I wrote an email to Nina Planck about the subject of trans fats in grass-fed beef, and she pointed me to some research indicating that trans fat from natural sources is much better for you than trans fat from hydrogenated oils (i.e., margarine, or a wide variety of other foods). For example, pages 27-28 of this report state:
The epidemiological studies published to date do not permit any definite conclusions about differences in the associations between the risk of heart disease and the intake of industrially produced trans fatty acids and trans fatty acids from ruminants. However, the largest epidemiological study, the Nurses’ Health Study, showed a significant, positive association with the intake of industrially produced trans fatty acids and a non-significant, inverse association between the intake of trans fatty acids from ruminants and the risk of heart disease (6). The same pattern was found in the Finnish Alpha- Tocopherol, Beta-Carotene Cancer Prevention Study, in which the increased risk of cardiac death was found to be positively associated with total trans fatty acids as well as elaidic acid and trans fatty acids from hydrogenated vegetable fat, but not with trans fatty acids from ruminants, in connection with which a slightly insignificant, negative association was found (12).See also this page.