When Studies Mislead: The Skinny on Low Fat Diets

When I read the front page headline in thefollow-up--from the Nurses' Health Study of
February 7 edition of the New York Times,dietary fat intake and risk of coronary heart
LOW-FAT DIET DOES NOT CUT HEALTH RISKS,disease. It showed clearly favorable results. In
my 35 years as a cardiologist-researcher told meJanuary of this year, a report in The Lancet
something was probably amiss. The article thatanalyzed the effect of fruit and vegetable
followed seemed to faithfully report theconsumption in eight studies that included a total
conclusions of an 8 year, $4.15 million study ofof 257,551 men and women with a 13 year
nearly 49,000 postmenopausal women from theaverage follow-up period. The investigators
Women's Health Initiative (WHI) Trial. But afterconcluded: "Our results provide strong support for
carefully reviewing the original reports in thethe recommendations to consume more than five
Journal of the American Medical Association, Iservings of fruit and vegetables per day, which is
discovered the problem. Fundamental flaws in thelikely to cause a major reduction in strokes."
research invalidated the dangerously misleadingSince the WHI study was undertaken, a revolution
headline.has taken place in our understanding of specific
The government sponsored study followedtypes of dietary fat. Intakes of specific fats are
women, ages 50 to 79, to determine whether arelated far more strongly to heart disease risk
group assigned to a low-fat diet lowered their riskthan total fat. Collectively, these analyses
of breast and colon cancer, heart attacks anddemonstrate that a diet lower in saturated fat
strokes when compared to those allowed to eat(fatty meats and butter) and trans fat
whatever they pleased. The researchers found no(processed foods, and stick margarines), and
difference for any of the diseases between thehigher in monounsaturated (olive, canola and
two groups.peanut oils) and polyunsaturated fat (safflower,
Authorities hailed the report. Newspaper quotessesame and corn oils), as well as amounts of fruit
read: "revolutionary," "the Rolls-Royce of studies,"and vegetables not approached in the WHI Trial,
"overturning three decades of wisdom," "largelyhelp prevent heart disease. In fact, a trend was
closes the book on a highly publicized chapter ofobserved toward reduction of cardiovascular
dietary history." Does it? If the women who atedisease risk in the quartile of women who ate the
whatever they pleased did as well as thoselowest amounts of saturated and trans fat, and
struggling to cut fat intake, doesn't that meanhighest monounsaturated and polyunsaturated
that we are finally and forever free to pursue avarieties. If the study had been carried out longer,
diet of bacon cheeseburgers, and chocolatethis observation might well have become
cheesecake? Unfortunately, the answer is no. Thestatistically significant.
reason? The problems with the WHI study makeThe WHI investigators noted this, stating that
it impossible to draw valid conclusions."Trends toward greater reductions in CHD
The women assigned to the low-fat group were(Coronary Heart Disease) risk was observed in
instructed to reduce their total fat to 20% ofthose with lower intakes of saturated fat or trans
total energy intake. They fell far short of thatfat or higher intakes of vegetables/fruits." They
goal, decreasing the fat to 29%. Additionally, theconcluded by suggesting that "more focused diet
comparison group (after receiving a copy of theand lifestyle interventions may be needed to
Dietary Guidelines for America, and otherimprove risk factors and reduce CVD
health-related materials) also decreased their(cardiovascular) risks."
dietary fat to approximately 35%.So, what to do? My advice may surprise you.
Given the minor dietary differences between theThe primary goal of healthy eating is to reach and
two groups, the resulting minor differences in theirmaintain a normal body weight in order to lower
"bad" (LDL) cholesterol levels was predictable. Inthe risks of diabetes, high blood pressure or the
the "low-fat" group, average LDL-cholesterol fellmetabolic syndrome (the combination of diabetes,
from 133 to 123 mg/Dl, while the "eat anything"hypertension and a particularly malignant form of
group also fell, from 134 to 127! Both levels arehigh LDL-cholesterol). This is best achieved, not by
well within the recently revised Federal guidelines"going on a diet," but by learning to develop
that recommend LDL-cholesterol be kept belowsensible eating habits. Heart-healthy eating is easier
130 in individuals without additional cardiovascularand more satisfying than one might think. There is
risk factors.no need to deprive yourself of an occasional
In addition to the low "bad" cholesterol levels, bothsteak or delectable dessert, while nibbling
groups had high amounts of "good" (HDL)miserably on raw carrots for the rest of your
cholesterol, ranging from 58 to 60 mg/Dl. Normaldays. Healthy eating is a long-term commitment. It
"good" cholesterol levels are 30 to 60, and thoseis about choosing nutritious foods that are
in the higher ranges are at a significantly lowersatisfying by making sensible substitutes,
risk for cardiovascular disease. Thus, both groupsmodifying favorite recipes, adopting an
had highly desirable cholesterol profiles.experimental attitude, and discovering over time
It should come as no surprise that the "eatwhat works best for you.
anything group" had a 30% lower incidence ofTo round out a heart-healthy lifestyle, become
developing cardiovascular diseases than thephysically active. Exercise is the great health
researcher-statisticians originally anticipated. Thefacilitator because it increases HDL ("good")
higher prediction of disease occurrence was thecholesterol, lowers blood pressure, helps prevent
main reason why the study was designed to bediabetes, and improves heart function. In addition,
only eight years in duration.physical activity is a natural antidepressant, and a
How does this study apply to men? According togreat way to rediscover the wonders of your
the Los Angeles Times, "it probably applied tobody. Research has shown that you can reap
men as well because the disease mechanisms aremajor health benefits with a minimum amount of
the same." Even if the study was valid, thateffort and time. Begin by taking brisk walks for
conclusion would not be, because the assumption30 minutes or more, several times a week.
about similar disease mechanisms omits a crucialDecrease sodium intake if you have a tendency
fact. Since men typically have much lower "good"towards high blood pressure, and of course, avoid
(HDL) cholesterol levels than women, decreasingtobacco exposure.
their "bad" (LDL) cholesterol is considerably moreDespite the findings from the WHI Trial, it is vital
important.for women, and men, to understand that simple
Confused? Don't be. A solid body of evidencelifestyle changes do provide invaluable health
supports the notion that lifestyle changes dobenefits. They also provide a wonderful bonus. In
decrease the risk of cardiovascular disease. Lastaddition to being healthier, you will look and feel
year, the American Journal of Epidemiologyhealthier too!
published a large report-with a 20 year