F Few topics have had as mixed a reception in the news as supplements.  Over the years, I’ve seen a series of headlines flip-flopping on the situation, such as when omega-3 fatty acids were lauded as heart-healthy . . . then that position reversed in 2020 when suddenly news articles switched to saying omega-3’s have no effect on cardiovascular health.  I’ve seen similar with the cognitive benefits of magnesium and vitamin D3.

When you review the studies on various supplements, the mixed message is there, though in greater detail.  You’ll see a handful of studies showing one demographic/age range/etc. clearly doing better on cognitive tests, then another block of them declaring the supplements to make zero difference.  I attribute this to a blurred line that comes from taking a supplement to fix a deficiency vs. one that will actually raise your baseline.

A prime example here is taking magnesium.  There are plenty of studies where supplementing magnesium boosted cognitive test results.  Meanwhile, others tried giving it to “healthy young subjects” and concluded it was irrelevant.  Unfortunately, those studies didn’t do much to confirm if users were deficient in magnesium or not via blood testing, so it’s up to us to guess.

Are supplements just fixing deficiencies?
Image by John Hain

I don’t think anyone would argue that fixing deficiencies is A Good Thing.  If you’re lacking in something crucial to your brain’s operation, even if it’s capable of at least partially compensating (our bodies can synthesize a significant amount of what we need to function, though hardly all of it), supplementing it will help.

The tough call then is if it’s still worth supplementing, assuming you generally have a solid diet and are not deficient.  The only definitive answer anyone can give would require specifically testing a supplement in young, healthy people divided into four groups:

  1.  First split them into deficient and sufficient;
  2. Then further split those groups into supplemented and placebo.

In fact, while researching my work-in-progress book, that’s exactly the sort of study I’ve looked for, and I find them lacking.

How I would test this

How I would test this hypothesis…as I’ve so expertly drawn for you

Unfortunately, I have yet to find something like that.  If you come across it for any supplements, please send it my way!  In the meantime, the best path forward I’ve found is to compare and contrast the studies we do have, and look for a consistent mode of action that’d explain if the substance in question is effective or not for supplementing people who already have decent levels.

In magnesium’s case, the record is quite strong for it helping to boost cognitive function in anyone deficient and also those on the older-and-wiser side of the age-related cognitive decline curve.  For the young and healthy crew, meanwhile, I point to rat studies using Magnesium L-Threonate which showed both young and old adult mice getting a boost (such as [1]Slutsky, Inna, Nashat Abumaria, Long-Jun Wu, Chao Huang, Ling Zhang, Bo Li, Xiang Zhao, et al. “Enhancement of Learning and Memory by Elevating Brain Magnesium.” Neuron 65, no. 2 (January 28, … Continue reading).  This variant penetrates the blood-brain barrier in a way other forms don’t, increasing levels in the brain, so there’s a mode of action for it helping you regardless of age.

While there are human studies supporting this, they’re focused on the aging population dealing with degenerative conditions.  That means for anyone younger than say 35, it’s a judgment call if boosting magnesium will help you . . .  though I can tell you a 25-year-old Alex would have taken it, if I knew what I know now then!


1 Slutsky, Inna, Nashat Abumaria, Long-Jun Wu, Chao Huang, Ling Zhang, Bo Li, Xiang Zhao, et al. “Enhancement of Learning and Memory by Elevating Brain Magnesium.” Neuron 65, no. 2 (January 28, 2010): 165–77. https://doi.org/10.1016/j.neuron.2009.12.026.