Download Setting the Record Straight on Saturated Fat and Heart Disease Risk

Setting the Record Straight
on Saturated Fat and Heart
Disease Risk
Ronald M. Krauss
Children’s Hospital Oakland Research Institute
UCSF and UC Berkeley
What is saturated fat?
Saturated fats consist of fatty acids
where the carbon chains are full
(“saturated”) with hydrogen.
There are dozens of types with
differing chain length; most common
are lauric, myristic, palmitic, & stearic.
Saturated fats are mainly consumed in
animal foods such as dairy products
and red meat, and oils such as
coconut, palm, and palm kernel oil.
Why limit saturated fat?

Main rationale is to reduce risk of heart disease:
 When
substituted for other types of fat, saturated fats
raise levels of LDL (“bad”) cholesterol.
 Levels of LDL cholesterol are strongly linked to heart
disease risk.
 Reducing
LDL cholesterol can
reduce heart disease risk.
LDL is comprised of subclasses of particles
with differing cholesterol content and CVD risk
Large
more cholesterol/particle
Medium
Small and very small
less cholesterol/particle
Increased CVD risk
Reduced plasma clearance
Greater entry into artery
Greater retention
Faster oxidation
Distribution of subclasses varies widely among individuals and is
independent of total LDL cholesterol
Berneis and Krauss, JLR 43:1155, 2002
LDL cholesterol level can misrepresent the
number of LDL particles
100 mg/dL
LDL-Cholesterol
100 mg/dL
Larger LDL particles
Smaller LDL particles
More cholesterol/particle
Less cholesterol/particle
Fewer LDL particles
More LDL particles
Small & very small LDL particles are reduced by low
carb (26 vs. 54%) even on high vs. low SFA (15 vs. 8%)
Change mg/dL
SFA increases
large LDL
Krauss et al. AJCN 83:1025, 2006
Does increase in LDL cholesterol with
higher SFAs translate to higher CVD risk?

Main effect of SFAs is on larger LDL particles, which
are less strongly associated with CVD risk than
smaller LDL
 Thus,
SFA-induced increases in LDL cholesterol may not
signify a proportional increase in CVD risk.

Carbohydrates (especially sugars) have a major
influence on smaller LDL particles
 Since
smaller LDLs have less cholesterol/particle, their
levels can increase with higher carb intake without a
proportional increase in LDL cholesterol.
How much saturated fat should we
be eating?



There is actually no need for SFAs in the diet since
the body can make them from other food sources,
primarily carbohydrates.
US Dietary and American Heart
Association (AHA) Guidelines have
traditionally advocated <10% of total
calories as saturated fat (~30g/d for
men and 20 g/d for women).
In the latest guidelines (2010), this has
been reduced to <7% of calories.
What is the evidence that reducing
SFAs will reduce risk of heart disease?



To study such an effect without complicating the results by
weight loss, something must be substituted for SFAs.
The best evidence from clinical trials is that substituting
polyunsaturated for saturated fat reduces heart disease
risk, although a recent meta-analysis has challenged this.
However, from epidemiologic studies, when SFAs are
replaced by carbohydrates (both sugars and simple
starches) there is no reduction in heart disease risk, and
there is some evidence that the risk may be greater.
Effects on heart disease risk of replacing
SFAs by other fats and carbohydrates
Dietary replacement (each 5% of calories)
Polyunsaturated fat
Predicted from lipid change
Randomized clinical trials
Observational cohort studies
Carbohydrate
Predicted from lipid change
Randomized clinical trials
Observational cohort studies
Monounsaturated fat (e.g., olive, canola)
Predicted from lipid change
Randomized clinical trials
Observational cohort studies
Relative Risk
Mozaffarian et al., PLoS Med Mar 23;7:e1000252, 2010
Consensus statement: Replacing SFAs with
polys may be beneficial for heart disease risk


The evidence from epidemiologic, clinical, and
mechanistic studies is consistent* in finding that the
risk of CHD is reduced when SFAs are replaced with
polyunsaturated fatty acids.
In populations who consume a Western diet, the
replacement of 1% of energy from SFAs with PUFAs
lowers LDL cholesterol and is likely to produce a
reduction in CHD incidence of ~2–3%.
Astrup A., et al. Am J Clin Nutr 2011;93:684–688.
*challenged by recent meta-analysis
Although monounsaturated fats (e.g. olive and
canola oil) also reduce LDL, they may not reduce
heart disease risk
On high cholesterol diets, SFAs and monos have
similar effects on atherosclerosis (in monkeys
and mice); polys are better than both.
Rudel L L et al. ATVB 15:2101-2110, 1995
Mediterranean diet: is it the olive oil?


Test of “low-fat” vs. “Mediterranean diet” in 7500 Spaniards.
Mediterranean diet:
Recommended:
Fresh fruits,≥3/d, vegetables ≥2/d, fish (especially fatty fish), seafood ≥3/wk,
legumes ≥3/wk, peanuts ≥3/wk, sofrito ≥2 servings/wk, white meat Instead of
red meat, wine with meals (optionally, ≥7 glasses/wk) and either:
A) Olive oil ≥4 tbsp/day of polyphenol-rich virgin olive oil, or
B) Tree nuts: Walnuts 15g, almonds 7.5 g, hazelnuts 7.5 g ≥3/wk
Discouraged
Soda drinks <1/d, commercial bakery goods, sweets, and pastries <3/wk,
spread fats <1 /d, red and processed meats <1/d
Estruch et al., N Engl J Med. 368:1279-90, 2013
Incidence of primary
CVD endpoint
Mediterranean diet: is it the olive oil?
30% reduction in CVD
(most significant for
stroke)
Significant diet differences in Med diets vs. control:
virgin olive oil(w/ polyphenols) nuts, fish and seafood, legumes
Estruch et al., N Engl J Med. 368:1279-90, 2013
Substitution of high glycemic starch for SFAs
increases risk for heart attack
Relative risk of heart attack
per 5% energy substitution
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Lowest
Medium
Highest
Tertiles of glycemic starch intake
Jakobsen et al.,Am J Clin Nutr. 91:1764-8, 2010
The role of reducing intakes of SFAs in prevention
of heart disease: where does the evidence stand?


No clear benefit of substituting carbohydrates for
SFAs has been shown, although there might be a
benefit if the carbohydrate is unrefined and has a
low glycemic index.
No clear association between SFA intake relative to
refined carbohydrates and the risk of insulin
resistance and diabetes has been shown.
Astrup A., et al. Am J Clin Nutr 2011;93:684–688.
Women's Health Initiative trial of low-fat diet:
no reduction risk of heart disease or stroke
>45,000 women; LDL-C reduced by 3.6%
Stroke
Cumulative Risk
Heart disease
Years
Years
Howard, B. V. et al., JAMA 295:655-666, 2006
Meta-analysis of 21 prospective cohort trials shows no significant
association of saturated fat intake with heart disease or stroke
Coronary heart disease
relative risk = 1.07
Stroke relative risk =0.81
Overall risk = 1.00
Siri-Tarino et al., Am J Clin Nutr. 91:535-546, 2010
Hazard ratio
But - higher red meat intake is
associated with increased mortality
Men (n=51,529)
Hazard ratio
Women (n=121,700)
Total red meat intake, servings per day
Pan et al., Arch Intern Med. 172:555-563, 2012
SFAs from meat are associated with higher CHD risk
while SFAs from dairy are associated with lower risk
Meat SFAs
Other
SFAs
Dairy SFAs
% increase high vs. low SFAs
Increase in LDL particles with high SFAs is much
higher when beef is the major protein source
12
Same increase in saturated fat (8%  15%)
10
8
6
4
2
0
Mixed proteins
Krauss et al., AJCN 2006
High beef
Mangravite et al., J, Nutr. 2011
Recipe for disaster
+
+
?
We should focus on eating healthy foods and
worry less about grams of saturated fat

The effect of particular foods on coronary heart
disease cannot be predicted solely by their content
of total SFAs because:
 individual
SFAs may have different cardiovascular
effects and
 major SFA food sources contain other constituents that
could influence CHD risk.
Astrup A., et al. Am J Clin Nutr 2011;93:684–688.
Maintaining a healthy LDL level is important but
there are many other effects of foods that can
affect heart disease risk

The effect of diet on a single biomarker [such as
LDL cholesterol] is insufficient evidence to assess
heart disease risk. The combination of multiple
biomarkers and the use of clinical end-points could
help substantiate the effects on heart disease.
Astrup A., et al. Am J Clin Nutr 2011;93:684–688.
More on foods vs. saturated fat



LDL cholesterol levels are lower after eating cheese
than after eating butter with the same amount of
saturated fat.
Recent epidemiologic studies suggest that
fermented dairy products are associated with
reduced risk of heart disease independent of
saturated fat.
It may be that intake of red meat is responsible for
much of the risk of heart disease (and diabetes)
attributed to saturated fat. And new evidence that
it’s not just the fat in beef that contributes to risk.
Summary: Points to consider about
saturated fat

It is not clear to what extent dietary saturated fat has
effects that are directly harmful to arteries as opposed to
having a neutral role; whereas other dietary factors have
more direct effects:
 Good:
 Fatty
fish, nuts, other polyphenol-rich foods, legumes
 Bad
 Trans
fats
 Sugars, glycemic starches

The foods with which SFAs are eaten can make a difference
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