In its November 23, 1989 issue, the New England Journal of Medicine (Vol. 321, No. 21, Page 432) published an article by Annette Bak, M.D. and Diederick Grobbee, M.D., Ph.D. entitled "The Effect of Serum Cholesterol Levels of Coffee Brewing by Filtering or Boiling." It was headed by an abstract which read as follows:
"Previous reports have indicated that coffee consumption may increase serum cholesterol levels. We have studied the effects of coffee prepared by two common brewing methods, (filtering and boiling) on serum lipid levels in a 12-week randomized trial involving 107 young adult subjects with normal serum cholesterol levels. After three weeks run-in period during which they all consumed filtered coffee, the participants were randomly assigned to one of three groups receiving four to six cups of boiled coffee a day, four to six cups of filtered coffee a day, or no coffee, for nine weeks.
"As compared with the change from base level in the filtered coffee group, the serum total cholesterol level increased after the consumption of boiled coffee by 0.48 minimals per liter; and the low density liproprotein cholesterol level increased by 0.39 mmol. per liter. There was no difference in the change in serum total or low density lipoprotein cholesterol between the filtered coffee group and the group that drank no coffee. Level of high density cholesterol was not affected by boiled or filtered coffee.
"We conclude that drinking filtered coffee does not affect serum lipid levels. The consumption of boiled coffee, however, has an effect on serum cholesterol levels amounting to a mean net increase of 10 percent of the base line level after nine weeks."
The media read this statement and enjoyed another instance of coffee bashing, by headlining in newspapers, radio and television: "Boiled Coffee Increases Cholesterol 10%." The National Coffee Association commented that the "Conclusion on filtered coffee was good news for the coffee industry," while the media completely ignored this positive information in the abstract. The public continued to be confused. Coffee technologists were naturally and correctly skeptical.
The bias of the authors of this report is immediately apparent from the first sentence of the body of the article: "The possibility that the consumption of coffee may increase the risk of coronary heart disease has been suspected for many years." This is a reference to a report published in 1911 on the persistent effect of caffeine on the circulation. At that point in time there had been no scientific evidence that coffee was harmful. It was based on a still prevalent widespread medical belief that if coffee isn't unhealthy, it should be.
Examination of the details of procedures in this study raise a number of questions as to the validity. 107 volunteers out of a large group who had been in a cardio-vascular risk program participated. Those over eighteen who habitually drank coffee were selected, half male and half female. This is much too small a group to afford conclusions of this nature.
The nine weeks period of differentiation of the three groups is too short a period for reliable conclusions: "All the participants had to drink three cups of tea per day, in order to make the groups similar with respect to their intake of caffeine from the source." Blood samples were taken twice during the run-in and after three, six and nine weeks of the test.
At a minimum, after the nine weeks, the groups should have been rotated twice so that each group underwent all three variations.
Their report of a 10 percent increase in cholesterol level after nine weeks is highly suspect. Chemical analysis for cholesterol in the blood stream is not too accurate, and a five percent deviation in results for two tests of the same sample is not unusual. There is an additional variation in the same individual from day to day depending on diet, exercise, alcohol consumption, stress and many other factors.
But the greatest discrepancy in the concept of this research is their brewing methods which are described as follows:
"The filtered coffee was prepared in a commercially available coffee maker by dripping hot water on coffee and filtering it through paper. The subjects using boiled coffee prepared it by pouring 0.5 liters of boiling water on twenty grams of coarsely ground coffee in a thermos bottle and waiting at least ten minutes before drinking. Just before drinking, the liquid is decanted without the use of a filter. This protocol is like all those used in previous studies involving boiled coffee. Coffee and the brewing devices were given to participants free of charge. The coffee was drunk from 140 ml. cups. Similar blends of coffee were used to prepare both the boiled and filtered coffee, and the degree of roasting was also similar. Coffee for boiling was ground more coarsely than coffee for filtering."
"Just after boiling water was poured on coffee, the temperature was 92.7 [degrees] C and it decreased by 1.7 [degrees] per hour. Water dripping onto coffee in an electric coffee maker averaged 90 [degrees] to 95 [degrees] C. The temperature of the sediment was 91.6 [degrees] C and decreased to 87.5 [degrees] C after three minutes. The temperature of the coffee fluid in the device's glass container was about 85 [degrees] C."
This data casts an entirely different light on the results of this research and on all other reports covering "boiled" coffee. This method of preparation is a complete misnomer, since at no time in its preparation is the ground coffee exposed to the direct heat of boiling. Essentially, this type of preparation is little different from percolation where grounds are extracted by boiling water. Boiled coffee, to most people, is analogous to camp coffee where the grounds and water are both heated over an open flame. It is imaginable that exposing coffee and water over an open flame might cause change or deterioration of the coffee particles, but this has never been scientifically demonstrated.
Extraction of coffee has been intensively studied by soluble producers for well over half a century. Practically no difference in extractives has been found at any temperature below 100 [degrees] C. Studies on extraction between 100 [degrees] C and 200 [degrees] C exhibited substantial increases in extractives proportional to elevated temperatures. If this research had been run on filtered or percolated coffee vs. solubles, the difference in percent solids extracted might have some physiological effect, but none has been observed hitherto. It is inconceivable that a 10 degree differential in coffee extraction between 95 [degrees] C and 85 [degrees] C could produce the results claimed in this research report, particularly since it is never drunk at these burning temperatures.
If the results of this report had any validity, coffee buyers should be constantly alert to having their cholesterol evaluated. Their procedure for cup testing, involving pouring boiling water on ground roasted samples, is identical to that for preparing "boiled" coffee. It is true they expectorate most of what they inhale; but they do retain a small residue which could have a cumulative effect.
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|Title Annotation:||coffee and risk of heart disease|
|Publication:||Tea & Coffee Trade Journal|
|Date:||Feb 1, 1990|
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