A dichotomy is a division into two entirely different and often contrasting domains, interests or activities (1). Examples of true dichotomies are black or white. Tall or short.
A false dichotomy is an argument giving a false illusion of there being only two choices whereas in reality there can be at least one other or even many possibilities (2). The argument is set up in such a way as the first choice is eliminated due to it being seen as a terrible choice, and the only other alternative is the second choice.
Over the last decade dietary guidelines have come under attack. Arguments against them are often presented in the manner of a false dichotomy. These are the steps used in that line of fallacy:
Step 1. Present Diet A as the government dietary guidelines.
Step 2. Present Diet A as flawed, weak or scary … making people sick in some way.
Step3. Present Diet B < insert name of alternative diet > as the only other choice.
Step 1. Present the government guidelines as Diet A
Government dietary guidelines were first issued in the early 1980s recommending we eat mainly bread and cereals (preferably wholegrain), vegetables, fruit and legumes; moderately lean meat, low-fat dairy, eggs, fish, and nuts; and only small amounts of added fats, sugar and salt (3, 4). With its emphasis on plant foods, moderate animal foods, and lower fat than previous intakes, the guidelines were labelled as a low-fat diet.
Step 2. Present Diet A as flawed, weak or scary.
Arguments attacking guidelines suggest they were based on flawed science, there are toxic foods we were not warned about and, due to consumption of those toxic foods, there are scary biochemical mechanisms disrupting our metabolism making us sick. Statistics are presented showing a rise in obesity and non-communicable diseases since the first issue of the guidelines, implying they are to blame or are contributory. (5)
Step 3. Present Diet B as the alternative diet.
Having presented the dietary guidelines as scary, the alternative Diet B < insert name of diet advocated by presenter or author of book > as the only other choice.
The false dichotomy
Apart from weaknesses in presented arguments of supposed flaws in the guidelines, such as whether foods suggested as toxic actually are, or whether people actually followed the guidelines; the false dichotomy narrative completely falls over in the presentation of there being no other alternative. No other reason for the rise in obesity and disease risk other than foods we eat. No changes in the fabric of society other than changes in our food environment. No change in our food environments other than the dietary guidelines. No other choice for a healthy diet other than Diet B.
In reality …
There are dozens of contributing factors to obesity and disease. There have been scores of changes in the fabric of our society. There have been a multitude of changes to our food environments (6). There are varying reasons people choose the diet they do (7). There are numerous dietary patterns shown to be healthful (8).
What slips through …
Apart from those weaknesses in the false dichotomy argument, what slips through of concern to me is there has been an emphasis on supposed flaws in the guidelines without strong evidence supporting long-term safety and effectiveness of the alternative diets presented.
Is there any evidence?
It is suggested advice for a safe effective long-term diet requires key supporting evidence across several domains including (a) plausible biochemical/ physiological mechanisms; (b) reliable epidemiological (within populations) studies; (c) clinical studies; (d) evidence for long-term safety and effectiveness; and (e) application of the nutrient or diet in question to complex bodily processes, the total diet and eating patterns. (9, 10)
As most dietary guidelines advocate a diet higher in carbohydrate and lower in fat, the commonly presented exact opposite diet (low in carbohydrate, high in fat) is often depicted as the only alternative. This has become a popular trend. Sometimes the carbohydrate content advised is so low whole foods are excluded including starchy vegetables, all cereals and most fruit. A diet that low in carbohydrate is by default either high in protein and / or high in fat.
I have wondered about this suggested alternative, in particular advocated low levels of certain whole-foods such as starchy vegetables, fruit and cereals; and consuming diets higher in protein or added fat. Where is the evidence for its safety and effectiveness? Does the evidence extend to long-term application?
Five years ago I began hunting for such evidence …
Disclaimer: Nothing in this article or on this website should be taken as medical or dietary advice. Anyone reading any information provided within should seek advice from their own medical practitioner for any issue, disease, illness or health-related problem they may have. Always seek your own advice from a medical practitioner or dietitian before changing your own diet.
Notes and References:
(1) Miriam-Webster dictionary: dichotomy
(2) False dilemma or dichotomy. Logically Fallacious. Retrieved 07/11/2018
(3) The Australian Dietary Guidelines were first issued in 1982, then 1992, 2003 and 2013.
(5) Arguments presented include: recommendation to eat a low-fat diet (being bland and boring) drove people to sugar for flavour; due to toxicity of fructose in sugar, addiction, or simply over-consumption of empty calories this leads people to overeat, become over-weight and develop disease; carbohydrate foods trigger insulin, driving fat into storage, holding fat in storage, and raising blood glucose levels; recommendations for a low-fat diet drive us to eat more processed foods. I will address these claims in future posts.
(6) There are many factors that can effect diet and disease. Social changes over the past 50 years include: a change in liquor licensing laws; higher ownership of cars; people drive cars more often, do less housework, eat less at home, eat out more; there are more women working. People can be affected by stress, life events and personal catastrophes.
There has been a massive change in our food environments to include more fast food, pre-prepared food, confectionery, sugar-sweetened beverages; a rise in supermarkets and convenience stores; larger refrigerators, home freezers; chilled beverages, aseptic packaging; high availability of fatty and sweet foods; social trends for gourmet foods, cafe dining, a coffee culture and taste festivals.
(7) Nutritional Guidelines: are we getting them so wrong, or are we getting lost in translation: Duane Mellor, Nutrition and Health August 1, 2018 Editorial.
Dr Mellor suggests diet choices are not simply based on health but also include affordability, accessibility, culture and hedonism (pleasure).
(8) The Dietary Guidelines for Americans 2015; the modelling system behind the 2013 revision of the Australian Dietary Guidelines; and the Dietary Guidelines for the Brazilian Population, all offer varying choices of eating patterns for a healthy diet.
(9) Dietary Reference Intakes. Institute of Medicine. 2011. (Calcium)
The report outlines the hierarchy of evidence to support nutrient intake with clinical trials being highest form of evidence followed by observational studies. There is also reference to requiring plausible mechanisms of biochemistry or physiology being required behind recommendations.
(10) The Longevity Diet. Dr Valter Longo. (New York: Avery/Penguin Books, 2018). Dr Longo describes five pillars of evidence required to support recommended diets for longevity including Juventology, epidemiology, clinical studies, epidemiology, and complex systems.