Eddie Vedder
2011-09-13, 14:45
Cochrane collaboration är kanske den mest betydelsefulla av alla stora oberoende granskare av forskning inom det medicinska området. Deras databas är helt enorm så den som inte redan känner till det kan ju kolla in. Nu har de precis släppt en stor översikt med randomiserade kliniska prövningar där man undersökt reducerat eller modifierat fettintag (alltså samma mängd men med olika sammansättning) och hur detta kan påverka risken för hjärt- kärlsjukdom.
Abstract
BACKGROUND:
Reduction and modification of dietary fats have differing effects on cardiovascular risk factors (such as serum cholesterol), but their effects on important health outcomes are less clear.
OBJECTIVES:
To assess the effect of reduction and/or modification of dietary fats on mortality, cardiovascular mortality, cardiovascular morbidity and individual outcomes including myocardial infarction, stroke and cancer diagnoses in randomised clinical trials of at least 6 months duration.
SEARCH STRATEGY:
For this review update, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE, were searched through to June 2010. References of Included studies and reviews were also checked.
SELECTION CRITERIA:
Trials fulfilled the following criteria: 1) randomised with appropriate control group, 2) intention to reduce or modify fat or cholesterol intake (excluding exclusively omega-3 fat interventions), 3) not multi factorial, 4) adult humans with or without cardiovascular disease, 5) intervention at least six months, 6) mortality or cardiovascular morbidity data available.
DATA COLLECTION AND ANALYSIS:
Participant numbers experiencing health outcomes in each arm were extracted independently in duplicate and random effects meta-analyses, meta-regression, sub-grouping, sensitivity analyses and funnel plots were performed.
MAIN RESULTS:
This updated review suggested that reducing saturated fat by reducing and/or modifying dietary fat reduced the risk of cardiovascular events by 14% (RR 0.86, 95% CI 0.77 to 0.96, 24 comparisons, 65,508 participants of whom 7% had a cardiovascular event, I(2) 50%). Subgrouping suggested that this reduction in cardiovascular events was seen in studies of fat modification (not reduction - which related directly to the degree of effect on serum total and LDL cholesterol and triglycerides), of at least two years duration and in studies of men (not of women). There were no clear effects of dietary fat changes on total mortality (RR 0.98, 95% CI 0.93 to 1.04, 71,790 participants) or cardiovascular mortality (RR 0.94, 95% CI 0.85 to 1.04, 65,978 participants). This did not alter with sub-grouping or sensitivity analysis.Few studies compared reduced with modified fat diets, so direct comparison was not possible.
AUTHORS' CONCLUSIONS:
The findings are suggestive of a small but potentially important reduction in cardiovascular risk on modification of dietary fat, but not reduction of total fat, in longer trials. Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates. The ideal type of unsaturated fat is unclear.
http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD002137.pub2/pdf
Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Database Syst Rev. 2011 Jul 6;(7):CD002137.
Alla lågkolhydratstudier och alla studier som adderat mer omega-3 exkluderades dock. Och om man i studien uppmanades till mer frukt och grönt exkluderads den, samt om någon av grupperna uppmanades till mer fysisk aktivitet utan att en annan gjorde det. Om samtliga grupper uppmanades till mer fysisk aktivitet inkluderades den dock.
Inklusionskreiterierna kan vara bra att ha klart för sig så man vet vad som faktiskt testats och vad som inte testats.
Types of interventions
All randomised controlled trials of interventions stating an intention
to reduce or modify dietary fat or cholesterol, such as would
be expected to result in improvement of serum lipid profile, were
considered. These included an intention to reduce total fat intake,
modify fat intake (while maintaining total fat intake), and reduction
and modification of fat intake, all compared to a usual diet
type control or modification of dietary fat compared to reduced
total fat. The intervention had to be dietary advice, supplementation
(of fats, oils or modified or low fat foods) or a provided diet,
and the control group usual diet, placebo or a control diet.
A low fat diet was considered to be one that aimed to reduce fat
intake to < 30%E from fat, and at least partially replace the energy
lost with carbohydrates (simple or complex), protein or fruit and
vegetables. Amodified fat diet was considered to be one that aimed
to include 30%ormore energy fromtotal fats, and included higher
levels of mono-unsaturated or poly-unsaturated fats than a ’usual’
diet.
Interventions excluded (unless they were present in addition to
those above) were addition of alpha-linolenic acid, omega-3 fats
or fish oils (as the effect of these is dealt with in a separate review),
high fibre diets and garlic (as pulses, fruits and vegetablesmay have
various effects other than lipid lowering) or exploration of varying
forms of carbohydrate (unless also specifically low in fat or fat
modified). Also excludedwere allmultiple risk factor interventions
other than diet or supplementation (unless the effects of diet or
supplementation could be separated, as in a factorial design, so
the additional intervention was consistent or randomised between
the intervention and control groups), and studies that aimed for
weight loss in one arm but not the other. Atkins-type diet aiming
to increase protein and fat intake were excluded, as were studies
where fat was reduced by means of a fat-substitute (like Olestra).
Enteral and parenteral feedswere excluded, aswere formulaweight
reducing diets.
Examples: studies that reduced or modified fats and encouraged
physical activity in one armand compared with encouraging physical
activity in the control were included; studies that reduced or
modified fats and encouraged physical activity in one arm and
compared with no intervention in the control were excluded; studies
that reduced or modified fats and encouraged fruit and vegetables
in one arm and compared with no intervention in the control
were included.
Abstract
BACKGROUND:
Reduction and modification of dietary fats have differing effects on cardiovascular risk factors (such as serum cholesterol), but their effects on important health outcomes are less clear.
OBJECTIVES:
To assess the effect of reduction and/or modification of dietary fats on mortality, cardiovascular mortality, cardiovascular morbidity and individual outcomes including myocardial infarction, stroke and cancer diagnoses in randomised clinical trials of at least 6 months duration.
SEARCH STRATEGY:
For this review update, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE, were searched through to June 2010. References of Included studies and reviews were also checked.
SELECTION CRITERIA:
Trials fulfilled the following criteria: 1) randomised with appropriate control group, 2) intention to reduce or modify fat or cholesterol intake (excluding exclusively omega-3 fat interventions), 3) not multi factorial, 4) adult humans with or without cardiovascular disease, 5) intervention at least six months, 6) mortality or cardiovascular morbidity data available.
DATA COLLECTION AND ANALYSIS:
Participant numbers experiencing health outcomes in each arm were extracted independently in duplicate and random effects meta-analyses, meta-regression, sub-grouping, sensitivity analyses and funnel plots were performed.
MAIN RESULTS:
This updated review suggested that reducing saturated fat by reducing and/or modifying dietary fat reduced the risk of cardiovascular events by 14% (RR 0.86, 95% CI 0.77 to 0.96, 24 comparisons, 65,508 participants of whom 7% had a cardiovascular event, I(2) 50%). Subgrouping suggested that this reduction in cardiovascular events was seen in studies of fat modification (not reduction - which related directly to the degree of effect on serum total and LDL cholesterol and triglycerides), of at least two years duration and in studies of men (not of women). There were no clear effects of dietary fat changes on total mortality (RR 0.98, 95% CI 0.93 to 1.04, 71,790 participants) or cardiovascular mortality (RR 0.94, 95% CI 0.85 to 1.04, 65,978 participants). This did not alter with sub-grouping or sensitivity analysis.Few studies compared reduced with modified fat diets, so direct comparison was not possible.
AUTHORS' CONCLUSIONS:
The findings are suggestive of a small but potentially important reduction in cardiovascular risk on modification of dietary fat, but not reduction of total fat, in longer trials. Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates. The ideal type of unsaturated fat is unclear.
http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD002137.pub2/pdf
Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Database Syst Rev. 2011 Jul 6;(7):CD002137.
Alla lågkolhydratstudier och alla studier som adderat mer omega-3 exkluderades dock. Och om man i studien uppmanades till mer frukt och grönt exkluderads den, samt om någon av grupperna uppmanades till mer fysisk aktivitet utan att en annan gjorde det. Om samtliga grupper uppmanades till mer fysisk aktivitet inkluderades den dock.
Inklusionskreiterierna kan vara bra att ha klart för sig så man vet vad som faktiskt testats och vad som inte testats.
Types of interventions
All randomised controlled trials of interventions stating an intention
to reduce or modify dietary fat or cholesterol, such as would
be expected to result in improvement of serum lipid profile, were
considered. These included an intention to reduce total fat intake,
modify fat intake (while maintaining total fat intake), and reduction
and modification of fat intake, all compared to a usual diet
type control or modification of dietary fat compared to reduced
total fat. The intervention had to be dietary advice, supplementation
(of fats, oils or modified or low fat foods) or a provided diet,
and the control group usual diet, placebo or a control diet.
A low fat diet was considered to be one that aimed to reduce fat
intake to < 30%E from fat, and at least partially replace the energy
lost with carbohydrates (simple or complex), protein or fruit and
vegetables. Amodified fat diet was considered to be one that aimed
to include 30%ormore energy fromtotal fats, and included higher
levels of mono-unsaturated or poly-unsaturated fats than a ’usual’
diet.
Interventions excluded (unless they were present in addition to
those above) were addition of alpha-linolenic acid, omega-3 fats
or fish oils (as the effect of these is dealt with in a separate review),
high fibre diets and garlic (as pulses, fruits and vegetablesmay have
various effects other than lipid lowering) or exploration of varying
forms of carbohydrate (unless also specifically low in fat or fat
modified). Also excludedwere allmultiple risk factor interventions
other than diet or supplementation (unless the effects of diet or
supplementation could be separated, as in a factorial design, so
the additional intervention was consistent or randomised between
the intervention and control groups), and studies that aimed for
weight loss in one arm but not the other. Atkins-type diet aiming
to increase protein and fat intake were excluded, as were studies
where fat was reduced by means of a fat-substitute (like Olestra).
Enteral and parenteral feedswere excluded, aswere formulaweight
reducing diets.
Examples: studies that reduced or modified fats and encouraged
physical activity in one armand compared with encouraging physical
activity in the control were included; studies that reduced or
modified fats and encouraged physical activity in one arm and
compared with no intervention in the control were excluded; studies
that reduced or modified fats and encouraged fruit and vegetables
in one arm and compared with no intervention in the control
were included.