Sugar Consumption, Cognition, Correlation, and Causality

Late last week, the American Journal of Preventive Medicine published a correlation study of sugar and diet soda consumption in mothers during pregnancy and soon after childbirth. The researchers found that mothers who consumed more sugar during pregnancy and after childbirth tended to have children with lower cognition scores. But the researchers note correctly:

As in any observational study in which exposures are not randomized, unmeasured confounding may explain estimated associations. The chance of a Type I error may have also been higher than desired in this study because of multiple tests.

More simply said, this correlation study proves nothing about cause and effect.

Limit Sugar, Protect Cognition?

Despite those limitations, the journal issued a sensational press release, claiming that pregnant mothers could protect their babies’ brain function by cutting added sugars from their diet. Cutting added sugar is not a bad idea. But the promise of better brain function is false. And the headlines spawned by that press release were even worse:

Too Much Sugar During Pregnancy Can Affect Children’s Intelligence
Spare the Sugar, Moms to Be, to Protect Tot’s Brains
Too Much Sugar or Diet Drinks During Pregnancy Negatively Affects Your Child’s Brain

These warnings are big on fear, but lacking in facts. This study proves nothing about how sugar or diet drinks consumed by a mother will alter brain function in a child. Many other factors clearly affect cognitive development. Some of the well-established factors include under-nourishment of the mother, stunting, deficiencies of specific nutrients, exposure to violence, inadequate stimulation, and environmental toxins. By comparison, the role of sugar and diet sodas is highly speculative.

A Breach of Integrity?

Overloading pregnant women with threats and fears is unhelpful. False information crowds out potentially more important information. Within the journal, AJPM did not publish the unsupported claim of cause and effect for added sugar and cognition. So the journal clearly should not be issuing a press release making that claim.

It might be a good idea to limit added sugar for other reasons. But a lie in service of the truth is still a lie.

Click here for the study and here for more on false claims of causality. For more on actual causes of impaired cognitive development, click here and here. Finally, you can find further perspective on sensational press releases from supposedly academic sources here.

Coffee Without Sugar, photograph © Bertalan Szürös / flickr

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April 24, 2018