Epidemiological Studies And Diet

The most recent posts have been about the molecular biology of the high potassium foods diet. They have shown how the potassium sodium ratio affects every cell process, because this ratio controls the electric field of the cell. If the ratio is too far off, the electric field is too weak and the timing of cell processes is disturbed. No other healthy diet recommendations do this. They do not explain the basic molecular biology of the diet, but rely on epidemiological studies.

Bell Curve
Normal distribution of many epidemiological studies

There are many posts on this website about epidemiological studies that support the health promoting ideas of the high potassium foods diet. However these types of studies cannot determine what it is about a diet that makes it healthy. All they can do is say that the group eating a particular diet had fewer problems (heart attacks, strokes, or cancers for example) than another group eating the usual American diet.

These epidemiological studies are the types of studies that are usually quoted by the press and other media sources. The reason the press uses these types of studies is that they are easier to understand. They seem more significant because they involve humans and what they eat.

It is also easy to make claims beyond the actual findings of a study by saying that the findings imply something more. For example, people in France have less heart disease and drink more red wine than Americans. Wine has resveratrol. Therefore, resveratrol reduces heart disease.

But often epidemiological studies are at odds with each other. They result in what a recent study (1) refers to as the “here today, gone tomorrow nature of medical wisdom.”

Epidemiological Studies Today

This recent article (1) by a leading epidemiologist discusses the problems with modern epidemiological studies, and why such studies often differ in their conclusions. Early in the history of epidemiology – the golden era of epidemiology – there were very large associations of diseases with their causes. So even if a study were flawed, it would find an association that was true. The findings then could be used to design a plan to help the entire public.

But today most of the risks and associations are small, and the diseases they are studying are complex. Yet the mindset of the researchers and the tools that the researchers use are the same as those used during the golden era of epidemiology. A new approach is needed.

The early studies tackled major risk factors with large differences between those with disease and those free of disease. In the area of cancer, one of the earliest associations found was a 200 fold increase in scrotal cancer in chimney sweeps compared to the average man.

How Modern Epidemiological Studies Differ

Today the associations found in studies are much smaller. They are related to lifestyle, and they are concerning chronic diseases with a long induction period between risk exposure and disease presentation. When there is a long induction period, it is harder to see a causal link than when it is a short period.

The author felt that it was time to reevaluate the use of the usual types of epidemiological studies. The most commonly used are observational studies, such as case-control and cohort studies. These types of studies were felt to be appropriate for the first two major historical eras – the sanitary era and the infectious disease era.

During these two eras the induction periods were short. Disease occurred within a few days of exposure. Direct intervention led to quick and noticeable changes.

However today, with chronic disease, long induction periods, and small associations and risk factors, interventions take longer and require much larger numbers of participants to see noticeable results.

No Black Box

What has evolved is a black box paradigm. The risk shows up and goes into the black box, and the disease comes out the other side. Nobody knows what happened inside the box. There is no scientific explanation. There is a lack of what Austin Bradford Hill (see post here) would call plausibility and coherence.

The reason the recent posts on this website have been mostly about molecular biology is to show that the high potassium food diet satisfies Hill's criteria of plausibility and coherence. These criteria mean that the importance of the potassium sodium ratio must be plausible with known biological facts and coherent with facts known about the disease. The posts discuss studies demonstrating those facts.

The era of observational studies identified major risks to health such as smoking, hypertension, hypercholesterolemia, and malnutrition. When there was a large association, such as smoking and lung cancer, even flawed studies were able to work. But today associations are smaller. Bias and confounding can affect cohort and case-control studies when the associations are small. Because of these problems, guiding hypotheses are needed.

A New Framework For Studies

For many studies today the evolutionary perspective can help provide such a guiding framework. One obvious area is in nutrition and physical activity. For studies involving nutrition and physical activity, observational data may result in systematic difficulties in group assembly. People who are concerned about their health tend to eat well and exercise. And they have other factors in common. Being better off economically and better educated are just two such factors. It becomes difficult to know which of these factors is the causal one. It becomes difficult to account for such confounders in an epidemiological study.

The author points out that there are many factors concerning diet and nutrition that are hardwired into us by nature. The preferences for energy dense foods and certain food tastes are hardwired because of scarcity during humankind's evolution. The scarcity of salt is one such example. Likewise our biologic set up (the hardwiring), such as our body's ability to balance sodium and potassium, means that many of our present day approaches will not work.

An Evolutionary Perspective

But having an evolutionary perspective can help guide against trying to fight these hardwired characteristics. The author gives a suggestion concerning weight loss. He suggests altering food taste and energy density of food in line with our hardwired nature. He feels this should work better than the usual approach of trying to revise our behavior to go against that hardwired nature.

For the potassium sodium ratio this would mean developing foods that have satisfactory taste, and satisfy the desire for energy density, while providing foods with a high potassium sodium ratio. This approach only worked somewhat in Finland, discussed here, because they only changed the potassium sodium ratio of food somewhat. In Finland they improved the potassium sodium ratio of food slightly and got a reduction in stroke and cardiovascular disease. Finland went from the highest mortality for strokes to having approximately the same mortality as the United States.

Much of the intervention in Finland was an attempt at behavioral modification. Rather than focusing on the potassium sodium ratio of food, Finland tried to educate the public about the risk factors emphasized at the time – smoking, exercise, saturated fat, and drinking.

Although these are still risk factors to consider, the most important factor is the dietary potassium sodium ratio. Today much is known about the potassium sodium ratio of food and how the ratio found in high potassium foods affects our bodies to prevent disease. It is no “black box paradigm,” but a well characterized, scientifically sound basis for action.
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1. Point-counterpoint. The triumph of the null hypothesis: epidemiology in an age of change. Maziak W. Int J Epidemiol. 2009 Apr;38(2):393-402. doi: 10.1093/ije/dyn268. Epub 2008 Dec 17.