ייעוץ Saturated fat and heart disease

[EMZ]

מה דעתכם על הביקורת הבאה ?
http://www.ajcn.org/cgi/content/full/92/2/459-a
לגבי המחקר שמצורף.

 

[מר לטיסימוס]

זה summary לא? יש כאן משהו חדש?

 

[Someone...]

This item requires a subscription to American Journal of Clinical Nutrition Online?
איך רואים את זה בכלל

 

[מר לטיסימוס]

לוחצים על הקובץ המצורף...?

 

[EMZ]

הבהרה:
הקובץ המצורף הוא ניתוח על (מטא אנליסיס) של מחקרים שנעשו לאורך השנים בנושא הקשר בין צריכת שומן רווי לבין מחלות קרדיווסקולריות. הקובץ טוען כי לא נמצא קשר מובהק בין השניים. (פורסם ב2009)

הלינק שפרסמתי זוהי ביקורת לניתוח-על הנ"ל שנעשתה על ידי:
Martijn B Katan and Ingeborg A Brouwer
[SIZE=-1]Department of Health Sciences, VU University, De Boelelaan 1085, 1081 HV Amsterdam, Netherlands [/SIZE]
Robert Clarke
[SIZE=-1] Clinical Trial Service Unit, University of Oxford, Oxford, United Kingdom [/SIZE]
Johanna M Geleijnse
[SIZE=-1] Division of Human Nutrition, Wageningen University, Wageningen, Netherlands [/SIZE]
Ronald P Mensink
[SIZE=-1] Department of Human Biology, NUTRIM School for Nutrition, Toxicology, and Metabolism, Maastricht University, Maastricht, Netherlands [/SIZE]

אין לכם גישה ל:
http://www.ajcn.org/cgi/content/full/92/2/459-a
?
במידה ואין, תגידו לי ואני אעתיק את זה בהודעה מסודרת.

 

[מר לטיסימוס]

אין גישה, בגלל זה חשבתי שאתה מפנה לסיכום.

 

[EMZ]

אז הנה הביקורת (אם אתם רוצים את הרפרנסים שלהם, תגידו):

In a meta-analysis of observational studies, Siri-Tarino et al (1) concluded that there was no association of intake of saturated fat with risk of cardiovascular disease. There are several weaknesses in their report, which question the validity of their conclusions.
First, the notion that there exists such a thing as "the effect of saturated fat" is flawed. A lower intake of saturated fat implies an increased intake of some other source of calories to maintain caloric balance. Different substitutions for saturated fat have different effects on risk of coronary heart disease (CHD) and need to be discussed separately.
Replacement of saturated fat by polyunsaturated fat lowers both plasma concentrations of LDL cholesterol and the LDL/HDL-cholesterol ratio (2). Moreover, replacement of saturated fat by polyunsaturated fat is also associated with a lower risk of CHD in prospective cohort studies (3) and with lower risk of CHD in randomized trials (4). Thus, the benefit of replacing saturated by polyunsaturated fat is proven beyond reasonable doubt. However, Siri-Tarino et al failed to find this effect in their meta-analysis, just as they failed to find a significant association of saturated fat with CHD in general. The null results of their meta-analysis may reflect a lack of statistical power or an overreliance on mathematical models. To estimate the effect of replacing saturated by polyunsaturated fat, Siri-Tarino et al selected 5 studies that reported relative risks adjusted for intake of carbohydrate, protein, and fats but not of polyunsaturated fat. They then combined these 5 numbers and presented the outcome as the effect of replacing saturated by polyunsaturated fat. It requires a leap of faith to assume that the outcome of such a calculation truly represents what happens when saturated fat is replaced by polyunsaturated fat.
A major weakness of the meta-analysis is the imprecision of dietary assessment methods used in the underlying studies. About half of the studies used 1-d dietary assessments or some other unvalidated method. Food intake varies from day to day, and there is a substantial literature showing that a single 24-h recall provides a poor estimation of the usual dietary intake of an individual (5). Such methods cannot reliably rank individuals by their long-term intake, especially within populations with a uniformly high saturated fat intake. Such imprecision in the assessment of disease determinants systematically reduces the strength of association of determinants with the disease. This is referred to as attenuation (6) or regression dilution bias (7). Observational studies that used such dietary assessment methods failed to show an association between diet and serum cholesterol concentrations (6). This shows the shortcomings of such dietary methods, because the effect of diet on serum cholesterol concentrations has been well established in randomized controlled trials (2, 8). Thus, the lack of a significant association between saturated fat intake and CHD may well reflect the consequences of regression dilution bias.
Intakes of saturated fat, and to a lesser extent trans fats, are important determinants of LDL cholesterol, which is a causal risk factor for CHD. Intake of saturated fat in the United States and Europe has fallen markedly since the first recommendations on dietary fat quality were issued 50 y ago. The resulting fall in LDL cholesterol led to a distinct decrease in CHD (9), especially in the early period before the arrival of statins in the 1990s. CHD and stroke still account for most deaths in the United States and Europe and increasingly also in other parts of the world. We believe that the conclusions of Siri-Tarino et al are invalid and are likely to mislead the general population.
Our final comment concerns conflicts of interest. Involvement with industry does not discredit scientists, but it does need to be disclosed. Siri-Tarino et al reported the various grants that funded their research but otherwise stated "No conflicts of interest." However, the website of the senior author (RMK) mentions advisory activities for the dairy industry (10). We wonder whether these should have been disclosed under the American Society for Nutrition Journals' Conflict of Interest Guidelines for Authors.

 

[bentzurm]

נפלא, מפריכים מטא-אנליזה אחת בעזרת מטא-אנליזה אחרת. העיקר שלסטטיסטיקאים יש פרנסה.

 

[EMZ]

אני צריך לפרסם את השאלה הזאת בפורום סטטיסטיקה.

 

[Mike Bikov]

זה כמו שלמורים בציור יש פרנסה, PHD ב ART זה ממש הישג.