2016 Edited to Add: When I first began writing here I generated a searchable database for references and I have since done away with that option. This entire series remains to be edited to include the full references within each piece. As time allows, this series will be edited to include complete references at the end of each part in the series.
We Should Not Eat Fat…or Should We?
Dietary fats do not equal fat stores. The approach to our biological systems where we assume it is a one-for-one equation is too simplistic and usually just plain wrong.
Our brains developed, and are maintained, on diets high in essential fatty acids. Our hearts also appear to function much more effectively on diets high in essential fatty acids as well.
The essential fatty acids are the Omega-3 and -6 acids. The optimal ratio for these essential fatty acids in humans is between 1:1 and 1:4 (Omega-3 to -6). Our modern diets create a disproportionate ratio where we get far more Omega-6 than -3.
“Intake of omega-3 fatty acids is much lower today because of the decrease in fish consumption and the industrial production of animal feeds rich in grains containing omega-6 fatty acids, leading to production of meat rich in omega-6 and poor in omega-3 fatty acids. The same is true for cultured fish and eggs. Even cultivated vegetables contain fewer omega- 3 fatty acids than do plants in the wild.” [A. Simopolous, 2002]
More Science on Omega-3 essential fatty acids (EFAs).
Plant sources provide an omega-3 EFA called alpha linolenic acid (ALA). Fish sources provide, to varying degrees, both eicosapentaenoic acid (EPA) and docosahexonic acid (DHA). DHA is a key structural fatty acid for the brain and retina. For more details on all things Omega-3, this is a reasonable site to visit: dhaomega3.org.
Here are good plant-based sources of Omega-3 (ALAs):
- flax and hemp seeds and their oils
- rapeseed oil
- pumpkin seeds
- wildberries (blackberries, blueberries, cloudberries, raspberries, strawberries)
- leafy green vegetables (small amounts present, but good 3 to 6 ratio)
Here are the fish-based sources of EPA and DHA (Omega-3 content per 3.5 ounces fish): mackerel 2.6, lake trout 2.0, herring 1.7, bluefin tuna 1.6, salmon 1.5, sardines 1.5, Atlantic sturgeon 1.5, albacore tuna 1.5, lake whitefish 1.5, anchovies 1.5, bluefish 1.2. striped bass 0.8, brook trout 0.6, rainbow trout 0.6, pacific halibut 0.5, pollock 0.5, shark 0.5, sturgeon 0.4. freshwater bass 0.3, catfish 0.3, ocean perch 0.3, flounder 0.2, haddock 0.2, red snapper 0.2, swordfish 0.2 and sole 0.1 [A. Simopolous et al., 1999]
Problem is, we now have to balance how much fish we can consume against our ever-increasing body burdens of heavy metals and other toxins.
The Trouble with Fish
The heaviest mercury contents in fish are found in the following species: mackerel, marlin, orange roughy, shark, swordfish, tilefish, tuna, ahi, bluefish, grouper, mackerel from the Spanish gulf, sea bass (Chilean), albacore tuna and yellowfin tuna.
Those fish that should only be eaten less than once per month due to mercury content are: striped bass, carp, Alaskan cod, halibuts (both pacific and atlantic) jacksmelt, lobster, mahi mahi, monkish, perch, sablefish, skate, snapper, tuna (canned chunk, light) and sea trout. [Natural Resources Defense Council]
Most of our dioxin exposure is from dairy and meats (93%), but farmed fish and shellfish are often high in dioxins, PCBs and antibiotics.
And this also says nothing about how many of these lake and seafood species are severely endangered as well.
Generally, studies suggest that the benefits of eating fish in modest amounts outweigh the risks of toxic bio-accumulation [D. Mozaffarian, E. Rimm, 2006; J. Domingo, 2007].
Other studies suggest that all but middle-aged men, older men and post-menopausal women should shift to non-fish essential fatty acid options, or fish or krill oil supplements.
The challenge to eating fish while minimizing toxic exposure is that it really requires more rigorous monitoring (levels vary greatly geographically and seasonally) and providing consumers with details on where the fish is caught. Dioxin levels vary greatly with Pacific salmon catches as an example. [M. Gladyshev et al., 2009; I. de Silva Rabitto et al., 2011; A. deBruyn et al., 2004; J. Spromberg, J. Meador, 2009]
Pregnant and lactating women are warned against consuming large predatory fish because the mercury levels are dangerous to the fetus and baby. Yet essential fatty acid consumption during pregnancy and lactation is critical for the baby’s healthy development. To further muddy the waters, a very large longitudinal study in 2007 showed that limiting fish intake (under 340 g per week) was problematic for the growing fetus and childhood development, and that outcomes were very good for the babies of mothers who had consumed over 340 g per week. The children were assessed from 6 months to 8 years of age [J.R. Hibbeln et al., 2007].
While some fish oil and krill oil supplements are suitable for avoiding mercury, they too have drawbacks. Fish oil supplements are all over the map when it comes to PCB levels and there isn’t enough broad or consistent testing (just the odd trial or study for publication) to determine which brand might be dependably low for all toxins [www.fishoilsafety.com]. Krill bio-accumulate less toxins, however there are no long term studies indicating the efficacy of ingesting krill oil supplements as a way to provide the body with Omega-3 EFAs.
The next alternative is microalgae-derived DHA supplements. The problem is nutritional supplements in North America enjoy heavy lobbying that has ensured these products remain outside any rigorous food and drug testing protocols. As an example, commercially available Echinacea supplements in North America have between a 10-50% chance of containing no measurable level of Echinacea in the product [C. Bergeron et al., 2000; C. Gilroy et al, 2003].
Generally, the body is best designed to extract what it needs from whole foods, not supplements. However, access to EPA and DHA is not straightforward when water-based food sources are variably and randomly contaminated. If supplementation is your preference in this case, then consider European products. The products must all adhere to EU legislation on allowable levels of toxins, and the ultra-refined fish-oil options (more expensive) have the lowest levels of heavy metal contamination [A. Richardson, 2008].