Tag Archives: shellfish

Bucket of Fish


Anyone concerned about climate change should pay attention…and that means you…and you…and you too! Yes, we all must be concerned about climate change, regardless of whether it is a result of natural climatic cyclicality, or because of human activity.

OK, I’m going to get off of the fence on this one and say it’s man-made—caused by human activities. I usually try to stay neutral because I’m not a climatologist. But, as a scientist, I am compelled by recent evidence that strongly suggests the contribution of greenhouse gases to global warming and climate change.

And this problem is only accentuated by the fact that, because of increasing population, we will need more and more food to satisfy us. About 10 billion people will live on the planet in 2050—up from the current 7.5 billion1. So, a reasonable person would think, well, it’s one-third more people, so we need one-third more food. Not so.

The World Resources Institute paints a rather solemn picture of our dietary future in a recent report without action on our part1. Scarcity of food calories, insufficient land for agriculture, and a significant increase in greenhouse gas emissions are just some of the challenges we face.

According to a recent article on CNN2 and quoting calculations from the World Resources Institute, the demand for food will increase by more than 50 percent, given the higher average standard of living that is expected to exist in 30 years.

The article goes on to say that beef production accounts for 41 percent of livestock greenhouse emissions, and 14.5 percent of emissions overall. The suggestion in the article is that Americans need to eat less beef—and for that matter, dairy as well (you get dairy from cows; they all eat the same stuff.)

Well, I will put myself out on a limb here and say, the chance of that happening is about as likely as Americans giving up cars. It’s not going to happen! While per capita consumption may fall, total consumption will rise with the increasing population. As the advertising slogan says, “Beef: It’s what’s for dinner.”

Making things worse is all the space that cattle need and use. If we keep on the current path with beef, we will need additional space – the equivalent size of India to accommodate our tastes and demand1. That’s quite frightening, considering additional arable space of that magnitude simply does not exist!

Wait! There’s more bad news! (Spoiler alert: There’s good news at the end.)

Beef cattle and all ruminant cattle have the nasty habit of the expelling methane gas as they digest their food. We continually hear about carbon dioxide (CO2) as the preeminent greenhouse gas that we need to control. But methane is 80 times more efficient at trapping heat in our atmosphere than carbon dioxide3.

Here’s how dire our situation may be. Two scientists actually propose turning atmospheric methane into carbon dioxide because of the beneficial trade-off in heat-trapping capability3. Under our current circumstances, that seems very reasonable. How freaky is that? This is the corner into which we have painted ourselves!

While I believe the total consumption of beef and dairy will continue to rise on an absolute basis, I do think per capita consumption will fall, based on what appears to be people’s “new-found” appetite for all things vegetarian, and the unwavering increase in demand for fish and seafood4. I want to focus on the second part of that equation.

We have known for a long time that fish and shellfish are the champs at converting food to edible flesh—better than chickens, better than hogs, and certainly better than cattle5. On average, finfish and shellfish convert feed at a rate of about 1.5 kg of feed for every kg of live fish. Chickens and other terrestrial livestock—especially cattle—don’t stand a chance of beating fish at this game. The best beef cattle can do is about 6 to 1 (usually worse at 8 or 10 to 1 or higher), and that’s horrible.

You probably wonder how fish make feed conversion look so easy. It all boils down to their environment. Finfish and shellfish “decided” evolutionarily that maintaining a constant body temperature is too difficult and too energetically costly in water. Only very large marine mammals with much smaller surface to volume ratios (heat loss occurs much more slowly) such as whales and seals can maintain body temperature and that requires the help of thick layers of insulating fat and blubber. Instead, finfish and shellfish have body temperatures at or very close to their surrounding aquatic environment. That means all the calories they consume can be spent on movement (a very small percentage) and growth, with virtually no consideration for heating or cooling.

Consider this as well. Seventy percent of the earth is covered in water. Why not use some of that space for food production? Land is becoming too precious for us to pasture cattle and other terrestrial livestock at low densities.

Food production in water also provides the added benefit of a three-dimensional space. Not only is the surface available, but the depths below the surface as well.

So, if you look at the situation objectively, it makes the most sense for us to focus our livestock efforts away from terrestrial species and toward aquatic species. In other words, aquaculture. This includes the production of aquatic plants—30 million metric tons in the year most recently reported4. Some marine macroalgae are directly consumed by people, such as nori for sushi, or “sea lettuce.” Other aquatic plants become fertilizer for terrestrial agriculture or cosmetics, and some provide protein and fat extracts for animal feeds6.

It’s time for us to develop our planet and the resources we require in more imaginative, innovative, and sustainable ways. In all likelihood, our long-term survival as a species depends on it.



1Searchinger, T., R. Waite, C. Hanson, and J. Ranganathan. 2018. Synthesis report: creating a sustainable food future: a menu of solutions to feed nearly 10 billion people by 2050. World Resources Institute, Washington, D.C. 92pp.

2Christensen, J. 2019. To help save the planet, cut back to a hamburger and a half per week. CNN. https://www.cnn.com/2019/07/17/health/beef-environment-resources-report/index.html

3Jackson, R., and P. Canadell. 2019. A crazy-sounding climate fix. Scientific American 321(2; August):10.

4FAO. 2018. FAO yearbook. Fishery and aquaculture statistics 2016. Food and Agriculture Organization of the United Nations. http://www.fao.org/3/i9942t/I9942T.pdf

5Anonymous. 2018. Feed conversion ratio. Wikipedia. https://en.wikipedia.org/wiki/Feed_conversion_ratio#Beef_cattle

6Chase, C. 2019. Veramaris opens USD 200 million algal oil facility. https://www.seafoodsource.com/news/aquaculture/veramaris-opens-usd-200-million-algal-oil-facility

Bill Manci is president of Fisheries Technology Associates, Inc., a Fort Collins, Colorado-based aquaculture, aquaponics, and fisheries consulting firm.

Shellfish | The Paleo Diet

If you happen to have nutritional apps or software that allows you to analyze your diet or the specific foods that you eat, you can determine the exact amount of protein, fat and carbohydrate present in any food.1  Protein, fat and carbohydrate are called macronutrients and are found in both plant and animal foods.

Plant foods almost always have all three macronutrients and typically contain primarily carbohydrate (~ 60 to 80% by calories), some protein (15-25% by calories) and generally little fat. There are some notable exceptions here regarding fat in plant foods – like avocados, olives and nuts which contain lots of fat (mainly monounsaturated) and little carbohydrate. I know of almost no naturally occurring plant food which is both high in carbohydrate and high in fat.

This combination of macronutrients (high in both fat and carbohydrate) occurs routinely in almost all processed and human-made foods like cookies, potato chips, pastries, ice cream, French fries, pizza, doughnuts, crackers, tortilla chips, breads, chocolates, salad dressings, tacos, hamburgers, enchiladas, candy, sandwiches and many more. These are the ubiquitous foods of “civilization” and represent  the “comfort” or “fast” foods of the 20th and 21st century that are largely responsible for the obesity epidemic sweeping the US and the western world along with its associated health problems (hypertension, cardiovascular disease, type 2 diabetes, acne, gout, cancers and others).2-4

Numerous nutritional scientists and authorities worldwide now recognize that by reducing the carbohydrate content of our diet we can lose weight and reduce our risk for the chronic diseases that plague western civilization – particularly if we reduce high glycemic load carbohydrates (refined sugars, refined grains, potatoes and most processed foods). This formula (lowering the dietary carbohydrate content of the diet) has been the strategy behind the Atkins Diet and other low carb programs for weight loss. Nevertheless, improving health and well being is not just about lowering carbs, but rather about multiple nutritional parameters which ultimately help us to maintain normal body weights and reduce our risk for disease. This approach is what the Paleo Diet is all about. Atkins and other low carb diets, popular diets failed to consider what we now know as an important element of healthful diets — acid/base balance. Cheese (a high fat, practically zero carb food) which can be a mainstay of almost all, low carb contemporary diets is extremely net acid producing in our bodies and promotes bone loss, hypertension, kidney stones and contributes to stroke risk.3 The Paleo Diet circumvents these nutritional shortcomings by allowing you unlimited carbohydrate consumption in the form of fresh veggies and fruits which are net base or alkaline yielding in our bodies and actually reduce the risk for osteoporosis, high blood pressure, kidney stones and stroke.3

Over the past two decades as I researched commonly available modern foods that should be included in contemporary Paleo Diets, I was somewhat startled to discover that not all animal foods (meat, poultry, pork, lamb, beef, eggs, fish, shellfish, organ meat, etc.) were completely composed of only protein and fat.  From my undergraduate and graduate nutritional courses, I had learned the traditional dogma that meat and fish contained no carbs and were simply a mixture of protein and fat.

Coming from my academic background in exercise physiology, I knew that all muscle tissue contained carbohydrate in the form of glycogen, a polymer of glucose, and that human muscle glycogen content could easily be increased by augmented consumption of  carbohydrates. Which endurance athlete among us has not heard of “carbohydrate loading” to improve performance?5 So the question I posed to myself was, “If human muscle contains glycogen, then why doesn’t beef muscle meat, or any other animal meat which we buy at the supermarket, contain a small or residual amount of carbohydrate in the form of glycogen?”

Virtually all of the nutritional databases1 showed fresh meat to contain nearly no dietary carbohydrate. As I researched this anomaly further, it became apparent that supermarket meats contained almost no carbohydrate for a basic physiologic reason – rigor mortis – a condition in which the muscles go into rigid contraction for the few minutes and hours after death. The fuel that supplies rigor mortis is stored muscle glycogen, and once this fuel is expended, rigor mortis resides and muscle meats contain virtually zero glycogen and hence zero carbohydrate.

An interesting sidelight of this observation is that only a very few animal foods contain carbohydrate after  death. Liver in mammals escapes rigor mortis and typically contains about 5% carbohydrate. Fish flesh contains virtually no carbohydrate. Not so for shellfish. The table below shows the carbohydrate content of various shellfish long after their death.1 Note that a number of shellfish contain a significant percentage of calories (10 – 25%) as carbohydrate including  oysters, mussels, abalone, whelk, clams, octopus and scallops.1

Shellfish | The Paleo Diet

Does this information mean that you should restrict shellfish consumption on a contemporary Paleo Diet? Absolutely not! Overall, their carbohydrate content is minimal and occurs with a high protein and omega 3 fatty acid intake – both factors which improve your carbohydrate metabolism. Shellfish are one of the most healthful, high protein foods you can consume to improve your glucose and insulin metabolism and reduce your risk for chronic disease.  Additionally shellfish are nutrient dense foods rich in zinc, B vitamins and omega 3 fatty acids which improve immune function and resistance to the diseases of western civilization.


Loren Cordain, Ph.D., Professor Emeritus


1. Nutritionist Pro Software.

2. Cordain L, Eades MR, Eades MD. Hyperinsulinemic diseases of civilization: more than just Syndrome X. Comp Biochem Physiol A Mol Integr Physiol. 2003 Sep;136(1):95-112

3. Cordain L, Eaton SB, Sebastian A, Mann N, Lindeberg S, Watkins BA, O’Keefe JH, Brand-Miller J. Origins and evolution of the Western diet: health implications for the 21st century. Am J Clin Nutr. 2005 Feb;81(2):341-54.

4. Carrera-Bastos P, Fontes Villalba M, O’Keefe JH, Lindeberg S, Cordain L. The western diet and lifestyle and diseases of civilization. Res Rep Clin Cardiol 2011; 2: 215-235.

5. Cordain L, Friel J. The Paleo Diets for Athletes. Rodale Press, NY, NY, 2011.

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