Processed flours, corn syrup, pesticides, artificial flavors – the modern human diet is vastly different from that of our ancestors. Americans in the 21st century consume about three and a half times more sugar daily than our 19th century predecessors and polyunsaturated fat consumption has nearly tripled. In fact, nearly everything is more abundant.
Except, perhaps, the omega-3 fatty acids.
Omega-3 fatty acids are often referred to as “brain food” in discussions of our prehistoric ancestors. DHA (an omega-3 fatty acid) is found in high concentrations in the brain and retina of healthy mammals, in whom an omega-3 deficient diet has been known to cause a decrease in cellular DHA concentrations concomitant with decreased visual and neural performance[3,4].
In fact, some anthropologists hypothesize that, because of our brain’s reliance on DHA, key evolutionary advancements in our mental capacity could only have occurred in protohuman populations consuming marine-based diets.[5, 6] Seafood is the most abundant source of omega-3 fatty acids, especially DHA.
This is a key reason the USDA recommends consumption of seafood. The USDA recommends that pregnant and breastfeeding women consume 6 to 12 ounces of omega-3-rich seafood per week . DHA is critically important during gestation and early childhood, with deficiency negatively affecting visual and cognitive development. Sadly, DHA deficiency is not uncommon. This is not surprising, given that most women (pregnant or not) do not consume the recommended amount of seafood and many do not consume seafood at all. Unfortunately, there are few other options for obtaining dietary DHA today. The National Institute of Health reports that, on any given day, 25% of Americans don’t consume any DHA at all.
There are, of course, plenty of reasons for the modern human to not eat seafood. Cost, taste, and convenience may deter women from seafood consumption. Amongst environmentalists and oceanographers, concerns over the negative impact of many forms of fishing make it even more difficult to incorporate a healthy amount of seafood into the diet. Most important, though, is concern over contaminants. Though our ancestors could eat seafood indiscriminately without risk of consuming PCBs, dieldrin, or methylmercury, these are serious concerns in our post-industrial world.
Recent archaeological discoveries suggest that our ancient ancestors (some ~150k years ago) may have been eating a marine-based diet when they began to evolve important conceptual abilities such as symbolism. However, many anthropologists still talk of human mental evolution only occurring some ~50k years go, in humans who may have done more hunting than fishing.
Whether our ancestors ate more or less seafood than we do, they certainly obtained more dietary omega-3 fatty acids — especially DHA and EPA — than we do . Though meat is not considered a source of omega-3s today, wild meats were and are. Our domestication practices result in a markedly different fatty-acid profile in the animals that we consume, and cattle fed on a grain-based diet generally produce meat high in omega-6s and low in omega-3s.
And so the same is true of our diets. Our diets have far more omega-6 fatty acids and somewhat less omega-3 fatty acids. Unfortunately, in the case of these fatty acids, the consumption of one cannot be accurately considered without looking at the consumption of the other.
When taking our increased consumption of omega-6s into account, the state of omega-3 consumption becomes much more concerning. These two types of fatty acids vie for preference in the human body. If there are significantly more omega-6 fatty acids in our blood stream for our body to use, our body will end up using them, rather than the omega-3s present. This results in lower omega-3 fatty acid concentration in key neural and retinal tissue, just as a dietary deficiency does.
The ratio of omega-6s to omega-3s use to be 1:1 or 2:1.
Now it’s more like 20:1.
Though we have an abundance of polyunsaturated fatty acids in our diet, it’s not an abundance of the right ones.
Check back next week for a discussion on omega-6s – what they do, and why we’re consuming so much of them!
2 Hiza, H.A.B.Bente, L. “Nutrient content of the US food supply, 1909-2004: A summary report.” US Department of Agriculture, Center for Nutrition Policy and Promotion, Washington, DC; 2007 (Home Economics Research Report No. 57).
8 Mulder KA, King DJ, Innis SM (2014) Omega-3 Fatty Acid Deficiency in Infants before Birth Identified Using a Randomized Trial of Maternal DHA Supplementation in Pregnancy. PLoS ONE 9(1): e83764. doi:10.1371/journal.pone.0083764
9 Razzaghi H, Tinker SC. Seafood consumption among pregnant and non-pregnant women of childbearing age in the United States, NHANES 1999–2006. Food & Nutrition Research 2014;58:10.3402/fnr.v58.23287. doi:10.3402/fnr.v58.23287.