Spermidine, Sleep and Autophagy: Part One: The Trial That Found Nothing

Abstract

Spermidine is sold on autophagy — the cellular recycling process it reliably induces. The most rigorous test of whether that translates into anything a person would notice was published in JAMA Network Open in 2022, and it found nothing.

This is the first of four parts, one per publication. Part Two covers a synthesis of 22 studies and the three measurement problems that explain their disagreement. Part Three covers an animal study showing what else autophagy induction does. Part Four covers a trial now recruiting, which is asking a narrower question with better instruments.

We use no spermidine and have no interest in the answer. This part is about a null result that was handled unusually well, by a team with unusually strong reasons to want a different one.

1.The Trial

SmartAge was a phase 2b, randomised, double-masked, placebo-controlled trial conducted at an academic clinical research centre in Berlin between January 2017 and May 2020, reported by Claudia Schwarz, Miranka Wirth, Agnes Flöel and colleagues.

One hundred adults aged 60 to 90 with subjective cognitive decline — people who notice their memory slipping while testing normally, a group at elevated risk of later dementia — were randomised one to one. The intervention was a spermidine-rich wheat germ extract delivering 0.9 mg of spermidine daily; the comparator was microcrystalline cellulose. The intervention ran for twelve months and 89 per cent of participants completed it.

The primary outcome was memory, operationalised as mnemonic discrimination on the Mnemonic Similarity Task — a measure sensitive to the hippocampal pattern-separation function that declines early in this population. It was pre-specified, and the analysis was intention-to-treat.

2.The Result

Over twelve months, the between-group difference in mnemonic discrimination was −0.03, with a 95 per cent confidence interval from −0.11 to 0.05, and a p-value of 0.47.

The secondary outcomes — additional neuropsychological, behavioural and physiological parameters — showed nothing either. Adverse events were balanced between groups.

Exploratory analyses indicated possible beneficial effects on inflammation and verbal memory. The paper labels them as exploratory and does not build on them.

The key-points summary states the conclusion in the plainest available form: longer-term spermidine supplementation with an increased daily supply of spermidine by about 10 per cent did not modify memory and other biomarkers in a group of older adults at risk for Alzheimer disease.

3.The Ten Per Cent

That phrase — an increased daily supply of about 10 per cent — is the most important number in the paper and the one most often left out when the trial is cited.

Spermidine is present in ordinary food. Wheat germ, soybeans, aged cheese and mushrooms all contain it, and a normal diet supplies several milligrams a day. Adding 0.9 mg raises that total by roughly a tenth.

A null result from a ten per cent increase in intake says something quite limited. It does not establish that spermidine is inert; it establishes that a small dietary increment, sustained for a year, does not measurably change memory in this population.

A commentary on the trial made exactly this point, arguing that insufficient dosage may explain the absence of effect, and noting that the dose was chosen for safety and tolerability rather than to maximise the chance of a signal. Part Four covers the trial that responded to this objection.

4.Who Ran It, and Why That Matters Here

The commercial exposure in this trial was substantial and it is declared in full.

Three authors reported equity interests and advisory roles at The Longevity Labs GmbH, a company selling spermidine. A fourth was its chief executive during the planning, initiation and conduct of the trial, holding equity until December 2019. One author holds a pending US patent for technology related to spermidine. The company provided funds toward developing the wheat germ extract used.

Core funding came from the German federal research ministry and the German Research Foundation, and the paper states that funders had no role in the design and conduct of the study, in data collection, management, analysis or interpretation, in preparation or approval of the manuscript, or in the decision to submit.

We have spent several articles in this section documenting the opposite pattern: a null primary outcome quietly replaced in the abstract by a positive secondary. This trial did not do that. It leads with the null, in the key-points box, in a high-visibility journal, with a supplement company inside the author list.

That is why we treat this particular null as strong rather than as one result among several. A negative finding reported plainly by people who would have preferred a positive one is worth more than a positive finding reported by anyone.

5.What It Establishes and What It Does Not

It establishes that 0.9 mg a day of spermidine from wheat germ extract, over twelve months, does not improve mnemonic discrimination in older adults with subjective cognitive decline. That is a specific, well-tested, useful claim.

It does not establish that higher doses do nothing. It does not address sleep, which is the endpoint of the trial in Part Four. And with 100 participants it could not have detected a small effect even had one existed.

What it does do is set the standard the rest of this literature has to clear. When a synthesis of 22 studies reports that spermidine looks promising for cognitive ageing — as Part Two describes — the single largest and longest randomised trial inside it is the one reported here.

Editorial Comment

MindHeaven® does not use spermidine in any formulation and has no plans to. Spermidine has no authorised health claim in the European Union and we make none.

We are opening this series with the negative trial deliberately. The ordinary way to write about spermidine is to begin with autophagy, proceed through the mouse data, and mention the human trials briefly near the end. Reversing that order is not a rhetorical trick — it reflects where the evidence actually is.

Part Two takes up the wider literature, and explains why studies of this compound disagree with each other so consistently. The answer turns out to have less to do with spermidine than with how it is measured.