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I have in my fridge a delicious-looking bowl full of fat rendered from making stock with a kilo of very fatty beef ribs. Trouble is... it's not grass-fed beef.

After making the stock, I ate the strips of meat on the ribs, and nibbled on some of the abundant fat on them, but resisted the urge to eat all of it, as I wasn't convinced it was a good idea nutritionally speaking. But I kept the rendered fat from the stock, just in case...

So my question is this: should I use this fat? Will it do more harm than good or vice-versa?

The two main things I'm concerned about, given the non-grassfed (and non-organic) origin of the meat, are: 1) presence of high concentrations of toxins in the fat; 2) high omega-6/omega-3 ratio (i.e. pro-inflammatory).

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4 Answers

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On the subject of the toxins from antibiotics, hormones etc, unfortunately I think the answer is that we don't know, due to simple lack of evidence on the matter. By definition, the people who decide safe levels think the levels in food are safe, but their general outlooks seems to be that they don't know for sure, but there's no evidence of any danger. Fwiw, I eat tonnes of conventional meat and am sure it's beneficial compared to less conventional meat.

[Edit: This website- credit to Acton- suggests that contaminants in meat aren't a concern.]

The omega 6:3 thing is a worry. My solution is to not worry in general about the omega 6 in meat, but avoid what fat I can by trimming and pouring off excess. At first when I went high-fat paleo I thought "right, I ought to get start eating the fattiest cuts I can find!" but then soon realised that butter was likely far more nutritious (A, K2, butyrate) than animal fat and far less omega 6. I've heard the claim that properly raised animal fat should contain a wealth of nutrients, including goodly sums of vitamin D, but on paper (i.e. www.nutritondata.com it doesn't come across. Grass raised fat works out about the same as butter, just more MUFA less SFA (up to debate if that's good/bad/neutral). Stephan has a ncie group of charts comparing fats here.

For all that, I'd be tempted to use the tasty animal fat anyway, at least beef's the least omega-6y conventional animal meat!

Second edit! This new piece has some nice graphs showing the differences between conventional and grassfed animals.

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For some reason it refuses to show the link I added re. antibiotics, so: ncbi.nlm.nih.gov/pubmed/…$=pmtitlesearch4 – David Moss Feb 19 2010 at 21:00
Don't trust nutritiondata as any sort of authoritative source. They merely compile the official USDA data. I trust this fatty acid analysis of grass-finished ruminant much more: texasgrassfedbeef.com/id73.htm – Acton Feb 20 2010 at 1:14
Nutritiondata do get some of the details randomly wrong (e.g. not believing in [bothering to measure] vitamin K2), but I see no reason not to think that USDA data is pretty representative of the mean (probably more so than the individual results of the few farms who're so dedicated they had their meat tested themselves. I wouldn't be surprised if grass-fed meat varies between around 1:1 like the one you cite and the 1:5 ratio on ND. WAP seemed to find huge variation among cattle for nutrient levels, for example. – David Moss Feb 20 2010 at 7:42
Frankly, it is impossible for a strictly grass-fed ruminant to consume more omega 6 than 3. It is the nature of plant leaves. The USDA is the one with the food pyramid-- I wouldn't trust anything they say when my values are on the line. The USDA does not even give any information on their methodology or the sample they used for the grass-fed beef in their database. nal.usda.gov/fnic/foodcomp/search – Acton Feb 20 2010 at 8:17
Good point about the butter, especially if it's pastured. I use it all the time to supplement fat intake (by itself or in cooking), but I couldn't help feeling it's a shame to let all the lovely beef fat go to waste!... – archaea Feb 20 2010 at 14:48
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There are some misconceptions about grass-fed meat floating around these days.

First, grass fed meat does have a better n-3/n-6 balance, but it has, in absolute terms, more omega 6 than does grain fed meat. Of course, it also has more omega 3s and more PUFA overall. However, for those that try to restrict all PUFAs (and achieve balance) and have unlimited SFAs, it is as good (or better) to buy grain fed meat and take a fish oil pill on the side.

Second, grass fed meat has 3-5X as much ruminant trans fat as grain fed meat. CLA and vaccenic acid may be good for you, but likely only up to a point. Recent studies have shown that after a point such trans fats are as bad as industrial trans fats. Since I like to eat a very high fat diet (and ruminant fat is a convenient source of low PUFA fat), I have to be careful about having to much ruminant trans fat.

Lastly, I pretty sure it is a myth that grass fed meat is safer from an e coli perspective than organic grain fed meat.

Thus, organic grain fed meat (which tastes better -- superior marbling) might be better for some people.

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 can you back up either of your claims that grass fed has > O-6 or is not safer than grain fed? I also completely disagree that grain fed tastes better. I do agree that cuts without slabs of fat (just the marbling) need some additional fat to taste as good from a fat perspective as grain fed. – HealthRediscovery Feb 20 2010 at 2:42
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 I can but so can you-- Google scholar. If I had the links handy, I would provide them. It's not hard to find numerous papers on the fat content of grass fed meat. Most indicate more n-3 and n-6. Also, on google scholar, type in ruminant trans fat. There were two papers in 2009 and a review by willet. Both papers found that at high doses (which would translate into a decent percentage of dialy calories from dairy or meat fat) ruminant trans fat worsens lipid numbers as much as industrial trans fats. Take that for what it is worth. – Jay Feb 20 2010 at 15:43
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 This- jas.fass.org/cgi/content/abstract/78/11/2849- study found that animals fed on pure grass (for 85 days before slaughter) had 3.14g O-6; 1.36g O-3 for a ratio of 2.33, where concentrate+hay gave 3.21g O-6, 0.84g O-3 for a ratio of 4.15, but the grassfed had a ratio of PUFA to SFA of 0.13 whereas the concentrate+hay had 0.09. There's a linear increase in PUFA:SFA the more actual grass they get, but one assumes there'd be a more extreme version of the same trend between properly grass-fed and grain fed animals. – David Moss Feb 20 2010 at 19:52
Interesting...much of the organic beef in my area (Spain) is grass and grain fed. I've been wondering what kind of difference their is between the two... – Primal Mama Feb 20 2010 at 20:49
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I don't know about the toxins. Omega-6 is strongly implicated by many as disease promoting. Ideally you really don't want to be eating any omega-6 at home besides what comes from naturally raised animal. You will get plenty of omega-6 from eating outside of home. The other concern here is that the fat comes from rendering stock, which could mean you have already applied a lot of heat to your fat, which could make the omegas go rancid. Normally you want to eat your ribs (including the fat) and then make stock with (just) the left over bones, which should yield only a small amount of fat.

We all have to compromise on our nutrition, so it is up to you and your budget if you want to compromise on this. If you do, I would supplement with omega-3 (fish oil) so you aren't omega imbalanced.

Edit: Someone has claimed that grass fed has more total n-6 PUFA (because it has greater total PUFA). From this page: http://www.csuchico.edu/agr/grassfedbeef/research/lipid/index.html there is a study demonstrating a lower n-6 percentage of total fat in grass fed beef And lets keep in mind that grass fed contains less total fat. This study is from Argentina, but they looked at different breeds and found diet to be much more important than breed.

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So to minimise heat damage to the fats, the idea is that I should first cook the ribs as little as possible and eat them, then make stock from just the bones? How best to cook the ribs - slowly simmered in water on low heat (which is how I made the stock anyway, it would just be for less time), or in the oven (dry heat)? – archaea Feb 20 2010 at 14:44
You should ask these questions to everyone. I do think minimizing fat oxidation is important. Sometimes it is recommended to put tough cuts of meat in stock because they contain connective tissues, but you can always make stew with tough meat. The real benefits of stock are from the bones and attached cartilage. Anything you are already eating you are getting the benefit of. Since you aren't eating the bones, you gain extra benefit from making stock from them. – HealthRediscovery Feb 20 2010 at 18:30
Maybe I cook my stock longer than I should, but I usually bring it to a boil and then let it simmer for several hours. Most meat would be done shortly after the boiling. I have cooked meat this way before- take the meat out fairly quickly and then thrown the bones back in to continue to make stock. – HealthRediscovery Feb 20 2010 at 18:31
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Regarding O6 -- I don't think we can say that grass-fed has more. Per http://www.nutritionj.com/content/pdf/1475-2891-9-10.pdf:

"Table 2 shows no significant change to the overall concentration of n-6 FAs between feeding regimens, although grassfed beef consistently shows a higher concentrations of n-3 FAs as compared to grain-fed contemporaries, creating a more favorable n-6:n-3 ratio."

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