In his book, Eat, Drink, and Be Healthy, Walter Willett, Chair of the Department of Nutrition at Harvard Medical School disassembles
the US Department of Agriculture (USDA) Food Pyramid and replaces
it with one based in part on years of research done at Harvard
School of Public Health and the Harvard Medical School. Commenting
on why he wrote the book, Willett commented"We now have more than
20 years of research looking at the long-term health consequences
of diets. This work has been published in many scientific journals,
but I wanted to gather the material together in one place that
was accessible and understandable." Willett believes there is
a lot of misinformation and that the public has received messages
that have not been borne out by research. An example is women
being told to drink milk to strengthen their bones and prevent
osteoporosis, but long-term studies have not shown reduced risk
of fractures with high dairy intake. Willett believes the USDA
food pyramid is based on shaky scientific ground; "the Food Pyramid
is tremendously flawed. It says all fats are bad; all complex
carbohydrates are good; all protein sources offer the same nutrition;
and dairy should be eaten in high amounts. None of this is accurate."
Willett believes the main problem with the US diet today is too
many calories, whether from fat or carbohydrates, in relation
to our level of physical activity."Trans fat is also a major problem.
This kind of fat is found in many kinds of margarine and other
foods, especially fast food, but it is actually worse for your
arteries than lard. Americans, particularly teens, are eating
large amounts of it in the form of fried, fast food. Trans fat
developed from the notion that saturated fats are not good for
you, so therefore, anything else must be better, and margarine
was promoted. Trans fat not only increases levels of bad cholesterol
in the bloodstream, but it also decreases levels of good cholesterol."
A relatively new concern is glycemic load, which results from
carbohydrates that increase blood sugar levels. The USDA Food
Pyramid promotes eating complex carbohydrates without differentiating
among them, but there are major differences between carbohydrates.
For example, the body breaks down glucose in a potato more rapidly
than pure sugar, spiking glucose levels in the blood and increasing
the risk of diabetes.
Willett goes to say a common mistake that people make when they
try to eat more healthily is to cut out all fat. "The USDA has
promoted the strategy, but it can be really dangerous. Not all
fats are bad and, in fact, some should be required in any diet.
Monounsaturated and polyunsaturated fats found in foods such as
nuts, avocados, fish, olives, and most oils help lower bad cholesterol
levels without affecting good cholesterol levels.People also
tend to replace fat in their diets with foods high in sugar or
refined carbohydrates. A lot of people think that a plain bagel
with jam can be a healthy thing to eat in the morning, but actually
that is one of the unhealthiest duos you can eat because it has
a high glycemic load. Youd be better off with scrambled eggs
cooked in corn oil or a whole-grain cereal."