Crazy to consider, but I just realized that I posted the whole overview of the Mediterranean Diet & Metabolic Syndrome meta-analysis, but left out the "why I care" part....
3 out of 4 of my grandparents had some sort of cardiac disease, my 71 year old dad is not overweight, active, and fit, and has already had a heart attack with arterial blockages present...both of my parents have hypertension...my sister, my brother, and I all have hypertension as well (none of us is obese, we all eat well, and exercise). So, if I am to fight genetics, I need some ammunition! Pass the olives & wine, please....
Tuesday, March 15, 2011
Friday, March 11, 2011
More study types...So do the olives & wine help, or what?
Prospective studies, also known as cohort studies, are longitudinal, follow individuals that have been identified as being “exposed” or not, to something being studied (such as the Mediterranean Diet), and following these two groups to see how many develop the “disease” or condition (in the formerly discussed study, Metabolic Syndrome). One of the big problems with cohort, or prospective, studies is that they can take long periods of time, even decades. Sometimes one can use historical data (such as infant immunization records), and then compare two groups (ones with a specific immunization, or vaccination, and the ones that did not get the vaccine), and then investigate how many in each group had gotten a disease or not (such as measles). This gives an idea of the relationship between an exposure (vaccine), and whether or not it affects the outcome (disease) being studied....this is called a “retrospective” cohort study (Gordis, p. 170).
What does it all mean?!
What did they find?
When looking at multiple studies, comparisons are made of results. If several studies are seen to have similar (or heterogeneous) results, it is seen as a good indicator that the result (disease, health state, or desired outcome) is indeed related to the exposure.
The comparison of the studies in this meta-analysis found that following the Mediterranean Diet did not significantly consistently affect the following things:
Waist circumference measurements, blood pressure measurements
Adopting the Mediterranean Diet did significantly affect:
Lowered triglyceride levels (this is a type of blood fat that you want lower), increased HDL levels (this is a type of blood fat you want higher), decreased fasting blood glucose levels (this is good, as a high fasting blood sugar is an indicator of diabetes & increasing insulin resistance), and insulin resistance was reduced.
What Caused Confusion? Some of the studies combined the diet with other factors, such as exercise. The studies varied greatly in length. And the studies in the Mediterranean countries showed improvement in all health indicators significantly, except waist circumference. So, if your ancestors ate lots of olives, it is not too surprising that your own body responds well to them too (you still carry their DNA!)....
So, Does it Help, or What?!
Overall, the Mediterranean Diet appears to be associated with lower rates of Metabolic Syndrome, and its development, as several key risk factors are improved by following the diet.
Since Metabolic Syndrome is an increasing public health problem, adopting the Mediterranean dietary habits can be an cost-effective intervention & prevention tool.
What does it all mean?!
What did they find?
When looking at multiple studies, comparisons are made of results. If several studies are seen to have similar (or heterogeneous) results, it is seen as a good indicator that the result (disease, health state, or desired outcome) is indeed related to the exposure.
The comparison of the studies in this meta-analysis found that following the Mediterranean Diet did not significantly consistently affect the following things:
Waist circumference measurements, blood pressure measurements
Adopting the Mediterranean Diet did significantly affect:
Lowered triglyceride levels (this is a type of blood fat that you want lower), increased HDL levels (this is a type of blood fat you want higher), decreased fasting blood glucose levels (this is good, as a high fasting blood sugar is an indicator of diabetes & increasing insulin resistance), and insulin resistance was reduced.
What Caused Confusion? Some of the studies combined the diet with other factors, such as exercise. The studies varied greatly in length. And the studies in the Mediterranean countries showed improvement in all health indicators significantly, except waist circumference. So, if your ancestors ate lots of olives, it is not too surprising that your own body responds well to them too (you still carry their DNA!)....
So, Does it Help, or What?!
Overall, the Mediterranean Diet appears to be associated with lower rates of Metabolic Syndrome, and its development, as several key risk factors are improved by following the diet.
Since Metabolic Syndrome is an increasing public health problem, adopting the Mediterranean dietary habits can be an cost-effective intervention & prevention tool.
Kinds of Studies....
Study Types: This meta-analysis combined several kinds of studies....35 clinical trials, 2 prospective studies, and 13 cross-sectional studies.
The clinical trials included ranged in sample size (number of people in the study) from the smallest (8 participants) to much larger (11,000+). They were conducted in multiple countries (Spain, Israel, Italy, U.S., U.K., Denmark, Australia, Sweden, Finland, Germany, France). The studies lasted differing periods of time, from 4 weeks, to 5 years.
Clinical trials are used in evaluating whether a drug, diet, or other type of treatment is effective. The best clinical trials include “randomization” (called a randomized clinical trial, or RCT), with people picked randomly from the population being studied. Even further randomization can be used to choose the participants that get the treatment/drug being studied, and the ones that are getting the old treatment, or no treatment (called controls). Then, the end result being measured (weight loss, decreased blood fats, etc.) is evaluated in all of the participants. To avoid any other bias or effect on the study results, it is helpful if neither the researchers or the participants know who got the new drug/treatment, and who got the old drug/treatment...this is called a double-blind study. Randomized clinical trials are considered to be some of the most reliable studies in measuring effectiveness (Gordis, 2009, p. 132).
Cross-sectional studies are used to get a “snap-shot” of a current situation, in trying to find out if there is a possible connection between an “exposure” and a “disease”. Both the exposure and disease are surveyed at the same time. So, in this particular situation, both diet and health indicators would be surveyed at the same time. This assessment of some health condition, or disease, in an identified population is the “prevalence” (how many people in a specific population have a specific condition). Limits of a cross-sectional study are that it can’t be used to measure look backward (measuring how long this disease has existed in the population, or duration), or which came first, the exposure or the disease (temporality)...So, these studies can be used to link or associate, but not to determine cause and effect....(Which came first, the chicken or the egg???....we know that they are associated, but don’t know what came first).
The clinical trials included ranged in sample size (number of people in the study) from the smallest (8 participants) to much larger (11,000+). They were conducted in multiple countries (Spain, Israel, Italy, U.S., U.K., Denmark, Australia, Sweden, Finland, Germany, France). The studies lasted differing periods of time, from 4 weeks, to 5 years.
Clinical trials are used in evaluating whether a drug, diet, or other type of treatment is effective. The best clinical trials include “randomization” (called a randomized clinical trial, or RCT), with people picked randomly from the population being studied. Even further randomization can be used to choose the participants that get the treatment/drug being studied, and the ones that are getting the old treatment, or no treatment (called controls). Then, the end result being measured (weight loss, decreased blood fats, etc.) is evaluated in all of the participants. To avoid any other bias or effect on the study results, it is helpful if neither the researchers or the participants know who got the new drug/treatment, and who got the old drug/treatment...this is called a double-blind study. Randomized clinical trials are considered to be some of the most reliable studies in measuring effectiveness (Gordis, 2009, p. 132).
Cross-sectional studies are used to get a “snap-shot” of a current situation, in trying to find out if there is a possible connection between an “exposure” and a “disease”. Both the exposure and disease are surveyed at the same time. So, in this particular situation, both diet and health indicators would be surveyed at the same time. This assessment of some health condition, or disease, in an identified population is the “prevalence” (how many people in a specific population have a specific condition). Limits of a cross-sectional study are that it can’t be used to measure look backward (measuring how long this disease has existed in the population, or duration), or which came first, the exposure or the disease (temporality)...So, these studies can be used to link or associate, but not to determine cause and effect....(Which came first, the chicken or the egg???....we know that they are associated, but don’t know what came first).
Thursday, March 10, 2011
EAT LIKE YOU ARE GREEK?
“What you mean, he don’t eat meat? Oh, it’s OK, I make him lamb!” (quote from “My Big Fat Greek Wedding”, 2002 movie, released by IFC films).
In our house, my family frequently works favorite movie quotes into the daily dialogue…Maybe more than other houses (a topic for yet another post)…
What does this have to do with Epidemiology? And why I care…
In the recent news, there have been several articles posted (see links & titles below) regarding a newly released meta-analysis in the March issues of the Journal of the American College of Cardiology, entitled “The Effect of Mediterranean Diet on Metabolic Syndrome and its Components”.
Mediterranean diet linked to lower heart disease risk (Kirk McKoy / Los Angeles Times)
March 8, 2011 |By Mary Forgione, Tribune Health
Why to Eat Like a Greek By RON WINSLOW
Several terms here require definition. Metabolic Syndrome (MS) is a fancy name for a combination of risk factors for cardiovascular (heart and blood vessels) disease. This includes high blood pressure (hypertension), high blood fats (hypercholesterolemia), being fatter than you should be (obese, especially around the belly-area, shaped like an apple, some definitions say women with a waist measuring 40 inches, or over, for men, and 35 inches, or over, for women), and having increasing blood sugar (insulin-resistance) (Kastorini, et al., 2011). The World Health Organization (WHO) has said that MS is increasing in prevalence (how much disease/condition exists in a specific population during a specific time) (Gordis, 2009, p. 43) throughout the world, along with diabetes and obesity. This is an increasingly serious, global public health problem (Kastorini, et al., 2011), with prevalence estimates of 13.4% to 70% (Kastorini, et al., 2011).
The Mediterranean Diet has been talked about since the 1960’s. It is loosely defined as a eating a higher amount of olives/olive oil (monounsaturated fats, avocados have this too), along with larger daily portions of vegetables, whole grains, legumes (beans), fruits, and low-fat dairy products. Every week, fish & poultry are included, along with nuts from trees (almonds, walnuts, pecans, pistachios). Moderate daily alcohol intake is included (some studies say primarily red wine with meals). Red meat consumption (such as beef, lamb, & pork) is limited to once, or twice, a month (Kastorini, et al., 2011). Higher garlic consumption has also been included in some definitions. Numerous studies have linked this type of diet as being “cardioprotective” (protecting the heart & blood vessels from damage and disease).
(FOOD ALERT….By the way, this is an easy way to eat! Our menu last night consisted of olive-oil & garlic sautéed mahi-mahi, spinach salad with almonds, strawberries, low-fat feta cheese (drizzled with balsamic vinaigrette/olive oil dressing…should have added avocado, or olives!), brown rice, and steamed broccoli, with a glass of red wine, was very, very tasty! The focus is on keeping foods simple, using as few “processed” foods as possible…This was a very quick meal to fix as well).
So, just to be clear, the “exposure” (epidemiological word for the thing being studied to see if it is related to a good, or bad, health situation/outcome) in this study is the Mediterranean Diet. The “disease” (word for health situation/outcome being studied) here is Metabolic Syndrome.
Only this isn’t just one study. It is a combination of 50 different studies, with over 500,000 participants, called a meta-analysis. A meta-analysis looks for common findings. If it is done well, it searches scientific literature for the exposure and disease being examined, weeds out the studies that were poorly done, and then measures the strength of the associations noted in the studies (Gordis, 2009, p. 342). At first glance, it is tempting to believe that a meta-analysis enables one to draw more powerful conclusions (after all, this study includes 50 studies, with over 500,000…IT IS BIG!). However, its reliability and generalizability (can you trust its conclusions? can you apply the results to many populations/situations?) are only as good as the studies you put into it…as the old saying goes, “Garbage in, garbage out”. Also, where a more rigid definition of a meta-analysis might only use a combination of similar studies of one type (such as randomized control trials), more and more meta-analyses are combining several study types (clinical trials, case studies, cross-sectional studies, etc.) (Gordis, p. 342). So, if you are comparing “apples to oranges”, then, how reliable are the results of the meta-analysis?
One particular noted limitation of meta-analysis is that the results can be affected by publication bias, as in only published studies are included. The reasons some studies get published in the first place may not be un-biased…such as readers are more interested in a specific topic with specific results (Gordis, p. 343)…(a current non-scientific media example would be all the attention garnered by the antics of actor Charlie Sheen! Mental illness and substance abuse are more worthy topics, however, nothing satisfies the American public better than a big, juicy public meltdown…). So the amount of published studies on a specific topic may not truly reflect risk, or results).
(More on this particular meta-analysis later today…).
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