Walnuts Improve Cholesterol Levels
April 7, 2000 (Atlanta) -- A handful of walnuts every day can work wonders
on lowering cholesterol levels -- if it's combined with a Mediterranean
"By incorporating a single food that is easy to consume, easy to carry,
doesn't need to be cooked -- just by changing one food in an already healthy
diet -- you can accomplish a great health benefit," Joan Sabaté, MD, tells
WebMD. A study authored by Sabaté and his colleagues appears in this month's
Annals of Internal Medicine.
"All heart-healthy diets lower total and LDL cholesterol; however,
during the walnut diet we observed a 5% and 6% reduction, respectively, beyond
the effects of the Mediterranean diet alone," says Sabaté. "It's
significant from a statistical standpoint, but relevant from a practical
point." Walnut oil could have similar effects to whole walnuts, but that
has not yet been investigated.
This study expands on Sabaté's previous research to include women, people
with high cholesterol, and middle-aged and older people. Also, other studies
have been conducted with meals prepared in a laboratory setting, while this
study involved "free-living persons" who were advised to eat a
Mediterranean diet, says Sabaté, professor and chair of nutrition at Loma Linda
University's School of Public Health in Loma Linda, California.
In his study, conducted in Barcelona, Spain, the 49 men and women all had
high total cholesterol and high LDL ("bad") cholesterol. People with a
family history of high cholesterol levels -- whether genetic or not -- were not
included in the study.
All were asked to eat a Mediterranean diet composed of fresh fruits and
vegetables, fish (no red meat or eggs), and olive oil for cooking. Those on the
"walnut diet" substituted eight to 11 walnuts a day for part of the
olive oil/fat portion of the diet. Patients followed each diet for six weeks,
since it takes four weeks for cholesterol levels to stabilize after diet
The overall cholesterol level decreased by 9% during the walnut diet but
only by 5% when eating the no-walnut diet. Similarly, the LDL, "bad,"
cholesterol levels decreased by about 11% during the walnut diet and almost 6%
during the no-walnut diet. Cholesterol ratios also improved with walnuts.
"Except for almonds, no other nut has been as well studied as
walnuts," Sabaté tells WebMD. "In a couple of studies, almonds have
been shown to lower total cholesterol and LDL levels without changing
["good" cholesterol]. They showed very similar results to our study.
It's a reasonable assumption that any nuts from the same group could have that
effect, but as a scientist, I cannot say so. Research has to be done to prove
His study also helps quiet a controversy in nut research. "It has been
suspected that nuts, because they are high in polyunsaturated fat, could
actually increase LDL ["bad" cholesterol] levels. However, we did not
observe [this] in the walnut diet," says Sabaté.