Reducing saturated fat intake for cardiovascular disease: What's the evidence?

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Reducing saturated fat intake
for cardiovascular disease:
What's the evidence?
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What’s the evidence?
Hooper L., Martin N., Abdelhamid A., & Smith
G.D. (2015). Reduction in saturated fat intake
for cardiovascular disease. Cochrane
Database of Systematic Reviews, Art. No.:
CD011737.
http://www.healthevidence.org/view-article.aspx?a=28821
Evidence Summary:
http://www.healthevidence.org/documents/byid/28821/Hooper2015_Evid

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Poll Question #4

Dr. Lee Hooper
Reader in Research Synthesis,
Nutrition & Hydration in the
Norwich Medical School at the
University of East Anglia

Reducing saturated fat intake lowers the
risk of cardiovascular events
A.Strongly agree
B.Agree
C.Neutral
D.Disagree
E.Strongly disagree
18
Poll Question #5

Review
Hooper L., Martin N., Abdelhamid A., & Smith G.D.
(2015). Reduction in saturated fat intake for
cardiovascular disease. Cochrane Database of
Systematic Reviews, Art. No.: CD011737.
If you would like a full text copy of the review please
visit the Cochrane Library or request a copy from
Lee (l.hooper@uea.ac.uk).
Springs from: Hooper L et al. (2012) Reduced or modified
dietary fat for preventing cardiovascular disease. Cochrane
Database of Systematic Reviews, Art No.: CD002137

Review authors
• Lee Hooper, Norwich Medical School, University
of East Anglia, England
• Nicole Martin, Managing Editor, Cochrane Heart
Group, London, England
• Asmaa Abdelhamid, Royal College of
Paediatrics & Child Health, London
• George Davey Smith, University of Bristol,
England

Rationale (a)
Public health dietary advice on prevention of
cardiovascular disease (CVD) has changed over
time, with a focus on
•fat modification during the 1960s and
•fat reduction during the 1990s
•In 2006 the American Heart Association (AHA) suggested
“limit intake of saturated fat to 7% of energy” (Lichtenstein
2006).
•In 2013 the AHA suggested “Aim for a dietary pattern that
achieves 5% to 6% of calories from saturated fat” (strong
evidence, Eckel 2013).
US and European guidance are both based on
dietary effects on lipids.

Rationale (b)
If we reduce saturated fat in our diets we will replace
the energy with other fats, carbohydrate, protein
and/or alcohol. Which nutrients are used in place of
saturated fat will affect our health.
•Joint British Societies’ (JBS) guidance on preventing CVD
recommends “Replace saturated fat with polyunsaturated fat”
(JBS3 2014),
•UK National Institute for Health and Care Excellence (NICE)
guidance suggests that people at high risk of or with CVD eat
so that “saturated fats are 7% or less of total energy intake…
[and] replaced by mono- and poly-unsaturated fats” (NICE
2014).

Rationale (c)
The World Health Organization (NUGAG subgroup)
wanted to understand the following to enable them to
set guidance for saturated fat intake:
•the evidence of the effects on mortality and cardiovascular
health of reducing saturated fat, and
•how any effects differ depending on what type of energy is
used to replace the saturated fat.
•What cut-off of saturated fat to recommend
We chose to include only randomised controlled trials as
dietary patterns are highly confounded by other lifestyle
factors such as smoking, physical activity and socioeconomic
status which themselves have a huge impact on our
outcomes. This means that cohort studies provide less
trustworthy answers than long term trials.

Review Focus:
• Participants – adults, with or without CVD at
baseline
• Intervention – reduction in saturated fat by dietary
advice, supplementation (of fats, oils or modified fat
foods) or provision of a whole diet, over at least 2
years (24 months)
• Comparison – usual diet, placebo or control diet
• Outcomes – all-cause mortality, CVD mortality,
CVD events (plus secondary outcomes)

Review Focus:
Secondary Outcomes –
•Myocardial infarction (MI)
•Stroke including stroke incidence (type of stroke), stroke
mortality, and stroke morbidity
•CHD mortality (includes death from MI or sudden death
•CHD events (includes any of: fatal or non-fatal myocardial
infarction, angina or sudden death)
•type II diabetes incidence
•Blood measures (including serum blood lipids and measures
of glucose tolerance)
•Other outcomes & adverse effects reported by study authors
(including cancer diagnoses & deaths, body weight, BMI, blood
pressure (BP), quality of life

Methods - Searching
• Searched to March 2014, on Cochrane
CENTRAL, Medline, EMBASE
• Bibliographies & experts
• assessed 23,471 titles & abstracts
• 662 full text papers assessed
• 15 RCTs
– planned an intervention of ≥24 months, AND
– either stated an aim to reduce saturated fat OR
achieved statistically significant SFA reduction
• These 15 RCTs were included in this review

Methods – review process
• Independently duplicated assessment of
titles and abstracts, and of full text papers
retrieved
• Duplicated data extraction and
assessment of risk of bias
• We contacted authors to request missing
outcome and risk of bias data
• Tabulated reasons for exclusion,
characteristics of included studies, risk of
bias of included studies

Risk of bias of
included
studiesWe assessed study risk of bias using
the Cochrane Risk of Bias tool (see
Cochrane Handbook,
http://training.cochrane.org/handbook
) and added other factors important
to this review:
•Free of systematic differences in
care
•Stated aim to reduce SFA
•Achieved SFA reduction
•Achieved serum cholesterol
reduction

Methods – analysis (a)
• Mantel-Haenszel random-effects meta-
analysis (RevMan 5) to assess risk ratios
• I2
was used to assess heterogeneity
(considered important when I2
>50%)
• Outcome data extracted for the latest time
point (always ≥24 months).
• Effects of SFA reduction compared with
usual or standard diet on all (primary and
secondary) outcomes and adverse effects.
• Funnel plots used to assess small study bias

Methods – analysis (b)
Prespecified subgroups included:
•energy substitution for SFA (MUFA, PUFA,
carbohydrate, protein)
•Baseline SFA intake
•Sex (men, women and mixed populations)
•Baseline CVD risk
•Study duration
WHO requested:
•Degree of SFA reduction
•Serum total cholesterol reduction achieved
•Ethnic group

Methods – analysis (c)
Sensitivity analyses excluded studies that:
•Did not state an aim to reduce SFA
•Did not report SFA intake during the trial, or
find a significant reduction in SFA in the
intervention compared to the control
•Did not reduce total cholesterol (TC)
•Were the largest study (WHI 2006)
Analyses run with Mantel-Haenszel fixed-
effect model and Peto fixed-effect model
•GRADE assessment

15 Included RCTs:
Baseline health status, people…
•post-MI or with angina 6
•with DM or glucose intolerance 4
•with cancer risk or diagnosis 3
•With no specific risks 2
Geography
•USA or Canada 6
•Europe 7
•Australia or NZ 2

What is the effect of
saturated fat (SFA)
reduction on all-cause
mortality?

SFA reduction on all-cause mortality
RR 0.97 (95% CI 0.90 to 1.05)
I2
3%
3276 deaths, >55000 people

SFA reduction on all-cause mortality - funnel

Replacement criteria
• Replacement of SFA by PUFA, MUFA, CHO,
protein and trans were discerned from aims (if
possible) or from dietary intake within the study
(if necessary)
• categorised as any or all of PUFA, MUFA, CHO,
protein
• AND
• there was a statistically significant difference
(during the experimental diet) between
intervention and control for PUFA, MUFA, CHO,
or protein

SFA reduction on all-cause mortality – replacements
RR 0.96 (95% CI 0.82 to 1.13)
I2
26%
RR 3.00 (95% CI 0.33 to 26.99
4 deaths, 52 people
RR 0.98 (95% CI 0.91 to 1.05)
I2
0%
RR 0.98 (95% CI 0.91 to 1.06)
2protein
CHO
MUFA
PUFA

No effect of ↓ SFA on all-cause
mortality
• No sensitivity analysis (using 2 fixed
effects analyses, excluding largest RCT,
excluding studies with non-fat dietary
interventions, excluding studies with
different intensity of interventions) altered
the risk ratio (0.96 to 0.99) or altered the
lack of statistical significance
• No subgrouping altered the verdict of no
effect for all-cause mortality

saturated fat (SFA)
reduction on
cardiovascular mortality?

Effect of reduced SFA on CVD mortality
RR 0.95 (95% CI 0.80 to 1.12)
I2
30%,
1096 CVD deaths, >53,000 participants

Effect of reduced SFA on CVD mortality

Reduced SFA on CVD mortality -
replacements

No effect of ↓SFA on CVD
mortality
• No sensitivity analysis altered the effect size
(RR 0.92 to 1.00) or lack of statistical
significance
• No subgrouping altered the verdict of no
effect for CVD mortality except suggestion of
effect with greater reduction in SFA
– 1 study which reduced SFA by >8%E found a
30% reduction in CVD mortality, RR 0.70 (95%
CI 0.51 to 0.96, Veterans Admin study 1969

saturated fat (SFA)
reduction on
cardiovascular events?
Cardiovascular events included any of the following:
cardiovascular deaths, cardiovascular morbidity (non-fatal
myocardial infarction, angina, stroke, heart failure, peripheral
vascular events, atrial fibrillation) and unplanned cardiovascular
interventions (coronary artery bypass surgery or angioplasty)

Effect of reduced Saturated Fat on CV
events
RR 0.83 (95% CI 0.72 to 0.96)
I2
65%,
4377 events, >53000 participants

Reduced SFA on CV events – funnel plot

Effect of reduced Saturated Fat on CV
events
RR 0.73 (95% CI 0.58 to 0.92)
I2
69%,
884 events, >3000 participant
RR 1.00 (95% CI 0.53 to 1.89)
22 events, 52 participants
RR 0.93 (95% CI 0.79 to 1.08)
I2
57%,
3785 events, >51000 participan
RR 0.98 (95% CI 0.90 to 1.06)
I2
15%,

Reduced Saturated Fat on CV events - SA
Analysis RR (95% CI) of
CVD events
I2
No. of
events
No. of
particip
ants
Main 0.83 (0.72 to 0.96) 65% 4377 >53000
Sensitivity
analyses
Stated aim to reduce SFA 0.84 (0.72 to 0.97) 69% 4354 >52000
SFA significantly reduced 0.91 (0.79 to 1.04) 53% 4012 >52000
TC significantly reduced 0.81 (0.68 to 0.98) 77% 4092 >52000
Minus WHI 0.75 (0.61 to 0.91) 51% 932 >4000
Mantel-Haenszel Fixed
effects
0.93 (0.88 to 0.98) 65% 4377 >53000
Peto Fixed effects 0.92 (0.86 to 0.98) 72% 4377 >53000

Reduced SFA on CV events - subgrouping
Analysis, RR (95% CI) of CVD
events
I2
No. of
events
No. of
participan
ts
Subgroup by
replacement
p=0.14
PUFA replacement 0.73 (0.58 to 0.92) 69% 884 >3000
MUFA replacement 1.00 (0.53 to 1.89) NA 22 52
CHO replacement 0.93 (0.79 to 1.08) 57% 3785 >51000
Protein replacement 0.98 (0.90 to 1.06) 15% 3757 >51000
Subgroup by
duration,
p=0.15
Up to 24 months 0.96 (0.78 to 1.16) 0% 330 >2000
>24 to 48 months 0.73 (0.56 to 0.95) 50% 383 >1000
>48 months 0.93 (0.79 to 1.11) 75% 3599 >49000
Unclear duration 0.43 (0.17 to 1.08) NA 65 >200
Subgroup by
baseline SFA,
p=0.13
Up to 12%E SFA NA
>12 to 15%E SFA 0.98 (0.91 to 1.05) 6% 3765 >51000
>15 to 18%E SFA 0.41 (0.22 to 0.78) NA 28 55
>18%E SFA 0.79 (0.63 to 1.00) NA 219 846
Subgroup by
SFA change,
p=0.005
Up to 4%E SFA
difference
0.98 (0.91 to 1.05) 6% 3763 >51000
>4 to 8%E SFA
difference
0.40 (0.22 to 0.74) 0% 30 >100
>8%E SFA difference 0.79 (0.63 to 1.00) NA 219 >800

Reduced Saturated Fat on CV events -
subgrouping
Analysis, RR (95% CI) of CVD
events
I2
No. of
events
No. of
participan
ts
Subgroup by
sex, p=0.05
Men 0.80 (0.69 to 0.93) 24% 859 >3000
Women 1.00 (0.88 to 1.14) 60% 3445 >48000
Mixed, men & women 0.59 (0.23 to 1.49) 71% 73 >500
Subgroup by
CVD risk,
p=0.67
Low CVD risk 0.89 (0.75 to 1.06) 40% 3130 >47000
Moderate CVD risk 0.59 (0.23 to 1.49) 71% 73 >500
Existing CVD 0.86 (0.71 to 1.05) 63% 1174 >5000
Subgroup by
serum TC
reduction,
p=0.03
TC ↓ by ≥0.2mmol/L 0.74 (0.59 to 0.92) 63% 887 >4000
TC ↓ by <0.2mmol/L 0.99 (0.90 to 1.08) 15% 3488 >49000
Unclear TC change 0.20 (0.01 to 4.15) NA 2 >100

Reduction of CV events with SFA
reduction
• Sensitivity analyses
–Consistent reduction in CV events with
reduced SFA for almost all sensitivity anal
• Subgrouping explained some
heterogeneity - greater reduction in CV
events with
–(SFA replaced by PUFA)
–Greater SFA reduction
–Greater serum cholesterol reduction

Meta-regression – effect of individual
factors on degree of reduction of CVD
events
• greater reduction in serum total cholesterol
was associated with greater improvement in
CVD events with SFA reduction (p=0.04,
accounting for 99% of between study
variation)
• greater reductions in SFA intake and
greater baseline SFA intake were loosely
associated with reduced CVD events
• Gender, study duration and baseline
cardiovascular risk did not appear to
influence effect size

Effects of SFA reduction on serum
chol.
Pooled effect on serum total cholesterol was a fall of 0.24mmol/L
(95% CI -0.36 to -0.13), I2
60%, >7000 participants
0.24 mmol/L total cholesterol = 9.3 mg/dl

Secondary outcomes
There were no statistically significant effects of
reducing saturated fats on
•MI: RR 0.90 (95% CI 0.80 to 1.01, p=0.09) I2
10%, 1714 MI
•Stroke: RR 1.00 (95% CI 0.89 to 1.12) I2
0%, 1125 events
•Cancer deaths: RR 1.00 (95% CI 0.61 to 1.64) I2
49%,
2472 events
•Cancer diagnoses: RR 0.94 (95% CI 0.83 to 1.07) I2
33%,
5476 events
•Diabetes diagnoses: RR 0.96 (95% CI 0.90 to 1.02) I2
NA,
3342 events
•CHD mortality: RR 0.98 (95% CI 0.84 to 1.15), I2
21%, 886
deaths
•CHD events: RR 0.87 (95% CI 0.74 to 1.03, p=0.12), I2
66%, 3307 events

Cut-offs
Testing cut-offs for saturated fat
intake
• While the review suggests that reducing
saturated fat reduces cardiovascular
events there are no clear data suggesting
what cut-offs may be appropriate
• This is one way of exploring what cut-offs
may be appropriate
• I used the forest plot of the effects of
saturated fat reduction on CV events:

intake
• I tested cut-offs from 7% of energy from
SFA to 15% of energy from SFA
• For each cut-off I chose the studies that
had an intervention group intake less
than the cut-off, and the control group
greater than the cut-off

intake
• Example 1: the only study with an
intervention group achieving <7% E from
SFA and control >7%E from SFA was
Black 1994, so this was the only study in
the 7% analysis.
• Example 2: Ley 2004 obtained 10%E from
SFA in the intervention group, and
13.4%E from SFA in the control. This
study appears in the cut-offs for 11%, 12%
and 13%.

intake
Graph of RR of a CVD event vs. cut off points (as %
energy from saturated fat) tested.

Testing cut-offs for saturated fat intake
Graph of RR of a various outcomes vs. cut off points (as %
energy from saturated fat) tested.

WHO Specific questions (a)
• In adults what is the effect in the population of
reduced percentage of energy (%E) intake from
saturated fatty acids (SFA) relative to higher
intake for reduction in risk of non-communicable
diseases (NCDs)?
• We see clear reductions in cardiovascular
events
• Marginally statistically significant reductions in
myocardial infarction
• No clear effects (over these time scales) on all-
cause mortality or cardiovascular mortality,
stroke, CHD mortality or CHD events

WHO Specific questions (b)
• What is the effect on coronary heart disease
mortality and coronary heart disease events?
• There are no clear effects of SFA reduction
on CHD mortality or CHD events BUT
evidence here is limited

WHO Specific questions (c)
• What is the effect in the population of replacing
SFA with PUFAs, MUFAs, CHO (refined vs.
unrefined), protein or trans fatty acids (TFAs)
relative to no replacement for reduction in risk of
NCDs?
• SFA replacement with PUFA is
– associated with reductions in CVD events
– Marginal significance for reduced MI
• Replacement with CHO, protein
– Associated with no clear effects on outcomes
• No trans fat data available
• Very limited MUFA data

WHO Specific questions (d)
• What is the effect in the population of
consuming <10%E as SFA relative to >10%E
as SFA for reduction in risk of NCDs?
• Limited RCT evidence
• What evidence there is supports better
health a <10%E from SFA

Reduction in saturated fat intake compared to usual saturated fat intake for adults
Outcomes No of
Participants
(studies)
Follow up
Quality of the
evidence
(GRADE)
Relative
effect
(95% CI)
Anticipated absolute effects
Time frame is at least 2 years
Risk with Usual
saturated fat intake
Risk difference with Reduction in
saturated fat intake (95% CI)
All-cause mortality 55858
(11 studies)
56 months1
⊕⊕⊕⊕
HIGH2,3,4,5,6
RR 0.97
(0.9 to
1.05)
Study population
57 mortality per
1000
2 fewer mortality per 1000
(from 6 fewer to 3 more)
Moderate
Cardiovascular
mortality
53421
(10 studies)
53 months1
⊕⊕⊕⊕
HIGH2,3,4,6,7
RR 0.95
(0.8 to
1.12)
Study population
19 CV mortality
per 1000
1 fewer CV mortality per
1000
(from 4 fewer to 2 more)
Moderate
-
Cardiovascular
events
53300
(11 studies)
52 months1
⊕⊕⊕⊝
MODERATE2,4,6,8,9,10
due to inconsistency
RR 0.83
(0.72 to
0.96)
Study population
83 CV events per
1000
14 fewer CV events per
1000
(from 3 fewer to 23 fewer)
Moderate

Reducing saturated fat intake lowers the
risk of cardiovascular events
A.Strongly agree
B.Agree
C.Neutral
D.Disagree
E.Strongly disagree
68
Poll Question #6

Poll Question #7
Do you agree with the findings of this
review?
A.Strongly agree
B.Agree
C.Neutral
D.Disagree
E.Strongly disagree

Poll Question #8
The information presented today was helpful
A.Strongly agree
B.Agree
C.Neutral
D.Disagree
E.Strongly disagree

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Poll Question #9
What are your next steps?
A.Access the full text systematic review
B.Access the quality assessment for the review
on www.healthevidence.org
C.Consider using the evidence
D.Tell a colleague about the evidence

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Reducing saturated fat intake for cardiovascular disease: What's the evidence?

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