High blood fats generally increase cholesterol levels in the blood, which in turn increases the risk of hardening of the arteries and heart attacks. Now a new study at Lund University has shown that butter produces a significantly lower increase in blood fats after a meal compared with olive oil and a new type of rape- and linseed oil. The difference was particularly noticeable in men, while in women it was more marginal.
The primary explanation for the relatively low increase in blood fats caused by butter is that around 20 per cent of the fat in butter is comprised of short and medium-length fatty acids. These are used straight away as energy and therefore never affect the blood fats to any large degree. These fatty acids are used in healthcare for patients who have difficulty absorbing nutrients – in other words, they are good fatty acids. “A further explanation that we are speculating on is whether the cells in the intestines prefer to store fat from butter than the long-chain fatty acids from vegetable oils. However, butter produces a somewhat higher level of free fatty acids in the blood, which is a burden for the body”, explains Julia Svensson, doctoral student in Biotechnology and Nutrition at Lund University. The larger difference in men can be attributed to hormones, size of fat deposits and fundamental differences in metabolism between men and women, which were already known. The situation makes testing on women more difficult because they must be tested during the same period in the menstrual cycle each time to obtain reliable results.
“The results enhance the picture of different dietary fats. Olive oil has been studied incredibly much and its merits are often highlighted. It is well known that butter raises blood cholesterol in the long term, while its short-term effects have not been studied as much. Of course olive oil is good, but these results show that different dietary fats can have different advantages”, says Julia Svensson. “Finally, all fats have high energy content and if we do not burn the energy we consume this results in weight increase and increased risk of disease in the long term”, points out Ms Svensson.
Nineteen women and twenty-eight men participated in the study. Each person ate three test meals containing rape- and linseed oil, butter or olive oil. The day before the test they fasted from 21.00. The following morning a fasting blood test was taken, which checked their state of health and all blood fats. The test meal comprised the test fat mixed into semolina, milk, blackberry jam and a slice of bread and ham. The meal contained 35g of the test fat and around 810kcal. Blood tests were taken 1 hour, 3 hours, 5 hours and 7 hours after the meal and all blood fats were analysed. The test subjects fasted during the day.
Julia Svensson is on maternity leave until April 2010. When she returns she will first and foremost finish studying how women react to the different fats. She and her colleagues will also be studying whether the different fats are more or less filling. In addition they will evaluate whether hormone status, exercise, abdominal fat and daily diet in general affect how the body absorbs fat after the meal.
For more information please contact Julia Svensson, doctoral student in Biotechnology at the Faculty of Engineering, Lund University, Julia.Svensson@biotek.lu.se, Tel +46 (0)709 54 46 47. Photo Julia Svensson, researcher Lund University.
