Not All Table Spreads "Butter
Up" Blood Cholesterol
Physiologist David Baer sorts vials of plasma and serum stored at -80°C
that will be used for lipid analyses.
The 46 volunteers in a study at the Agricultural Research Service Beltsville
(Maryland) Human Nutrition Research Center could tell the difference between
butter and those other spreads.
But they couldn't distinguish between the margarines with and without trans
fats. Only the dietitians who prepared the meals knew for sure. Researchers and
volunteers were kept in the dark during the 15-week study, to ensure
On weekdays, the volunteers ate breakfast and dinner in the Beltsville
center dining rooms and carried lunch to their jobs. Weekend meals were carried
home in a cooler for later warming. Volunteer Sandra Laase says, "You had
to eat everything they gave you--and you couldn't eat anything extra."
According to Vickie Lopez, a veteran of several studies at the Beltsville
center, "The study got hard when there were holiday luncheons. We had to
carry our brown bags with our prepared lunch and eat that." But the
researchers agreed to let the volunteers eat their own dinner on Thanksgiving
and Christmas, as long as they used the butter or margarine provided and
recorded what they ate.
The question asked by researchers Joseph T. Judd, David J. Baer, and Beverly
A. Clevidence was: "Do differences in blood lipids show up with minor
changes in fatty acid profiles among the three spreads?" says study leader
Judd. "Butter is the standard. Americans desire hardened fats in their
spreads and baked goods."
They also want fats that reduce risk of cardiovascular disease. So the food
industry partially hydrogenates vegetable oils for consumer acceptance. And
that process produces trans fatty acids, or trans fats.
Scientists have been concerned about their health effects for nearly as long
as oils have been hydrogenated. Until 1990, the evidence leaned toward no
Then a Dutch study showed that high intakes of trans fats did indeed raise
cholesterol, says Judd--especially the artery-damaging LDL cholesterol. Four
years later, Judd, Baer, Clevidence, and colleagues reported similar effects on
blood lipids when volunteers in an earlier study at the Beltsville center
consumed as little as one-third the trans fats fed in the Dutch study.
It's possible to harden products such as table spreads without
hydrogenation, says Judd. The margarines in this study were specially made by
Lipton in Baltimore, Maryland.
Their composition is compared in the chart on page 15.
Trans-Free Fats Look Best
The 23 men and 23 women volunteers consumed each spread for 5 weeks as part
of a typical U.S. diet. That is to say, 35 percent of total calories were fat,
15 percent were protein, and 50 percent carbohydrates.
Most Americans don't eat as much butter or margarine as fed in this study,
says Baer, noting that the spreads accounted for 8 percent of total calories.
That's about 2 to 3 tablespoons each day. "We wanted to be able to see
small changes in blood lipids," he says.
In studies to detemine the effects on cholesterol of eating different table
spreads, food service workers Sarah Mayock (left) and Diana Shegogue prepare
meals for controlled diets while chemist Joseph Judd looks on.
Analysis of the volunteers' blood samples showed a stairstep effect from the
· Butter evoked the highest LDL and total cholesterol levels.
· After eating the trans-fat margarine for 5 weeks, the volunteers'
total cholesterol was 3.5 percent lower than with butter, and their LDL was
down 5.4 percent.
· Five weeks of consuming the non-trans-fat margarine hardened with the
innocuous stearic acid produced the lowest levels. Compared to butter, total
cholesterol was down 4.7 percent and LDL was 6.7 percent lower.
"There's only one conclusion that can be reached," says Judd.
"You limit trans fats in the diet where you can. But don't get overly
concerned to the point where you substitute saturated fats for trans fats.
Saturated fats average about 12 percent of the total calories in the diet and
are a major dietary factor in cardiovascular disease risk.
"If it's tub margarine, which softens at room temperature, and the
primary fat on the label is liquid vegetable oil, it's okay," says Judd,
"even if it contains some trans fats.
"Even better," he notes, "may be some of the economical
trans-free margarines that are coming on the market." More of these will
follow as consumers demand alternatives.
Chemically speaking, trans fatty acids are monounsaturated fatty acids like
oleic acid--the principal fatty acid in olive and canola oils. Healthwise, they
are not equal. The body perceives trans fats more like the cholesterol-raising
saturated fats. Vegetable oils high in oleic acid, on the other hand, tend to
reduce blood cholesterol when they replace saturated fats.
Baer says that on average, 2 to 3 percent of total calories in the American
diet comes from trans fats. And only about 10 percent of that intake is
contributed by the naturally occurring trans fats in red meat, milk, and other
dairy products. The rest comes mostly from partially hydrogenated oils in
margarines, in shortening used in baked goods such as cookies, pastries, and
icings, and in restaurant fried foods.
Noting that she normally eats junk food, Lopez says, "I've always felt
healthier when I've done a study because I eat better."
Laase concurs. "I was probably the healthiest when I was on the
controlled diet," she says. "And we took no vitamins. It's probably
the only time I ate breakfast." Laase says she enjoyed the study, noting
that the discipline got difficult only toward the end.
One Fatty Acid at a Time
With the table spread study under their belts, Judd, Baer, and colleagues
wanted to tease apart the effects of individual fatty acids that raise, lower,
or have no effect on blood lipids. As each table spread was changed, several
fatty acids changed in the diets, explained Baer. The follow-up study varied
levels of one fatty acid or mixture of them at a time.
Over the course of 7 months, the researchers tested five diets differing in
fatty acids and one with extra carbohydrates. Two fatty acids--oleic and
stearic--and extra carbohydrates served as controls. The other three fatty
acids tested were trans fats, trans fats plus stearic acid, and a combination
of three cholesterol-raising saturated fats. When results are finalized, they
will help clarify the evidence needed for expert panels to reach consensus on
the remaining dietary fat questions.
To make informed choices, "the public needs clear health messages from
organizations like the American Heart Association, National Institutes of
Health, and the U.S. Department of Agriculture," says Judd.--By
Judy McBride, Agricultural
Research Service Information Staff.
Joseph T. Judd and
David J. Baer are at the USDA-ARS
Diet and Human Performance
Laboratory, Beltsville Human Nutrition Research Center, Bldg. 308, 10300
Baltimore Ave., Beltsville, MD 20705-2350; fax for both (301) 504-9098; [Judd]
phone (301) 504-9014. [Baer] phone (301) 504-8719.
"Not All Table Spreads "Butter Up" Blood
Cholesterol" was published in the September 1998 issue of
Agricultural Research magazine. Click here to see this
issue's table of contents.