Research Checks queries recently published studies and how they are reported in the media. The analysis is undertaken by one or more academics not involved in the study, and reviewed by another, to ensure that it is accurate.
Don’t we all want to do what we can to reduce the impact of age-related decline on our memory?
A new study suggests that a daily multivitamin and mineral supplement is a simple and inexpensive way to help older adults slow the decline in some aspects of memory function.
The new study, from a long-term clinical trial, shows there may be a slight benefit to taking a daily multivitamin and mineral supplement for a type of cognitive task (immediate word recall) in older adults Caucasians who work well. At least in the short term.
But that doesn’t mean we should all rush out and buy multivitamins. The results of the study do not apply to the entire population, nor to all types of memory functions. The study also does not show long-term benefits.
How was the study conducted?
The COSMOS Global Study is a well-designed, double-blind, randomized controlled trial. This means that participants were randomly assigned to receive the intervention (a daily multivitamin and mineral supplement) or a placebo (dummy pill), but neither the participants nor the researchers knew which they were taking.
This type of study is considered the gold standard and allows researchers to compare various results.
The participants (3,562) were over the age of 64 for women and 59 for men, with no history of heart attack, invasive cancer, stroke or serious illness. They could not use multivitamins or minerals (or cocoa extract, which they also tested) during the trial.
Participants completed a battery of cognitive tests online at the start of the study (called the baseline) and then annually for three years, of which only three were reported in this article:
- ModRey, measuring immediate recall. Participants were given “a list of 20 words, one at a time, for three seconds each,” then had to type the list from memory
- ModBent, measurement of object recognition. Participants were given 20 prompts with a shape, then had to select the correct match from a pair of similar prompts. After that, they were prompted with 40 shapes in turn and asked if each was included in the original 20 or not.
- Flanker, measuring “executive control”. Participants had to select a color block corresponding to an arrow in a matrix of arrows, which could have the same color (or a different color) as the surrounding arrows, and the same (or different) direction as the prompt block .
What did the researchers find?
Of all the tests carried out by the researchers, only immediate recall (ModRey) at one year showed a significant effect, meaning the result is unlikely to be simply the result of chance.
At two and three years the effect was no longer significant (i.e. it could have been due to chance).
However, they added an “overall estimate” by averaging the results from the three years to arrive at another significant effect.
All reported effect sizes are very small. The largest effect is for participants’ immediate recall at one year, which was 0.07 – a value generally considered to be very low without justification.
Also of note, the multivitamin and placebo groups had higher immediate word recall scores at one year (compared to baseline), although the increase in the multivitamin group was significantly greater.
In the researchers’ previous study, the increase in word recall scores was described as a “typical learning (practice) effect.” This means that they attributed the highest scores at one year to familiarization with the test.
For some reason, this “learning effect” was not discussed in the current article, where the treatment group showed a significantly greater increase compared to those who received the placebo.
What are the limitations of the study?
The team used appropriate statistical analysis. However, it did not take into account demographic characteristics such as age, gender, race and level of education.
The authors do detail the main limitation of their study: it is not very generalizable, because it used “mostly white participants” who had to be very computer-savvy and, one could say, would function quite well cognitively.
Another limitation not mentioned is the advanced age of their sample, which means that long-term outcomes for young people cannot be assessed.
Moreover, the baseline food score of their sample was abysmal. The researchers say participants’ dietary scores “were consistent with averages for the US population,” but the cited study noted “overall dietary quality… (was) poor.”
And they didn’t measure dietary changes over the three years, which could impact the results.
How should the results be interpreted?
The poor food quality of the sample begs the question: can better nutrition be the simple solution, rather than multivitamin and mineral supplements?
Even for the effect they observed, which micronutrient in the supplement was the contributing factor?
Researchers speculate on vitamins B12 and D. But you can find cognitive function research for any arbitrarily chosen ingredient, including selenium, which can be toxic at high levels.
So should I take a multivitamin?
Health authorities advise that daily use of multivitamins is not necessary because you can get all the nutrients you need by eating a wide variety of healthy foods. However, supplementation may be appropriate to address an individual’s specific nutritional deficiencies.
Using a good quality multivitamin at the recommended dose shouldn’t hurt, but at best, this study shows that well-functioning older Caucasians might show additional benefit in a type of cognitive task of the use of a multivitamin supplement.
The case for most of the rest of the population, and the long-term benefits for young people, cannot be made.
Blind peer review
Clare Collins writes:
I agree with the reviewer’s assessment, which is a comprehensive review of the study. The key finding was a small effect size of taking a daily multivitamin and mineral (or “multinutrient”) supplement on memory recall at one year (but not later) and is equivalent to an effect of training where you get better at passing a test the more you do it.
It should also be noted that the study authors received support and funding from commercial companies to undertake the study.
Although the study authors state that they do not believe that the quality of the baseline diet had an impact on the results, they did not assess this comprehensively. They used a brief diet quality assessment score only at baseline. Participants may have changed their eating habits during the study, which could then have an impact on the results.
Given that all participants reported low diet quality scores, an important question is whether giving participants the knowledge, skills, and resources to eat healthier would have a greater impact on cognition than taking supplements. 
Jacques Raubenheimer, Senior Researcher, Biostatistics, University of Sydney
This article is republished from The Conversation under a Creative Commons license. Read the original article.