The traditional medical approach is to simply view diet as a means of preventing deficiency induced diseases. This method has been quite successful: the treatment of scurvy with vitamin C; goitre with iodine; beriberi with thiamine; kwashiorkor with protein; and rickets with vitamin D; etc. So successful, perhaps, that the single-ingredient approach has dominated nutritional research now for most of its history.
Focusing on a single food component fits quite nicely into the pharmaceutical model (a pill for every ill) and the reductionist paradigms preferred by most scientists. Industry, understandably interested in promoting the ingredients that they produce, has played its part in promoting such focus. After all, researchers must do research that is fundable and the proportion of nutritional research funded by government sources is vanishingly small. Hence, bias often occurs based on what topic is actually studied.1 One dietary component may be no more important than another; yet, it is studied because grants are available (grants, for instance, are rarely available to simply study the effects of diet/lifestyle more holistically and during longer time periods).
The industry that funds such studies also tends to help to promote the findings, often (again, understandably) emphasizing the positives and ignoring the negatives. The net effect is that a relatively small percentage of isolated food components are ever studied. Information regarding the results of those studies is then filtered through a media that exists on advertising and one that increasingly trends towards shallow reporting and sensationalized findings.
Perhaps it is not surprising that nutrition as a field must deal with obfuscation and bias so regularly
Perhaps it is not surprising that nutrition as a field must deal with obfuscation and bias so regularly. Few topics are quite so lucrative while being so intensely personal. Food (and supplements) is a multibillion-dollar industry. Food selection encompasses much of human psychology (it is a source of worry, stress and pleasure). Eating takes a significant amount of time in a person’s day and, worldwide, costs more money than any other single category of expenditure.
According to the United Nations (www.fao.org), the price of food across the world is now the highest it has ever been. On average, individuals spend about half of their family’s income on food.2 This can range, of course. For example, in the USA, the amount of income spent on food ranges from about 9% in high-income families to about 37% in low-income families (www.ers.usda.gov, accessed 7 February 2012).
In any event, food, food products, supplements etc., represent a major industry. Bookstores often contain a section devoted to food selection (health, cooking, etc.), many magazines are devoted to food, and advertising for food or supplements is a significant part of every form of media (even including professional scientific journals).
Information and Education
When considered in this light, it is perhaps not surprising that the public is often confused about what constitutes a 'good diet'. In contrast to the style of hunter and gatherers (a diet comprising many varieties of mostly fresh plant foods), the modern diet is largely composed of a very limited range of fruits and vegetables and meats. The genetic variability of these foods has been dramatically reduced as farmers use fewer varieties of seeds and select foods based on high yield. The dramatic homogenising of the food supply to feed the ever-growing population has led to a concomitant decline in food quality.3 Even individuals that largely 'shop the perimeter’ at the grocery store are buying foods that are often shipped from a great distance and hence must be either chemically treated for preservation (after already being treated for pest resistance) or ripen en route (hence, they are far from being 'vine fresh').
The lay public tend to be informed by the popular media rather than actual nutritional scientists
The confusion surrounding what constitutes a good diet (note the proliferation of foods with the relatively new labels of organic, cage-free, free-range, gluten-free, etc) is likely further amplified by the unconscious desire to be confused. Humans have genetic predilections to crave fat, salt and sugar and are therefore often unmotivated to eat diets that are sometimes described as Paleolithic (lots of raw fruits and green leafy vegetables). The lay public, now enamoured with information delivered in glossy sound bites, tend to be informed by the popular media rather than actual nutritional scientists. Medical doctors, both rightly and wrongly, tend to be suspicious of research funded by corporate sponsors, etc. (although this worry appears to be much more focused on nutrition than pharmaceuticals).
What, though, is the net effect of doctors eschewing nutritional research on the one hand and a poorly informed public on the other? Obesity rates across the world have increased so rapidly that now they are considered pandemic.4 Childhood obesity has increased dramatically and now it is not uncommon to find children with diseases that once were considered characteristically age-related (for example, Type II diabetes in children has increased by about 33% during the last decade).5
Children now are the first in decades that are predicted to experience an actual decrease in longevity
Paradoxically, the proportion of individuals suffering from malnutrition has increased concomitantly. Because of these trends, children now are the first in decades that are predicted to experience an actual decrease in longevity.6 Medical problems related to poor diet are becoming such a significant cost for most countries that it is beginning to threaten their very solvency. Although many medical doctors cast a suspicious eye towards the therapeutic efficacy of nutrition, the results of poor nutrition are literally piling up around them.
The Magic Bullet
Diet has become the metaphorical 'bullet' that can save or kill. In developed countries, such as the US, food choice has become more of an indicator of socioeconomic status than income.7 Society has bifurcated to those that eat poorly and those that tend to be educated about health risks and eat relatively well. For these latter individuals (often high-income baby boomers), diet has become an anti-ageing tool for continued health and vitality. Scientific research, paralleling such sentiments, has started focusing on diet as a means of preventing degenerative diseases.
The basic premise can be stated as follows: diet influences the balance between stressors and diathesis; by promoting protection for decades of life, it can reduce the probability (modified by genetic predilection) of an individual developing a degenerative disease. The reverse may also be true, poor diet (excess saturated fat, for example) is a stressor that when also considered with time, and with genetic diathesis, can increase the probability of degenerative disease. This focus on diet and degenerative disease is not accidental. In most well nourished countries, such as the US, deficiency disease is rare. The leading killers in the USA for instance are cardiovascular disease and stroke, acquired cancers and chronic obstructive pulmonary disease — all conditions wherein lifestyle and diet (obesity) is thought to play a major role. Linking diet to risk of degenerative disease was a natural transition.
The healthy eating paradox
The challenge with such research is that the approach that worked so well with deficiency disease does not work nearly as well when studying the pathogenesis of diseases that are as complex as ageing itself. The old drug model simply does not work. Take, for instance, degenerative diseases of the central nervous system. It is unlikely that any food component or nutrient (or drug for that matter) can reverse decades of cell loss within the central nervous system. Degenerative diseases occur well past an individual’s reproductive life. The nervous system evolved mechanisms (such as plasticity and redundancy) to compensate for damage as long as possible to maintain optimal function and ensure fecundity.
Diet can help to prevent that loss but it cannot reverse it (neurons do not undergo mitosis; once gone, they cannot be brought back). Diet, in this context, is not the same as isolated ingredients. A food such as spinach contains hundreds of components that operate synergistically.
Food cannot be tested and evaluated using the same evidentiary standards as drugs
One can remove one or two but these purified supplements are not the same as the food from which they are derived. Food (even more than food components) cannot be tested and evaluated using the same evidentiary standards as drugs: for example, there are no real placebo controls (all individuals have been on the “drug” for the entirety of their life).
Imagine, for instance, that one wanted to test the efficacy of statins on preventing heart disease (a connection that has been nearly impossible to prove). If the population had been on statins for their entire life and you simply gave one group a little bit more statin (and you compared them with a group that was just getting a bit less), it would dramatically reduce your ability to see an effect (most of the effect of a drug is based on being drug naïve and on the initial dose of the drug).
In the absence of formal recommendations, consumers must depend on sources that are ultimately biased
Drugs are, by definition, exogenous agents that target a single metabolic pathway. Our regulatory bodies (such as the European Food Safety Authority, EFSA) have chosen to evaluate the efficacy of food components using a similar metric (hence, health claims being related mostly to food components that are essential). This approach cannot be sustained. The charge of bodies such as the US Food and Drug Administration is to inform the public, not deny them the critical information they need to make vital choices about their health. In the absence of formal recommendations, consumers must depend on sources that are ultimately biased.
Despite a difficult history, nutritional science has made enormous advances. The cure to most degenerative disease, for instance, has been clear for some time. The cure is prevention. Mares et al., for instance, showed that the combination of three healthy behaviours (healthy diet, physical activity and not smoking) reduced the risk of age-related macular degeneration by 71%.8 Most individuals know the importance of avoiding processed foods, eating a whole plant-based diet, of regular exercise, etc. The real question for those who can afford to eat well is why don’t they?
References
1. S. Krimsky, “Do Financial Conflicts of Interest Bias Research? In Inquiry into the ‘Funding Effect’ Hypothesis,” Science, Technology & Human Values: http://sth.sagepub.com/content/early/2012/09/17/0162243912456271 (2012)
2. R. Trostle, et al., "Why Have Food Commodity Prices Risen Again?" ERS, USDA: http://ers.usda.gov/publications/wrs-international-agriculture-and-trade-outlook/wrs1103.aspx#.UekvCrysZqc (2011)
3. G. O'Kane, “What is the Real Cost of Our Food? Implications for the Environment, Society and Public Health Nutrition,” Public Health Nutrition 15(2), 268–276 (2012)
4. J. Roth, et al., "The Obesity Pandemic: Where Have We Been and Where Are We Going?” Obesity Research 12(S11), 88S–101S (2012).
5. F.R. Kaufman, “Type 2 Diabetes Mellitus in Children and Youth: A New Epidemic,” Journal of Pediatric Endocrinology and Metabolism 15(Supplement), 737–744 (2011).
6. S.J. Olshansky, et al., "A Potential Decline in Life Expectancy in the United States in the 21st Century,” New England Journal of Medicine 352(11), 1138–1145 (2005)
7. I. Yarret and J. Ellison, “Divided We Eat: What Food Says About Class in America,” Newsweek (accessed on 5 November 2012 at www.thedailybeast.com/newsweek/2010/11/22/what-food-says-about-class-in-america.html), 2010
8. J.A. Mares, et al., "Diet and Supplements in the Prevention and Treatment of Eye Diseases" in A. Coulston (Ed.), Nutrition in the Prevention and Treatment of Disease (Elsevier, Atlanta, Georgia, USA, 2012)
For more information
Professor Billy R. Hammond, Jr.
Behavioral and Brain Sciences
University of Georgia
Athens, Georgia 30602, USA