Home Healthy Eating - Fall 2010 Session 5 - Fat Metabolism: When Fat Is Good For You
Session 5 - Fat Metabolism: When Fat Is Good For You Print E-mail
2010 Classes - Fall - Fundamentals of Healthy Eating 2010
Written by Chris Walquist   
Friday, 10 September 2010 06:07

Fat Metabolism:  When Fat Is Good For You

 

Agenda

- Opening comments

- Hypothesis-generating evidence vs. firm evidence - The fiber myth, p. 134 gcbc

- Why is fat viewed as bad for you?  (Mostly review)

- What kind of fat is good for you?

- Essential fatty acids

- Omega-3 and Omega-6 fats

- Trans fats

- What does a healthy diet look like?  (Broad strokes)

- If time: Analyze an article or two

 

When Fat Became Bad For You (we've covered a lot of this already)

 

- January 13, 1961 - Ancel Keys appears on the cover of Time, touting fat/cholesterol as the likely cause of heart disease.

 

- 1960's - The consumption of fat began to be tangled in social issues...

- 1968 - (p. 43) Paul Ehrlich bestseller "The Population Bomb", predicted "hundreds of millions of people are going to starve to death in spite of any crash programs embarked upon now."  (It didn't happen, but raised consciousness of world hunger).

- Fat began to be seen as a luxury indulged in by rich nations.  1971 bestseller "Diet for a Small Planet", by a 26-yr-old vegetarian named Francis Moore Lappe.  US livestock industry required 20 million tons of soy & veg. protein to produce 2 millions of beef.  The 18 million tons lost in the process could provide 12 grams of protein to everyone in the world.

- Meat-eating became a social and moral issue, not just a health issue. Activist Jennifer Cross, 1974, "The Nation": "we are inadvertently depriving hungry nations of food".

- AHA (a private group) revised its guidelines every two years, making its advice to eat less fat increasingly unconditional.  By 1970, they applied their prescription to everyone.  Meanwhile the press and public came to view the AHA as the primary source of expert information on the issue.

 

- 1965 - A New York TImes article quotes Harvard nutritionist Jean Mayer as claiming that to prescribe carbohydrate-restricted diets to the public was the equivalent of "mass murder".  ["Why We Get Fat", p. 161]  (In WWGF p. 49, Taubes characterizes Mayer this way: "Mayer was among the very first of a new breed, a type that has since come to dominate the field...his job never actually required that he reduce a fat person to a healthy weight, and so his ideas were less fettered by real-life experience.")

 

- April 1973 p. 404 - Robert Atkins testified before George McGovern's Senate Select Committee on Nutrition and Human Needs.  Harvard nutritionist Fred Stare did not attend, but his condemnation of Atkins' diet was read into the record:  "The Atkins diet is nonsense...Any book that recommends unlimited amounts of meat, butter and eggs, as this does, in my opinion is dangerous.  The author who makes the suggestion is guilty of malpractice."

 

- Around June 1973, same George McGovern committee, now hosting hearings on "Sugar in the Diet, Diabetes, and Heart Disease".  Those on the committee saw no connection between the two sets of hearings.  They believed Atkins was peddling dietary nonsense, whereas Cleave, Campbell, and the others were promoting reasonable science...The congressmen did not comprehend that both sets of hearings were about the role of refined and easily digestible carbohydrates and the damage they might cause. Thirty years later, the committee staff director, Kenneth Schlosser, commented that his and the committee's failure to make this connection "was not very bright".

 

- July 1976 - p. 405 - McGovern's committee returned to the subject of disease and diet, leading ultimately to publication of "Dietary Goals for the United States".  Assistant Secretary of Health Theodore Cooper was 1st witness, and he testified, "it is true that the consumption of high carbohydrate sources [by which he meant starches and refined carbs, not green leafy vegetables] with the induction of obesity constitutes a very serious health problem in the underprivileged and the economically disadvantaged."  Then Cooper was asked to provide a rule of thumb for eating habits to prevent disease and lengthen our lives:  "I think what we need to consider doing is to reduce our total fat intake"...and now he had contradicted himself: the problem was no longer overconsumption of high-carbohydrate sources, but overconsumption of fatty foods.

 

- Friday, Jan 14, 1977 - The day when the controversy shifted permanently in favor of Keys' hypothesis:  George McGovern announced the publication of the first "Dietary Goals for the United States"--first time any gov't institution had told Americans they could improve their health by eating less fat...the document itself became gospel.  It is hard to overstate its impact.

 

Almost single-handedly drafted by Nick Mottern.  Believed the the changing-American-diet myth was the most compelling evidence.  W.r.t. fat and cholesterol, Mottern relied almost exclusively on a single Harvard nutritionist, Mark Hegsted, who by his own admission was an extremist on the dietary-fat issue.  With Hegsted's guidance, Mottern perceived the food industry as no different from the tobacco industry...He believed those scientists who lobbied actively against dietary fat, like Hegsted, Keys, and Stamler, were heroes.

The report acknowledged that no evidence existed to suggest that reducing the total fat content of the diet would lower blood-cholesterol levels, but justified its recommendation on the unproven "dense-fat-calorie" hypothesis: less calorie-dense foods mean less likelihood of weight gain.  The recommendation was also based on the AHA's 30-percent-maximum for dietary fat calories.

After the press conference, as Hegsted recalled, "all hell broke loose...Practically nobody was in favor of the McGovern recommendations."

 

- March 26, 1984 - Time Magazine publishes an article loosely based on the results of a very large and very expensive study, the $150 million Lipid Research Clinics (LRC) Coronary Primary Prevention Trial, led by Basil Rifkind of the NHLBI (Nat'l Heart, Lung, and Blood Institute), with the headline, "Sorry, It's True.  Cholesterol Really Is A Killer".  The study showed virtually no improvement in overall mortality from lowering blood cholesterol, but this was not mentioned in the article.  Instead, the researchers focused on the observed decrease in heart attacks *from a drug trial* as conclusive evidence that cholesterol was dangerous, and made the additional giant leap to our diet, with Rifkind saying for instance, "It is now indisputable that lowering cholesterol with diet and drugs can actually cut the risk of developing heart disease and having a heart attack."  (emphasis mine).  The article barely mentioned the fact that (a) the study showed nothing about heart disease mortality and cholesterol, and completely neglected to mention that the drug (cholestyramine) significantly increased the risk of dying from other causes.  See commentary by Tom Naughton here.

 

If a low-fat diet is not a healthy diet...then what kind of high-fat diet is a healthy diet?

 

- First, although it's unambiguous that carbohydrates are new to all human bodies, it's not so clear which fats are best for which people. (p. 455, GCBC).  "The fat content of the diets to which we presumably evolved...will always remain questionable."

 

However, there are a few things we have learned about fats, some of which you are already aware.  We will cover those topics now:

- Saturated-vs-unsaturated - What does that mean?

- Essential fatty acids - What does that mean, and what are the essential fatty acids?

- Omega-3 vs Omega-6 - What do they mean?

- What foods have high amounts of the omega-3 EFA?

- Trans fat - What is that?

 

Saturated vs. Unsaturated

Quiz: Docosahexanoic acid (DHA) -- is it saturated or unsaturated?  mono or poly unsaturated?

Oleic acid - same question

How about Stearic Acid?

 

Essential Fatty Acids

Linoleic Acid

Alpha-Linolenic Acid (ALA)

 

Omega Fats

What are omega-6 and omega-3 fats?

Read Weston Price, Johanna Budwig, MND p. 40 - "fat-soluble activator"

Ideal ratio of Omega-6 to Omega-3 is between 4:1 and 1:1 (MND p. 36).  Typical ratio in the American diet is 30:1

 

What foods are high in Omega-3 fats, especially the essential one?   Flax, Walnuts, fish oil

 

What are the implications of an unbalanced omega ratio?  Go over the "Essential Fatty Acid Metabolism" diagram.   Insulin activates Delta-5 desaturase (why is it called that?), which tips the balance of metabolism toward arachidonic acid and inflammatory PG-2 prostaglandins.  EPA inhibits Delta-5 desaturase.  Delta-5 desaturase prefers Omega-3, which means that in proper omega balance, delta-5 desaturase will be kept busy and limit the omega-6 flow of DLGA to arachadonic acid and its harmful metabolites.

"An excess of the eicosanoids derived from arachidonic acid is responsible for many common chronic diseases."  MND, p. 45

 

Trans fat - http://en.wikipedia.org/wiki/Trans_fat - decreases HDL cholesterol significantly (KYF, p. 42)

Recall our oleic acid picture:  (http://en.wikipedia.org/wiki/File:Oleic-acid-3D-vdW.png)

What if it were turned into a trans fat?  Then it would be Elaidic acid - same chemical formula (C9H17C9H17O2) but different structure.  http://en.wikipedia.org/wiki/File:Elaidic-acid-3D-vdW.png.  Now it's straight instead of bent, which gives it much different properties.

 

Many natural fats have a small amt of trans.  Ruminants have 2-5% trans fats.  Most of this trans is in the delta-11 position.  (p. 39, Know Your Fats).  This fat is a precursor to the anti-carcogenic CLA.

By contrast, partially hydrogenated vegetable fats have their double trans bonds in the delta 8,9,10,11, and 12 positions.  Delta 9 trans is identified as a health problem.  9, 10, and 12-trans usually make up 1/2 or more of the total trans fats in these oils.  (ruminant fats have about 1/5 of their trans in these positions).

 

 

If Time: Go back to notes from Session 4 and practice analyzing a couple of articles with the class.

 

Last Updated on Sunday, 30 October 2011 06:27