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The Fat and Cholesterol Hypothesis

The Fat and Cholesterol Hypothesis. Advanced Healing Methods GCU Holistic Health Fall 2009. Note- The powerpoints on nutrition are mostly drawn from Good Calories, Bad Calories, by Gary Taubes. 19 th Century. Banting - 1863- Letter on Corpulence

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The Fat and Cholesterol Hypothesis

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  1. The Fat andCholesterolHypothesis Advanced Healing Methods GCU Holistic Health Fall 2009 Note- The powerpoints on nutrition are mostly drawn from Good Calories, Bad Calories, by Gary Taubes

  2. 19th Century • Banting- 1863- Letter on Corpulence • lost 35 lbs. in 9 mos., 50 in the next few months by avoiding sugar and minimizing starch • Medical community skeptical • Lancet-“old news,” then “dangerous”: “We advise Mr. Banting, and everyone of his kind, not to meddle with the medical literature again, but be content to mind his own business.” Then a “fair trial.” • “The great progress in dietary control of obesity was the recognition that meat… was not fat producing; but that it was the innocent foodstuffs, such as bread and sweets, which lead to obesity.” -Hilde Bruch, 1957 • For over a century, this was the common wisdom

  3. 20th century • Sea change by 1970’s- now carbs “help you lose weight.” • AMA- low carb diets are dangerous- “bizarre concepts of nutrition and dieting [that] should not be promoted to the public as if they were established scientific principles.” -1973 • Even as major conferences were demonstrating their effect at losing weight without hunger • Now low-fat diets are good to prevent heart disease and to reduce weight • Diet-heart hypothesis- dietary fat raises cholesterol and leads to atherosclerosis • Obesity from too many calories • USDA food pyramid- fats and oils “sparingly,” 6-11 servings of grains

  4. 20th century • In the US, average fat intake has dropped from 45% of total calories to 35%, and cholesterol has fallen • 40% decline in HTN btw 1976 and 1996, 28% decline in chronic high cholesterol • But without improvements in health • Incidence of heart dz little change • Death rates from heart dz down, but due to better tx • Obesity 12-14% of population from 1960’s thru 1980, but in 2004, 1 in 3 Americans obese- diabetes up too • The surge in obesity and diabetes came along with the message that fat is bad and carbs are good

  5. The Diet-Heart Hypothesis • AKA the “Fat and Cholesterol Hypothesis” • 2 pillars • The “great epidemic” of heart disease • The “changing American diet” • The nation turned away from grains and cereals and toward fat and red meat and paid the price

  6. The Heart Disease Epidemic • CVD uncommon until 1920’s, then became #1 killer • But diagnosis bias- at one hospital, CVD dx up 400% btw 1920 and 193o, but incidence unchanged • 1949- ICD- new category for “arteriosclerotic HD” • And suppression of infectious disease and nutritional deficiency increased lifespan • American Heart Association- public-health advertising, raising research funds • Evidence against the “epidemic” ignored

  7. The Changing American Diet • Shift in American diet during 20th century, leading to heart disease “epidemic” • But data before WWII are unreliable • USDA has estimated 178 pounds of meat per person in 1830’s, 40-60 more than a century later • Population nearly doubled 1880-1910, and meat production couldn’t keep up • Also Upton Sinclair The Jungle • The grainy diet of the early 20th century is itself a deviation from normal

  8. The Changing American Diet • From WWII, during the supposed “epidemic,” through the 1960’s, the American diet increased in total fat • But mainly vegetable fats, considered “heart-healthy” • And increase in vegetables and citrus fruits • Decrease in animal fats

  9. Cholesterol • Found in all body tissues • Essential component of cell membranes • Involved in many physiologic processes • Metabolism of human sex hormones • Also abundant in atherosclerotic plaques • So… it must cause the plaques, right? • Atherosclerosis in rabbits fed olive oil and cholesterol- 1913- but rabbits are herbivores, and lesions in tendons and CT suggest more a storage disease • Plaques in chickens, too, but could also be induced in pigeons fed corn and corn oil, and in a variety of animals, including baboons, eating predominantly vegetarian diets

  10. Cholesterol • Doctors could measure the levels as of 1934 • So it remained important • Science unable to establish that atherosclerotic patients had more blood cholesterol • Also unable to establish that people with high cholesterol had arteries any more clogged • And, dietary cholesterol has very little effect on blood cholesterol • Weight gain and stress raise, exercise and weight loss lower, also fx from sex hormones, diuretics, alcohol

  11. Fat and Cholesterol • Ancel Keys- physiologist at U Minnesota- starting 1940’s • Naples (and Madrid)- rich more HD than poor, and rich ate more fat • Dietary fat raises cholesterol leads to HD • Data from several countries • HD disappeared in Sweden during WWII food rationing • Dietary fat down- less meat, eggs, dairy • But also fewer calories consumed, weight loss • Increased physical activity, sugar and flour eaten less too • Study of six countries- the more dietary fat, the more HD mortality- but data available for 22 countries, and the effect vanishes when all are included

  12. Debate • Keys- CHD strongly influenced by dietary fat • Skeptics- “show us the science” • Proponents- obligation to help patients- need to act- urgency • Press fed the fire also- positive feedback loop • Selection (or confirmation) bias- choosing evidence that supports conclusion • Everything else “misinterpreted, irrelevant, or bad data”- like studies of Navajos, Irish immigrants, African nomads, monks, etc, showing no relation btw dietary fat and HD • Masai nomadic herders live on milk, blood, and meat, and have blood cholesterol levels among the lowest ever measured • Extensive atherosclerosis, but no HD • Cholesterol up when they then ate Western diet • First “feedback mechanism to suppress endogenous chol synthesis” • Then “The peculiarities of those primitive nomads have no relevance to diet-cholesterol-CHD relationships in other populations”

  13. Framingham Heart Study • 1950- 5100 residents given physicals, the examined every two years to see who got HD • Risk factors- HTN, abnormal EKG, obesity, smoking, family history • Cholesterol- blood levels over 260 assoc with 5x greater HD risk than chol under 200- compelling evidence • But- the men who died of HD more likely to have low chol, and little assn for women at all • And (despite NIH preventing publication) men with very high (>300) and very low (<170) chol have same amount and types of dietary fat • No correlation btw dietary fat and either blood chol or HD- true in virtually every study comparing these within a single population

  14. Western Electric Study 1957 • 5400 male employees- looking at HD among those who ate the most and the least fat • 88 cases of HD- 14 in high-fat group, 16 in low-fat • Dietary fat not assoc with death from CHD • So- “If viewed in isolation, the conclusions that can be drawn from a single epidemiologic study are limited. Within the context of the total literature, however, the present observations support the conclusion that the [fat] composition of the diet affects the level of serum cholesterol and the long-term risk of death [from CHD] in middle-aged American men.” • This analysis then cited in AHA and NHLBI (Nat’l Heart, Lung, and Blood Institute) report The Cholesterol Facts as one of seven “epidemiologic studies showing the link btw diet and CHD [that] have produced particularly impressive results,” … “showing a correlation btw saturated fatty acids and CHD.”

  15. Seven Countries Study • Ancel Keys, 1956 • 13,000 middle-aged men, mostly rural populations • Prospective study- physicals at the beginning, then assess health periodically • 3 Keys lessons • Blood cholesterol levels predict HD risk • Saturated fat (not total fat anymore) predicts blood chol and HD • Monounsaturated fat is protective • But- why do eastern Finns have 3x the HD of Western Finns with the same diet? • And- Keys chose countries in advance that he knew would support the hypothesis! • French paradox- lots of saturated fat, not much HD • Spain and Italy, too

  16. Studies • Prospective (or other epidemiological studies) tend to be biased, of low quality, or incomplete • Data also subject to interpretations • Controlled trials are better- create two identical groups, change one variable • Placebo-controlled • Double-blind • Blinding impossible in diet trials, and it’s impossible to make just one change in a diet • When eliminating saturated fat, do you replace it with carbs or polyunsaturated fat? Veggies or starches?

  17. Studies of Fat and HD • Many studies from 1950’s to 1970’s studying cholesterol-lowering diet (replacing saturated fat with polyunsaturated) • Only two studied low-fat diet and HD (!), testing middle-aged men who had already had MI’s • Hungary- lowering dietary fat reduces HD • Britain- it does not- cholesterol down, but HD the same • Anti-Coronary Club Trial- late 1950’s- comparing saturated with polyunsaturated- 1100 patients • Members on the “prudent diet” had 1/3 the HD of controls • But 26 members died, 8 from HD, and only 6 controls, none from HD

  18. More Studies • UCLA VA 1969- replacing animal fat with vegetable oil- cholesterol down 13%, 66 HD deaths, compared with 96 controls • But 31 CA deaths in experimental group, 17 controls • Risk of death equal in two groups • Helsinki study- 1965-71- 2 mental hospitals- cholesterol-lowering diet • HD deaths down by half, men (not women) lived a little longer • Minnesota Coronary Survey- 1968- 9000 mental patients • Half got American diet, half cholesterol-lowering • Low in cholesterol and saturated fat, high in polyunsaturated • Cholesterol down 15%, men fewer MI’s, women more, overall increased rate of HD • 269 deaths in experimental group, 206 in controls • Study unpublished for 16 years: “We were just disappointed in the way it came out.” • AHA- started recommending low-fat diets in 1961 • NIH- called for a “definitive test” of the fat-cholesterol hypothesis in 1971 • But ended up with two smaller tests • That HD could be prevented with cholesterol-lowering drugs • That HD could be prevented with cholesterol-lowering diet, smoking cessation, and BP meds • Neither of these actually tests the hypothesis

  19. 1960’s and ‘70’s • Anti-fat, anti-meat movement • Moral- resource use • AHA- fewer conditions- not just high-risk men with past MI, high chol, or smoking hx • Now everyone recommended low-fat diet- 1970 • And AHA seen as main source of expert info • 1970’s- polyunsaturated fats assoc with CA in animals • So advice to eat less fat and less saturated fat

  20. Dietary Goals for the US • 1977- now government says eating less fat helps health • Staff director Marshall Metz: “We really were totally naïve, a bunch of kids who just thought, Hell, we should say something on this subject before we go out of business.” • 55-60% carbs, fats from 40% to 30%, only 1/3 saturated • They admit there’s no evidence that lowering dietary fat lowers blood chol, but justify it with weight loss • “Fat supplies 9 calories per gram, whereas protein and carbohydrates … supply only 4 calories per gram. … Consequently, … the consumption of a diet deriving 40 percent of its calories from fat may result in a continual struggle to lose weight.” • So… USDA Dietary Guidelines for Americans • “Avoid Too Much Fat, Saturated, Fat, and Cholesterol” • And (in NEJM), “To be a dissenter was to be unfunded because the peer-review system rewards conformity and excludes criticism.”

  21. Yet More Studies • 4 studies, 1980-84, trying to establish a relationship btw dietary fat and health- none succeeded • And low cholesterol levels found to be associated with higher risk of CA- many studies (p. 54 GCBC) • NHLBI: “Surprise and chagrin” • So… now they’re combing the literature for those few studies showing no link, then arguing the evidence is inconsistent • And (more NHLBI), high chol causes HD, but low chol only a sign of people who might be CA-prone • Cause and effect?

  22. NHLBIstudies • Multiple Risk Factor Intervention Trial (MRFIT) • 12K men with chol >290 • Half advised to quit smoking, take BP meds, eat low-fat, low-chol diet • 7 years later, more deaths in experimental group • Lipid Research Clinics (LRC) Coronary Primary Prevention Trial • 3800 men with chol >265 • All told to eat chol-lowering diet, half given chol med • 71 deaths in control group, 68 in experimental • So… Keys was right, and lowering chol saves lives (?) • “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.” • But- extrapolation from drug study to diet • Now- massive health campaign (see p. 59) • The LRC results “strongly indicate that the more you lower cholesterol and fat in your diet, the more you reduce your risk of heart disease.” • AHA president: If everyone ate chol-lowering diet, “we will have [atherosclerosis] conquered” by the year 2000 • 1984- NIH “consensus conference” to establish unanimity

  23. Getting the Word Out • 1988- Surgeon General’s Report on Nutrition and Health • The “disproportionate consumption of food high in fats” could be held responsible for 2/3 of the 2.1 M US deaths in 1988 • “The depth of the science base… is even more impressive than that for tobacco and health in 1964.” • National Academy of Sciences- Diet and Health • “Highest priority is given to reducing fat intake, because the scientific evidence concerning dietary fats and other lipids and human health is strongest and the likely impact on public health the greatest.” • The media reports it, and now the debate is about low-fat vs. very low-fat

  24. The Fat-Cholesterol Hypothesis • Lowering cholesterol prevents HD • Evidence ambiguous –statins, for example, work to lower chol and reduce MI’s, but the heart effect is probably more by reducing inflammation, like aspirin • Eating less fat or saturated fat lowers cholesterol and prevents HD • Evidence ambiguous • And prolongs life • Evidence ambiguous, diets may cause more harm than good

  25. Ancel Keys • 1970’s: The HD epidemic may have been a mirage • “No basis” to make the claim that trends in HD mortality reflect changes in diet • 1984: Misdiagnosis in Japan in 7 Countries Study now possible: The cardiologists “might have been misled by the local physicians who signed the death certificates and provided details.” • 1987: “I’ve come to think that cholesterol is not as important as we used to think it was.”

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