Recently, I received an inquiry in response to a post I wrote about the types of fat we should and should not cook at high temperatures with. I mentioned that ghee wasn’t an option as it’s a dairy product and dairy products are not Paleo.
One reader, who happened to be a microbiologist, wrote in and asked:
“Since ghee has milk solids removed and ostensibly has negligible amounts of lactose and casein, what is harmful about the animal fat left behind? Does it have to do with Omegas? I apologize if you have discussed this previously, I am new to this site. Also, I have a doctorate in microbiology, so feel free to get technical!”
Since she clearly is far more the scientist than I, I went straight to the source, my mentor, Dr. Cordain, and asked him for his input. He kindly shared the following explanation, which will be sure to satisfy the technical request of the reader’s question!
For those who are interesting in cutting straight to the chase, all you need to do is read his last sentence: “My advice to Paleo dieters would be to bag ghee completely and replace it with virgin olive oil for cooking and salads.”
“Ghee (from the Sanskrit word Ghrita meaning bright) is clarified butter fat in which most of the water has been boiled off and the nonfat solids removed by continued heating, filtration or decanting the remaining oil mixture (1). Traditional societies in India and elsewhere have produced and consumed ghee since at least 1500 BC (1). There are four methods commonly used for the manufacture of ghee 1): milk butter or desi method, 2) direct cream method, 3) cream butter method and 4) pre-stratification method (1). All four commercial procedures to produce ghee rely upon heating at temperatures from 105 to 118 C to remove the water (1). Ghee typically contains milk fat (99 to 95 %), water (< 0.5%) and protein (0.1 %) (1, 2). The butter fat remaining in ghee after boiling and removal of nonfat solids contains 1) saturated fatty acids (53.9 to 66.8 %), polyunsaturated and monounsaturated fatty acids (22.8 to 38 %), free fatty acids bound to albumin (1-3 %), and cholesterol (0.15 to 0.30 %) (1, 2).
In 1987, Jacobson (3) first pointed out that ghee contained high concentrations (12.3 %) of oxidized cholesterol, otherwise known as oxysterols. Further, he suggested that consumption of ghee, with its high levels of oxidized cholesterol, by Indian immigrant population in the UK likely represented an important dietary risk factor for atherosclerosis and heart disease. In subsequent years, it has been conclusively demonstrated in human, animal and epidemiological studies that dietary intake of oxidized cholesterol accelerates the rate of atherosclerosis (hardening of the arteries) and size of the arterial plaque (4-6). Hence, because of their atherogenic, cytotoxic and pro-inflammatory effects (7), oxidized cholesterol food products are almost universally recommended to be reduced or minimized in our diets (7-9).
The final aspect of the ghee story that requires further scrutiny is the purported high concentration (12.3 %) of oxidized cholesterol that Jacobson initially reported in 1987 (3). This value has been questioned (9) because of the analytical procedures used to measure the oxidized cholesterol, and more recent studies (10, 11) clearly demonstrate this value likely is incorrect. Fresh butter and cream samples contain barely detectable concentrations of oxidized cholesterol (10), whereas ghee manufactured at temperatures below 120 degrees C contained 1.3 % oxidized cholesterol. Whether or not regular consumption of oxidized cholesterol at this concentration can still induce atherosclerosis in humans is currently not known. However, part of the problem with ghee is that it is frequently used to fry food or is re-used many times in the cooking process. Both of these cooking procedures are known to increase oxidized cholesterol to levels (fried ghee 7.1% oxidized cholesterol; intermittently heat ghee 8.1 to 9.2 % oxidized cholesterol) (10) known to cause atherosclerosis in animal models (4).
My advice to Paleo dieters would be to bag ghee completely and replace it with virgin olive oil for cooking and salads.
1. Sserunjogi ML, Abrahamsen RK, Narvhus J. A review paper: Current knowledge of ghee and related products. Int Dairy J. 1998;8:677–88
2. Sarojini JK, Ubhayasekera SJ, Kochhar SP, Dutta PC. Lipids and lipid oxidation with emphasis on cholesterol oxides in some Indian sweets available in London. Int J Food Sci Nutr. 2006 Nov-Dec;57(7-8):451-8.
3. Jacobson MS. Cholesterol oxides in Indian ghee: possible cause of unexplained high risk of atherosclerosis in Indian immigrant populations.Lancet. 1987 Sep 19;2(8560):656-8.
4. Soto-Rodríguez I, Campillo-Velázquez PJ, Alexander-Aguilera A, Rodríguez-Estrada MT, Lercker G, Garcia HS. Biochemical and histopathological effects of dietary oxidized cholesterol in rats. J Appl Toxicol. 2009 Nov;29(8):715-23
5. Staprans I, Pan XM, Rapp JH, Feingold KR. The role of dietary oxidized cholesterol and oxidized fatty acids in the development of atherosclerosis. Mol Nutr Food Res. 2005 Nov;49(11):1075-82
6. Staprans I, Pan XM, Rapp JH, Moser AH, Feingold KR. Ezetimibe inhibits the incorporation of dietary oxidized cholesterol into lipoproteins. J Lipid Res. 2006 Nov;47(11):2575-80
7. Otaegui-Arrazola A, Menéndez-Carreño M, Ansorena D, Astiasarán I.Oxysterols: A world to explore.Food Chem Toxicol. 2010 Dec;48(12):3289-303
8. Hur SJ, Park, GB, Joo ST. Formation of cholesterol oxidation products (COPs) in animal products. Food Control 2007;18:939-947.
9. Sieber R. Oxidised cholesterol in milk and dairy products. Int Dairy J 2005;15:191-206
10. Kumar, N. and Singhal, O. P. (1992), Effect of processing conditions on the oxidation of cholesterol in ghee. J. Sci. Food Agric., 58: 267–273.
11. Kumar MV, Sambaiah K, Lokesh BR. Effect of dietary ghee–the anhydrous milk fat, on blood and liver lipids in rats. J Nutr Biochem. 1999 Feb;10(2):96-104.”
Thank you again, Dr. Cordain!