By Helen Kollias
For
fifty years, scientists told us that too much saturated fat was bad for our
hearts, and advised us to switch to polyunsaturated fats instead. Oops.
It
turns out that polyunsaturated fats are not all equal, and some of them
actually increase the odds of cardiovascular disease and death.
In
this week’s Research Review, we’ll explore why mistaken conclusions in science
can sometimes become accepted wisdom – and which fats you really should
eat for better health.
Introduction
Ever
notice how a particular food can become all the rage – only to drop out of
fashion a few years later?
And
how the food or nutrient that our doctors told us to get more of in 1990 can
morph into the one they are warning us against in 2013?
It’s
enough to harden a person’s arteries.
With
so much conflicting information out there, it can be tough to figure out what
to believe.
But
as you’ll learn in this article, health is about balance. Too
much or too little of any nutrient can lead to trouble.
Keep
that in mind as we explore the complicated world of fats and their role in
heart health.
What
fats should I eat?
In
the last half of the 20th century, doctors and nutrition professionals agreed:
too much saturated fat was bad for the heart.
The
recommendations were clear: If you want to avoid heart disease and keep your
arteries free of build-up, you should increase polyunsaturated fats and
decrease saturated fats in the diet.
That’s
what they told us – and most of us listened.
But
lately, there’s been a shift in scientific understanding.
- Saturated fats don’t seem to be as
bad for us as doctors used to think.
- Polyunsaturated fats are not equal
in their effects.
- And the type of
polyunsaturated fat you eat may be just as important as how much of
it you eat.
Keep
fats real
Here’s
one simplified way to understand the relationship between some different fat
types.
Notice
that generally, fat type alone doesn’t determine the
healthiness – rather, healthy fats are found in whole,
unprocessed foods, while unhealthy fats are found in processed
foods.
For
example, you’ll notice that naturally occurring saturated fats (such as
coconut) are important in a healthy diet. On the other hand, artificially
created saturated fats (fats that start out unsaturated and are then
chemically processed – for instance, through hydrogenation — to become
saturated, such as margarine) are not as healthy a choice.
Our
bodies know what to do with real food. They don’t know what to do with the
other stuff.
Keep
fats in balance
Here
at PN, Dr. John Berardi has long recommended getting:
- 1/3 of your fatty acids from
saturated fats;
- 1/3 from monounsaturated fat; and
- 1/3 from polyunsaturated fat (with a good
amount of omega-3 fatty acids)
Of
course, these should mostly come from whole, unprocessed foods. (We’ll give you
some ideas below.)
Are
polyunsaturated fats bad for your heart?
Every
once and awhile a food or nutrient gets vilified. (By food I mean anything that
has been around for at least 100 years. Low fat, low cal, low-sugar cookies —
not food.)
But
the truth is, there’s really no such thing as a “good” food or a “bad”
food. And almost anything we swallow can be good or bad
for us, depending on whether we have a deficiency or a massive overabundance.
Don’t
believe me?
Let’s
take a look at water. Pure, innocent, cornerstone-of-life water.
You’re
mostly water – about 70%. You need water daily to live. So water is good,
right?
But
even water can kill you. If you over-hydrate yourself you can get water
intoxication. Too much water causes a decrease in key electrolytes that are
really important for important things like your heart pumping.
And
of course, your lungs like to be moist but not full of water.
Again,
it’s all about balance. The right amount in the right place at the right
time.
Finding
fatty acids in the grocery store
Now
you know which fats you should eat in what proportions. But there’s no “fat”
aisle at the grocery store, and most nutrition labels don’t classify fats
beyond telling you whether they’re saturated or unsaturated.
Here’s
how to recognize what kind of fats you’re buying and eating.
- Saturated fats come mostly
from animal fats (e.g. butter, meat fats) and tropical oils (e.g. coconut
oil). They’re usually solid at room temperature.
- Monounsaturated fats come mostly
from avocados, nuts, and olive oil.
- Most other oils are
polyunsaturates.
Start
with whole foods
If
you’re looking to add good fats to your diet, start with whole food-based
fats in their natural, least-processed state. This includes things like:
- fatty fish and seafood; sea
vegetables
- raw nuts and seeds
- avocados
- fresh olives
- fresh coconut; raw cacao
- pastured butter and full-fat dairy
- fatty meats if pastured /
grass-fed
Choose
cooking oils wisely
Unless
you’re grinding and pressing your own olives or seeds, remember that all
oils have undergone at least some processing.
Look
for “cold-pressed” or “extra-virgin” varieties of oil where possible.
The
table below (source) breaks down the fatty acid
composition of different types of oils that can be used for cooking – along
with butter, for comparison. Highlighted oils are lower in omega-6 fatty acids.
|
Cooking Oil
|
Sat/Mono/Poly
Fatty Acids (%)
|
Omega-6 (%)
|
Omega-3 (%)
|
Omega-9 (%)
|
Smoke point
|
|
Almond
oil
|
8.2/69.9/17.4
|
17.4
|
0
|
69.4
|
420
F (216 C)
|
|
Avocado
oil
|
11.6/70.6/13.5
|
12.5
|
1.0
|
67.9
|
400
F (204 C)
|
|
Butter
|
63.3/25.9/3.8
|
3.4
|
0.4
|
24.6
|
300
F (149 C)
|
|
Butter
oil
|
62.3/28.9/3.7
|
2.3
|
1.5
|
25.2
|
485
F (252 C)
|
|
Canola
oil
|
7.4/63.3/28.1
|
19.0
|
9.1
|
61.7
|
400
F (204 C)
|
|
Coconut
oil
|
86.5/5.8/1.8
|
1.8
|
0
|
5.8
|
350
F (177 C)
|
|
Corn
oil
|
13.0/27.6/54.7
|
53.5
|
1.16
|
27.3
|
450
F (232 C)
|
|
Cottonseed
oil
|
25.9/17.8/51.9
|
51.5
|
0.02
|
17.0
|
420
F (216 C)
|
|
Flaxseed
oil
|
9.4/20.2/66.0
|
12.7
|
53.3
|
20.3
|
225
F (107 C)
|
|
Grapeseed
oil
|
9.6/16.1/69.9
|
69.6
|
0.1
|
15.8
|
420
F (216 C)
|
|
Hazelnut
oil
|
7.4/78.0/10.2
|
10.1
|
0
|
77.8
|
430
F (221 C)
|
|
Macadamia
oil
|
12.5/83.5/4.0
|
2.0
|
2.0
|
83.0
|
413
F (210 C)
|
|
Mustard
oil
|
11.6/59.2/21.1
|
15.3
|
5.9
|
11.6
|
489
F (254 C)
|
|
Olive
oil
|
13.8/73.0/10.5
|
9.8
|
0.8
|
71.3
|
375
F (191 C)
|
|
Palm
oil
|
49.3/37.0/9.3
|
9.1
|
0.2
|
36.6
|
455
F (235 C)
|
|
Peanut
oil
|
16.9/46.2/32.0
|
32.0
|
0
|
44.8
|
450
F (232 C)
|
|
Safflower
oil
|
7.5/75.2/12.8
|
12.7
|
0.1
|
74.8
|
510
F (266 C)
|
|
Sesame
oil
|
14.2/39.7/41.7
|
41.3
|
0.3
|
39.3
|
510
F (266 C)
|
|
Soybean
oil (refined)
|
15.3/22.7/57.3
|
50.3
|
7.0
|
22.6
|
460
F (238 C)
|
|
Sunflower
oil
|
13.0/46.2/36.4
|
35.3
|
0.9
|
46.0
|
440
F (227 C)
|
|
Walnut
oil
|
9.1/22.8/63.3
|
52.9
|
10.4
|
22.2
|
400
F (204 C)
|
Notice
the smoke point of the various oils. That’s the temperature at which they begin
to burn.
When
you’re cooking, you want to prevent oil from burning because overheating causes
chemical deterioration and produces toxic compounds that circulate in your body
and lead to inflammation. Not good.
Cooking
with oils high in omega-3 fatty acids is a bad idea because these oils are
especially sensitive to heat, and break down easily into trans fats.
Research
question
To
recap: For many years, conventional wisdom held that polyunsaturated fats were
good for the heart.
Recall,
also, that omega-6 fat (linoleic acid) is a type of polyunsaturated fat.
So
what happens when people with coronary heart disease increase omega-6 fatty
acids (linoleic acid) in their diets? Today’s research review seeks to
answer that question. And the answers may surprise you.
Methods
First
surprise: This study is more than 50 years old! True, it was published just
this year, but the raw data was collected between 1966-1973.
Typically
in science we tend to put the highest value on the most recent discoveries. Yet
here, a collection of old data has given us new insights. And in some ways, the
age of this study may even be an advantage. Hindsight allows us to put its
findings in context.
That’s
precisely what the researchers here attempted to do. They took raw data from
the Sydney Diet Heart Study and re-evaluated it in light of recent mortality
data for coronary heart disease and cardiovascular disease, hoping to learn
what kind of fats are really good for the heart.
Subjects
The
original Sydney Diet Heart Study involved a total of 458 men between the ages
of 30-59, each of whom had suffered a recent “coronary event.” Coronary events
included acute myocardial infarction (86%) and acute coronary insufficiency or
angina (14%).
- The average age was 49, and the
average BMI was 25, which is borderline overweight.
- Their total blood cholesterol
levels were high (281 mg/dL on average), but there’s no data on the
subtypes of cholesterol (LDL vs. HDL).
- Their blood triglycerides were
considered borderline (at 187.5 mg/dL on average).
- Blood pressure was at the high end
of normal (at 136/89 on average).
- Most of the subjects smoked (about
70% admitted to this) and fewer than 7% had diabetes.
Dietary
changes
About
half the men (237) were assigned to a control group. Researchers didn’t ask
them to change their diets in any way, although some voluntarily stopped using
butter in favor of the (supposedly) healthier margarine.
Meanwhile,
the rest of the participants (221) were asked to make two changes.
- First, they ate more
polyunsaturated fatty acids (PUFA), aiming to get about 15% of their daily
calories from these fats.
- Meanwhile, they reduced their
saturated fatty acids to less than 10% of their daily calories and tried
to keep dietary cholesterol to less than 300 mg per day.
Even
today, many doctors would give you similar advice.
Subjects
continued with this regime for up to seven years. The median length of
participation in the study was three years.
To
get their PUFA intake up, researchers gave the men safflower oil and margarine
(aka solid safflower oil) for their cooking needs.
Both
groups got advice to stop smoking and to lose weight.
This
might be the first instance of dramatic irony I’ve seen in a recent research
study.
Two
things we know today, that nobody knew or cared about 50 years ago:
- Margarine contains trans fats.
- Trans fats are bad for you.
It
wasn’t until the 1990s that eating margarine containing trans fats was linked
to heart disease (2). Whoops.
Results
The
authors of the original study (3) hypothesized that eating more polyunsaturated
fat would contribute to lower levels of saturated fat in the diet. Lower levels
of saturated fat would, in turn, decrease cardiovascular risk factors such as
total cholesterol and total triglycerides.
Ultimately,
they believed that this would reduce the incidence of cardiovascular and
coronary disease and lead to lower death rates.
True
to their expectations, 12 months after the study’s start, the intervention
group showed more significant changes than the control group in the following
dietary and blood measures:
- polyunsaturated fat intake (↑)
- saturated fat intake (↓)
- total cholesterol intake (↓)
- total blood cholesterol levels (↓)
- total blood triglycerides levels (↓)
In
other words, one year into the Sydney Diet Heart Study, all findings supported
the original hypothesis.
Four
years later, it was a different story.
By
then, it had become clear that the intervention group was experiencing higher
death rates, higher rates of cardiovascular disease and higher rates of
coronary disease!
In
the original study – published in 1978 – researchers did report these findings.
But they didn’t try to explain what had caused the increased death rates (4).
Why?
We don’t know for sure. But it’s possible that these findings confused them,
because they went against accepted wisdom.
How
could a clear decrease in cholesterol be linked to higher rates of
cardiovascular and coronary disease? It didn’t make sense, given the state of
knowledge at the time.
Looking
back at other studies
In
the meta-analysis under review, the scientists scrutinized a number of other,
similar studies to try to figure out what caused the increased death rates in
this particular study.
Their
review of eight different papers revealed that the type of
polyunsaturated fats used in an intervention seemed to be key.
Increasing
omega-6 oils exclusively in an intervention seemed to lead to a higher risk of
cardiovascular disease and death. Using
mixed omega3/omega-6 polyunsaturated fats actually decreased these
risks.
Conclusion
There
are two main conclusions we can draw from this study:
- Eating more polyunsaturated fats
in the form of omega-6 fatty acids increases rates of death,
cardiovascular disease, and coronary disease.
- Science is context-dependent.
If
you follow PN, the first conclusion – that eating more omega-6 fatty acids
could increase the risk of disease – won’t come as a huge surprise. You already
know that some omega-6 fats have been linked to inflammation. (See All About Bad Fats.)
But
for many people, this is big news. And after years of being told by doctors,
nutritionists, and the media to eat vegetable oils high in polyunsaturated
fats, they’re understandably confused and exasperated.
Our
second conclusion, that science is context dependent, can help us make sense of
this.
Most
of us tend to imagine that science proceeds in a linear fashion. Start with an
idea (hypothesis), gather data, interpret the data, and presto-bingo, you have the
answer! Or, even more misleading, you have Truth.
But
that’s not really the way that scientific knowledge advances.
In
the Sydney Diet Heart Study, researchers hypothesized that more polyunsaturated
fats would decrease death due to cardiovascular and coronary disease, and that
cholesterol is a good measure of predicting coronary disease.
If
you look at the data today, with the benefit of hindsight, it appears that
hypothesis was wrong.
But
back in 1970, all other available data supported a diet low in saturated fat,
high in unsaturated fat, and low in cholesterol. And researchers agreed that
this was the type of diet that was best for heart health.
It’s
almost impossible to publish data that refutes the accepted wisdom in a given
period – especially if you have no plausible explanation for your anomalous
results. And the results of the original study were, quite simply, impossible
to interpret, given what the scientific community knew and accepted in 1970.
Fast
forward to 2013.
With
the advantage of 50 years further study and experimentation, we know that
not all polyunsaturated fats are equal.
Omega-6
polyunsaturated fats, in particular, can increase the risk of death from
coronary disease – probably because they increase inflammation.
But
in 1970, scientists didn’t distinguish between the sub-types of polyunsaturated
fat, and didn’t recognize that cholesterol is not a good measure for predicting
coronary disease.
That’s
why, in the end, it’s important to understand that science is a
process. Knowledge builds over time.
This
is why we shouldn’t jump on every nutritional bandwagon; sometimes we need
context to make sense of recent discoveries. Common sense and patience are key.
Bottom
line
There
are no “good foods” or “bad foods” and no good or bad nutrients,
either. Eating whole foods is always the safest (and healthiest) bet.
So
whenever you hear somebody speak in absolutes about a particular nutrient (e.g.
“Carbs are bad for you”, or “No one should ever eat saturated fat”) it is best
to take this suggestion with a (healthy) serving of salt.
The
Sydney Diet Heart study revealed the uncomfortable truth that diets high in one
type of fat (omega-6 fatty acids, particularly from processed sources like
cooking oils) contribute to higher rates of death from heart disease.
But
the solution is not to base your diet on another type of fat.
The
healthiest diets include a balance of different fatty acids, ideally
from a diverse diet of whole, unprocessed foods.
Keep
it simple. Keep it real. Keep it in balance.
Putting
it into practice
Today,
look at your fat intake. What could you get more of? What could you get less
of?
Make
small changes to keep it simple, real, and in balance.
Choose
whole foods.
Decrease
your intake of processed fats.
Get
more omega-3 fatty acids, ideally from fish or other marine sources.
