black: Saturated; grey: Monounsaturated; green: Polyunsaturated; blue: Trans
Butterfat contains about 3% trans fat, which is slightly less than 0.5 grams per US tablespoon. Trans fats occur naturally in meat and milk from ruminants. The predominant kind of trans fat found in milk is vaccenic acid. Trans fats may be also found in some industrially produced foods, such as shortenings obtained by hydrogenation of vegetable oils. In light of recognized scientific evidence, nutritional authorities consider all trans fats equally harmful for health and recommend that their consumption be reduced to trace amounts.
However, two Canadian studies have shown that vaccenic acid could be beneficial compared to vegetable shortenings containing trans fats, or a mixture of pork lard and soy fat, by lowering total LDL and triglyceride levels. A study by the US Department of Agriculture showed that vaccenic acid raises both HDL and LDL cholesterol, whereas industrial trans fats only raise LDL with no beneficial effect on HDL.
In the U.S., there are federal standards for butterfat content of dairy products. Many other countries also have standards for minimum fat levels in dairy products. Commercial products generally contain the minimum legal amount of fat with any excess being removed to make cream, a valuable commodity.
^Bassett, C. M. C.; Edel, A. L.; Patenaude, A. F.; McCullough, R. S.; Blackwood, D. P.; Chouinard, P. Y.; Paquin, P.; Lamarche, B.; Pierce, G. N. (Jan 2010). "Dietary Vaccenic Acid Has Antiatherogenic Effects in LDLr-/- Mice". The Journal of Nutrition. 140 (1): 18-24. doi:10.3945/jn.109.105163. PMID19923390.
^Wang Y, Jacome-Sosa MM, Vine DF, Proctor SD (20 May 2010). "Beneficial effects of vaccenic acid on postprandial lipid metabolism and dyslipidemia: Impact of natural trans-fats to improve CVD risk". Lipid Technology. 22 (5): 103-106. doi:10.1002/lite.201000016.
^Bassett C, Edel AL, Patenaude AF, McCullough RS, Blackwood DP, Chouinard PY, Paquin P, Lamarche B, Pierce GN (2010). "Dietary Vaccenic Acid Has Antiatherogenic Effects in LDLr-/- Mice". The Journal of Nutrition. 140 (1): 18-24. doi:10.3945/jn.109.105163. PMID19923390.