HarvardReview ofEvidence Verifies eating trans-fats Increases Heart Disease Ri

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Harvard Review of Evidence Verifies that eating " trans-fats "

increases risk of Heart Disease

JoAnn Guest

May 29, 2006 18:25 PDT

 

Boston, MA -- Over the course of the last decade, numerous studies

have examined the relationship between the consumption of trans fatty

acids found in partially " hydrogenated " oils and coronary heart

disease

(CHD).

 

 

A comprehensive review of the scientific evidence confirms that

eatingtrans fatty acids increases the risk of CHD.

 

The review, published in the June 24, 1999, New England Journal of

Medicine, is authored by researchers at the Harvard School of Public

Health and the Wageningen Centre for Food Sciences in the

Netherlands.

 

Lead author, Alberto Ascherio, said " Coronary heart disease kills

500,000 Americans each year. According to our estimations, if trans

fats

were replaced by monounsaturated oils, we would expect to see at

least 30,000 fewer persons die prematurely from CHD each year. "

 

Trans fatty acids are found in most margarines, in many commercially

baked goods, and in the fats used for deep-frying in many

restaurants.

 

The commercial advantages trans fats hold over monounsaturated oils

isthat they are solid at room temperature, they can remain on the

shelffor a longer time before becoming rancid, and they allow for

deep-

fryingat higher temperatures.

 

" Because of concerns that trans fatty acids increase risk of CHD, "

saidAscherio. " The Food and Drug Administration is considering new

regulations for nutrition labels that will require manufacturers to

report the amount of trans fatty acids. "

--------------------------------

Under current guidelines, a consumer who is trying to be heart-

healthy

might choose a product that is labeled as being low in cholesterol

andsaturated fat,

but which is high in harmful " trans- fats " .

 

The researchers reviewed more than 25 metabolic and epidemiological

studies. The metabolic studies showed that trans-fats have a two-

pronged

harmful effect on blood cholesterol levels: trans fats increase

" low-density " lipoprotein cholesterol (LDL-- " bad cholesterol " ) and

decrease " high-density " lipoprotein cholesterol (HDL-- " good

cholesterol " ).

 

The epidemiological studies tracked people's eating habits and

examined

occurrence of CHD later in their lives. These studies found a link

between consumption of trans fats and CHD that was higher than

expected

from the results of the metabolic studies.

 

" We don't fully understand all of the ways that trans fats increase

riskof CHD, " said Ascherio, " but it seems clear that they do increase

risk. "

 

Ascherio and colleagues urge the food industry to replace the

partiallyhydrogenated fats used in foods and in food preparation with

unhydrogenated oils: " Such a change would substantially reduce the

risk

of coronary heart disease at a modest cost. "

 

Alberto Ascherio is an associate professor of nutrition and

epidemiology

at the Harvard School of Public Health.

 

See also: Trans Fatty Acids and Coronary Heart Disease, The New

EnglandJournal of Medicine -- June 24, 1999 -- Vol. 340, No. 25.

 

For further information, please contact:

Bob Brustman

Harvard School of Public Health

Department of Nutrition

665 Huntington Avenue

Boston, MA 02115

Phone: 617-432-3952

Email: br- ;

====================================================================

 

Study shows how different types of dietary fat

affect coronary heart disease risk

Harvard School of Public Health PRESS RELEASE

For immediate release: November 18, 1997.

 

Boston, MA -- Harvard School of Public Health and Brigham and

Women'sHospital researchers report from the Nurses' Health Study

that it is

thetype of dietary fat, not total fat, that affects coronary heart

diseaserisk.

 

Saturated fat (found in meats and dairy foods) and trans unsaturated

fat (margarine, packaged cookies, crackers, and fast foods) increase

the

risk of coronary heart disease.

 

A relatively higher intake of

monounsaturated fat (high in extra-virgin olive oils) actually

reduces

risk. The study is reported in this week's New England Journal of

Medicine.

 

" Results from previous studies have been mixed concerning a possible

association between fat and risk of coronary heart disease.

This has

probably occurred because some studies have been small and did not

takeinto account different types of fat.

 

Because numerous metabolic studies have strongly suggested different

fats act in different ways to affect blood lipid levels, we were

veryinterested in examining the impact of different types of fat on

coronaryheart disease risk, " comments Frank Hu, MD, PhD, lead author

on thestudy and a research fellow at the Harvard School of Public

Health.

 

" In this large prospective study of nurses, which included over 900

cases of heart disease, we enhanced our ability to examine the

strength

of the associations between fat and heart disease risk by obtaining

repeated measurements of fat intake, " continues Dr. Hu. Our results

suggest that replacing saturated and trans fats in the diet with

monunsaturated sources of fat is an effective way to reduce coronary

heart risk. "

 

---

-The study also finds that trans fat is associated with the highest

relative risk of coronary heart disease,

twice that associated with

the

same intake of energy from carbohydrates.

 

This large effect is probably explained, say the researchers, not

only

by the impact of trans fat on blood lipid levels but its

interference

with essential fatty-acid metabolism and ability to elevate

triglyceridelevels.

 

While both monounsaturated and saturated fats are present in meats,

thepotential beneficial effect of monounsaturated fat is

counterbalanced bythe saturated fat in those same food sources.

 

Some oils, including

avocado and olive oils, excellent sources of monounsaturated fat,

are

not yet widely consumed by Americans.

 

The authors point out that the high carbohydrate diet recommended by

some heart disease prevention programs, which are intended to lower

LDL

levels, also lower the " good " HDL levels.

 

Consequently, an alternative strategy -- changing the composition of

fats in the diet with the dual aims of lowering LDL and raising HDL

levels -- may be a better way to lower coronary heart disease risk.

 

The Nurses' Health Study is an on-going prospective study of women,

age

30-55 at enrollment in 1976. The study is directed by Frank Speizer,

MD,

 

Brigham and Women's Hospital and Harvard Medical School. Subjects

were

subsequently followed every two years answering questionnaires

concerning their diet, lifestyle and health.

For further information, please contact:

Beverly Freeman, Director of Public Affairs

617-432-3863, email: bf-

 

Frank Hu, MD, PhD, 617-432-0113

 

Nutrition Researcher Frank Hu: Fat Quality More Important Than

Quantity

Around the School: News and Notices of the Harvard School of Public

Health

April 30, 1999.

 

 

Frank Hu, research associate in the Department of Nutrition, has

been

receiving a lot of attention lately from the popular media. The

reason

for this attention is that he has been lead author of a number of

studies that have produced good news about a popular and necessary

activity: eating.

 

Specifically, his work has examined the relationship between diet

and

heart disease.

 

In November, 1998, Hu reported in the British Medical Journal that

eating nuts reduced the risk of coronary heart disease in

women.

 

In April, his paper in the Journal of the American Medical

Society showed that there was no link between moderate egg

consumption

and heart disease.

 

Most recently, in the May issue of the American

Journal of Clinical Nutrition, his analysis demonstrates that

linolenic

acid, an omega-3 fatty acid found in monounsaturated oils may

protect

against fatal heart attacks.

 

Hu's work has comprised a series of collaborations with Walter

Willett,

Fredrick John Stare professor of epidemiology and nutrition, and

other

colleagues in the Nurses Health Study and the Health Professionals

Follow-up Study.

 

This same group, in 1997, published an article in the

New England Journal of Medicine indicating that total fat

consumption

was less important to heart disease than the *type* of fat

consumption.

 

" The problem is that 'total fat' is not a useful term, " said

Hu. " There

are good fats and bad fats. In the public's mind, fat has become

public

enemy number one.

 

Reducing dietary fat has become a priority. But the

truth is that if you reduce your total fat *consumption*, you're

also

reducing the amount of good fats that you eat--

 

fats that have a protective effect against heart disease. "

 

Bad fats are those that are frequently found in dairy, meat, and

other

animal products. These are saturated fats that have been shown to

increase levels of low-density-lipoprotein (LDL) cholesterol in the

bloodstream.

 

If the body has more " LDL " cholesterol than it requires, the

excess is deposited on the walls of arteries in the form of plaque.

Too

much plaque and the arteries become plugged--a condition known as

arteriosclerosis.

 

When arteries in the heart become clogged, it causes a heart attack.

If

arteries that lead to the brain are plugged, then the result is a

stroke.

 

Good fats, on the other hand, are found in cold-pressed oils. These

include monounsaturated " oleic " fats. These fats lower LDL

cholesterol

levels, resulting in lower risk of cardiovascular

disease.

 

---

 

Trans fats muddy the waters. " Trans-fats are vegetable oils that are

partially hydrogenated, " explained Hu.

 

" Adding hydrogen to the oils

makes them solid at room temperature, a characteristic that makes

them

useful in the production of baked goods. Products made with

hydrogenated

oils have long shelf lives.

 

" Unfortunately, trans fats are more

dangerous than saturated fats. Not only do trans fats increase LDL

cholesterol levels like saturated fats, they also reduce levels of

HDL

cholesterol--the *helpful* cholesterol.

 

Trans-fats do double harm. "

 

Explicating the relationships between types of fat and risk of heart

disease has been the basis of Hu's recent work. " We did the nut

study to

prove our point.

 

Many people avoid nuts because they're notoriously high in fats--up

to

80% of the energy in a nut comes from its fat content.

 

Therefore, many people assumed that eating nuts would increase risk

of

heart disease. But, because nuts contain primarily unsaturated fats,

eating nuts substantially reduces risk of heart disease. "

 

Next, Hu and his colleagues turned to eggs: " Eggs have been

perceived as

unhealthy food for many years because of their cholesterol content.

People have assumed that egg consumption would lead to increased

risk of

heart disease. "

 

Hu was not surprised by the results of the study.

 

" Moderate egg consumption, which we defined as one egg per day, is

not

associated with

increased risk of heart disease.

 

These results are consistent with data

from previous metabolic studies that suggested relatively small

effects

of dietary cholesterol on cholesterol levels in the bloodstream, " he

said.

 

" The slight adverse effect of an egg's cholesterol content is

balanced by the beneficial contents of its other nutrients (i.e. the

naturally occurring lecithin in the yolk) . "

 

The researchers did find, however, that egg consumption is dangerous

for

people with diabetes, possibly because of their altered ability to

metabolize cholesterol.

 

Moderate egg consumption led to a 40-to-50%

increased risk of heart disease for diabetics.

 

Hu's next project is an examination of the relationships between

types

of fat consumption and heart disease in people with diabetes.

 

" Previous studies have demonstrated that monounsaturated fat has

particular " benefits " on blood lipids and glucose response among

diabetics, " said Hu.

 

 

Around the School

is published weekly by the Office of Academic Communications

Harvard School of Public Health

665 Huntington Ave., 1204

Boston, Massachusetts 02115

617-432-3952

 

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JoAnn Guest

mrsjo-

www.geocities.com/mrsjoguest/Diets