Main Menu Health Library Fats, Polyunsaturated & Omega3 Fats, Polyunsaturated & Omega3
The Mediterranean Diet
Background: In 1994 and 1995 two research papers appeared that shocked researchers studying the effect of diet on heart disease. Although the study sample size of 300 heart disease patients per group was modest, the experimental diet tested produced with significance a 70% lower rate of subsequent patient cardiovascular events and deaths. This was in spite of the fact that serum cholesterol then assumed as the primary factor of risk - was similar in both groups. ((Lorgeril, M, Lancet 1994; 343:1454 and Renaud, S; Am J Clin Nutr 1995;61S:1360S)
A most evident difference in the two diets tested was a three-fold higher amount of alpha-linolenic acid an omega-3 fatty acid - in the experimental group. But the amounts of linolenic involved were small, and diet of this benefited group also included less meat, butter and cream, and more fruits and vegetables. At the time there was no way for positively identifying which of these factors or other unknown factors was responsible for the large and unexpected benefit of the experimental diet.
More Recent Research: Since 1995 much research including more than 40 population studies has emerged on the benefits of omega-3 fats. About a dozen of these provided information on the cardiovascular risk of alpha linolenic acid. We also now have far more research on meat, fats and fruits and vegetables on the risk of cardiovascular disease from very large studies. The conventional reviews of studies of omega-3 fats shows that these factors are most probably beneficial, but useful quantification of benefits is confused by some apparently conflicting conclusions of some authors and study statistics. Although there has been further support for the hypothesis that linolenic acid could have been the key contributor to the benefits of the Mediterranean diet, this has not been clearly verified.
The Life Ahead project has involved comprehensive and objective reviews of all of the key population research found on each of twenty three diet nutrient factors. This casually based analysis avoided the usual statistical confusion in different study results with use of a global engineering analysis of a data base of the accumulated actual data from each useful research study found. The analyses of the effects on cardiovascular risk of fruits and vegetables and detailed research results are summarized in a paper on this http://Lifeahead.net web site Verifying Health Values of Foods that in turn refers to sixteen other analyses of the involved nutrients also included on the site. The analysis of linolenic acid and cardiovascular risk is provided in the paper Polyunsaturated and Omega-3 Fats----- on this web site.
The Risk Benefit: A quantification of the affect of alpha linolenic acid on cardiovascular risk was derived from a data base of 17 risks from 4 studies that provided the best quantified and mostly dose related risks of cardiovascular disease. The actual level of linolenic differed in the different studies. Thus dummy variables were used to segregate these differences and obtain a best value for risk vs. amounts of linolenic. The result was:
Cardiovascular risk = exp(A + 0.83 * gms/day linolenic acid)
r=0.87; t of coefficient = 6.1; 5%-95% limits = 0.83 (0.56-1.10)
Although the number of studies and data were fewer than those used for most factors involved in Life Ahead, a t value of 6.1 for the key coefficient vs. only 2 needed for the usual 95% target identifies high significance. Other less quantified study risks for linolenic acid were statistically consistent with this result. The value of A varied probably in part because methods for measuring amounts of linolenic acid varied among the different studies. But an average population value for A of 0.5 seems appropriate, and is consistent with the basis for measuring linolenic acid now used in the Life Ahead diet library.
The actual amount of linolenic acid provided in the above Mediterranean diet research was estimated as 0.67 grams/day in the control group and 1.79 grams/day in the experimental group. These amounts produced risk factors from the above formula of 0.945 and 0.309 respectively for a net value of 0.32 or a risk reduction of 68%. The actual study result in the above 1994 paper was 73% (5-95% limits 41%-88%).
This provides positive verification from entirely independent and multiple research that the difference in linolenic acid probably was largely responsible for the large reduction in cardiovascular risk involved. This verifies further the importance to health-interested persons for maintaining an adequate level of omega-3 fats in their usual diet.
A More Comprehensive Analysis: A remaining question could be "To what extent could differences in other diet nutrients also explain the benefits of the Mediterranean diet?" The Life Ahead model now includes well verified effects of 23 nutrients in an entered diet on risks of cardiovascular disease and cancer. In its present form the model produces values of these needed nutrient factors from an actual diet entry of specific foods, and thus does not value directly from usual input a diet from amounts of its basic nutrient factors. Thus a special version of the model was established that provided as direct input the actual nutrient values of the above control and experimental diets that are valued in the program. These values were from the research reports shown or estimated were as follows:
Nutrient Control Experimental
Saturated Fat, % of calories 11.8 8.3
Mono unsaturated fat, % of calories 10.4 12.9
Poly unsaturated fat, % of calories 10.9 9.4
Dietary cholesterol, mg 320 217
Alpha linolenic Acid, grams 0.67 1.79
EPA+DHA, mcg 70 65
Vitamin C, mg 101 118
Vitamin E, mg 13.6 12.1
Carotene, ug 5539 6478
The computer program for a five year ahead period and the using above nutrient values estimated a reduction in cardiovascular risk of 61% for a population of coronary patients of the study age 53 for the experimental group. This compares with the above 73% (95% limits 41%-88%) measured. Of this, only 3% was due to the above difference in antioxidant vitamins, and 6% was due to differences in free cholesterol, saturated and other dietary fats. This shows again that by far the major contributor to the risk benefit of this Mediterranean diet was alpha-linolenic acid.
Conclusion: It seems evident from the above analysis that small amounts of alpha-linolenic acid in a diet can provide a substantial protection against cardiovascular disease. This is verified both from the now classic direct population studies and from the expected effects of nutrients in the diets measured via entirely independent research. It is noted that this type of quantitative casually based verification cannot be obtained by practical direct population study research. It can be obtained only from the appropriate analysis as above of results from multiple research.
Disturbingly and despite two decades of substantial research, many in the US public are unaware of the key importance to health of omega-3 fatty acid intake. The public concept of diet health still focuses on amounts of saturated fats and cholesterol. Unfortunately, there is little relationship between the omega-3 content of foods and their content of saturated fat. Recommendations To eat fish are useful but far from adequate, and overlook the companion contribution of the above18:n-3 linolenic acid. There has been no convenient method for individuals to learn the omega-3 fatty acid content of their diet. Except for those few that have been encouraged to take flaxseed oil and walnuts, most people may have benefited little from the important research on alpha-linolenic acid.
The Life Ahead program does identify conveniently the amounts of both linolenic acid and other omega-3 fats from fish oils in nearly any diet, compares these amounts with desirable goals, and shows both an change in risk of heart disease and a likely loss in Well-Days of life from an any diet deficiency in omega-3 fats vs. healthful targets used regularly over the long term. And the program provides a variety of acceptable dietary options that individuals can select from to remedy this deficiency. Download and install the computer program from Download Life Ahead, enter your habits and factors, and try entering a usual daily or weekly diet, and compute your outlook as detailed by the program. From the result display, access 'Actions for More Well-Days' and then 'Diet Analysis' to bring up the listing of diet nutrients for healthful targets. This will display your intake of total omega-3 fatty acids vs. targets from both fish and linolenic acids. Life Ahead may now be be the only available computer program that can develop this valuation from most user diets.