Any discussion of n-6 and n-3 fatty acids in general, and in beef in particular, ought to include the following points: the strength of data suggesting their importance; the importance of the n-6:n-3 ratios; and the n-3 content of beef vs. other foodstuffs.
The literature discussing the benefits of n-3 fatty acids is replete with words like “associated,” and “linked.” Tom Naughton’s “Science for Smart People” presentation is a great introduction to interpreting these words and the importance of claims made with them. The following statement comes from a “A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef” (Daley, et al. 2010):
“Danish physicians observed that Greenland Eskimos had an exceptionally low incidence of heart disease and arthritis despite the fact that they consumed a diet high in fat.”Can you say “Greenland Paradox?” I doubt that was the only dietary difference. It would seem prudent to keep this in mind while we discuss the reduction in coronary heart disease, diabetes, obesity, depression, etc. that have been listed as beneficial effect of n-3 supplementation. In addition, evidence exists to suggest that concern about ingesting too much polyunsaturated fatty acids in general, and n-3 fatty acids in particular, is warranted.
Cordain, et al. reported the n-6:n-3 ratio in tissues from wild ruminants and compared them to values for beef that had been published previously. This paper was then referenced in a post on Science Blog from Purdue University:
"Both grass-fed steers and the wild ruminants have a ratio of omega-6 to omega-3 fatty acids slightly above two in meat. In other words, two parts omega-6 to one part omega-3," Watkins says. "That ratio is much lower than the ratios of 5-to-1 to 13-to-1 reported in previous studies for grain-fed steers."However, the published range in n-6:n-3 ratios in “grass-fed” and “grain-fed” beef is far greater than that suggested in this paper, as shown in the data from eight papers presented in Table 1. Three of the studies cited in Table 1 having a lower ratio in grain-fed beef than the range stated by Cordain, et al.
Given that many variables (i.e. age of animal, sex, breed, tissue, management details) can affect the n-6:n-3 ratio, it is unwise to make blanket statements about what those ratios are. In addition, Garia, et al. demonstrated that some amount of grain can be fed to cattle without producing a high-value n-6:n-3 ratio in the beef.
Statistical significance does not necessarily equate to biological significance. It does not appear that we know enough to clearly state that these are important differences. Tom Naughton’s presentation, once again, makes this point. In addition, there appears to be a range in what the desirable range ought to be.
The World Health Organization recommends that polyunsaturated fats make up 3 - 7% of the energy in the diet. Some experts advise that one should consume a minimum of 3% of energy from omega-6 fatty acids and between 0.5% and 1% from omega-3. Research scientists recommend ratios varying from 5:1 to 10:1 omega-6 to omega-3. Other experts suggest a ratio of between 1:1 and 4:1 as being optimal. What are we getting? The current ratio in our diet is estimated to be 14:1 to 20:1 (from here).
Focusing on ratios instead of quantity can be misleading. A helpful list of n- 6 and n- 3 amounts in various foodstuffs is published here. Soybean oil has an n-6:n-3 ratio of 7.42, less than 4 of the ratio values for grain-fed beef presented in Table 1. But an ounce (28g) of soybean oil contains 14,361 mg of n-6 fatty acids, 21.5 times the amount contained in 4 ounces of raw grain-fed ground beef (668 mg n-6)! The n-6:n-3 ratio of roasted chicken leg meat is 9.53, essentially the same as listed for conventional ground beef. But one cup (140 g) contains 2,268 mg of n-6.
This same source states that grass fed ground beef contains 100 mg of n-3 per 4 ounces (raw). Considering that one 3.75 ounce (106 g) can of Vital Choice’s albacore solid white tuna (yes, tuna!) in extra virgin olive oil contains almost 3 grams (2,926 mg) of n-3 fatty acids it is, at best, an exaggeration to call grass fed beef a “rich” source of n-3 fatty acids. Even a comparison of grass fed ground beef with grain fed ground beef doesn’t justify the label: This same source shows only a 22 mg difference per 4 ounces of raw meat. What happens when the meat is cooked? A 4 ounce (cooked weight), pan-browned ground beef patty only contains 20 mg, so cooking loss appears to be significant.
Examining the data in these papers demonstrates the fact that beef, no matter how it’s produced, is not a rich source of n-3 fatty acids. And beef, not matter how it’s produced, is not a rich source of n- 6 fatty acids, either.
I want to emphasize that I’m focusing solely on the nutritional aspect of the beef, not on the issues of confined animal feeding operations, grain production, animal health, etc. I’m aware of these matters and I am NOT minimizing them. I celebrated my 55th birthday by presenting a poster at the Ancestral Health Symposium, but my celebratory birthday steak was postponed until the following morning. I pulled off the interstate and enjoyed a delicious steak and eggs breakfast. The very next thing I encountered as I got back on the highway was a large beef feedlot. The sight and smell were impressive, to say the least. Addressing these issues by exaggerating nutrient differences and their importance, however, is NOT a winning strategy. Instead, we might want to look at the monetary side.
It’s a good time to be a grass farmer – turning green grass into dollars, via a grazing ruminant. Today’s market has created a tremendous potential for income from the stocker business – buying beef calves and feeding them on pasture - gaining 200 – 300 lbs in 150 days or less - before selling them as feeder cattle. The following is from a Beef Magazine on-line article, which seems to be quoting this Oklahoma State University Extension Service publication:
"Heavy-feeder prices increased to new seasonal highs in early July and are still holding at remarkably strong levels," says Derrell Peel, Oklahoma State University Extension livestock marketing specialist. "The rollback between calf and feeder prices is very narrow; almost zero in some cases, resulting in very high stocker value of gain."
Peel offered this example for the first week of August: the Oklahoma combined auction price for Medium and Large #1 steers weighing 515 lbs. was $138.56/cwt.; it was $138.05/cwt. for steers weighing 727 lbs.
"This implies a value of gain of $1.37/lb. for 212 lbs. of gain," Peel says. For steers weighing 825 lbs., the price was $132.50/cwt., resulting in a value of gain of $1.22/lb. for 310 lbs. of gain."
For the record, value of gain is defined as the gross sale price of a head of cattle minus the gross purchase price, divided by the pounds of gain. High calf and feeder prices, and the narrow price rollback, magnify the current opportunity.
"There is more incentive than there has ever been to grow and manage forage," Peel emphasizes. "Wheat pasture prospects in the southern Great Plains appear very poor at this point but the market is clearly encouraging somebody, somewhere, that has forage to put stocker gains on feeder cattle.
"The feeder cattle price structure will continue to offer high value of gain as a market incentive to add weight to cattle prior to feedlot placement. Stocker margins will generally be attractive for stocker production over a wide range of beginning and ending weights and total weight gain."
So, once again, there are valid reasons for eating grass fed beef – including the taste! But promoting grass fed beef because of its n-6:n-3 ratio is, at best, misleading. Beef, regardless of how it is fed, in not a “rich” source of n-3 or n-6 fatty acids. If you want more n-3 fatty acids in your diet, eat fatty fish and/or take a supplement. If you want less n-6 fatty acids in your diet, cut the grains and vegetable oils.
References:
Cordain, L., B.A. Watkins, G.L. Florant, M. Kelher, L. Rogers, Y Li. 2002. Fatty acid analysis of wild ruminant tissues: evolutionary implications for reducing diet-related chronic disease. European Journal of Clinical Nutrition 56, 181–191
Daley, C.A., A. Abbott, P.S. Doyle, G.A. Nader, S. Larson. 2010. A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef. Nutrition Journal 9:10
Descalzo, A., E.M. Insani, A. Biolatto, A.M. Sancho, P.T. Garcia, N.A. Pensel. 2005. Influence of pasture or grain-based diets supplemented with vitamin E on antioxidant/oxidative balance of Argentine beef. Meat Science 70:35-44.
Garcia, P.T., N.A. Pensel, A.M. Sancho, N.J. Latimori, A.M. Kloster, M.A. Amigone, J.J. Casal. 2008. Beef lipids in relation to animal breed and nutrition in Argentina. Meat Science 79:500-8.
Leheska, J.M., L.D. Thompson, J.C. Howe, E. Hentges, J. Boyce, J.C. Brooks, B. Shriver, L. Hoover, M.F. Miller. 2008. Effects of conventional and grass-feeding systems on the nutrient composition of beef. Journal Animal Science 86:3575-85.
Nuernberg, K., D. Dannenberger, G. Nuernberg, K. Ender, J. Voigt, N.D. Scollan, J.D. Wood, G.R. Nute, R.I. Richardson. 2005. Effect of a grass-based and a concentrate feeding system on meat quality characteristics and fatty acid composition of longissimus muscle in different cattle breeds. Livestock Production Science 94:137-47.
Ponnampalam, E.N., N.J. Mann, A.J. Sinclair. 2006. Effect of feeding systems on omega-3 fatty acids, conjugated linoleic acid and trans fatty acids in Australian beef cuts, potential impact on human health. Asia Pacific Journal of Clinical Nutrition 15(1):21-9.
Realini, C.E., S.K. Duckett, G.W. Brito, M.D. Rizza, D. De Mattos. 2004. Effect of pasture vs. concentrate feeding with or without antioxidants on carcass characteristics, fatty acid composition, and quality of Uruguayan beef. Meat Science 66:567-77.
S. K. Duckett, J. P. S. Neel, J. P. Fontenot and W. M. Clapham. 2009. Effects of winter stocker growth rate and finishing system on: III. Tissue proximate, fatty acid, vitamin, and cholesterol content. Journal Animal Science 87:2961-2970.
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