Speaking of which... Today we are moving away from the history books and into the science texts. I'll need you guys to keep your minds open and your B.S. antennae on high. Forget everything anyone has ever told you and start from the beginning. Build the facts slowly, like a jigsaw puzzle, and soon you'll sit back in satisfaction at the full picture. Remember what we're after here? Health. Longevity. Vitality. Joy. I promise, it's worth the effort.
In my last post, I mentioned the time period in the United States when we started forming our current nutritional recommendations and guidelines. In this post, I want to get into the science behind the scenes. Instead of adopting the opinions of others, let's take a closer look at the data and the scientific opinions surrounding it and form our own interpretations and conclusions. If we think about the continuum of scientific knowledge over the centuries, humans have made scientific laws based on relatively concrete facts, until those hypotheses got disproved, revised, and/or refined. (Remember learning about Galileo? He was tried as a heretic for saying the Earth orbited the Sun.) Human beings are constantly enhancing collective societal knowledge with each generation. Therefore, questioning the current state of things isn't so heretical when you pull back and think about the fact that this is what we as humans do... we take what we know and we build on it. Sometimes we get it wrong, sometimes we get it right, but it's a process that's refined by many people over time.
Bringing this back to the present... This is where people trying to lose weight and be healthy need help. The research is so conflicting and all over the map that it takes some real sifting to get through to the facts. And there's still a lot that we cannot neatly conclude, but we are certainly making progress.
American
scientist Ancel Keys was at the forefront of the influence of diet on
health in the 1950s. He had a particular interest in the epidemiology of
cardiovascular disease (CVD) and its relationship to dietary fat. Among
many highlights in his career, he developed the CVD-lipid hypothesis.
Keys observed that the highest rates of CVD were among the most well-fed
and affluent members of society and that incidents of CVD decreased
during WWII. When he proposed the idea that fat causes CVD to a meeting of experts on heart
disease at the World Health Organization in Geneva in 1955, his
argument was swiftly dismantled. Two experts (Jacob Yerushalmy and
Herman Hilleboe—Berkeley statistician and New York State Commissioner of
Health) even went so far as to publish a chiding follow-up called "Fat
in the Diet and Mortality from Heart Disease: a Methodological Note" (no
open source, but if you have access:
http://www.ncbi.nlm.nih.gov/pubmed/13441073). Here's a highlight: “….the
evidence from 22 countries for which data are available indicates
that the association between the percentage of fat calories available
for consumption in the national diets and mortality from
arteriosclerotic and degenerative heart disease is not valid; the
association is specific neither for dietary fat nor for heart disease
mortality. Clearly this tenuous association cannot serve as much support
for the hypothesis which implicates fat as an etiologic factor in
arteriosclerotic and degenerative heart disease.” Undeterred, Keys pushed forward with his research. His epidemiological studies, which began in 1958, lasted for decades. He gathered data on 12,000 healthy middle-aged men living in over 22 countries. He continued to observe a statistically significant association between higher intakes of saturated fats and heart disease. The problem with Keys's research is that we cannot prove causation from association. There are so many other compounding factors to this association. For instance, what other elements are involved in these individuals' diets? What other access do they have to healthcare and food? How long are they living compared to people not dying of CVD? (i.e., what is the correlation between fat and overall longevity?) How good are the cause of death records in these countries? Perhaps in countries with better records there are more cases of CVD?
Furthermore, when we look at Ancel Keys's raw data from the WHO presentation, we see a negative association between saturated fat consumption and all other deaths not from heart disease. We can also observe with high significance that those with a higher percent of calories from carbohydrates had the greatest mortality in men ages 55 to 59. In addition, overall, countries with higher average fat intake had the longest life expectancies. However, the only reason I'm presenting you with this information is to show how easily the statistics can be manipulated to prove a point. There are still many compounding factors, which is the great challenge nutritional data faces and a major reason why it's so all over the place.
I find the most compelling compounding factor for Key's research to be this (from Yerushalmy and Hilleboe): "The amount of fat and protein available for consumption is an index of a country’s development, industrially, nutritionally, medically, and no doubt in other respects as well."
Our health system is not holistic, we look at a symptom and we treat the symptom, but we don't treat the entire person and we don't focus on prevention. The other major difficulty here is that we are not dealing with a singular "BIG" as in Big Tobacco. We are dealing with Big Pharma, Big Sugar, Big Soda, Big Food, Big Alcohol... the list goes on. This is a problem that has to be solved by educating the consumer (ourselves) and making economic choices that force change.
Keys didn't get it all wrong however. He lived to the age of 100 and was a big proponent of the Mediterranean diet. I'll discuss the Mediterranean diet in more detail later, but remember two key components of this diet are olive oil and fish. He and his wife retired comfortably to a villa in Naples and they certainly weren't eating low fat sugar-laden vanilla-flavored yogurt from Aisle 9. (Side note: I doubt that Keys partook in this, but cooking with lard was a huge part of the actual diet of people living in the Mediterranean region -- you won't find that in the diet book however.)
SO... Keys is one piece of the puzzle, read up on him and his time period and you will get a much fuller picture of why our current health recommendations are what they are. If you enjoy a good drama, read about his feud with British scientist John Yudkin. However, Keys is not the whole picture. We haven't solved the mystery yet, but now we have a bit more background for our case.
Additional Sources and Further Reading:
If you don't read anything else here, read this post by Denise Minger of Raw Food SOS, she does an incredible job assembling Ancel Key's raw data and interpreting the results here: http://rawfoodsos.com/2011/12/22/the-truth-about-ancel-keys-weve-all-got-it-wrong/
http://www.epi.umn.edu/cvdepi/essay.asp?id=33
http://openheart.bmj.com/content/1/1/e000032.long
http://www.telegraph.co.uk/health/dietandfitness/10634081/John-Yudkin-the-man-who-tried-to-warn-us-about-sugar.html
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1470496/
http://www.nytimes.com/2004/11/23/obituaries/23keys.html?_r=0
No comments:
Post a Comment