers of dietary supplements? We asked magnesium expert Jeroen de Baaij from Radboud University Medical Center.

How does magnesium function in the body?

‘Magnesium is important for muscles, bones, brain, blood vessels, and the heart. Muscles use calcium to contract and magnesium for relaxation. People with a magnesium deficiency may experience muscle cramps, as relaxation doesn't work properly.

In the Netherlands, one to two percent of the population has a magnesium deficiency, measured in the blood. The recommended daily amount of magnesium is 350 mg for men and 300 mg for women. This can be obtained through a varied diet rich in green vegetables.

A magnesium deficiency is more common in people taking certain medications, such as strong antacids. This doesn't apply to mild remedies like Rennies.’

When should you supplement magnesium?

‘Supplementing magnesium only makes sense if a deficiency is proven in the blood. We often see people consulting a doctor with muscle cramps, making it difficult for them to sleep, for example. Influencers sometimes claim that you can identify a magnesium deficiency with a questionnaire, but that's not true. You need to consult a doctor to have it measured.

If the blood magnesium level is normal, taking extra magnesium is not very effective. The excess magnesium is excreted. Studies on the effects of extra magnesium on sleep, muscle complaints, and fatigue in people with normal blood values showed little to no increase in blood magnesium levels. In people with sleep problems, a cautiously positive effect of magnesium on symptoms was demonstrated. However, this was not objectively measured, in small groups and only through questionnaires. Better studies with a placebo as a control and better measurements are needed to truly demonstrate any potential effect.

Some people claim that you can still have a magnesium deficiency even if your blood values are normal. This is based on the fact that most magnesium is not in the blood but in the bones and soft tissues, such as muscles and the liver. However, there is no evidence that the concentration in these tissues can be low while the blood value is normal. And that doesn't make sense either.’

Can taking extra magnesium be harmful?

‘Taking too much magnesium can lead to diarrhea and other gastrointestinal issues, affecting the absorption of various nutrients. However, these issues only arise with high intake. Taking extra magnesium is not harmful quickly, but be cautious about the quantity.

What I find dangerous about influencer claims is that they can encourage people to avoid the medical world and self-treat, as if you can solve various complaints only with diet. I see the strangest claims, such as magnesium helping with depression. There is no evidence for that. If you have complaints, go to a doctor and find out what's going on. After that, you can still consider a diet or supplement.’

How should you best take extra magnesium?

‘You can take it in tablet form. There is much debate about the best form of magnesium, such as oxide, chloride, or sulfate. Radboudumc has conducted research on this. It turns out that the absorption in the blood varies per person. Chloride may work better for one person, while sulfate works better for another. This likely depends on various factors, such as diet and acidity in the intestines. So, we cannot designate one pill as the best and cannot provide a general recommendation.

It has also never been proven that magnesium absorption improves in combination with other vitamins, such as B6. However, it has been proven that a combination with a fiber-rich meal increases absorption. We observed this ourselves in a study with dietary fibers, namely inulin. It doesn't matter whether that fiber-rich meal is breakfast, lunch, or dinner.’

Do oils and creams with magnesium work?

‘There is no evidence for the effectiveness of oils and creams with magnesium. The skin does not absorb magnesium. When you apply such a cream, the massage may have a relaxing effect on the muscle, but the magnesium does nothing. We know from people who swim in the Dead Sea, which has a high magnesium content, that the magnesium level in their blood does not increase. Absorption does not occur through the skin.’

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