The Finnish Mental Hospital Trial

This diet trial was conducted between 1959 and 1971 in two psychiatric hospitals near Helsinki, Finland. One hospital served typical fare, including full-fat milk and butter, while the other served "filled milk", margarine and polyunsaturated vegetable oils. Filled milk has had its fat removed and replaced by an emulsion of vegetable oil. As a result, the diet of the patients in the latter hospital was low in saturated fat and cholesterol, and high in polyunsaturated fat compared to the former hospital. At the end of six years, the hospitals switched diets. This is known as a "crossover" design.

The results were originally published in 1972 in the Lancet (ref), and a subset of the data were re-published in 1979 in the International Journal of Epidemiology (ref). They found that during the periods that patients were eating the diet low in saturated fat and cholesterol, and high in vegetable oil, male participants (but not females) had roughly half the incidence of heart attack deaths. There were no significant differences in total mortality in either men or women. The female data were omitted in the 1979 report.

This study is often cited as support for the idea that saturated fat increases the risk of heart attack. The reason it's cited so often is it's one of a minority of trials that came to that conclusion. The only other controlled trial I'm aware of that replaced animal fat with polyunsaturated vegetable oil (without changing other variables at the same time) and found a statistically significant decrease in cardiovascular deaths was the Los Angeles Veterans' Administration study. However, there was no difference in total mortality, and there were significantly more heavy smokers in the control group. The difference in heart attack deaths in the V.A. trial was 18%, far less than the difference seen in the Finnish trial.

I can cite three controlled trials that came to the opposite conclusion, that switching saturated fat for vegetable oil increases cardiovascular mortality and/or total mortality: the Anti-Coronary Club Trial (4 years), the Rose et al. corn oil trial (2 years), and the Sydney Diet-Heart trial (5 years). Other controlled trials found no difference in total mortality or heart attack mortality from this intervention, including the National Diet-Heart Study (2 years) and the Medical Research Council study (7 years). Thus, the Finnish trial is an outlier whose findings have never been replicated by better-conducted trials.

I have three main bones to pick with the Finnish trial. The first two are pretty bad, but the third is simply fatal to its use as support for the idea that saturated fat contributes to cardiovascular risk:

1) A "crossover" study design is not an appropriate way to study a disease with a long incubation period. How do you know that the heart attacks you're observing came from the present diet and not the one the patients were eating for the six years before that? The Finnish trial was the only trial of its nature ever to use a crossover design.

2) The study wasn't blinded. When one wants to eliminate bias in diagnosis for these types of studies, one designs the study so that the physician doesn't know which group the patients came from. That way he can't influence the results, consciously or unconsciously. Obviously there was no way to blind the physicians in this study, because they knew what the patients in each hospital were eating. I think it's interesting that the only outcome not susceptible to diagnostic bias, total mortality, showed no significant changes in either men or women.

3) The Finnish Mental Hospital trial was not actually a controlled trial. In an editorial in the November 1972 issue of the Lancet, Drs. John Rivers and John Yudkin pointed out, among other things, that the amount of sugar varied by almost 50% between diet periods. In the December 30th issue, the lead author of the study responded:

In view of the design of the experiment the variations in sugar intake were, of course, regrettable. They were due to the fact that, aside from the fatty-acid composition and the cholesterol content of the diets, the hospitals, for practical reasons, had to be granted certain freedom in dietary matters.

In other words, the diets of the two hospitals differed significantly in ways other than their fat composition. Sugar was one difference. Carbohydrate intake varied by as much as 17% and total fat intake by as much as 26% between diet periods (on average, carbohydrate was lower and total fat was higher in the polyunsaturated fat group). The definition of a controlled trial is an experiment in which all variables are kept constant except the one being evaluated. Therefore, the Finnish trial cannot rightfully be called a controlled trial. This places it in the same category as other observational studies, in which variables are not controlled and one can only guess what factors caused the difference in disease incidence. The fact that the result has never been replicated casts further doubt on the study.

I could continue listing other problems with the study, such as the fact that the hospital population included in the analysis had a high turnover rate (variable, but as high as 40%), and patients were included in the analysis even if they were at the hospital for as little as 50% of the time between first admission and final discharge (i.e., they came and went). But what's the use in beating a dead horse?

The Finnish trial is still very useful, however. I use it as a litmus test to determine which papers are solid and which are desperate for data that confirm their biases. Any author who cites the Finnish trial in support of the idea that saturated fat causes heart attacks either isn't familiar with it, or is not objective.

Unrefined vs. Refined Carbohydrates and Dental Cavities

There's a definite association between the consumption of refined carbohydrates and dental cavities. Dr. Weston Price pointed this out in a number of transitioning societies in his epic work Nutrition and Physical Degeneration. Many other anthropologists and dentists have observed the same thing.

I believe, based on a large body of anthropological and medical data, that it's not just an association-- sugar and flour cause cavities. But why? Is it that they lack micronutrients-- the explanation favored by Price-- or do they harm teeth by feeding the bacteria that participate in cavity formation? Or both?

I recently found an interesting article when I was perusing an old copy of the Journal of Dental Research: "A Comparison of Crude and Refined Sugar and Cereals in Their Ability to Produce in vitro Decalcification of Teeth", published in 1937 by Dr. T. W. B. Osborn et al. (free full text). I love old papers. They're so free of preconceptions, and they ask big questions. The authors begin with the observation that the South African Bantu, similar to certain cultures Dr. Price visited, had a low prevalence of tooth decay when eating their native diet high in unrefined carbohydrate foods. However, their decay rate increased rapidly as modern foods such as white flour and refined sugar became available.

To test whether refined carbohydrates have a unique ability to cause tooth decay, the investigators took pieces of teeth that had been extracted for reasons other than decay (for example, crowding), and incubated them with a mixture of human saliva and several different carbohydrate foods:

• crude cane juice
• refined cane sugar
• whole wheat flour
• white wheat flour
• whole corn meal
• refined corn meal

After incubating teeth in the solutions for 2-8 weeks at 37 C (human body temperature), they had trained dentists evaluate them for signs of decalcification. Decalcification is a loss of minerals that is part of the process of tooth decay. Teeth, like bones, are mineralized primarily with calcium and phosphorus, and there is a dynamic equilibrium between minerals leaching out of the teeth and minerals entering them.

The researchers used teeth incubated in saline solution as the reference. The dentists were "blinded", meaning they didn't know which solution each tooth came from. This is a method of reducing bias. Here are some of the results. Cane juice vs. refined sugar:

Unrefined cane juice was not very effective at causing decalcification, compared to refined sugar. This was a surprise to me. Here is the result for wheat:Note that the scale is different on this graph. Wheat, and particularly refined wheat, is very good at decalcifying teeth in vitro. Corn:

Refined corn is much more effective at decalcifying teeth than whole meal corn. Next, the investigators performed an experiment where they compared the three types of refined carbohydrate to one another:
As one would predict from the graphs above, refined wheat is worse than refined corn, is worse than refined sugar. This is really at odds with conventional wisdom.

It's important to keep in mind that these results are not necessarily directly applicable to a living human being, who wouldn't let a mouthful of wheat porridge sit in his mouth for five weeks. But it does show that refining carbohydrates may increase their ability to cause cavities due to a direct effect on the teeth (rather than by affecting whole-body nutritional status, which they do as well).

The authors tested the acidity of the different solutions, and found no consistent differences between them (they were all at pH 4-5 within 24 hours), so acid production by bacteria didn't account for the results. They speculated that the mineral content of the unrefined carbohydrates may have prevented the bacterial acids from leaching minerals out of the teeth. Fortunately for us, they went on to test that speculation in a series of further investigations.

In another paper, Dr. T. W. B. Osborn and his group showed that they could greatly curb the decalcification process by adding organic calcium and phosphorus salts to the solution. This again points to a dynamic equilibrium, where minerals are constantly leaving and entering the tooth structure. The amounts of calcium and phosphorus required to inhibit calcification were similar to the amounts found in unrefined cane sugar, wheat and corn. This suggests the straightforward explanation that refined sugar and grains cause decay at least in part because most of the minerals are removed during the refining process.

However, we're still left with the puzzling fact that wheat and corn flour decalcify teeth in vitro more effectively than cane juice. I suspect that has to do with the phytic acid content of the grains, which binds the minerals and makes them partially unavailable to diffusion into the teeth. Cane juice contains minerals, but no phytic acid, so it may have a higher mineral availability. This explanation may not be able to account for the fact that refined sugar was also less effective at decalcifying teeth than refined wheat and corn flour. Perhaps the residual phytic acid in the refined grains actually drew minerals out of the teeth?

No, I'm not saying you can eat sugar with impunity if it's unrefined. There isn't a lot of research on the effects of refined vs. unrefined sugar, but I suspect too much sugar in any form isn't good. But this does suggest that refined carbohydrates may be particularly effective at promoting cavities, due to a direct demineralizing effect on teeth subsequent to bacterial acid production. It also supports Dr. Price's contention that a food's micronutrient content is the primary determinant of its effect on dental health.

Reversing Tooth Decay
Preventing Tooth Decay
Dental Anecdotes