Fish

 

Fish as food and the activity of fishing itself were both integral to human evolution - more integral than is generally realized.  However, we may need to look critically at the lessons some have suggested we take from the Pleistocene experience to apply to our own lives in the 21st century.

 

At one end is the appealing picture painted for us by Dr Barry Sears in his The Omega Rx Zone (2002; pages 14-19).  Sears' picture is appealing because it is well-written, it gets the main facts pretty right (his simplifications will irritate paleoanthropologists) and has about it a charming touch of the romantic.  Sears' account is written to show us how important long-chain omega-3 polyunsaturated fats were in the emergence of Homo sapiens.  (For Sears, the corollary is that we need these fats no less today and the bulk of his book explains why, how they are beneficial, where we can get these fats in the form he recommends: high dose, pharmaceutical grade.)

 

Later, in his biochemistry chapter (page 24) he summarizes: "... our prehistoric ancestors would have gotten these fats from ... shellfish 150,000 years ago then adding fish some 40,000 years ago.  Once we began consuming higher amounts of these long-chain omega-3 fats, our frontal cortex (which controls thinking and reasoning) began to expand rapidly.  This is because DHA [Docosahexaenoic acid] is the critical long-chain omega-3 fatty acid required for the building of neural tissue.  Furthermore, it appears that only DHA can stimulate the growth of nerve cells.  This probably explains why DHA is preferentially transported across the placenta into the fetal circulation for maximum impact on brain development ... The second reason high-dose fish oil is so important is that it also contains EPA [Eicosapentaenoic acid], the other long-chain omega-3 fat that controls our health by modulating the balance of "good" and "bad" eicosanoids ..."

 

Sears' account is interesting as it raises for us issues we need to think through before we can settle on the ideal prescription for the role of fish, fish oil and long-chain omega-3 fatty acids in our diets.

 

1.  Shellfish or finfish? - Fish are not easy to catch!  Sears - sensibly - suggests that the pre-Homo sapiens species made the large (equilibrial punctuation) leap, fed by shellfish rather than finfish.  Does this mean that we should look primarily to shellfish rather than finfish when re-creating our paleo diet today?

 

2.  Pollution of fish - Shellfish today are among the animals most affected by toxins - both chemical and biological - generated by humans.  Sears recommends, therefore, that we get our DHA and EPA from 'pharmaceutical grade' fish oil - of which his company is one of the few US manufacturers.  Sears explains that fish oil capsules contain varying levels of contaminants such as PCBs and mercury and, at the dose he recommends, these could be dangerous.  Whatever you think of the possibility that his cautions may be self-serving, they are undoubtedly important.  In Australia, with some of the cleanest ocean waters on the planet, the Fisheries Research and Development Corporation, while saying that 'There have been no reported cases of mercury poisoning in Australia as a result of seafood consumption', also tells Australian fish retailers to 'consider up to about 400g of finfish a week as safe in relation to heavy metals ... or other contaminants.' ('What's so healthy about Seafood?' pages 15 and 27)  Top

 

3.  Coastal or ocean fish? - Our human ancestors would have had far more access to shellfish than finfish and of the finfish, they would early on have had more access to freshwater fish (which could be more easily trapped) than ocean fish.  Of the ocean fish, many recommended today for their oil content would have been virtually unknown to our ancestors in the Pleistocene.  Even salmon, which could be caught in streams, would have had a depleted oil content because, during their long migration from the ocean to the freshwater streams, they used up the fat reserves they accumulated in their ocean feeding grounds.

 

4.  Fish oil capsules - There were no capsules in the Pleistocene.

 

5.  How much fish oil do we need? - Loren Cordain (p.134) recommends 2-3g of EPA and 1.2g of DHA daily.  This works out at 5-8 capsules a day of the higher-dose end of the products available in health food stores.  Barry Sears' recommended 'maintenance dose' (p.79) is 1.6g EPA and 0.8g DHA.  The EPA:DHA ratio is similar, but the quantities are not.  This may be explained by Sears having recommendations of a combined dose of up to 25g/day for patients with certain neurological conditions.  Sears also says that the traditional Inuit had 7-10g/day (p.89) and that the average US intake in 2000 was 0.12g/day.  If we translate Cordain's and Sears' recommendations into quantities of fish flesh we come up with some surprising amounts.

 

For Spanish mackerel - 3% of edible flesh is lipids (a moderately oily species), 20.3% of that is PUFA with a DHA content of 281mg/100g fresh edible flesh and an EPA content of 75mg/100g.  This would require 427g of flesh to meet Cordain's recommended DHA intake and 3333g to meet his EPA recommendation.  For Sears' recommended intake, the amounts are 285g and 2133g respectively. (See note at the foot of the page.)

 

For Yellowfin tuna - the figures are 0.5% lipids, 53.9% PUFA, DHA 100mg/100g and EPA 14mg/100g requiring daily fish flesh intake of 1200g and 17,857g (sic) to meet Cordain's recommendations and 800g and 11,429g to meet Sears'.

 

For other fish the size of the suggested portions is similarly large - well in excess of '400g of finfish a week' (see above) and in excess of practicality, even for an enthusiast.

 

We welcome comments on the above analysis as the dietary recommendations of both Cordain and Sears appear to be well in excess of any plausible Paleolithic model.  Top

 

6.  Fresh fish or farmed fish? - The total oil content of farmed fish as well as the fatty acid profile of the flesh varies radically with the food fed to the farmed (cultured) fish.  Omega-3s in fish are not produced by the fish but accumulate in them from the algae (which do produce them) consumed by plankton and then by larger predators up the food chain.  If farmed fish are not fed products from this food chain (or other plants such as flax which do produce Omega-3 oils) they will not contain the oils themselves.

 

Farmed fish are confined unnaturally and, like feedlot pigs and cattle cannot use energy through exercise.  They quickly accumulate body fat.  FRDC scientists have tested Australian farmed fish and reported on their analysis in 'Seafood-the Good Food II' in May 2002.

 

Highlights of the FRDC findings are:

 

(a) total oil content of the tested cultured fish was much higher than equivalent wild fish.

 

    Striped trumpeter-wild: 0.9%; cultured: 31.1%

    Barramundi          -wild: 0.4%; cultured: 10.0%

    Barramundi cod  -wild: 1.0%; cultured on fish oil: 22.2%; cultured on vegetable oil: 18.8%

 

(b) the fatty acid profile of the cultured fish was also different from the wild fish, but not by a comparably large factor.

 

    Striped trumpeter       -wild: SAT: 24.5%; MUFA: 20.2%; PUFA: 54.8%

    Striped trumpeter-cultured: SAT: 26.8%; MUFA: 42.4%; PUFA:30.8%

 

    Barramundi       -wild: SAT: 39.3%; MUFA: 17.7%; PUFA: 43.0%

    Barramundi-cultured: SAT: 31.1%; MUFA: 37.0%; PUFA: 30.3%

 

    Barramundi cod                        -wild: SAT: 37.7%; MUFA: 21.7%; PUFA: 40.7%

    Barramundi cod-cultured on fish oil: SAT: 26.9%; MUFA: 44.1%; PUFA: 29.0%

    Barramundi cod-cultured on veg oil: SAT: 28.3%; MUFA: 36.5%; PUFA: 35.1%

Top

(c) the PUFA profile of the cultured fish was quite different from that of wild fish.  The following data indicate mg of each fatty acid per 100g of fresh edible flesh.

 

    Striped trumpeter       -wild: AA: 19; EPA: 27; DHA: 311

    Striped trumpeter-cultured: AA: 250; EPA: 2500; DHA: 300

 

    Barramundi       -wild: AA: 42; EPA: 11; DHA: 76

    Barramundi-cultured: AA: 75; EPA: 600; DHA: 900

 

    Barramundi cod       -wild: AA: 45; EPA: 22; DHA: 112

    Barramundi cod-cultured: AA: 125; EPA: 1000; DHA: 1800

 

Again, large differences; these are not misprints!

 

7.  The loss of the Pleistocene environment - Cordain's solution to the contamination of a basic human food stock is to use high tech means to refine out the contaminants.  The Evfit position is that this is OK as a first, inward-looking first step.  But the implications are that we should (a) acknowledge the damage we are doing to our oceans and (b) campaign against human pollution of the oceans so that we can, once again, have access to an unpolluted food source of Pleistocene quality.

 

Note - the oil content data used here come from recent Australian research by the Fisheries Research Development Corporation.  These data show that Australian fish generally have lower levels of oil than northern hemisphere equivalents but the relative level of PUFA is generally higher.  Specifically, Australian fishes generally have higher levels of DHA than northern hemisphere equivalents.  Top

 

8.  Dangers from farmed fish   New Scientist, in August 2003, reported that one of the dangers from farmed fish is that, now that today's farmed fish have been out of the wild for many generations, they will have lost or atrophied the ability to survive in the wild.  Not only will they have lost the ability to feed themselves advantageously in the wild, avoiding bad foods and seeking the best, they will have lost the ability to migrate up from the oceans into the freshwater streams for breeding.  When farmed fish escape into the wider environment and mate with wild fish, it is likely that the offspring of that mating will also lack the full range of survival skills normally associated with their species.

 

References:
Fisheries Research and Development Corporation: 'Seafood - the Good Food', 'Seafood - the Good Food II', 'What's So Healthy about Seafood?'

Sears - The Omega Rx Zone (2002)

 

Evfit home   Food page   Top