Nutrition Science or Pseudoscience?

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Why Is Nutrition Science Confusing for Consumers?

Nutrition science can be confusing for people with little or no training in nutrition science particularly those who also have little understanding of human physiology. One reason for such confusion can be often found in the often distorted messages from would be nutrition “experts” who are in reality more nutritional gurus. Both nutrition researchers and the often far more popular nutrition gurus often talk about nutrition research and cite scientific data to support their opinions but with one major difference: The gurus ignore research that conflicts with their beliefs whereas the scientists attempt to look at all data and provide a logical explanation as to why some data appears to conflict with a more comprehensive view of the evidence.

Gurus have a standard explanation as to why data and particularly better quality data that conflicts with their dietary advice and that is the researchers who disagree with them are biased and so their data and opinions cannot be trusted. And the gurus claims of bias are not always without some merit because the commercial food industry and the food supplement industry both can see sales soar or slump based on what consumers believe the scientific evidence suggests is likely true of what they are selling. Those selling questionable food supplements tend to select or "cherry pick" only scientific data suggesting their supplements promote health. By contrast, the commercial food industry puts more effort into undermining scientific data linking their products to some adverse health outcome by cherry picking data that suggests their product and/or its components may not be harmful. For the commercial food industry and the nutritional gurus economic success often depends on distorting what the scientific evidence suggests is most likely true. The commercial food industry and the nutrition gurus selling questionable food products and/or supplements are far more savvy than most nutrition researchers when it comes to promoting their distorted view of the scientific evidence. As a result the average lay person hears so many different opinions from people the media treats as nutrition experts that they end up confused about what nutrition science is actually showing is likely true or almost certainly false. Oddly enough confusing people about nutrition science is often a win for the commercial food industry selling foods high in dietary components research shows are harmful in excess.

Confusion Causes Illness

When most people are confused they ignore all pronouncements about nutrition and disease and simply eat whatever they feel like. Eventually for most Americans such dietary nihilism leads to one or more diet related illness. Those diet related ills are then treated medically with drugs and surgery but such medical treatments ignore the cause of the disease and so they do not eliminate the disease. As medical treatments produce less than optimal results sooner or later many patients succumb to the siren call of some nutritional guru who promises far better health if only people subscribe to his dietary advice. Scientifically unsubstantiated claims can be hard to resist when they promise you better health. And even 100% useless "treatments" can "work" via the placebo effect. As a result many people become delusional followers of these pseudoscientific nutritional gurus who fancy themselves to be experts in nutrition science, even though many have no real training in nutrition science or clinical nutrition. Some of these self-proclaimed "nutrition experts" can develop quite a following and their followers often have such a cult-like devotion to their nutrition guru's pronouncements as the "gospel truth" that they spend a lot of time and energy trying to "convert" others to their new-found "nutrition religion".

Putting The Evidence Together

There is clearly scientific research into how diet and nutrition impact human physiology, disease and longevity. However, when you get into the nutrition research you quickly see that not all of the dissemination of nutrition advice conflicts with a preponderance of the most credible scientific evidence. Some would be nutrition gurus are not all that talented at putting all the nutrition evidence together so it fits into a fairly coherent big picture. This is not a problem for the pseudo-scientist who simply ignores any data that conflicts with his ideology no matter how compelling the research data is. As an example, many self-proclaimed nutrition “experts” keep arguing against the role of saturated fats in promoting atherosclerosis and heart disease. The articles they cite in support of their point of view are generally not from well-controlled clinical trials, but either population or observational studies that failed to find any significant correlation between often very inaccurately measured dietary intake of saturated fat and subsequent cardiovascular disease events.

The fact is that multiple controlled clinical trials have proven beyond any reasonable doubt that dietary saturated fatty acids (and in particular, lauric, myristic, and palmitic fatty acids) raise both total-cholesterol (-C) and LDL-C when they isocalorically displace carbohydrate and/or unsaturated fats from the diet. And the evidence from long-term observational studies consistently show that higher total-C and LDL-C levels promote more atherosclerosis over time than lower levels. For the meat and dairy industry, for the tropical oils industry, and for self-styled nutrition gurus promoting an Atkins-style diet or a Paleo diet this compelling scientific evidence is not sufficient to convince them that saturated fatty acids actually do promote atherosclerosis and coronary artery disease.  They reject data from well-designed clinical trials showing increasing saturated fat in the diet raises LDL-C and point instead to population studies that failed to show a correlation between saturated fat intake and heart attacks. They ignore the fact that most people's diets vary a lot from day to day in terms of saturated fat content and any assessment of one's average saturated fat intake over a lifetime based on a single often inaccurately measured intake on a single day or a single period of someone's life has so much statistical "noise" that such data tells us very imprecisely how much saturated fat was actually consumed over that individual's lifetime. Pointing to cherry picked imprecise data while ignoring or dismissing data from better-designed clinical trials is not science but pseudoscience.

Clinical Observations Are Not Carefully Controlled Studies

People who fancy themselves experts in nutrition often come to believe many other things based on their limited perspective, such as for instance from their own clinical practices or observations. However, clinical observations tell us far less than most believe. For example, most medical doctors believe weight loss is better for lowering blood pressure than is salt restriction. So when a medical doctor has a patient who reports that they have been eating less salt and their blood pressure has changed little the clinician often concludes this patient must not be "salt sensitive" and so for them restricting salt would be of little benefit. By contrast, when the doctor sees a patient whose lost 20 lbs in the past three months and experienced a significant drop in blood pressure he concludes weight loss is often extremely helpful for lowering blood pressure. Many MDs note that nearly every patient they have who losses a lot of weight sees a big drop in their blood pressure. This leads most MDs to think weight loss is a better way to lower blood pressure than is salt restriction.

Couple these clinical observations with the fact that most population studies also find at best a weak correlation between salt intake and blood pressure or CVD events and it is easy to see why so many MDs begin thinking salt restriction is not all that important for blood pressure lowering. They believe weight loss is far more effective than salt restriction for BP reduction based on their own clinical observations and results they’ve read about population studies. Nevertheless, in carefully controlled clinical trials salt intake is consistently shown to be the single most hypertensive insult. Much of the benefit of weight loss can be due to eating less food and so less salt.

Why the discrepancy between clinical observation and population studies that also often fail to find an association between salt intake and change in blood pressure over time? Daily salt intake is hard to measure accurately and varies greatly from day to day in most individuals. By contrast, the measurement of body weight is very accurate. While weight loss independently has a modest and mostly transient blood pressure-lowering effect in clinical trials, this observation is complicated by the fact that if calorie intake is cut in half then so often is salt intake as well. By contrast, when patients tell their MDs they have been using a lot less salt and their blood pressure has not dropped this is often because it is very hard to really reduce salt intake without expert dietary counseling and major changes in dietary habits. Trying to the measure of salt intake with diet recall data or even data from diet logs is notoriously inaccurate for determining a person's average salt intake. Sadly most MDs are unaware of this and so almost never verify clinically that a patient salt intake was in fact actually reduced. This could be done with a urine analysis that compares sodium to creatinine excretion.

Controlled Clinical Trials Establish Causal Relationships

The reason controlled clinical trials are far better at establishing causal relationships than population data and simple clinical practice observations should be obvious to anyone with doctoral level training in nutrition science. It is apparently not so obvious to those who cite population data with very imprecise measured variables (e.g., saturated fat & salt intake) to support their beliefs when in fact there is strong evidence from well-designed and well-controlled clinical trials that specifically proves their beliefs wrong. Data from well-designed properly controlled clinical trials trumps clinical observations and data from population studies. Nutrition scientists and scientists in general recognize this obvious truth. Do not get me wrong, as data from a single clinical trial is also insufficient by itself to establish or rule out causality. Clinical trials can and do fail all the time because of confounding variables (that were not properly controlled for), poor control of some variables, too small a number of subjects and/or too short a time period to see effects. But well-designed clinical trials do provide far more convincing evidence than data from clinical observations or statistical associations seen in population studies and are thus considered the gold standard for establishing causal dietary relationships with diseases.

Bottom Line:

Science is a process and any credible evidence-based opinion ought to be based on the best data available and not on cherry picked data that superficially appears to support one's beliefs or claims. Basing health claims on such cherry picked data while ignoring more compelling scientific evidence is pseudo-science and not real science. Sadly pseudoscience is what most people read when they pick up a book by some supposed nutrition guru at the bookstore or when they GOOGLE some nutrition topic on the internet. TV and radio also provide a forum for those who promote nutrition quackery. Even news reports of new scientific data rarely put such data into a credible big picture view of how diet and nutrition impact health and longevity.

By James Kenney, PhD, FACN

Where to Go For Scientifically Sound Nutrition Advice

The best place to go for information about nutrition depends on the type of information people are looking for and why they are seeking that information.

The American Heart Association (AHA) now has pretty good information about diet and health, but if you checked out their recommendation for salt intake to prevent CVD anytime before late 2010, it was much higher than the "no more than 1500 mg sodium" guideline they have today. And while the AHA's goals for saturated fat, trans fat, and cholesterol are lower than they were 10 or 20 years ago, they are still well above optimal for someone with advanced atherosclerosis.

Information on US government sites is usually too general, although it is certainly better than getting it from a Google search or watching the Dr. Oz show. These helpful, if general, sites include,,,,, and

If getting reliable, up-to-date, science-based nutrition information was easy, we really would not need nutrition professionals. People are probably best advised to go to a nutrition expert who has been trained in nutrition science and who keeps up with the latest research. Of course, finding them is a lot like finding a good medical doctor. Even a so-so MD or RD ought to be able to provide their patients/clients with useful information about their health and the potential role nutrition could play in treating/preventing various ills. The trick is finding a health professional that really keeps up with all the latest research and can separate what can often seem like disparate scientific evidence into a logical big picture.

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