Believe it or not, sugar doesn't cause hyperactivity

Despite widespread belief in the myth that sugar causes hyperactivity, scientists have known for more than two decades that the link is all in the mind.

It's the oldest rule in the book - too much sugar makes kids hyperactive."  Being told we were on a "sugar high" is something we probably all remember from our childhood, it is only over recent decades that the scientific consensus has resoundingly shifted onto the other side of the fence. If this is news to you, then you're not alone. As a paper recently published in  Nature Reviews Neuroscience, covered here demonstrated, 57% of teachers in the UK believe the myth that sugar makes children less attentive.


The subject was thrown into the headlines again this week with stories conflating the effect of caffeinated drinks and sugary drinks. It is fairly obvious to anyone who understands the effects of caffeine, that drinks with very high levels of caffeine might not be the best thing for young children. But this sort of conflation of confounding factors is actually a big part of the reason so many of us associate sugar with hyperactivity. It is clear from an (admittedly rather unscientific) cursory glance at the Daily Mail's comment section that the myth lives on - and the recent speculation has done nothing to dispel the myth:

 

But the evidence is about as conclusive as scientific evidence can get. Nearly two decades ago, a meta-analysis of 23 placebo controlled, double blind studies published in the Journal of the American Medical Association found that when children, parents and researchers were blinded as to whether or not children were actually given sugar, all effects of sugar on behaviour or cognitive performance disappeared.

This is where things get interesting. It would be foolish to merely throw the claims of parents and teachers out of the window and announce "case closed". It is quite possible that you really have experienced witnessing children become hyperactive after drinking sugary drinks and eating sweets - but the reason for the hyperactivity isn't the sugar.

It's all in the mind

One group of researchers took a different approach, breaking the cardinal rule that you should never lie to your mother. Well alright, they didn't lie to their own mothers, so they can be forgiven. The researchers sought out mothers who believed their children to be sugar sensitive. The researchers deceived the mothers into believing that their five to seven year old children had been given a large dose of sugar. In reality all of the children actually received a placebo  - aspartame, the popular sugar substitute. The researchers found that the mothers who thought their children had been given sugar believed their children were more hyperactive - and this is where things get even more interesting. The mothers who thought their kids had just eaten a mountain of sugar behaved differently themselves, towards their children. They acted in ways that were more controlling, maintaining physical closeness to their children, criticising them more and talking to them more than did the mothers who were told their sons received a placebo. So there, take that mum!

Much as I'd like to end on that high, I should make clear that just because sugar doesn't cause hyperactivity, that doesn't mean it's not bad for you. Too much sugar will still rot your teeth and make you obese (which is a known risk factor for Type 2 diabetes). So mum wasn't entirely wrong after all.

What about soda?

Recent research has linked the drinking of soft drinks with behavioural problems, but researchers are stumped as to the cause. Again, this could be down to the placebo effect, confirmation bias or the expectancy effects we've discussed. Or it may be more to do with differences in the type of children who choose soft drinks and the types of parents why give their children soft drinks. It could simply be that parents who encourage sensible dietary choices are the same parents who also successfully encourage good behavior.

Of all science myths, the sugar-hyperactivity myth really stands out as one that deserves a good debunking. Not because sugar needs defending, but because a look at the evidence that debunks the sugar-hyperactivity myth is a tremendous lesson in science. Studies come out every day demonstrating X causes Y. But it is only after confounding variables are removed and studies are replicated, replicated and replicated again and the results systematically analysed that we can really begin to come to conclusions with any certainty. The myth demonstrates perfectly why it is so important that confounding variables are eliminated from experiments and why participants and researchers must be blinded, not to mention of course being a fabulous lesson on the placebo effect.

Most of all though, the myth is a lesson that it is possible for nearly everyone to be wrong, your parents, your teachers, and most importantly of all: you. None of the research cited in this blog post is new, with the exception of the finding that over half of British teachers, Dutch teachers and Chinese teachers still believe the myth. Scientists have known for decades that sugar doesn't cause hyperactivity, and decades it would seem, is the time it can take for genuine scientific findings to filter down into public consciousness.

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References:

Hoover D.W. & Milich, R. (1994). Effects of sugar ingestion expectancies on mother-child interactions, Journal of Abnormal Child Psychology, 22 (4) 501-515. DOI: http://dx.doi.org/10.1007/bf02168088

Howard-Jones P.A. (2014). Neuroscience and education: myths and messages, Nature Reviews Neuroscience, DOI: http://dx.doi.org/10.1038/nrn3817

Suglia S.F. Solnick, S. & Hemenway, D. (2013). Soft Drinks Consumption Is Associated with Behavior Problems in 5-Year-Olds, The Journal of Pediatrics, 163(5) 1323-1328. DOI: http://dx.doi.org/10.1016/j.jpeds.2013.06.023

Wolraich M.L., Wilson D. & White J. (1995). The effect of sugar on behavior or cognition in children. A meta-analysis, JAMA: The Journal of the American Medical Association, 274 (20) 1617-1621. DOI: http://dx.doi.org/10.1001/jama.274.20.1617

Image Credit: Shutterstock

Update 11/12/14: This article originally suggested too much sugar can cause diabetes, too much sugar causes obesity which is a known risk factor for Type 2 diabetes. The article has been edited to reflect this.

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New fossils suggest human ancestors evolved in Europe, not Africa

Experts argue the jaws of an ancient European ape reveal a key human ancestor.

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  • The jaw bones of an 8-million-year-old ape were discovered at Nikiti, Greece, in the '90s.
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Homo sapiens have been on earth for 200,000 years — give or take a few ten-thousand-year stretches. Much of that time is shrouded in the fog of prehistory. What we do know has been pieced together by deciphering the fossil record through the principles of evolutionary theory. Yet new discoveries contain the potential to refashion that knowledge and lead scientists to new, previously unconsidered conclusions.

A set of 8-million-year-old teeth may have done just that. Researchers recently inspected the upper and lower jaw of an ancient European ape. Their conclusions suggest that humanity's forebearers may have arisen in Europe before migrating to Africa, potentially upending a scientific consensus that has stood since Darwin's day.

Rethinking humanity's origin story

The frontispiece of Thomas Huxley's Evidence as to Man's Place in Nature (1863) sketched by natural history artist Benjamin Waterhouse Hawkins. (Photo: Wikimedia Commons)

As reported in New Scientist, the 8- to 9-million-year-old hominin jaw bones were found at Nikiti, northern Greece, in the '90s. Scientists originally pegged the chompers as belonging to a member of Ouranopithecus, an genus of extinct Eurasian ape.

David Begun, an anthropologist at the University of Toronto, and his team recently reexamined the jaw bones. They argue that the original identification was incorrect. Based on the fossil's hominin-like canines and premolar roots, they identify that the ape belongs to a previously unknown proto-hominin.

The researchers hypothesize that these proto-hominins were the evolutionary ancestors of another European great ape Graecopithecus, which the same team tentatively identified as an early hominin in 2017. Graecopithecus lived in south-east Europe 7.2 million years ago. If the premise is correct, these hominins would have migrated to Africa 7 million years ago, after undergoing much of their evolutionary development in Europe.

Begun points out that south-east Europe was once occupied by the ancestors of animals like the giraffe and rhino, too. "It's widely agreed that this was the found fauna of most of what we see in Africa today," he told New Scientists. "If the antelopes and giraffes could get into Africa 7 million years ago, why not the apes?"

He recently outlined this idea at a conference of the American Association of Physical Anthropologists.

It's worth noting that Begun has made similar hypotheses before. Writing for the Journal of Human Evolution in 2002, Begun and Elmar Heizmann of the Natural history Museum of Stuttgart discussed a great ape fossil found in Germany that they argued could be the ancestor (broadly speaking) of all living great apes and humans.

"Found in Germany 20 years ago, this specimen is about 16.5 million years old, some 1.5 million years older than similar species from East Africa," Begun said in a statement then. "It suggests that the great ape and human lineage first appeared in Eurasia and not Africa."

Migrating out of Africa

In the Descent of Man, Charles Darwin proposed that hominins descended out of Africa. Considering the relatively few fossils available at the time, it is a testament to Darwin's astuteness that his hypothesis remains the leading theory.

Since Darwin's time, we have unearthed many more fossils and discovered new evidence in genetics. As such, our African-origin story has undergone many updates and revisions since 1871. Today, it has splintered into two theories: the "out of Africa" theory and the "multi-regional" theory.

The out of Africa theory suggests that the cradle of all humanity was Africa. Homo sapiens evolved exclusively and recently on that continent. At some point in prehistory, our ancestors migrated from Africa to Eurasia and replaced other subspecies of the genus Homo, such as Neanderthals. This is the dominant theory among scientists, and current evidence seems to support it best — though, say that in some circles and be prepared for a late-night debate that goes well past last call.

The multi-regional theory suggests that humans evolved in parallel across various regions. According to this model, the hominins Homo erectus left Africa to settle across Eurasia and (maybe) Australia. These disparate populations eventually evolved into modern humans thanks to a helping dollop of gene flow.

Of course, there are the broad strokes of very nuanced models, and we're leaving a lot of discussion out. There is, for example, a debate as to whether African Homo erectus fossils should be considered alongside Asian ones or should be labeled as a different subspecies, Homo ergaster.

Proponents of the out-of-Africa model aren't sure whether non-African humans descended from a single migration out of Africa or at least two major waves of migration followed by a lot of interbreeding.

Did we head east or south of Eden?

Not all anthropologists agree with Begun and his team's conclusions. As noted by New Scientist, it is possible that the Nikiti ape is not related to hominins at all. It may have evolved similar features independently, developing teeth to eat similar foods or chew in a similar manner as early hominins.

Ultimately, Nikiti ape alone doesn't offer enough evidence to upend the out of Africa model, which is supported by a more robust fossil record and DNA evidence. But additional evidence may be uncovered to lend further credence to Begun's hypothesis or lead us to yet unconsidered ideas about humanity's evolution.