Monday, September 21, 2009

Science by Syllogism

A syllogism is a three-step deductive argument that moves logically from two premises to a conclusion. For example,

Premise #1: All whole foods are nutritious foods.
Premise #2: All whole foods are tasty foods.
Conclusion: Some tasty foods are nutritious foods.

If we assume that both of the premises are true, then logically the conclusion must also be true.

One way to express this is with a Venn Diagram.

The circle on the left represents all nutritious foods. The circle on the right represents all tasty foods. In the middle are whole foods, which are both nutritious and tasty. And we can see from the Venn Diagram that the conclusion of our syllogism is valid: Some tasty foods are also nutritious foods.

In November 1935 the explorer Vilhjalmur Stefansson published a series of articles called Adventures in Diet in Harper's Monthly Magazine. In these he described the health and diet of the Inuit, an indigenous people group of the arctic and subarctic of Canada. Sometimes low-carbers like to use Stefansson's descriptions to design scientific syllogisms. Once again, we will assume that the premises are accurate.

Premise #1: The early 20th century Inuit were free of the diseases of civilization.
Premise #2: The early 20th century Inuit ate meat, fat, and very little plant matter.
Conclusion: If a person in the 21st century eats meat, fat and very little plant matter, he or she will be free of the diseases of civilization.

Let's look at the Venn Diagram.

On the left are people who are free of the diseases of civilization. (For those unfamiliar with the term, the diseases of civilization have a greater prevalence in Westernized societies and include dental caries, obesity, heart disease and type-2 diabetes.) In the circle on the right are people who eat meat, fat and very little plant matter. In the center, occupying both the right and left circle, are the early 20th century Inuit. The Venn Diagram shows that there is an area of overlap between freedom from diseases of civilization and Inuit eating habits. The early 20th century Inuit fall in that area. But where do we find 21st century eaters of meat, fat and very little plant matter? They are not on the diagram, or if they are, we have no idea if they are in the area where the two circles overlap. The syllogism is invalid.

The other problem with the second syllogism is the definition of terms. Premise #2 states that, "The early 20th century Inuit ate meat, fat, and very little plant matter." For the Inuit, meat and fat meant seal, whale and polar bear, as well as arctic fish, which was sometimes eaten rotten. Plants meant grasses, tubers, roots, berries and seaweed. How many 21st century low-carbers would be willing to eat this type of food for an entire lifetime?

Science is done by making observations and formulating hypotheses. Logic does enter into the process, but logic is not enough. Once the hypothesis is formulated, it must be tested. The essential difference between science and syllogism is the experiment. The well-designed and repeatable experiment is the gold standard of science. If it turns out according to the hypothesis, the hypothesis remains intact and is subject to further testing. If the experiment does not turn out according to the hypothesis (and at least 90% of the time it will not), the hypothesis may need to be refined.

It is tempting to speculate that non-Inuit people living in Western cultures will be able to eat beef, pork, chicken and produce purchased from grocery stores or local farmers and experience the same health benefits observed in the early 20th century Inuit. However, without experiments comparing these two diets head-to-head in people of similar genetic background, engaged in similar lifestyles, over many years, it must be acknowledged that this type of justification for low-carb eating is based on syllogism, not on science.

Coincidentally, Jenny at Bloodsugar 101 Diabetes Update has just posted on the use of idyllic fantasies as arguments to support low-carbing: Let's Not Twist History To Support Our Beliefs.


LynMarie Daye said...

I like the way you think! Looking for potential "holes" in theories is the mark of a true scientist.

Regarding the Inuit diet - you make no mention of organ meat. My understanding of Stefansson's writings is that he contradicts himself on this issue, sometimes stating that they did consume organs, sometimes stating that they did not (they gave the organs to their dogs). Do yo have any thought on this?

Also, IMHO, it's not wise to base our knowledge of any population on the observations of just one person - everyone has biases and preconceived ideas that can influence our interpretation of what is going on around us. And what about the notion that people may not act as they normally would when a stranger is observing them? Do you think those people on "reality" shows act the same when the cameras are off? ;`)

I thought I'd share some thoughts. Keep up the good work!!

Stargazey said...

Hi, LynMarie!

I don't mention organ meat because not all organs are created equal. For instance, eating polar bear liver can kill you by Vitamin A hypervitaminosis. Presumably the Inuit knew this. Maybe the Inuit occasionally ate the kidneys and livers of some of the animals they killed, but we can be sure those organs didn't come from free-range hens or grassfed beef. It's also possible that their diets included testes, ovaries, thyroid glands and/or adrenal glands. Nearly a century later we have no way of knowing if they ate something from the animals they killed that they and Stefansson regarded as unimportant but which proved vital to the success of their diet. Without actual experimental data, it's only speculation that an all-meat 21st century diet is equivalent to the Inuit diet in terms of preventing the diseases of civilization.

LynMarie Daye said...

Thanks for your reply!

Personally, I don't think it's wise to eat an all modern muscle meat diet. If the Inuit ate some organ meat just a few times a month (or even a few times a year) or some berries or other plants when available, that could change the whole equation. In other words, it's their diet as a whole that is important, not just the major part of it (muscle meat).

Is osteoporosis considered a disease of civilization? I just read a chapter in a book titled "Mummies, Disease & Ancient Cultures" on Alaskan and Aleutian mummies and the Alaskan mummies showed evidence of the diease while the Aleutian mummies did not. The author states that the Aleuts' more varied diet of sea mammals, fish, invertebrates, and land and marine plants "appears to have resulted in osteological robusticity." One of the Alaskan mummies was estimated to be only in her mid-twenties at the time of death, yet showed "severe demineralization of the bones." Again, as a woman, another reason I wouldn't follow an all muscle meat diet.

Stargazey said...

You've made some good points, LynMarie. I wasn't aware of the comparison of the bone health of the Aleuts and the Alaskans. The example of the young woman with severe demineralization of her bones is especially interesting. Apparently her bones formed properly, but then demineralized for some reason. I wonder if that process was true of other Alaskans, or if her specific problem was unique in that culture. In any case, it's worth noting that something caused the difference in the incidence of osteoporosis. Did the book mention the arrival of Western explorers or settlers? If not, it may be that the osteoporosis was not the result of adopting Western practices, but had something to do with culturally determined differences in diet or perhaps the genetic variation of the two indigenous groups.

LynMarie Daye said...

The mummy of the young Alaskan woman was radiocarbon dated to AD 1510 + or - 70 years so she lived before any Westerners arrived. Another woman in her forties was found with her and she also had severe bone demineralization. The case of the older woman is very interesting: she apparently had given birth 2 to 6 months before her death. There was also evidence that she had survived bacterial endocarditis brought about by pneumonia. There was also evidence of kidney failure which may have been a complication of the endocarditis. The fact that she recovered from all that without the benefit of modern medicine is amazing!

The author of this chapter in the book is Michael R. Zimmerman. He was the person who did the autopsies on these mummies. Some of his writings are available for free on Pub Med.

Stargazey said...

I found a partial preview of the book here.

Scrolling to page 152 we find the quote you mentioned, "Osteoporosis poses a major health problem for modern Eskimos. With the antiquity of osteoporosis in this region established by the bodies from Barrow, it now appears that the westernized diet of modern Eskimos is not a direct factor and further investigation is needed. The disorder has been attributed to the Eskimos' meat based diet. In contrast, the Aleuts' wide selection of sea mammals, fish, invertebrates and land and marine plants appears to have resulted in osteological robusticity."