A Guide For Evaluating Nutritional Claims

Four Categories of Evidence

There are four categories of evidence that are important when assessing nutritional information. Think about the evidence you have been given and decide if it is:

1. Testimonials
2. Arguments
3. Correlations
4. Experiments

Testimonials

Testimonials (anecdotal evidence) can be found or created for almost any claim. Testimonial evidence is highly unreliable. It usually excludes people who took the treatment and did not benefit, as well as those who did not take the treatment and did improve. Testimonial evidence is not necessarily wrong; the problem is that it is almost impossible to evaluate. Sometimes even medical professionals use testimonial evidence and use the technical name “clinical case history.”

Arguments

Argumentative evidence consists in organizing known facts or experimental results, and reasoning from them that something ought to be so. Making a plausible case for something is not enough. Until the argument is supported by experimental evidence, it is just another theory waiting to be confirmed or disproved.

Correlations

Correlation implies that when two things occur together all or most of the time, there may be a direct causal relationship between them. Evidence of correlation can look compelling, but it is not actual proof. Even when phenomena are correlated, it does not prove that there is a causal relationship. Correlational evidence can be very useful, especially when dealing with phenomena that are not easy to study experimentally.

Experiments

The only kind of scientific evidence acceptable as genuine proof is that of repeatable experiments, usually accompanied by control data. And it is not enough for one person to be able to repeat the experiments in one place. Different people in different laboratories in different parts of the world have to be able to repeat the experiments, and obtain results that do not disprove the hypothesis. In fact, what actually happens is that different people in different laboratories in different parts of the world conduct experiments that seek to disprove the hypothesis. Only if these attempts fail is the experimental evidence considered to be confirmed.

Sound Evidence

Arguments are the building blocks of hypotheses, and help to guide the research in the right direction. The only really sound types of scientific evidence are correlational and experimental. Evidence from correlation, when extensive enough, and experiments, if well conceived and carried out, makes good scientific proof. Your goal is to identify the category of evidence being presented. See “Beyond the 120 Year Diet” by Roy Walford, M.D. for an extensive assessment of nutritional factors and the evidence of their importance.

Prove A Nutritional Claim Is Wrong

For every claim, there are those who disagree. Reputable scientific papers include an explanation of the differing opinions, and the evidence for or against them. When reviewing the evidence you have, check if it also describes the opposing point of view. If it doesn't, then look for the people who disagree, and find out what they say. This may help you to prove that a nutritional claim is wrong.

When you have assessed arguments for and against something, you may be ready to make your own decision.

Internet Search Tools

Most of the information you want can be found on the internet, if you know how to find it. Nutrionists will love Brain Boost, which has a special area for nutrition questions. The Metagenics web site contains a treasure trove of information for nutritionists. Some of it is only available to students and qualified health professionals, but much can be accessed by the general public.

To evaluate a website check its accuracy, authority, objectivity, recency and coverage. You can get a sense of how a site is indexed by different search engines using Market Leap. For more search tools and tips see the article about Internet Search.

Enjoy Your Adventure!

Doctor I. Johnson
Author, Speaker, Consultant