There are much more interesting theories of the evolution of hominin intelligence other than the tiring (yawn) cold winter theory. Last month I wrote on why men are attracted to a low waist-to-hip ratio in women. However, the relationship between gluteofemoral fat (fat in the thighs and buttocks) is only part of the story on how DHA and fatty acids (FAs) drove our brain growth and our evolution as a whole. Tonight I will talk about how fatty acids predict ‘cognitive performance’ (it’s PISA, ugh) in a sample of 28 countries, particularly the positive relationship between n-3 (Omega-3s) and intelligence and the negative relationship between n-6 and intelligence. I will then talk about the traditional Standard American Diet (the SAD diet [apt name]) and how it affects American intelligence on a nation-wide level. Finally, I will talk about the best diet to maximize cognition in growing babes and women.
Lassek and Gaulin (2013) used the 2009 PISA data to infer cognitive abilities for 28 countries (ugh, I’d like to see a study like this done with actual IQ tests). They also searched for studies that showed data providing “maternal milk DHA DHA values as percentages of total fatty acids in 50 countries”. Further, to control for SES influences on cognitive performance, they controlled for GDP/PC (gross domestic product per country) and “educational expenditures per pupil.” They further controlled for the possible effect of macronutrients on maternal milk DHA levels, they included estimates for each country of the average amount of kcal consumed from protein, fat, and carbohydrates. To explore the relationship between DHA and cognitive ability, they included foodstuffs high in n-3—fish, eggs, poultry, red meat, and milk which also contain DPA depending on the type of feed the animal is given. There is also a ‘metabolic competition’ between n-3 and n-6 fatty acids, so they also included total animal and vegetable fat as well as vegetable oils.
Lassek and Gaulin (2013) found that GDP/PC, expenditures per student and DHA were significant predictors of (PISA) math scores, whereas macronutrient content showed no correlation.
The predictive value of milk DHA on cognitive ability is only weak when either two of the SES variables are added in the multiple regression. When milk arachidonic (a type of Omega-6 fatty acid) is added to the regression, it is negatively correlated with math scores but not significantly (so it wasn’t added to the table below).
So countries with lower maternal milk levels of DHA score lower on the maths section of the PISA exam (not an IQ test, but it’s ‘good enough’). Knowing what is known about the effects of DHA on cognitive abilities, countries who have higher maternal milk levels of DPA do score higher on the maths section of the PISA exam.
Table 2 shows the correlations between grams per capita per day of food consumption in the data set they used and maternal milk DHA. As you can see, total fish and seafood consumption are substantially correlated with total milk DHA, while foods that are high in n-6 show medium negative correlations with maternal milk DHA. The combination of foods that explain the most of the variance in maternal milk DHA is total fat consumed and total fish consumed. This explained 61 percent of the variance in maternal milk DHA across countries.
Not surprisingly, foodstuffs high in n-6 showed significant negative correlations on maternal milk DHA. “Any regression including total fish or seafood, and vegetable oils, animal fat or milk consistently explains at least half of the variance in milk DHA, with fish or seafood having positive beta coefficients and the remainder having negative beta coefficients.”
The study showed that a country’s balance of n-3 and n-6 was strongly related to the students’ math performance on the PISA. This relationship between milk DHA and cognitive performance remains sufficient even after controlling for national wealth, macro intake and investment in education. The availability of DHA in populations is a better predictor of test scores than are SES factors (which I’ve covered here on Italian IQ), though SES explains a considerable portion of the variance, it’s not as much as the overall DHA levels by country. Furthermore, maternal DHA levels are strongly correlated to per capita fish and seafood consumption while a negative correlation was noticed with the intake of more vegetable oils, fat, and beef, which suggests ‘metabolic competition’ between the n-3 and n-6 fatty acids.
There are, of course, many possible errors with the study such as maternal milk DHA values not reflecting the total DHA in that population as a whole; measures of extracting milk fatty acids differed between studies; test results being due to sampling error; and finally the per capita consumption of foods is based on food disappearance, not amount of food consumed. However, even with the faults of the study, it’s still very interesting and I hope they do further work with actual measures of cognitive ability. Despite the pitfalls of the study (the main one being the use of PISA to test ‘cognitive abilities’), this is a very interesting study. I eventually hope that a study similar to this one is undertaken with actual measures of cognitive ability and not PISA scores.
We now know that n-6 is negatively linked with brain performance, and that n-3 is positively linked. What does this say about America?
As I’m sure all of you are aware of, America is one of the fattest nations in the world. Not surprisingly, Americans consume extremely low levels of seafood (very high in DPA) and more foods high in n-6 (Papanikolaou et al, 2014). High levels of n-3 (which we do not get enough of in America) and n-6 are correlated with obesity (Simopoulos, 2016). So not only do we have a current dysgenic effect in America due to decreased fertility of the more intelligent (which is also part of the reason why we have the effect of dysgenic fertility in America), obesity is also driven by high levels of n-6 in the Western diet, which then causes obesity down the generations (Massiera et al, 2010).
I also previously wrote on agriculture and diseases of civilization. Our hunter-gatherer ancestors were all around healthier than we were. This, clearly, is due to the fact that they ate a more natural diet and not one full of processed, insulin-spiking carbohydrates, among other things. Our hunter-gatherer ancestors consumed n-3 and n-6 at equal amounts (1:1) (Kris-Etherson, et al 2000). As I documented in my article on agriculture and disease, HGs had low to nonexistent rates of the diseases that plague us in our modern societies today. However, around 140 years ago, we entered the Industrial Revolution. The paradigm shift that this caused was huge. We began consuming less n-3 (fish and other assorted seafood and nuts among other foods) while n-6 intake increased (beef, grains, carbohydrates) (Kris-Etherson, et al 2000). Moreover, the ratio of n-6 to n-3 from the years 1935 to 1939 were 8.4 to 1, whereas from the years 1935 to 1985, the ratio increased to about 10 percent (Raper et al, 2013). We Americans also consume 20 percent of our daily kcal from one ‘food’ source—soybean oil—with almost 9 percent of the total kcal coming from n-6 linoleic acids (United States Department of Agriculture, 2007). The typical American diet contains about 26 percent more n-6 than n-3, and people wonder why we are slowly getting dumber (which is, obviously, a side effect of civilization). So our n-6 consumption is about 26 percent higher than it was when we were still hunter-gatherers. Does anyone still wonder why diseases of civilization exist and why hunter-gatherers have low to nonexistent rates of the diseases that plague us?
The bioavailability of n-6 is dependent on the amount of n-3 in fatty tissue (Hibbeln et al, 2006). This goes back to the ‘metabolic competition’ mentioned earlier. N-3 also makes up 10 percent of the overall brain weight since the first neurons evolved in an environment high in n-3. N-3 fatty acids were positively related to test scores in both men and women, while n-6 showed the reverse relationship (with a stronger effect in females). Furthermore, in female children, the effect of n-3 intake were twice as strong in comparison to male children, which also exceeded the negative effects of lead exposure, suggesting that higher consumption of foods rich in n-3 while consuming fewer foods rich in n-6 will improve cognitive abilities (Lassek and Gaulin, 2011).
The preponderance of evidence suggests that if parents want to have the healthiest and smartest babes that a pregnant woman should consume a lot of seafood while avoiding vegetable oils, total fat and milk (fat, milk and beef moreso from animals that are grain-fed) Grassfed beef has higher levels of n-3, which will balance out the levels of n-6 in the beef. So if you want your family to have the highest cognition possible, eat more fish and less grain-fed beef and animal products.
In sum, if you want the healthiest, most intelligent family you can possibly have, the most important factor is…diet. Diets high in n-3 and low in n-6 are extremely solid predictors of cognitive performance. Due to the ‘meatbolic competition’ between the two fatty acids. This is because n-6 accumulates in the blood and tissue lipids exacerbating the competiiton between linolic acid (the most common form of n-6) and n-3 for metabolism and acylation into tissue lipds (Innis, 2014). Our HG ancestors had lower rates of n-6 in their diets than we do today, along with low to nonexistent disease rates. This is due to the availability of n-6 in the modern diet, which was unknown to our ancestors. Yes, seafood intake had the biggest effect on the PISA math scores, which, in my opinion (I need to look at the data), is due in part to poverty. I’m very critical of PISA, especially as a measure of cognitive abilities, but this study is solid, even though it has pitfalls. I hope a study using an actual IQ test is done (and not Richard Lynn IQ tests that use children, a robust adult sample is the only thing that will satisfy me) to see if the results will be replicated.
I also think it’d be extremely interesting to get a representative sample from each country studied and somehow make it so that all maternal DHA levels are the same and then administer the tests. This way, we can see how all groups perform with the same amounts of DHA (and to see how much of an effect that DHA really does have). Furthermore, nutritonally impoverished countries will not have access to the high-quality foods with more DHA and healthy fatty acids that lead to higher cognitive function.
It’s clear: if you want the healthiest family you could possibly have, consume more seafood.
A theory being more interesting or less tiring doesn’t make it any more true. With an intro like that I think it’s fair to assume everything that follows is just masturbatory pseudo-science.
I don’t think it is fair to assume that what follows is pseudoscience. I’ve pretty much discarded climate hypotheses for intelligence (but not discarded them for differences in personality). Anyway you’re free to choose whether or not to believe the writing, it’s your choice. That doesn’t make it any less true. =^)