In her doctoral dissertation, Rita Nilsen McStay has examined whether cheese lowers blood pressure and whether cheese in large amounts affects cholesterol levels.
Previous studies of Gamalost, a traditional Norwegian skimmed milk cheese, show that the cheese contains peptides, which lower blood pressure. This was the reason why Rita Nilsen McStay wanted to find out more about how cheese affects our health.
She carried out a study that among other things examined the effect of cheese on blood pressure and cholesterol when participants ate cheese every day for eight weeks. The 153 participants in the study were randomly distributed among three groups: the first group was to eat 50 grams of Gamalost a day, the second group was to eat 80 grams of Norvegia a day, while the third group (the control group) was to abstain from cheese during the period.
On the first day of the intervention study, blood pressure was measured, blood tests were analysed for cholesterol and blood sugar, and height and weight were measured. After four weeks the participants had their blood pressure measured again, and after eight weeks, when the study was concluded, they were again fully tested.
No changes in cholesterol
There was a great variation in how much fat the participants got in themselves during the period. Norvegia contains 27% fat, while Gamalost contains no fat at all. Norvegia also contains much more calcium than Gamalost. Both calcium and fat are assumed to influence the cholesterol level in our blood. Rita Nilsen McStay wanted to examine whether there were any differences in the participants’ measured cholesterol levels during the period.
The authorities’ dietary recommendation is to eat less saturated fat. The argument is that too much saturated fat will increase the level of cholesterol, something that has an adverse effect on the heart. The dietary recommendation is that saturated fat should contribute with at most 10% of a person’s daily energy intake. For a man who needs 2,400 kcal per day, for example, the maximum recommended intake of saturated fat is 27 grams.
“I didn’t find any increase in cholesterol in the participants in this group,” McStay says. “That might suggest that cheese and dairy products do not have the negative effect that the authorities warn us against.”
Some of the participants with a high intake of cheese actually ended up with lower cholesterol compared with participants who ate no cheese. Among those who had a metabolic syndrome (that is, who tested positive on three of the following five variables: too high waist measurement, blood sugar, blood pressure, and triglycerides, and too low HDL cholesterol), McStay found a significant decrease in cholesterol – it seems likely this has a clinical effect. She found a decrease in cholesterol among both the Norvegia and the Gamalost groups.
“Since Gamalost contains no fat and contains much less calcium than Norvegia, it seems as though there are also other factors in the cheese that affect cholesterol levels,” McStay explains. “Now we want to conduct further research on what these factors are.”
Control group members on a stricter regimen?
Rita Nilsen McStay expected the Gamalost group to end up with lower blood pressure. But it turned out that the control group participants also lowered their blood pressure. Why did that happen?
“There are many factors that are decisive for the result,” McStay explains. “All the participants were told what their blood pressure was during the start of the study. It is possible that those who had high blood pressure in the control group changed their other dietary habits and exercise routines during the study period, since blood pressure did not change in the Norvegia group.”
Among those who ate Gamalost and who had a medium-high blood pressure, McStay found a decrease in blood pressure after four weeks, compared with the control group. Among those who had a high blood pressure, the PhD candidate found a decrease in blood pressure throughout the entire period, but there was no difference between the Gamalost group and the control group.
Did the study period last too long?
Rita Nilsen McStay found that participants with a medium-high blood pressure had significantly reduced their blood pressure after the first four weeks, while the decrease was significantly less after the next four weeks. What happened?
“Perhaps Gamalost does not work the way we thought it did, or perhaps cheese has a short-term effect?” McStay answers. “I think also it may be the case that participants with medium-high blood pressure did not eat the daily amount of Gamalost during the last four weeks. Eating 50 grams of Gamalost a day is pretty much, especially if you are not that enthusiastic about the cheese.”
She hopes we will see similar studies, particularly in the context of a meal, in order to obtain further results that can provide us with even more information about cheese’s effect on health.