Mediterranean Dies and Health

Research conducted by: De Longerill et al.


Case study prepared by: David Lane and Emily Zitek


Overview
Most doctors would probably agree that a Mediterranean diet, rich in vegetables, fruits, and grains, is healthier than a high-saturated fat diet. Indeed, previous research has found that the diet can lower risk of heart disease. However, there is still considerable uncertainty about whether the Mediterranean diet is superior to a low-fat diet recommended by the American Heart Association. This study is the first to compare these two diets.


The subjects, 605 survivors of a heart attack, were randomly assigned follow either (1) a diet close to the “prudent diet step 1″ of the American Heart Association (control group) or (2) a Mediterranean-type diet consisting of more bread and cereals, more fresh fruit and vegetables, more grains, more fish, fewer delicatessen foods, less meat. An experimental canola-oil-based margarine was used instead of butter or cream. The oils recommended for salad and food preparation were canola and olive oils exclusively. Moderate red wine consumption was allowed.


Over a four-year period, patients in the experimental condition were initially seen by the dietician, two months later, and then once a year. Compliance with the dietary intervention was checked by a dietary survey and analyses of plasma fatty acids. Patients in the control group were expected to follow the dietary advice given by their physician.


The researchers collected information on number of deaths from cardiovascular causes e.g., heart attack, strokes, as well as number of nonfatal heart-related episodes. The occurrence of malignant and nonmalignant tumors was also carefully monitored.


Questions to Answer
Is the Mediterranean diet superior to a low-fat diet recommended by the American Heart Association?


Design Issues
The strength of the design is that subjects were randomly assigned to conditions. A possible weakness is that compliance rates depended on reports rather than observation since observation is impractical in this type of reseach.


Descriptions of Variables

Variable	Description
Type of diet	AHA or Mediterranean
Various outcome measures of health and disease	does the patient have cancer, etc.?

References
De Longerill, M., Salen, P., Martin, J., Monjaud, I., Boucher, P., Mamelle, N. (1998). Mediterranean Dietary pattern in a Randomized Trial. Archives of Internal Medicine, 158, 1181-1187.


Links


Another study on the Mediterrainean Diet


Exercises


1. What percentage of people on the AHA diet had some sort of illness or death?
2. What percentage of people on the Mediterranean diet had some sort of illness or death?
3. Conduct a Pearson Chi-Square test to determine if there is any relationship between diet and outcome.
4. Compute a 95% confidence interval on the proportion of people who are healthy on the AHA diet.


Frequencies

	Cancers	Deaths	Nonfatal illness	Healthy	Total
AHA	15	24	25	239	303
Mediterranean	7	14	8	273	302
Total	22	38	33	512	605