How “Hard” Is Nutrition?
Nutrition Science Is More Than Physiology
Whenever I’m asked what an “ideal diet” is, I have no idea how to answer! In fact, I’ll go as far as to say that there’s no such thing as a perfect diet. This is something I can confidently assert after working in nutrition for more than 30 years. If this makes you feel that I lack validity as a nutritionist, I’m more than okay with that; I just don’t want you to buy into the nutrition bullshit that’s thrown around. It’s my duty, as an experienced nutrition professional, to help steer people away from the dietary misinformation we’re exposed to every day from the food industry, marketers, policymakers and even many nutritionists. I'll sleep soundly at night if this affects how people feel about my credibility because no one knows what anything close to an optimal diet looks like.
Nutrition science is rife with washy-washy answers to specific queries. How much protein do I need to grow 18-inch biceps? What calorie deficit do I need to lose 20 pounds? Will eating saturated fats give me a heart attack? Will taking a resveratrol supplement help me live to 120? Humans seek straightforward solutions to hugely complex issues, and nutrition science provides precious few answers. It’s no wonder that there’s so much misinformation out there.
Through decades of rigorous research, the extent of what we now know in the field of nutrition and dietetics is overwhelming. Indeed, humanity’s insight into the science of what we eat continues to grow at an exponential rate. This is a beautiful thing. However, this means that to possess a reasonable level of nutrition knowledge requires considerable work, a problem exacerbated by the need to wade through the ever-increasing amounts of contradictory information. Moreover, the more our knowledge of nutrition science grows, the more we realise the extent of what we don’t know, and it’s increasingly difficult to distinguish between truth and pseudoscientific quackery. Nutritionists are frequently castigated for always “changing their minds”, a criticism that’s not unfounded. The psychologist and writer Stuart Richie, in his book Science Fictions – in which he explores the disturbing flaws that undermine the validity of modern science – notes that “An incredibly complex physiological and mental machinery is involved in the way we process food and decide what to eat.” Richie refers to nutrition science as “an extraordinarily hyped field” and goes on to point out that the reason for the extreme hype in nutrition is that “nutritional epidemiology is hard” (emphasis in the original) [1]. How many times have you been told about the latest nutritional fad? So-called “cutting edge” information in the media sells stories. Hype is a huge problem in nutrition: it feeds beliefs and adds emotional bias. Understanding the complexities of the interaction of nutrients in the human body and the conflicting dietary information is, consequently, extremely hard.
Okay, so studying nutrition science is undoubtedly hard, but is nutrition science “hard”?
Science: “Hard” vs “Soft”
The terms “hard” and “soft” science are used to compare scientific fields on the basis of exactitude, degree of objectivity and perceived methodological rigour. Typically, the formal and natural sciences – such as physics, chemistry, physiology and pharmacology – are considered “hard”, whereas the social sciences – like sociology, psychology and anthropology – are described as “soft”. Traditionally, definitions have varied with features characteristic of hard science including the production of testable predictions, carefully controlled experiments, a reliance on quantifiable data and mathematical models, higher levels of consensus, greater replicability and generally applying a purer form of the scientific method. However, many academics have rightly challenged these characteristics of perceived hardness or softness, especially as so-called hard sciences don’t necessarily have a greater consensus or acceptance of new results, and commonly cited methodological differences are not a reliable indicator. Psychology, for example, makes extensive use of mathematical models but is considered a soft science. The metaphorical nomenclature is justifiably criticised for unduly stigmatising soft sciences, often creating an unwarranted inferior public perception and recognition of such disciplines.
Thankfully, the now widely accepted distinguishing difference is that hard sciences discuss physical objects, systems and processes, whereas soft sciences explore less tangible observations. Few would dare to denigrate the crucialness of soft sciences, especially as the most robust of objective truths involve utilising both hard and soft observations. Take psychopathy, for instance: psychopaths are assessed by the response to the Hare scale with a score of 30 or more denoting a psychopath [2] (soft science). Genetic tests and neuroscience add robustness to the diagnosis, for example, by identifying the warrior gene in the subject’s genotype, and fMRI and PET scans revealing brain patterns correlated with other psychopaths (hard science). Similarly, alcoholism is diagnosed through psychological dependence including the frequency of consumption of alcoholic drinks, associated mood and behaviours and its effects on the individual and others (soft), with measurable physiological markers, such as liver function tests and tissue biopsies (hard), providing information of the extent of alcohol-related damage.
How “Hard” is Nutrition?
Nutrition science involves exploring the interactions between what we eat and the body’s complex physiological processes, the aetiology of disease and physical performance. Through this lens, nutrition is typically considered a “hard” science. However, this view is incredibly limiting. Having an adequate grasp of nutrition and dietetics extends well into the psychological and sociological – even the philosophical – realms, exploring the effects of the food we consume and how it’s eaten. Hormones, like leptin, ghrelin and peptide-YY, influence the degree of appetite and satiety we experience, and neurotransmitters, such as dopamine, serotonin, glutamate and endorphin, affect our alertness, mood and drive to eat. These endogenous substances are affected by what we eat and when we last ate. The release of these chemicals is influenced by and influences what we put in our mouths, as well as being affected by other factors such as the aroma of food, what we observe others eating and how foods are marketed, all of which affect our cravings. How and with whom we eat also influence our biologies through mechanisms little understood, involving chemicals such as oxytocin. The psychology of nutrition involves exploring the influence of hormones and neuromodulators on our central nervous systems and our subjective perception of their effects – the physical and metaphysical.
How we were raised and the culture in which we were brought up also influences our likes and dislikes to an immeasurable degree. Food culture and its effects is another hugely under-researched subfield of nutrition, despite its profound influence on what we choose to eat. What we put in our mouths, in turn, affects physiological processes. Someone born and raised in Sri Lanka, for example, will likely be conditioned to enjoy strong culinary spices based on their traditions. Consequently, their digestive systems and palettes will have become adapted, and a native’s preferences and cravings will have become attuned to such spicy foods. Feed this kind of diet to a rural Norwegian unaccustomed to such dishes, and his mouth will not be the only thing on fire!
Some foods directly affect our brains: obvious examples are caffeinated and alcoholic drinks. Certain others contain small amounts of key neurotransmitters or their precursors, such as acetylcholine, the modified amino acids glutamate and GABA, and monoamines like dopamine, serotonin and histamine [3]. Again, this has been poorly researched, and the effects of these chemicals on our behaviour isn’t known. And despite being explored extensively for more than 30 years, the effect of the human microbiome on our behaviour is another area that we know precious little about. But we do know its effect is significant, especially since discovering that the enteric nervous system – our gut’s own nervous system – is responsible for releasing over 90% of the body’s serotonin [4]. Our understanding is further complicated by the fact that our microbiome changes every day in response to what we’ve recently eaten and how stressed we are.
Our behaviour when it comes to our diets extends much wider than its nutritional value. Nutrition science might not be as “soft” as some disciplines, but it’s certainly not as “hard” as we might think. Maybe we need to soften our perspective and be more open-minded about the level of robustness in what the current data in nutrition and dietetics is telling us, at least while we continue to discover more and more. Nutrition research is essential, and we absolutely must be led by it rather than the alternative: nutritional ideologies. Yet there remains so many things we don’t know.
On contemplating this, I’m reminded of Donald Rumsfeld’s famous quote: “there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – the ones we don’t know we don’t know.” Our current knowledge of nutrition, dietetics and food science has barely touched the surface. What we do know is that there's lots yet to be discovered that we have no idea about. Exciting, isn’t it?
(Article originally posted on LinkedIn on November 1, 2022)
References:
1. Richie, S. (2020) Science Fictions, London: The Bodley Head, p169.
2. http://www.minddisorders.com/Flu-Inv/Hare-Psychopathy-Checklist.html (Accessed: 1 November 2022).
3. Briguglio, M. et al. (2018) ‘Dietary Neurotransmitters: A Narrative Review on Current Knowledge’, Nutrients, 10(5), 591.
4. Camilleri, M. (2009) ‘Serotonin in the gastrointestinal tract’, Current Opinion in Endocrinology, Diabetes and Obesity, 16(1), 53-9.