Breastfeeding associated with intelligence later in life

Positive association between breastfeeding and intelligence, between three tiers of family income.  Five IQ points is 1/3 of a standard deviation. 

Editor’s note: I would like to tread very lightly on this topic because of the complexity of the relationships between all the factors discussed and the implications a study like this has.  I probably would not have written about it at all, had it not been published in such a prestigious medical journal, and had been as comprehensive as it was.

Breast milk is the ultimate pre- and probiotic.  It is essential in developing infants’ microbiomes by inoculating and enriching their guts in certain bacterial species.  There have been a number of studies showing alterations of the gut microbiomes of infants that are formula fed, and other studies showing that formula feeding results in a higher risk of asthma and allergies later in life.  The complicated relationship between breastfeeding, the microbiome, and phenotypes like autoimmune diseases are not understood at a mechanistic level.  Still though, it appears that formula feeding, rather than breastfeeding, may have long term consequences for the health of a child.

To that end, there had been a few small scale studies that demonstrated a general association between breastfeeding an IQ.  Just last week, a new study, much more comprehensive than any previous one, delved into this topic and found the same result: duration of breastfeeding was positively associated with IQ, educational level, and income.  The results of this study were published in The Lancet.

In 1982 researchers from Brazil began a longitudinal study using a cohort of over 500 newborn infants.  At that time, one of the things the scientists measured was the duration that each infant was breastfed.  Then, in 2012, the researchers followed up with 3000 of those people in the original study and surveyed them for their educational levels and incomes, as well as measured their IQs.  They discovered that each of these three variables was directly related with the length of breastfeeding, with the possibility that over 12 months of breastfeeding actually slightly decreased each.  Even after factoring in confounding variables such as maternal education, family income, and birthweight the relationship between breastfeeding and IQ, education, and income still held.  The researchers acknowledged the link was tenuous, and that there exists a whole host of other important variables that were not measured in 1982.  Nevertheless, the study suggests that breastfeeding improves intelligence upon adulthood.

Breastfeeding, if possible, is clearly preferred to formula feeding, and studies like this show that it may be in everyone’s interest to promote breastfeeding children.  It will be necessary to decipher the connection between breastfeeding, the microbiome, and these observations, but with more studies in the pipeline showing the value in breastfeeding everyone should be aware of its importance.

Is our virome lowering our intelligence?

We have talked about the virome and its possible substantial impact on human health on this blog before.  Lately, the virome has been getting a lot of press about its potential beneficial aspects, but today we want to discuss a negative one.  A paper was recently published in the Proceedings of the National Academy of Sciences that identified a specific virus in the virome that may be directly affecting the brain, and lowering our aptitude for spatial awareness and attention. 

Researchers were testing the oral microbiome of a cohort of people who were also taking intelligence tests as part of a separate, unrelated, study.  After genome sequencing they noticed the conspicuous existence of a virus, known as Chlorovirus ATCV-1, in about half the study population.  This virus was known to exist in algae, but had never been identified in humans, and there it was, affecting half there population.  Moreover, the virus cut across all demographics in there study, and was not related to age, race, or gender.  When the scientists compared the intelligence tests of those who had the virus versus those that did not, those that had the virus scored slightly less on tests involving spatial awareness.  However, they are quick to note that other tests for intelligence were unaffected.  They reiterate that these scores were related to the existence of the virus and not any specific demographic.

The scientists tried to recreate these results in mice.  They infected a group of mice with the virus and compared its scores on spatial tests with a control group.  The group that had the virus scored considerably lower on the tests.  When they measured specific genes that were affected in the infected mice they discovered some that related to dopamine regulation, which is known to be critical to memory formation and learning. 

Overall this fascinating study not only identified a new member of our virome, but showed that this virus may be altering our spatial reasoning abilities.  So the next time your significant other yells at you for getting lost, just blame it on your virome!