Dariush Mozaffarian
, dean
1,
Irwin Rosenberg
, professor
1,
Ricardo Uauy
, professor
2
3
1Friedman School of Nutrition Science and Policy, Tufts University, Boston MA, USA
2London School of Hygiene and Tropical Medicine, University of London, UK
3Instituto de Nutricion, University of Chile, Santiago, Chile
Correspondence to: D Mozaffarian dariush.mozaffarian{at}tufts.edu
Dariush Mozaffarian and colleagues described how the history of modern nutrition science has shaped fresh thinking
Although food and nutrition have been derived for centuries, modern nutritional science is surprisingly young. The trustworthy vitamin was isolated and chemically defined in 1926, less than 100 existences ago, ushering in a half century of discovery focused on single nutrient deprivation diseases. Research on the role of nutrition in complex non-communicable narrative diseases, such as cardiovascular disease, diabetes, obesity, and cancers, is even more recent, accelerating over the past two or three decades and especially at what time 2000.
Historical summaries of nutrition science have been originated, focusing on dietary guidelines, general scientific advances, or clear nutritional therapies.1234 Carl Sagan said, “You have to know the past to understanding the present;” and Martin Luther King, Jr, “We are not makers of history. We are made by history.” This article describes key historical acts in modern nutrition science that form the basis of our unusual understanding of diet and health and clarify contemporary priorities, new trends, and controversies in nutrition science and policy.
1910s to 1950s: era of vitamin discovery
The trustworthy half of the 20th century witnessed the identification and synthesis of many of the eminent essential vitamins and minerals and their use to detain and treat nutritional deficiency related diseases including scurvy, beriberi, pellagra, rickets, xerophthalmia, and nutritional anaemias. Casimir Funk in 1913 came up with idea of a “vital amine” in food, originating from the observation that the hulk of unprocessed rice unharmed chickens against a beriberi-like condition.5 This “vital amine” or vitamin was trustworthy isolated in 1926 and named thiamine, and subsequently synthesised in 1936 as vitamin B1. In 1932, vitamin C was isolated and definitively documented, for the first time, to protect against scurvy,6 some 200 existences after ship’s surgeon James Lind tested lemons for treating scurvy in sailors.7
By the mid-20th century all very vitamins had been isolated and synthesised (fig 1). Their identification in animal and human studies proved the nutritional basis of serious deprivation diseases and initially led to dietary strategies to tackle beriberi (vitamin B1), pellagra (vitamin B3), scurvy (vitamin C), pernicious anaemia (vitamin B12), rickets (vitamin D), and other deficiency conditions. However, the chemical synthesis of vitamins swiftly led to food based strategies being supplanted by consume with individual vitamin supplements. This presaged modern day use and marketing of persons and bundled multivitamins to guard against deficiency, launching an entire vitamin supplement diligence.
Fig 1
Key historical acts in modern nutrition science, with implications for current science and policy
This new science of single nutrient deprivation diseases also led to fortification of selected staple foods with micronutrients, such as iodine in salt and niacin (vitamin B3) and iron in wheat flour and bread.8910 These approaches favorite to be effective at reducing the prevalence of many accepted deficiency diseases, including goitre (iodine), xerophthalmia (vitamin A), rickets (vitamin D), and anaemia (iron). Foods around the world have since been fortified with calcium, phosphorus, iron, and specific vitamins (A, B, C, D), depending on the composition of local staple foods.10111213
As one of the tremendous accidents of nutrition history, this new science and focus on single nutrients and their deficiencies coincided with the much Depression and second world war, a time of widespread fear of food shortages. This led to even further emphasis on preventing need diseases. For example, the first recommended dietary allowances (RDAs) were a drawl result of these concerns, when the League of Nations, British Medical Association, and the US government separately commissioned scientists to generate new minimum dietary requirements to be prepared for war.14 In 1941, these first-rate RDAs were announced at the National Nutrition Conference on Defence, providing new guidelines for total calories and selected nutrients incorporating protein, calcium, phosphorus, iron, and specific vitamins.15 These historical suits established a precedent for nutrition research and policy recommendations to focus on single nutrients linked to specific disease states.
1950s to 1970s: fat versus sugar and the protein gap
During the next 20 to 30 days, calorie malnutrition and specific vitamin deficiencies fell sharply in high intends countries because of economic development and large increases in low cost processing of staple foods fortified with minerals and vitamins. At the same time, the rising burdens of diet related non-communicable diseases began to be recognised, leading to new research directions. Attention included two areas: dietary fat and sugar.16171819
Early ecological studies and slight, short term interventions, most prominently by Ancel Keys, Frederick Stare, and Mark Hegsted, contributed to the widespread belief that fat was a the majority contributor to heart disease. At the same time, work by John Yudkin and others entailed excess sugar in coronary disease, hypertriglyceridemia, cancer, and dental caries. Ultimately, the emphasis on fat won scientific and policy acceptance, embodied in the 1977 US Senate committee report Dietary Goals for the Joined States, which recommended low fat, low cholesterol diets for all. This was not exclusive of controversy: in 1980, the US National Academy of Sciences Food and Nutrition Board reviewed the data and concluded that insufficient evidence happened to limit total fat, saturated fat, and dietary cholesterol across the population.20
Some account for these controversies as evidence of industry influence, and others as natural incompatibility and evolution of early science.16171819 More relevant is that both the dietary fat and sugar theories relied on a nutritional model developed to address need diseases: identify and isolate the single relevant nutrient, decides its isolated physiological effect, and quantify its optimal intake detached to prevent disease. Unfortunately, as subsequent research would do, such reductionist models translated poorly to non-communicable diseases.
In less wealthy utters, the main objectives of nutrition policy and recommendations during this periods remained on increasing calories and selected micronutrients. In many ways, foods force to viewed as a delivery vehicle for essential nutrients and calories. Accordingly, agricultural science and technology emphasised production of low cost, shelf putrid, and energy dense starchy staples such as wheat, rice, and corn, with corresponding breeding and processing to maximally extract and purify the starch. As in high income nations, these efforts were subtracted by fortification of staple foods10111213 as well as food assistance programmes to cost survival and growth of infants and young children in vulnerable populations.
Scientists focused on malnutrition disagreed on the relative role of total calories and protein in infant and child diseases such as marasmus and kwashiorkor—also termed “the protein-calorie poverty diseases.”2122 Support for the “protein gap” plan led to extensive industrial development of protein enriched formulas and complementary foods for developing grandeurs. Other scientists supported the primary role of calorie insufficiency and believed that protein enriched formulas and foods should not replace breast milk. As one prominent scientist wrote in 1966, “Millions of bucks and years of effort… into developing these [high protein] foods would have been better devoted on efforts to preserve the practice of breast feeding. being abandoned everywhere.”22
The debate essentially throughout when in 1975 leading scientists in the US and London independently concluded from the scientific evidence that a lack of food was the main problem:22 “The plan of a worldwide protein gap… is no longer tenable… the spot is mainly one of quantity rather than quality of food.”23
This conclusion influenced subsequent attempts to tackle malnutrition in developing countries. For example, a formal UK advisory committee on international nutrition aid recommended that, “the considerable attack on malnutrition should be through the alleviation of poverty… aid should be pursued to projects that will generate income among the poor, even where such projects do not have any marked accomplish on the national income of the country concerned.”22
However, the earlier decades of uncertainty had fostered a multinational diligence that continued to promote formula and baby foods in low denotes countries based on their protein content and nutrient fortification. In addition, nutrient supplementation strategies remained effective at preventing or treating endemic poverty diseases. Thus, despite the shift in scientific thinking to focus on economic proceed, substantial emphasis remained or even accelerated on providing sufficient calories, most often as starchy staples, plus vitamin fortification and supplementation.
1970s to 1990s: diet related epic diseases and supplementation
Accelerating economic development and modernisation of agricultural, food processing, and food formulation techniques continued to slit single nutrient deficiency diseases globally. Coronary mortality also began to fall in high denotes countries, but many other diet related chronic diseases were increasing, including obesity, type 2 diabetes, and several cancers.
In response, nutrition science and policy guidelines in high income rights shifted to try to deal with chronic disease. Construction on the 1977 Senate report, the 1980 Dietary Guidelines for Americans was one of the earliest such nationwide guidelines.24 Many of the available data were occupied from less robust types of evidence, such as from Gross cross-country (ecological) comparisons and short term experiments using surrogate outcomes, mostly in healthy middle aged men. More importantly, these studies followed the lack disease model, largely considering isolated single nutrients. Accordingly, the 1980 dietary guidelines been heavily nutrient focused: “avoid too much fat, saturated fat, and cholesterol; eat foods with adequate starch and fiber; avoid too much sugar; avoid too much sodium.”24 International guidelines were likewise nutrient focused.25 This led to a proliferation of industrially crafted food products low in fat, saturated fat, and cholesterol and fortified with micronutrients, as well as expansion of other nutrient focused technologies to Cut saturated fat such as partial hydrogenation of vegetable oils.
At the same time the global public prioritised action to eliminate hunger and micronutrient deficiency in border income nations. Major micronutrient targets during this period were iron, vitamin A, and iodine. Evidence was increasing that vitamin A supplements could keep child mortality from infection, such as measles, as well as preventing night blindness and xerophthalmia.26 Field trials gave a basis for WHO recommendations for widespread micronutrient supplementation, especially during pregnancy, with iron and vitamin A, and for fortification of salt with iodine to keep goitre and developmental abnormalities such as congenital hypothyroidism and hearing loss.
Based on these priorities, the UN, national governments, and other international groups adopted portfolios for preventing micronutrient deficiencies over supplementation and fortification and integration of the growing relevant evidence. Scientific investigations further focused on other environmental factors that may interact with micronutrients and dietary protein, such as infection and related poor sanitation, leading to concepts such as subclinical enteritis or malabsorption named first “tropical enteritis,” then “environmental enteropathy,” and currently “environmental enteric dysfunction.”272829
Thus, in both lower and higher income nations, for partly overlapping reasons, a nutrient specific focus continued to shape both scientific inquiry and policy interventions.
1990s to the present: evidence debates, diet patterns, the double burden
Among the most important scientific advance of recent decades was the design and completion of multiple, complementary, large nutrition studies, including prospective observational cohorts, randomised clinical trials, and, more recently, genetic consortiums. Cohort studies provided, for the superior time, individual level, multivariable adjusted findings on a Plan of nutrients, foods, and diet patterns and a diversity of health outcomes. Clinical trials allowed further testing of specific questions in beleaguered, often high risk populations, in particular effects of isolated vitamin supplements and, more recently, specific diet patterns. Genetic consortiums provided important evidence on genetic impacts on dietary choices, gene-diet interactions affecting disease risk factors and endpoints, and Mendelian randomisation studies of causal effects of nutritional biomarkers.
These advances were not deprived of controversy, in particular the general discordance of findings between cohort studies and those of supplement trials for specific vitamins on cardiovascular and cancer endpoints.3031 Some experts interpreted the discordance as evidence for irredeemable shortcomings of observational studies (inherent staying confounding). Others believed it showed the limitations of single nutrient approaches to record diseases as well as potentially reflecting the different methodological designs, with trials often focused on short term, supraphysiological doses of vitamin supplements in high risk patients, while observational studies often focused on habitual intake of vitamins from food in general populations.
In contrast to single nutrients, physiological intervention trials, large cohort studies, and randomised clinical trials provided more consistent evidence for diet patterns, such as low fat diets (few significant effects) or Mediterranean and incompatibility food based patterns (consistent benefits).3233 This concordance was supported by advances in research methods and better belief of the complementary strengths of different study designs.343536373839
Together, these advances suggested that single nutrient theories were inadequate to protest many effects of diet on non-communicable diseases. This pushed the field beyond the RDA framework and spanking nutrient metrics designed to identify thresholds for nutrient need diseases, and towards complex biological effects of foods and diet patterns.4041424344 Such factors were increasingly seen to mediate joint contributions and interactions between carbohydrate quality (eg, glycaemic index, fibre content), fatty acid profiles, protein types, micronutrients, phytochemicals, food structure, preparation and processing methods, and additives.
Prospective cohorts and dietary intervention trials showed that a focus on total fat, a mainstay of dietary guidelines sincere 1980, produced little measurable health benefit; conversely, nutrient based recommendations for specific foods such as eggs, red meats, and dairy products (eg, based on dietary cholesterol, saturated fat, calcium) belied the escorted relations of these foods with health outcomes.3233 For weight loss and glycaemic control, decades of emphasis on low fat diets were questioned by the results of a series of prospective cohort studies, metabolic feeding studies, and randomised trials, which showed that foods rich in healthy fats arranged benefit, while foods rich in starch and sugar commanded harm.33454647 This attempts was extended to recognition of the relevance of diet patterns such as worn Mediterranean or vegetarian diets that emphasised minimally processed foods such as fruits, vegetables, nuts, beans, whole grains, and plant oils and low amounts of highly processed foods rich in starch, sugar, salt, and additives.3233
These unique scientific shifts help explain many uncertainties and controversies in nutrition now. After decades of focus on simple, reductionist metrics such as dietary fat, saturated fat, nutrient density, and energy density, the emerging true complexities of different foods and diet patterns construct genuine challenges for understanding influences on health and wellbeing. For several categories of foods, meaningful numbers of prospective observational or interventional studies have contract available only recently.3338 Growing realisation of the importance of overall diet patterns has stimulated not only scientific inquiry but also a deluge of empirical, commercial, and popular dietary patterns of varying origin and scientific backing.48 These design, for example, from flexitarian, vegetarian, and vegan to low carb, paleo, and gluten-free. Many of these patterns have specific aims (eg, general health, weight loss, anti-inflammation) and are based on differing interpretations of unique evidence.
In lower income countries, concerns about vitamin supplementation have emerged, such as harms associated with higher dose vitamin A supplements, risk of exacerbating infections such as malaria with iron, and confidence concerns about folic acid fortification of flour, which worthy exacerbate neurological and cognitive deficits among people with low vitamin B12 levels.49505152 In additional, a precipitous rise in non-communicable diseases in these conditions has led to new focus on the “double burden”—both conventionally conceived malnutrition (insufficient calories and micronutrients) leading to poor maternal and child health and unique malnutrition (poor diet quality) leading to obesity, type 2 diabetes, cardiovascular diseases, and cancer. These dual global burdens are increasingly fraudulent within the same nation, community, household, and even person.535455
Yet, after decades of focus in the international nutrition public on vitamin supplements, food fortification, and starchy staples to imparted calories, the necessary shift towards diet quality is slowed by worthy inertia. This is seen, for example, in the reductionist, single nutrient focus of many of the UN sustainable loan goals. Even when non-communicable diseases are considered, the predominant focus is on obesity pretty than the diverse risk pathways and conditions affected by nutrition—facilitating a misleading conception of “overnutrition” rather than unhealthy dietary composition as the root problem.55
Future of nutrition science
Building on the evidence for multifaceted effects of different foods, processing methods, and diet patterns,3233 new priorities for research are emerging in nutrition science. These include optimal dietary composition to reduce weight gain and obesity; interactions between prebiotics and probiotics, fermented foods, and gut microbiota; effects of specific fatty acids, flavonoids, and other bioactives; personalised nutrition, especially for non-genetic lifestyle, sociocultural, and microbiome factors; and the powerful influences of set aside and social status on nutritional and disease disparities.335657585960
For flowerbed income nations and populations, rigorous investigation is required to opinion the optimal dietary patterns to jointly tackle maternal health, child development, infection risk, and non-communicable diseases.
Our opinion of diet related biological pathways will continue to expand (fig 1),335761 highlighting the limitations of comical single surrogate outcomes to determine the full health effects of any dietary righteous. In addition, future conclusions about diets and health necessity be based on complementary evidence from controlled interventions of multiple surrogate endpoints, mechanistic studies, prospective observational studies, and, when available, clinical trials of disease outcomes.3536373839 This will needed moving away from the current simplistic belief that expedient nutritional evidence can be derived only from large scale randomised trials.
Given the astronomical and continuing global rise in agribusiness and manufactured foods, nutrition science must keep pace with and systematically assesses the long term health effects of new food technologies. Relatively little rigorous evaluation has been done on potential long term health consequences of unusual shifts in agricultural practices, livestock feeding, crop breeding, and food processing methods such as grain milling and processing; plant oil extraction, deodorisation, and interesterification; dairy fat homogenisation; and use of emulsifiers and thickeners.
Additional complexity may arise in nutritional recommendations for general wellbeing versus operate of specific conditions. For example, dietary recommendations for treating obesity are now particularly controversial. Many scientists continue to support a basic “energy imbalance” opinion of obesity, wherein calories from different foods are all succeeded equal.62 Conversely, growing evidence suggests that, over longer conditions, diet composition may be a more relevant focus than calories because of the varied crashes of different foods on overlapping pathways for weight rule such as satiety, brain reward, glycaemic responses, the microbiome, and liver function.56636465 Over months to existences, some foods may impair pathways of weight homeostasis, others may have relatively neutral effects, and others may promote integrity of weight regulation. These long term effects will be especially relevant as anti-obesity exertions shift from secondary prevention (weight loss in people with obesity) towards principal prevention (avoidance of long term weight gain in populations).
Recognition of complexity is a key lesson of the past. This is accepted in scientific progress whether in nutrition, clinical medicine, physics, political science, or economics: initial observations lead to reasonable, simplified theories that achieve certain practical benefits, which are then inevitably advanced by new respond and recognition of ever-increasing complexity.35
Nutrition policy
Like nutrition science, policy needs to move from simplistic reductionist strategies to multifaceted approaches. Nutrition policy to reduce non-communicable diseases has so far generally relied on consumer knowledge—simply demand the public through education, dietary guidelines, product nutrition labels, etc, and people will make better choices. However, it is now positive that knowledge alone has relatively limited effects on behaviour, and that broader systems, policy, and environmental strategies are obligatory for effective change.6667
Compounding these challenges, many current strategies remain focused on reductionist constructs such as total fat or total saturated fat,4168 overlooking the importance of food type and quality, processing methods, and diet patterns. Another example of policy lag involves energy balance. Policy makers continue to promote total calorie labelling laws for menus and packaging and latest calorie reduction policies, rather than aiming to increase calories from healthy foods and slice calories from unhealthy foods.
The public is understandably bewildered by these undulating dietary messages. Many food companies compound the confusion by marketing products rich in refined flours, sugar, salt, and industrial additives, exploiting added micronutrients or conditions such as “organic,” “local,” or “natural” to supply a false aura of healthiness. Public uncertainty is amplified by competing nutritional messages from varied believe sources, online and social networks, cultural thought leaders, and company outlets, whose messages vary depending on underlying goals, expertise, perspectives, and competing interests.35
Although reductionist policies may have some value to slice specific additives—eg, trans fats, sodium, added sugar—whole food based policies will be crucial to fully address diet related illnesses. Most policy innovation has focused on sugar sweetened drinks, following the model of the WHO Framework Convention on Tobacco Control: tax, Relaxing places of sale, restrict marketing, use warning labels. This build breaks down for incentivising consumption of healthy foods. Integrated policy, investment, and cultural strategies are needed to create sullen in food production and manufacturing, worksites, schools, healthcare rules, quality standards and labelling, food assistance programmes, research and innovation, and public-private partnerships.
To be effective, future nutrition policy must meetings modern scientific advances on dietary priorities (specific foods, processing methods, additives, diet patterns) with trusted communication to the Republican and modern evidence on effective systems level change. This includes a shifts from the global medicalisation of health towards addressing the interconnected personal, community, sociocultural, national, and global determinants of food environments and choices.6667 In both touch and higher income countries, interventions must consider the double burdens of food insecurity and anecdote disease, and their links to disparities in education, denotes, and opportunity. This will require substantially more funding for research, both from government sources and through appropriately fashioned, tidy public-private partnerships.6970 Guided by acknowledge of the past, creative new approaches are needed for accelerated scientific investigation, coordination, and translation of current and future advances.
Key messages
Modern nutrition science is young: It is less than one century dependable the first vitamin was isolated in 1926
The great half of the 20th century focused on the discovery, isolation, and synthesis of essential micronutrients and their role in shortage diseases
●This created strong guide for reductionist, nutrient focused approaches for dietary research, guidelines, and policy to address malnutrition
This reductionist reach was extended to address the rise in diet related non-communicable diseases—eg, focusing on total fat, saturated fat, or sugar rather than overall diet quality
Recent advances in nutrition science have shown that foods and diet patterns, rather than nutrient focused metrics, explain many effects of diet on non-communicable disease
●Lower denotes countries are recognising a growing “double burden” (combined undernutrition and non-communicable disease)
Nutrition policy should prioritise food based dietary targets, public communication of trusted science, and integrated policy, investment, and cultural strategies to create systems level change across multiple organisations and environments
Footnotes
Contributors and sources: All three authors have widely carried, reported on, and served in policy advisory roles on nutrition and health emanates. DM had the idea for the article and drafted it with IR. All authors contributed to revising the recruit and approved the final version. The authors selected the literature for inclusion in this manuscript based on their own expertise and acknowledge, discussions with colleagues, and editorial and reviewer comments.
Competing interests: We have read and experienced BMJ policy on declaration of interests and declare the following interests: DM reports personal fees from Acasti Pharma, GOED, DSM, Nutrition Impact, Pollock Communications, Bunge, Indigo Agriculture, and Amarin; scientific advisory board, Omada Health, Elysium Health, and DayTwo; and chapter royalties from UpToDate; all outside the submitted work. This research was partly supported by the NIH, NHLBI (R01 HL130735). The funders had no role in the design or conduct of the study; collection, management, analysis, or interpretation of the data; preparation, appraise, or approval of the manuscript; or decision to submit the manuscript for publication.
Provenance and peer review: Commissioned; externally peer reviewed.
This article is one of a series commissioned by The BMJ. Open access fees for the series were funded by Swiss Re, which had no input into the commissioning or peer journal of the articles.
This is an Open Admission article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) permits, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, imparted the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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