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Improving the Food Pyramid
by Jim English
In 1992 the US Department of Agriculture (USDA)
introduced the first official Food Guide. The food guide—presented
in the graphic form of a “pyramid”—was an early
attempt to educate the public with a simplified list of dietary
recommendations thought to improve health and reduce incidence of
chronic diseases. The current ubiquity of the food pyramid is a
good measure of just how successful the guide has been in bamboozling
the American public. In the short span of twenty years, the pyramid
revolutionized the dietary habits of tens of millions of people
and is the basis on which many doctors, nutritionists, laypersons
and food producers alike judge the quality of the diet.
Although the pyramid appeared sound at the time
it was produced, and continues to carry the ring of authority, many
of its recommendations are now recognized to be flawed, based on
emerging research. For the last decade, the food guide has been
criticized by scientists for being outmoded and presenting recommendations
that are potentially harmful.
One of the most far-reaching concepts promoted by the pyramid was
the notion that obesity and heart disease are linked to the consumption
of fats. This concept gave rise to a nutritional orthodoxy that
dictated that the majority of calories should come from complex
carbohydrates—primarily breads, cereals, rice, pasta, potatoes
and other starches (up to 11 servings a day!). Additionally, meats,
fish, eggs, and other protein sources were relegated to relatively
small portions (2 to 3 servings per day), while fats were severely
restricted (the guide grouped fats and oils with sweets and recommended
“use sparingly”). Many researchers have pointed out
that the practice of switching dietary fats for carbohydrates—particularly
those found in the food pyramid—mirrors the start of the rise
in obesity that is currently at epidemic proportions.
In response to growing criticism, the USDA’s Center for Nutrition
Policy and Promotion is currently re-evaluating the food pyramid.
At this same time, a group of Harvard researchers has already proposed
a revised food pyramid. In the January, 2003 issue of Scientific
American, Walter C. Willett and Meir J. Stampfer, professors
of epidemiology and nutrition at the Harvard School of Public Health,
introduced a food guide incorporating improvements designed to address
many of the problems in the old pyramid (see image above). In their
article, “Rebuilding the Food Pyramid,” Willett and
Stampfer proposed new nutritional recommendations that are based,
in large part, on a recent study they co-authored in the December
2002 issue of the Journal of Clinical Nutrition (see abstract
below).
Willet and Stampfer point out that the USDA pyramid provides misleading
guidance by “promoting the consumption of complex carbohydrates
and eschewing fats and oils,” stating, “not all fats
are bad for you, and by no means are all complex carbohydrates good
for you.” Complex carbohydrates form the base of the current
USDA food pyramid, yet scientists have found little evidence to
show that high daily intake of carbohydrates provides any benefit.
Refined carbohydrates, such as white bread and white rice, are quickly
broken down in the body, causing rapid elevation of blood glucose
levels. This jump in blood sugar levels triggers a large release
of insulin. Insulin subsequently clears glucose from the blood,
leading to increased feelings of hunger. In short, eating carbohydrates
contributes to overeating and obesity. Even eating a potato, which
is mainly starch, raises blood sugar levels higher than eating the
same amount of calories from table sugar. “In our epidemiological
studies, we have found that a high intake of starch from refined
grains and potatoes is associated with a high risk of type 2 diabetes
and coronary heart disease. Conversely, a greater intake of fiber
is related to a lower risk of these illnesses.”
To address this imbalance Willett and Stampfer
redesigned their food pyramid by first moving white rice, white
bread, potatoes, pasta and refined carbohydrates from the foundation
(base) of the pyramid up to the top with a “use sparingly”
recommendation. And they still recommend eating carbohydrates at
most meals, but the list of approved carbs are derived from “healthy
carbohydrates,” in the form of whole grain foods, such as
whole wheat bread, oatmeal and brown rice.
As mentioned previously, the USDA pyramid radically altered the
role of dietary fats in the American diet. This is because the original
intent of nutritionists who designed the food guide was to convey
a simple message—saturated fats (found in red meat and dairy
products) raise cholesterol levels and increase risks of developing
cardiovascular disease. Willett and Stampfer observe that, “The
notion that fat in general is to be avoided stems mainly from observations
that affluent Western countries have both high intakes of fat and
high rates of coronary heart disease. They point out that this correlation,
however, is limited to saturated fat. Societies in which people
eat relatively large portions of monounsaturated and polyunsaturated
fat tend to have lower rates of heart disease.” Unfortunately
the “all fat is bad” message so effectively conveyed
by the USDA pyramid obscured numerous studies showing that polyunsaturated
fats, as found in fish —can actually reduce cholesterol levels.
To correct the unbalanced view of fats codified
in the old pyramid, Willett and Stampfer drew on previous research
gleaned from the 1976 Nurses’ Health Study, and the Health
Professionals Follow-Up Study in 1986. When researchers compared
fat intake of some 90,000 women and 50,000 men, they found the risk
of heart disease increased substantially when eating trans-fats,
and only slightly when eating saturated fats. By contrast, a diet
that contained both monounsaturated and polyunsaturated fats was
actually found to decrease the risk of cardiovascular disease. Researchers
observed that, since these two effects counterbalanced each other,
“higher overall consumption of fat did not lead to higher
rates of coronary heart disease.” Noting that these findings
“reinforced a 1989 report by the National Academy of Sciences
that concluded that total fat intake alone was not associated with
heart disease risk.”
Willett and Stampfer also challenge the idea,
promoted by the American Heart Association and other groups, that
people get no more than 30 percent of daily calories from fat. “This
30 percent limit has become so entrenched among nutritionists that
even the sophisticated observer could be forgiven for thinking that
many studies must show that individuals with that level of fat intake
enjoyed better health than those with higher levels. But no study
has demonstrated long-term health benefits that can be directly
attributed to a low-fat diet. The 30 percent limit on fat was essentially
drawn from thin air.”
Willett and Stampfer now recommend a healthy diet
that includes generous servings of unsaturated fats, including liquid
vegetable oils—especially olive and fish oils. “If both
the fats and carbohydrates in your diet are healthy, you probably
do not have to worry too much about the percentages of total calories
coming from each.” Trans fat does not appear at all in the
pyramid, because “it has no place in a healthy diet.”
Willett and Stampfer note that high intake of fruits and vegetables
is perhaps “the least controversial aspect of the food pyramid,”
and recommend both should be eaten in abundance. Interestingly they
note that while reductions in risk of cancer are widely promoted,
evidence for this comes from case-control studies that are susceptible
to numerous biases, pointing out that recent findings from large
prospective studies tend to show “little relation between
overall fruit and vegetable consumption and cancer incidence. (Specific
nutrients in fruits and vegetables may offer benefits, though; for
instance, the folic acid in green leafy vegetables may reduce the
risk of colon cancer, and the lycopene found in tomatoes may lower
the risk of [lung and] prostate cancer.)”
Where Willett and Stampfer see a significant value
in fruits and vegetables is in their ability to reduce cardiovascular
disease. “Fruits and vegetables are also the primary source
of many vitamins needed for good health. Thus, there are good reasons
to consume the recommended five servings a day, even if doing so
has little impact on cancer risk.”
The revised pyramid addresses another flaw in the USDA pyramid by
recognizing important health differences between red meats (beef,
pork and lamb) and the other foods in the meat and beans group (poultry,
fish, legumes, nuts and eggs). Red meats, which are high in saturated
fat and cholesterol, are associated with an increased risk of coronary
heart disease, Type 2 diabetes and colon cancer. By contrast, poultry
and fish contain less saturated fats, and fish are a good source
of essential Omega-3 fatty acids. “Not surprisingly, studies
have shown that people who replace red meat with chicken and fish
have a lower risk of coronary heart disease and colon cancer.”
Willett and Stampfer also recommend up to three
servings per day of nuts. Nuts, which were restricted in the old
guide, likely due to their high fat content, are actually a good
source of unsaturated fats. Research has shown that “nuts
improve blood cholesterol ratios, and epidemiological studies indicate
that they lower the risk of heart disease and diabetes.” They
also note that people who eat nuts are “actually less likely
to be obese; perhaps because nuts are more satisfying to the appetite,
eating them seems to have the effect of significantly reducing the
intake of other foods.”
Another issue addressed by the new food guide is the old recommendation
of consuming the equivalent of two or three glasses of milk a day.
This advice was based on the belief that dairy products provide
calcium, which was thought to help prevent osteoporosis and bone
fractures. “But the highest rates of fractures are found in
countries with high dairy consumption, and large prospective studies
have not shown a lower risk of fractures among those who eat plenty
of dairy products. Calcium is an essential nutrient, but the requirements
for bone health have probably been overstated.”
Willett and Stampfer also challenge the notion
that high dairy consumption is safe: “in several studies,
men who consumed large amounts of dairy products experienced an
increased risk of prostate cancer, and in some studies, women with
high intakes had elevated rates of ovarian cancer. Although fat
was initially assumed to be the responsible factor, this has not
been supported in more detailed analysis. High calcium intake itself
seemed most clearly related to the risk of prostate cancer. More
research is needed to determine the health effects of dairy products,
but at the moment it seems imprudent to recommend high consumption.”
Last, but not least, Willet and Stampfer have replaced the bottom
of the USDA pyramid (previously recommending up to 11 servings of
complex carbohydrates) with a program of daily exercise to aid in
weight control. They also recommend a daily multivitamin for most
people, and allow alcohol consumption as an option (if not contraindicated
by specific health conditions or medications) based on numerous
studies showing moderate alcohol consumption to be of benefit to
the cardiovascular system.
To demonstrate that their improved pyramid is actually healthier
than the current USDA model, Willett and Stampfer, along with their
colleagues in the Harvard study, created the Alternative Healthy
Eating Index (AHEI) to measure what happens when people follow their
dietary recommendations. When epidemiological studies were compared
to the new index the researchers discovered that men and women following
the new guidelines have a lower risk of chronic diseases, particularly
cardiovascular disease. They state, “This benefit resulted
almost entirely from significant reductions in the risk of cardiovascular
disease—up to 30 percent for women and 40 percent for men.”
While the USDA continues to review the old food guide, Willett and
Stampfer have presented a new pyramid—based on twenty years
of research —that incorporates dietary strategies that are
proven to improve health. Willett and Stampfer recommend eating
vegetables and fruits in abundance, along with moderate amounts
of healthy sources of protein (nuts, legumes, fish, poultry and
eggs). They also recommend cutting back on consumption of refined
grains (including white bread, white rice and white pasta), potatoes
and sugar, and cutting consumption of dairy products to one or two
servings a day. Studies indicate that adherence to the recommendations
in the revised pyramid can significantly reduce the risk of cardiovascular
disease for both men and women, and reduce incidence of diabetes.
These recommendations are also more in line with the dietary recommendations
of Drs. Robert Atkins, Barry Sears, and Vladimir Dilman.
References
1. Willett, W.C., Stampfer, M.J. Rebuilding the Food Pyramid, Scientific
American, Jan. 2003., Vol. 288, No. 1:64-69.
2. McCullough, M.L., Feskanich, D., Stampfer, M.J., Giovannucci,
E.L., Rimm, E.B., Hu, F.B., Spiegelman, D., Hunter, D.J., Colditz,
G.A., Willett, W.C. Diet Quality and Major Chronic Disease Risk
in Men and Women: Moving Toward Improved Dietary Guidance. Am J
Clin Nutr 2002;76:1261–71.
McCullough ML, Feskanich D, Stampfer
MJ, Giovannucci EL, Rimm EB, Hu FB, Spiegelman D, Hunter DJ,
Colditz GA, Willett WC.
Am J Clin Nutr 2002 Dec;76(6):1261-71.
BACKGROUND : Adherence
to the Dietary Guidelines for Americans, measured with the
US Department of Agriculture Healthy Eating Index (HEI), was
associated with only a small reduction in major chronic disease
risk. Research suggests that greater reductions in risk are
possible with more specific guidance.
OBJECTIVE : We evaluated
whether 2 alternate measures of diet quality, the Alternate
Healthy Eating Index (AHEI) and the Recommended Food Score
(RFS), would predict chronic disease risk reduction more effectively
than did the HEI.
DESIGN : A total
of 38 615 men from the Health Professional’s Follow-up
Study and 67 271 women from the Nurses’ Health Study
completed dietary questionnaires. Major chronic disease was
defined as the initial occurrence of cardiovascular disease
(CVD), cancer, or nontraumatic death during 8-12 y of follow-up.
RESULTS : High AHEI
scores were associated with significant reductions in risk
of major chronic disease in men [multivariate relative risk
(RR): 0.80; 95% CI: 0.71, 0.91] and in women (RR: 0.89; 95%
CI: 0.82, 0.96) when comparing the highest and lowest quintiles.
Reductions in risk were particularly strong for CVD in men
(RR: 0.61; 95% CI: 0.49, 0.75) and in women (RR: 0.72; 95%
CI: 0.60, 0.86). In men but not in women, the RFS predicted
risk of major chronic disease (RR: 0.93; 95% CI: 0.83, 1.04)
and CVD (RR: 0.77; 95% CI: 0.64, 0.93).
CONCLUSIONS : The
AHEI predicted chronic disease risk better than did the RFS
(or the HEI, in our previous research) primarily because of
a strong inverse association with CVD. Dietary guidelines
can be improved by providing more specific and comprehensive
advice. |
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