Could daily sniffs of insulin boost your memory? Even more crucial, could
they improve the memories of Alzheimer's patients? Preliminary, yet building,
evidence suggests so.
A small study in the November Psychoneuroendocrinology found that
healthy young persons' memories can profit from inhaling insulin. The lead
investigator was Christian Benedict, M.D., a nutrition scientist at the
University of Lübeck in Germany.
In this trial, 38 healthy individuals aged 18 to 34 years sniffed either 40
I.U. of insulin four times a day during an eight-week period or saline (a
placebo) four times a day during the same period. Both at the start of the
study and seven weeks into it, the researchers had the subjects learn words,
then try to recall them a week later. Neither group's delayed word recall was
as good at the end of the study as it had been at the start—apparently
because of false recall of words from previous word lists. Nonetheless, the
group getting insulin performed significantly better at delayed word recall at
the end of the study than did the placebo group.
"Results indicate a direct action of prolonged intranasal
administration of insulin on brain functions, improving memory... in the
absence of systemic side effects," Benedict and his colleagues
concluded. "These findings could be of relevance for the treatment of
patients with memory disorders like Alzheimer's disease."
Intravenous insulin was known to improve memory before Benedict and his
team found that intranasal insulin can also do so, and it was that discovery
that spurred Benedict and his coworkers to undertake their study. The
advantage of using intranasal rather than intravenous insulin, however, is
that it does not cause systemic side effects like hypoglycemia.
At the 2003 annual meeting of the Society for Neuroscience, Suzanne Craft,
Ph.D., a professor of psychiatry at the University of Washington, and
colleagues reported the results from a small trial indicating that insulin
sniffs can boost memory in both healthy older adults and persons with
Alzheimer's, but especially the latter. The study included 20 healthy older
adults and 10 Alzheimer's patients. On three separate visits, the subjects
received intranasal administration of saline or one of two insulin doses (20
I.U. or 40 I.U.).
Shortly after administration, subjects were tested on story recall. Both
the healthy subjects and the Alzheimer's subjects performed significantly
better after getting insulin than getting a placebo, and the effect was even
greater in the latter.
Another pilot trial by Craft and coworkers, in fact, suggests that giving a
medication that boosts insulin's activity may be a way of halting memory loss
in Alzheimer's patients. The medication is rosiglitazone, which is used to
treat insulin resistance linked with type 2 diabetes. Results of this trial
were reported at the Ninth International Conference on Alzheimer's Disease and
Related Disorders in July.
GlaxoSmithKline, rosiglitazone's manufacturer, is conducting a larger trial
to explore further the medication's seemingly salutary effect on memory in
How insulin might improve memory remains to be determined. Intranasally
administered insulin is known to enter the cerebrospinal fluid, and insulin
receptors have been detected in the hippocampus, a prime memory center in the
And while the means by which rosiglitazone might stop memory loss in
Alzheimer's patients is unknown, scientists suspect that it may not only alter
brain levels of insulin, but also change brain levels of beta-amyloid
protein—purportedly a major culprit in the Alzheimer's disease
An abstract of the study, "Intranasal Insulin Improves Memory
in Humans," can be accessed online at<www.sciencedirect.com>
by clicking on "Browse Journals," "P," and then"
Psychoneuroendocrinology." The two studies reported by Craft and
coworkers at scientific meetings are under review by scientific journals.
Information about the GlaxoSmithKline rosiglitazone memory trial can be
obtained by e-mail at