Grass-Fed Pork? Not Really. Still the Difference in Fatty Acid Composition & Micronutrient Content Are Profound & Not Accounted for by Food Databases - Let Alone Epidemiology

You often hear that pigs are pretty closely related to us humans, but "are all pigs created equal"? Or what may be a more appropriate question for the SuppVersity: Is all pork really created equal?

If you like databases like nutritiondata.com or the USDA's very own detailed nutrient database in order to evaluate whether your diet is actually delivering all the nutrients you need you are probably missing half of the picture. At least as far as the more sophisticated details go, a recent paper from the Instituto de Ingeniería de Alimentos para el Desarrollo at the Universidad Politécnica de Valencia clearly indicates that you would at least have to consider what the animals, in this case pork, were fed and from which muscle of the animal the piece of meat you are eating has been cut, in order to get an approximate idea of how much of unquestionably health relevant micronutrients, such as coQ10, carnosine, anserine, taurine, creatine glutamine or haem you get - and in some cases the differences can be way larger than 100%!

If pizza salami equals pork...

... in epidemiological studies, how can these studies on the fallacies and advantages of eating red meat, which usually get a hell lo of media attention, be accurate, given the fact that the amount of unquestionably beneficial coQ10, for example, would differ by 60 percent, even if you would only ignore the difference between loin that was cut from the trapezius (= high coQ10 content) and the longissimus dorsi (=low coQ10 content)?

Figure 1: Content of selected amino acids and micronutrients in cuts from different muscle; data expressed relative to respective mean (total value is given in mg/100g above the bars) of all tested muscle samples (data based on previous studies by the co-authors that have been compiled for Reig. 2012).

Moreover, if you take a look at the complete data in figure 1 it should be clear that coQ10 is only one of several micro-nutrients / amino acids that are highly dependent on which muscle your particular steak or whatever you are about to eat was cut from. Let's take taurine as yet another example. A prolonged low dietary intake of taurine has been observed to be linked to a number of disorders including retinal degeneration, retardation of growth and development, cardiovascular dysfunctions, CNS abnormalities, immune impairment and hepatic disorders (Abebe. 2011). If you eat meat (fish & other animal products) only occasionally and are therefore at risk of not getting adequate taurine in your diet, eating sausages from a butcher you trust would be a better choice than a piece of ham, since the former do include the high taurine meat from the masseter (cheeks) of the animals, while ham does not.

Let's get to the obvious: Grass-fed is... ah, wait a minute

"Grass fed is best" as you will people say about beef obviously won't be the case for pork, because pigs, just like humans, by the way, are omnivores. The simple formula, grass-fed = most beneficial fatty acid and micronutrient profile that may (in general) be valid for beef doesn't apply and we will have to take a closer look at the actual data first to decide what would be the "best" feed for pigs, if the goal was not a maximal yield of lean meat (in that case adding some clenbuterol, like the Chinese like to do it would be the least you should do; cf. The China Post. 2011), but rather to produce the meat with the most beneficial fatty acid  composition.

Figure 2: Fatty acid composition (primary axis) and omega-6 to omega-3 ratio of pork from pigs fed different diets (corrected version of data Reig et al. re-pupublished based on previous studies; spec. the figure for the n6:n3 ratio in the "standard feed" group that's based on Enser et al. was off - a ratio of 1.54 is obviously unrealistic)

I we define "most healthy" as having the lowest omega-6 to omega-3 ratio - a practice that seems appropriate given that 95% of the inhabitants of the so-called 'Westernized World' consumes way too much of the former and (comparably) way too little of the latter type of polyunsaturated fatty acids, the data in figure 2 clearly argues in favor of *surprise* the standard feed - at least if you define that by the feed the animals the meat of which (50 samples) Enser et al. bought in British supermarkets in 1996 (note: these values are still higher than for the conventional beef samples from the same study, which had a n-6:n-3 ratio of ~2.2; cf. Enser. 1996). There are however more intricate patterns that are not evident from the overview in figure 2, but could have implications as far as the direction into which "pork production" could or should head to in the future is concerned (summarized based on Reig. 2012):

Do you notice a pattern? I guess even based on the data in figure 2 you will already have noticed that the "grainier" the diet, or in other words, the more corn and soy there is in the diet of the swine the less favorable is the fatty acid composition of their meats going to be. Now, I am asking an outrageous question: If swine are such a good model for human metabolism, what do you believe your belly was going to be made of, if you copied the pigs' diets and lived on "healthy grains", their oils and the uber-healthy soy beans for the (probably pretty short) rest of your life?
• more food (yet no excess) can produce overall leaner muscle meat in the type II fibers, while the total body fat is increasing
• aside from local desaturation and elongination effects, the overall muscular fatty acid pattern does (much like in humans, by the way) mirror the dietary intake
• canola or linseed oils produce a substantial increase in the content of linolenic acid (C 18:3), and slightly increase the eicosapentaenoic (EPA, C 22:5) and docosahexaenoic (DHA, C 22:6) acid contents in pork mea
• soy, peanut, corn, and sunflower increase the content of linoleic acid (C 18:2; omega-6), increase the n-6:n-3 ratio and reduce the content of mono-unsaturated fats (MUFAs)
• fish oils or algae added to the feed substantially increases the content of EPA and DHA and thus reduce the n-6:n-3 ratio
• a high saturated fat content as in tallow (see figure 2) increases the levels of palmitic, palmitoleic, stearic and oleic acids in pork meat and reduces the PUFA:SFA ratio 
• CLA supplementation can increase the CLA content of the fatty portion of the meats (1% CLA results in 5.5 mg CLA/100g) and the adipose tissue (2% CLA yields 1,490mg CLA/100g fatty acids).

As you can see, the same rule applies for humans, pigs and, as you know from a previous SuppVersity post, mice who are fed inferior, since soy-fed salmon, as well: You are what you eat, folks!

Wallowing, roaming, routing: Work out like a pig

Since pigs make a pretty decent model of human metabolism and in view of the fact that - aside from our diets - the amount of exercise we get is one of the fundamental determinants of the total and relative levels of body fat, it should not be forgotten that "exercise" or rather the ability to range freely and be as active as any swine should be, is another determinant of the quality of the meat you are buying at the supermarket, grocery store, butcher or your local farmer. In this context, Reig et al. point out that

If you have no idea of the different cuts and location of the individual muscle, I suggest you download the "Meat Cuts Manual" from the website of the Canadian Food Agency. It's free and bilingual.

"[i]t has been reported that pigs maintained in free-range conditions in the Mediterranean forest had subcutaneous and intramuscular fats with higher monounsaturated fatty acids and lower saturated fatty acids than those pigs housed individually and receiving acorns as feed. The subcutaneous fat depth increases with exercise being 15.9 mm for exercised pigs in comparison to 11.5 mm depth for those kept in confinement. The same applies for the intramuscular fat content where 3.36% for extensive vs 1.44% for intensive raised pigs have been reported in the semimembranosus muscle." (Reig. 2012)

And if you really intend to overcomplicate things, you would also have to ask your butcher, whether the sausages you are about to buy were made of the meat of male of female pigs. After all, meat from barrows typically contain more fat and marbling and a thicker subcutaneous fat layer than meat from gilts (Armero. 1999). But let's face it: If you start stressing about things like this, the quality of your meat is probably your least problem.

If you want to know read more about epidemiological overgeneralization andthe effects of "pork" and red meat on your health (spec. the prostate) I suggest you go back to the Meat-Ology post.

So what's the bottom line, then: I guess the bottom line of the above insides is twofold. As far as you as an individual are concerned, it would be yet another argument for getting your meats (pork or whatever else) from a farm nearby, where you know what you are getting. It is yet also evidence of the fact that meticulous nutrient counting as I often see it in former calorie counters who have nor grasped the notion that "a calorie is not a calorie" is of little avail - at least if you expect to be able to calculate them as precisely as you can read them on the nutrition labels of the 90% artificial and 100% standardized convenient foods that's probably much more the answer to the question "Why are we fat?" than the non-descript statement "insulin".

In fact, the real significance of these results lies elsewhere. It concerns the way epidemiological studies are conducted (I may remind you of the metaphorical pizza salami being red meat or pork), their over-generalizing interpretations and the conclusions on what the optimal human diet should look like. So, once the next study is telling you "red meat" or "pork" is bad for you - you may want to remind yourself of some of the things you have learned in today's blogpost and ask yourself (and if you incidentally have the chance, the researchers as well): What kind of "pork" are we talking about?

References:

• Abebe W, Mozaffari MS. Role of taurine in the vasculature: an overview of experimental and human studies. Am J Cardiovasc Dis. 2011;1(3):293-311.
• Armero E,  Flores M,  Toldrá F,  Barbosa JA,  Olivet J,  Pla M,  Baselga M.Effects of pig sire types and sex on carcass traits, meat quality and sensory quality of dry-cured ham.  Journal of the  Science of  Food  and  Agriculture. 1999; 79:1147-1154.
• Enser M, Hallett K, Hewitt B, Fursey GA, Wood JD. Fatty acid content and composition of english beef, lamb and pork at retail. Meat Sci. 1996 Apr;42(4):443-56.
• Reig M, Aristoy MC, Toldra.Variability in the contents of pork meat nutrients and how it may affect food composition databases. Food Chemistry. 2012 [ahead of print]
• The China Post. Clenbuterol-tainted pork latest China food scandal. March 18, 2011. < http://www.chinapost.com.tw/china/national-news/2011/03/18/295146/Clenbuterol-tainted-pork.htm > retrieved Dec 06, 2012.