In the previous entry, I wrote about how lots
of reported scientific findings are later found to be false. In no field is
this more evident to the lay public than in the field of
nutrition—specifically, dietary advice. In the 1973 Woody Allen film Sleeper, the protagonist is
cryogenically frozen in 1973 and wakes up 200 years later and learns that cream
pies and hot fudge are good for you. In looking over the landscape of
nutritional advice during the last few decades, I start to wonder if Sleeper might not be all that
far-fetched.
It wasn’t that long ago that we were told
that taking beta-carotene supplements was good for us, that doing so would
lower our risk of getting many types of cancer. It had become standard
nutritional advice. However, two prospective, controlled, double-blind studies
with thousands of subjects in the 1990s showed the exact opposite. One of them,
which looked at beta carotene and vitamin E supplementation in over 29,000 male
smokers (at high risk for the types of cancer that beta carotene was thought to
protect against) found that those who took beta carotene had a higher risk of
developing lung cancer than those who didn’t. (The risk of other types of
cancer was not significantly affected.) Death from heart attacks and strokes
were higher as well among the beta carotene takers [1]. The other study,
which looked at the effects of taking a combination of beta carotene and
vitamin A supplements, and enrolled over 18,000 smokers, ex-smokers, and
workers exposed to asbestos, found that the supplement takers had a 28% greater
risk of lung cancer during the four years of the study (halted early due to the
strong negative result that was already evident) and a 26% increased risk of
death from cardiovascular disease [2]. Neither of these studies suggests in any
way that eating foods rich in beta carotene is bad for you, and there’s a heap
of evidence that these foods are good for you. But taking beta carotene
supplements―well, maybe it’s not such a great idea.
What about the dictum to eat less saturated
fat, because it raises the risk of cardiovascular disease and stroke, as well
as packing on the pounds? Well, even that venerable advice is under assault.
Leading the charge is science journalist Gary Taubes, a contributing correspondent
for the journal Science. He lays out
his case against the standard dietary advice in two books: Good Calories, Bad Calories (Anchor Books, 2008; owned by the
University of Regina Library), a thick tome that examines diet in relation to
disease and obesity, and Why We Get Fat
(Alfred A. Knopf, 2011; owned by the U of R Library), a relatively slimmer book
that, as the title implies, focuses more specifically on obesity.
To summarize greatly, Taubes makes the case for the following assertions:
·
The primary driver of obesity
and, more generally, metabolic syndrome (obesity, insulin resistance, high
blood pressure, high triglycerides) is excess carbohydrate consumption,
especially refined carbohydrates.
·
Eating fatty foods does not
make you fat. Fat in your diet does not correspond to fat in your fat cells.
·
Exercise does not help you lose
weight or keep it off. Exercise is vital for your health, but it doesn’t help
you with your weight.
·
For people who are prone to
obesity, a very low-carbohydrate Atkins-style diet
may be a good way to help keep weight under control.
·
Fat, including saturated fat
(but with the notable exception of artificial trans fat), is blameless in the
development of cardiovascular disease.
·
Counting calories is pointless.
In regard to the last point, Taubes is
scornful of authorities who insist that “calories in vs. calories out” is a key
concept in overweight and obesity. Such assertions seem to imply that you
simply lower your intake of calories and increase your exercise, and voilà,
your weight problem is solved. If only it were that simple. As Taubes explains,
fat is always moving in and out of fat cells. In obese people, the cells tend
to suck in fat from the bloodstream and hold onto it more tenaciously than do
the fat cells of slim people. In other words, obesity is the result of the body’s
dysregulated management of fat, and in Taubes’s telling, excess consumption of
carbohydrates, especially refined ones, is a prime cause of this dysregulation.
In regard to the “standard line” on saturated
fat, that it causes atherosclerosis, which causes cardiovascular and
cerebrovascular disease, Taubes says that it’s all wrong. He goes into a great
deal of detail in Good Calories Bad
Calories on the history of thinking and research in this area. He places
the lion’s share of the blame for this incorrect (according to Taubes) line of
thinking on Ancel Keys, a University of Minnesota physiologist, who, says
Taubes, became convinced of the saturated fat-atherosclerosis hypothesis in the
1950s, and from then on looked favourably on research that supported his
hypothesis and heaped scorn upon any that tended to contradict it―and heaped
scorn as well upon researchers who disagreed with him. Through the force of his
domineering will and personality he made his view into the conventional wisdom.
An interesting fact about Ancel Keys’s
life, which Taubes doesn’t mention, is that he was one of the children who were
selected by Stanford University psychologist Lewis Terman for his life-long
study of gifted children. This study, which continued on after Terman’s death,
followed the children for the rest of their lives; most of them have died by
now. A fascinating book about this is Terman’s
Kids, by Joel N. Shurkin (Little, Brown, 1992; owned by the U of R Library).
Keys is one of several subjects in Terman’s study who are featured in the book.
In it, Keys comes across as productive, intellectually curious, possessed of a
driving energy, and impatient. Shurkin writes of him, “His work has probably
had greater influence on our welfare than the work of any other person in
Terman’s study.” (page 250) Taubes doubtless would agree, but not in the
positive way that Shurkin meant.
Another interesting fact about Keys is that
he lived to be 100 years old, dying in 2004. Make what you will of that.
Taubes writes persuasively and backs up his
arguments with loads of references to the literature, but I personally am not
entirely ready to consider myself a convert. As you can imagine, the books have
generated some controversy. In my own personal experiment with N=1, I’ve found
that whenever I’ve decided, for health reasons, to add nuts (low carbohydrate,
high fat†) as a regular part of my diet, my belt gets tighter.
Still, Taubes did completely convince me of one thing: that the standard advice
and conventional wisdom about diet and its relation to weight and disease rests
upon a surprisingly tenuous foundation. There is a tremendous amount we don’t
know about obesity, metabolic syndrome, and disease, and their relationship
with diet and other lifestyle factors. It will be fascinating to see how all
this unfolds in the years to come.
There is one thing we can count on: many of
the “facts” that will be uncovered as research in this area progresses will be
short-lived.
†
The label on a jar of mixed nuts in my kitchen says that a ¼ cup serving
contains 7 grams of carbohydrate, which is less than one-fourth as much as in a
bowl of oatmeal with a cup of whole milk, and 18 grams of fat, almost twice as
much as that bowl of oatmeal with whole milk.
REFERENCES
[1] The Alpha-Tocopherol Beta Carotene
Cancer Prevention Study Group. (1994). “The effect of vitamin E and beta
carotene on the incidence of lung cancer and other cancers in male smokers.” New
England Journal of Medicine, 330(15), 1029-1035. DOI: 10.1056/NEJM199404143301501
[2] Omenn, Gilbert S., Gary E. Goodman, et
al. (1996). “Effects of a combination of beta carotene and vitamin A on lung
cancer and cardiovascular disease.” New England Journal of Medicine,
334(18), 1150-1155. DOI: 10.1056/NEJM199605023341802
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