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Cholesterol Myths by Uffe Ravnskov MD, PhD: Myth 5: Animal Studies Prove the Diet-Heart Idea
Wednesday, November 12, 2014 10:22 am Email this article
“Rabbit tricks are positive successes.”
Animals eat the wrong food
Perhaps you’re finding the cholesterol question in man a little complicated and it is. But it’s nothing compared to the situation in the animal kingdom, although, if it will comfort you, I’ll say now that cholesterol studies just don’t apply to man.
None of the mammals of the world are exactly like us as regards cholesterol. They have other amounts of it in their blood, they rarely eat as we do, and most of them do not become arteriosclerotic.
Many mammals never eat food containing cholesterol. If they are force-fed a cholesterol-rich diet, the cholesterol level of their blood rises to values many times higher than ever seen in normal human beings. And since such animals cannot dispose of the cholesterol they have eaten, every organ soaks up the cholesterol as a sponge soaks up water.
If animals are so different from us, how can we use them to prove that fat food and cholesterol are dangerous to human beings? Using cholesterol-rich fodder, it is possible to induce in rhesus monkeys arterial changes that vaguely resemble human arteriosclerosis, but it is not possible in baboons. How do we know if man reacts like a rhesus monkey or like a baboon or in some very different way?
These obvious weaknesses of animal studies have not prevented thousands of scientists from thinking up numerous ways to test animals in their laboratories.
There are however, many experiments and observations that may give us food for thought. Let’s start by looking at arteriosclerosis and coronary disease in wild animals. What does arteriosclerosis look like in the arteries and heart of animals living outside the laboratories?
Arteriosclerosis with an appearance similar to that in man has been found in many animals, but more rarely and less widespread, probably because many wild animals suffer a violent death as youngsters and thus rarely reach the age of arteriosclerosis. An animal with pronounced atherosclerosis may also be an easy pray.
Arteriosclerosis is found most often in birds, possibly because their blood pressure is higher than in land animals. But animal fat or cholesterol in the diet is not the cause. The seed- and grain-eating pigeons, for instance, and the fish-eating penguins become just as arteriosclerotic as the birds of prey.
There is no support for the diet-heart idea from the four-legged creatures, either. Arteriosclerosis has not been observed in beasts of prey, but it is not unusual in the vegetarian mammals that they devour. Also, sea lions and seals become arteriosclerotic; obviously it doesn’t help them that their fish diet provides more polyunsaturated fat than most humans eat.
Unfortunately, it is not this naturally occurring arteriosclerosis that has interested the students of cholesterol and coronary heart disease in animals. In a scientist with an open mind many relevant questions should arise. For instance, if vascular changes similar to human arteriosclerosis are found in some wild animals but not in others, why do these changes occur in the vegetarians and the sea animals and not in those feasting on animal fat? And is it possible to prevent or treat spontaneous arteriosclerosis in animals? Why have scientists studied the vascular changes created by force-feeding in laboratories and totally ignored the spontaneous arteriosclerosis?
Obviously, before they start their animal experiments, almost all scientists have concluded on their own that it is dietary fat and cholesterol that cause arteriosclerosis and coronary heart disease. So, instead of studying the animals’ own arteriosclerosis they induce pathologic changes in the vessels by cholesterol-feeding and call it arteriosclerosis.
Let’s have a look at some of their results.
Rabbits and cholesterol
The rabbit is a docile and placid animal. It doesn’t bite, taking blood samples from its long ears is easy, and a rabbit is cheap. But the main reason that the rabbit has become the most common animal in the cholesterol laboratories is its way of reacting to cholesterol-rich fodder.
The rabbit, of course, is a vegetarian. If a rabbit is forced to eat food that it would never eat voluntarily and that it cannot digest or metabolize, its blood cholesterol rises to values 10-20 times higher than the highest values ever noted in human beings. Cholesterol percolates all through the rabbit; its liver and kidneys become fatty, its fur falls off, and its eyes become yellowish from a build-up of cholesterol that it can neither store, metabolize nor excrete. Finally, it dies, not from coronary disease but from loss of appetite and emaciation—it starves.
It is true that cholesterol is also deposited in the arteries of the rabbit, but nothing even remotely resembling human arteriosclerosis is seen. Cholesterol appears in different places in a rabbit’s vessels than in man’s, the microscopic changes are different, no haemorrhages or clefts appear as they do in man, no thrombus or aneurysms formation in the artery walls, and it is impossible to induce a heart attack by dietary means alone. The only effect that the rabbit shares with man is the increased cholesterol content of the arterial wall.
Overfeeding other beasts with cholesterol and animal fat produces varying results. The characteristics of the pathologic changes are similar to those in the rabbit, but the amount and location of cholesterol in the arterial walls vary. As a rule it is extremely difficult to provoke a heart attack in animals by dietary manipulations. To be successful, the scientist needs to combine diet with something else, such as a hormone injection or mechanical damage to the animal’s arteries.
In rare experiments heart attacks have been seen in laboratory animals fed with cholesterol and animal fat. But this is no proof that the food is the cause, because both arteriosclerosis and coronary heart disease can also be seen in zoo animals fed their natural food. To prove that the unnatural food is causal, two groups of laboratory animals should be studied, with one group given the fat food and the other group given its natural food.
Those who experiment with animals often forget that the animals don’t like it. This fact is crucial in studies of coronary heart disease, since frustrations and psychologic stress are considered a possible cause of the disease. In this context it may be interesting to look at some experiments performed by the American physician and scientist Dr. Bruce Taylor and his coworkers. (This is the same Dr. Taylor whom I discussed in Chapter 2.) The diet-heart proponents often cite these experiments as proof that animal fat causes arteriosclerosis and coronary heart disease in man.
Dr. Taylor and his colleagues studied wild rhesus monkeys captured from the jungle. To produce “arteriosclerosis,” they gave the monkeys a fodder to which had been added a great amount of cholesterol. Throughout the experiment, the monkeys were housed individually in small dog cages, an arrangement they obviously disliked. To prevent escape the cages were reinforced with solid metal sheets.
The monkeys disliked their food perhaps more than their housing. They ate only a little and threw the rest around their cages. For long periods they went on hunger strikes.
Taking blood samples from these unhappy monkeys was difficult for all involved. To get enough blood, the groin artery of the monkey was punctured. Obviously this measure was unpleasant because at the sampling the monkeys resisted violently: they screamed, urinated and defecated.
Of 27 monkeys, one had a heart attack after being experimented upon for four years in this basement laboratory in Chicago. Interestingly, this animal was hyperactive and extremely nervous, the scientists wrote.
They didn’t tell why it was interesting. Maybe factors other than the high blood cholesterol could have caused the heart attack in this intelligent animal isolated in a small cage for years, fed a bad-tasting diet and regularly subjected to terrifying blood samplings. Could that be? We don’t know. Taylor and his colleagues, and most others who have cited their study in later papers, consider the cause to be the food and the high cholesterol level, that and nothing else.
In these experiments, the cholesterol of the monkeys climbed to values as high as ever measured in human beings. But it was not the cholesterol level that determined the outcome. This fact was demonstrated in an interesting experiment by Dr. Dieter Kramsch and his coworkers at the Evans Department of Clinical Research and the Cardiovascular Institute in Boston.
Dr. Kramsch and his colleagues studied as many monkeys as Dr. Taylor did, but Dr. Kramsch’s project separated them into three groups. One group received fodder natural to monkeys, and the two others received fodder with added butter and cholesterol. The group fed the normal fodder and one of the groups fed the enriched fodder sat in their cages, inactive, throughout the experiment. The third group was allowed to exercise.
Only the inactive monkeys fed the butter and cholesterol developed coronary arteriosclerosis and coronary heart disease. But the monkeys that were allowed to exercise had wide, almost smooth coronary arteries, although their cholesterol was almost as high as that of the inactive monkeys!
Unfortunately Dr. Kramsch and his team did not report what happened with the inactive monkeys fed their normal fodder. This is most curious because had these monkeys not developed atherosclerosis, it would have meant that it is the combination of inactivity and high-fat food that produces atherosclerosis. And if these inactive monkeys on normal fodder had developed atherosclerosis just as did the inactive monkeys on high-fat fodder, it would have meant that inactivity, not high-fat food, is the culprit. Both alternatives would have added most interesting information. Could it be that the study results were so controversial that the researchers dared not report them? We don’t know.
Honest proponents of the diet-heart idea admit that it is by experimenting on human beings, not on animals—to prevent arteriosclerosis and coronary heart disease, not to create them—that the idea may be proved. And they think they have successfully proved it.
In the next chapter we shall see if they are right.
Here are links to the other chapters in the book.
- Cholesterol Myths by Uffe Ravnskov, MD, PhD: Forward to Book by Michael Gurr, PhD
- Cholesterol Myths by Uffe Ravnskov, MD, PhD: Author’s Foreword
- Cholesterol Myths by Uffe Ravnskov MD, PhD: Introduction: The Diet-Heart Idea: A Die-Hard Hypothesis
- Cholesterol Myths by Uffe Ravnskov MD, PhD: Myth 1: High-Fat Foods Cause Heart Disease
- Cholesterol Myths by Uffe Ravnskov MD, PhD: Triglycerides
- Cholesterol Myths by Uffe Ravnskov MD, PhD: Myth 2: High Cholesterol Causes Heart Disease
- Cholesterol Myths by Uffe Ravnskov MD: Familial hypercholesterolemia—not as risky as you may think
- Cholesterol Myths by Uffe Ravnskov MD, PhD: Myth 3: High-Fat Foods Raise Blood Cholesterol
- Cholesterol Myths by Uffe Ravnskov MD, PhD: Myth 4: High Cholesterol Blocks Arteries
- Cholesterol Myths by Uffe Ravnskov MD, PhD: Myth 5: Animal Studies Prove the Diet-Heart Idea
- Cholesterol Myths by Uffe Ravnskov MD, PhD: Cholesterol lowering in children
- Cholesterol Myths by Uffe Ravnskov MD: Myth 6: Lowering Cholesterol Will Lengthen Your Life (Part 1)
- Cholesterol Myths by Uffe Ravnskov MD: Myth 6: Lowering Cholesterol Will Lengthen Your Life (Part 2)
- Cholesterol Myths by Uffe Ravnskov MD PhD: Myth 7: The Statins — Gift to Mankind (Part 1)
- Cholesterol Myths by Uffe Ravnskov MD PhD: Myth 7: The Statins — Gift to Mankind (Part 2)
- Cholesterol Myths by Uffe Ravnskov MD PhD: “The most exact data base”—the screenee
- Cholesterol Myths by Uffe Ravnskov MD PhD: Myth 8: Polyunsaturated Oils are Good for You
- Cholesterol Myths by Uffe Ravnskov MD PhD: Dr. Ornish and The Lifestyle Heart trial
- Cholesterol Myths by Uffe Ravnskov MD PhD: Myth 9: The Cholesterol Campaign is Based on Good Science
- Cholesterol Myths by Uffe Ravnskov MD PhD: Insider Insight
- Cholesterol Myths by Uffe Ravnskov MD PhD: Myth 10: All Scientists Support the Diet-Heart Idea
- Cholesterol Myths by Uffe Ravnskov MD PhD: Epilogue
- Cholesterol Myths by Uffe Ravnskov MD PhD: References
This chapter is from the book
The Cholesterol Myths: Exposing the Fallacy that Saturated Fat and Cholesterol Cause Heart Disease
by Uffe Ravnskov, MD, PhD.
Dr. Ravnskov has given me the permission to share this version of his book to help educate the world about the cholesterol campaign.
Information about Uffe Ravnskov, MD, PhD is posted here.
More information about Cholesterol Myths is posted on his website here.
Dr. Ravnskov posted his book for free here.
Uffe Ravnskov, MD, PhD is the founder of The International Network of Cholesterol Skeptics (THINCS.org) which can be found here.
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