Dietary guidelines and health—is nutrition science up to the task?BMJ 2018; 360 doi: https://doi.org/10.1136/bmj.k822 (Published 16 March 2018) Cite this as: BMJ 2018;360:k822
All rapid responses
I am 60 years old, a teenager when dietary guidelines exhorted us all to switch to polyunsaturated fats, and carbohydrates in preference to meats. My family followed the news enthusiastically. Low fat products, cereals, feeling guilty at ordering a steak, which I hardly ever did. For the record I didn't eat sugar either - I did wholeheartedly embrace low fat though.
I distinctly recall conversations with my later, naturally slim husband, when he was tucking into his steak and I was eating my " boil in a bag" calorie counted, low fat, low sat fat , low salt option. He was so "Lucky" to be able to eat in such an unhealthy fashion.
Forty years on a perpetual roller coaster of hunger pangs, weight gain and ill health followed in 2016 by diabetes . I now find out that the " science" upon which this was all based was actually just a well -intentioned guess. One that went spectacularly wrong.
I found out a few more things too:
· That in 1915 we treated diabetics with a low carbohydrate diet - now totally counter to current carbohydrate heavy guidelines
· That in 1912 we knew how to fatten hogs -use cereals & skimmed milk - Official guidelines for all today.
· That in 1951 the advice to lose weight was to reduce carbohydrates.
· That food questionnaires upon which most of this epidemiological data has been generated are probably fundamentally flawed -
o Grapes & raspberries in the same box - why? because they are small ? they have totally different effects on the human body .
o Meat products "reconstituted animal by products wrapped in refined flours cooked in seed oils " confused with and now used to warn anyone from anyone eating traditional air dried meat products.
· That the questioners betray both their nutritional ignorance & their cultural bias, much of the meat consumed not even in the experience of the average American epidemiologist. (think cow's stomach - on the menu everywhere in Japan)
· That many of the studies of whatever origin come complete with a massive bias from the funder and that the "plant based" lobby largely represents the processed food industry.
· That this new standard diet is so appalling that just about anything will be an improvement - paving the way for an explosion in pharmaceutical interventions many simply attempting to deal with the consequences of poor diet.
I, like so many others, stopped going to my doctor, instead I turned to those with practical experience and sorted out my health myself .
I got rid of processed food, refined carbs. & polyunsaturated fats .
I got rid of anything with a " healthy" label - Low fat, low sat. fat, low salt = AVOID
If it's low sugar - turn over, find out just how many refined carbs are hidden in it - then AVOID
So in essence I moved back to eating traditional foods popular before epidemiologists "helped" to confuse us all as they continue to do.
The decision to vilify saturated fat and with it the food of our forefathers, paved the way to the current global catastrophe. Epidemiologists bear some responsibility for this catastrophe and continue to do so.
It is time that those responsible stood up and admitted to the world that they got it wrong, before we see an even greater fall in fertility and increase in suffering.
I , and thousands of others , are angry every time we see you justifying your existence blinded to the damage you have all done to us with your speculative pronouncements decrying the food we have eaten for generations.
I , watch with horror, as I see new generations being led down the same path - eat a carbohydrate heavy diet , experience massive hunger pangs but it's your fault if you can't resist the refined foods on display everywhere. Food aid of skimmed milk and cereals given to the poor. Cafe's where it's not even possible to put full fat milk in one's tea.
Doctors developing skills to remove parts of stomachs of those who succumbed to this evil brew of low fat, carbohydrate heavy processed foods.
I am only an N=1, my voice does not count. I IGNORE official guidelines and tell anyone I can think of that they need to do so too. The food pyramid derived from epidemiology is actively harming the population. and more importantly for me - ME.
Instead I eat - the same stuff my husband was eating to keep slim all those years ago - good quality proteins, meat of all types, offals, fish, vegetables. dairy, eggs. I avoid polyunsaturated fats and anything it gets put in, like the plague. Vegetables are side dishes, fruits - a sweet treat - nature's candy.
My reward ? weight loss, stable blood sugars, renewed energy, reversal of diabetes ( Hba1c 5.3% from 10.3%) improved cholesterol and all other health markers into a healthy range, no more hunger pangs, food cravings, need to snack . Such a simple fix - understand the power of real unprocessed foods - stuff that does not need a label at all.
When Harvard puts out a study suggesting that eating 63 portions of vegetables per day is a healthy option for humans, and governments stay silent, when instead they should withdraw funding, then you just know - we as human beings are on our own.
I am only N=1, but trust me, we number thousands and we will not put up with the current situation for much longer. It is time to be honest and let the world know that research got it wrong and that nutrition science as it currently stands is a total fail.
Competing interests: No competing interests
Re: Dietary guidelines and health—is nutrition science up to the task? - no because the problems is economics
Taking a long-term biological perspective, I assume as a null hypothesis that animal bodies will operate properly on a "traditional" diet, driven by hunger and available food sources.
Animals will seek particular nutrients based on instinct. I presume the senses of taste and smell are used to analyse nutrients, driving us to eat "what we like" and this biological drive will under natural circumstances lead us to consume what we need.
It seems modern food processing practices conspire to alter the balance of nutrients available, by selectively removing parts of food en-masse. Nutritionists have been complicit in this, assuming the nutritive value of "what we know" is in the food is as good as "what we don't know" got thrown away in the refining and processing.
Available evidence from the large prospective cohort studies and small randomised trials and experimental animal studies seems to be compatible with my view. (Or maybe just confiming my bias?)
The Seven Countries Study "suppressed" the evidence of the deleterious effects of sugar and potatoes, probably because it failed to confirm the bias against saturated fat intake.
So whilst the authors remind us of the never ending flip-flopping of food recommendations, they are all compatible with the long-term biological perspective. Less-refined food appears beneficial. Chewing results in less food consumption. All calories are not equal. Nutrition research to date keeps making mistakes, driven by assumptions on what effects the researchers are looking for.
There are still major gaps. Fat soluble vitamin consumption doesn't correlate well with blood levels. Liver could be a super food from the Mediterranean diet, except that it doesn't show up as significant when people round the world on traditional diets only consume it every 2-4 weeks.
The problem is that economics conspires against all of the intentions of the nutritionists, since people in the modern world will tend to choose what is economically efficient for them - convenient and affordable.
I believe the power of the market will continue to override the best nutrition advice and that the solution must be left to the economists and not the nutritionists. Sugar taxes are the beginning.
Competing interests: No competing interests
Drs. Mozaffarian and Forouhi raise a crucial question in their article, “Dietary guidelines and health—is nutrition science up to the task?” That task, of course, is whether our nutrition recommendations have effectively prevented the major chronic diseases of our time. The authors, both nutritional epidemiologists, present their vigorous defense of the discipline, affirming confidently that “Modern nutrition science is up to the task.”
The reason this issue is so critically important is that we face unprecedented epidemics of obesity and diabetes, and thus, it is indeed possible that nutrition science has failed us. The case for this alternate view must be heard as well.
The success of any policy or intervention must be evaluated by relevant outcome measures. Drs. Mozaffarian and Forouhi assert that “advances in the science and application of nutrition represent expected, reassuring progress,” yet they provide no outcome measures to substantiate this progress.
If we were evaluating infectious disease prevention -- AIDS, for instance-- decreases in disease prevalence would be required to conclude that public health interventions had succeeded. The relevant outcomes for nutrition science—prevalence of obesity, type 2 diabetes, fatty liver disease, cancer, cardiovascular disease and more—cannot remotely be seen as a success. This may be why the authors scarcely mention these diseases in their article. Another measure of healthy nutrition, US life expectancy, has declined over the past several years. 
The conventional rationalization for these disconcerting trends is that people simply fail to follow guidelines. The available evidence suggests otherwise. In the U.S., national survey data confirm that trends in both macronutrient consumption  and individual food categories  faithfully follow the prescriptions of the dietary guidelines.
Ultimately Drs. Mozaffarian and Forouhi argue for a primary role of prospective cohort studies in diet guidelines, when evidence from randomized controlled trials (RCTs) is ambiguous. But these cohort studies generate associations that can reliably infer causality only in rare instances when associations are so reproducibly large (e.g., the 10- to 20-fold increased risk of lung cancer in smokers vs. non-smokers) that plausible alternative causal explanations are unimaginable. For the far smaller associations of nutritional epidemiology, the question is, how do we know that causation can be reliably inferred? The existing evidence is not promising. A 2011 analysis of 52 claims made by nutritional epidemiology tested in 12 well controlled trials found that not one of the 52 claims—0%--could be confirmed.  A 2005 analysis by Stanford epidemiologist John Ioannidis concluded that highly-cited observational findings such as those in nutrition were confirmed by RCTs in only 20 percent of cases. 
Drs. Mozaffarian and Forouhi defend their position with a revisionist history of Hormone Replacement Therapy, employing a questionable post-hoc analysis to conclude that RCTs and observational studies are concordant. This conclusion is controversial.  More importantly, the authors tacitly assume that an example from pharmacoepidemiology can fairly be extrapolated to nutritional epidemiology. They further cite “1583 meta-analyses of 228 conditions,[that] find similar close concordance between randomised trials and observational studies.” These findings, too, address observations of pharmacological or other medical interventions, not nutrition. Yet these epidemiologic disciplines cannot, de facto, be assumed to be equivalent.
Nutritional epidemiology suffers from less precise assessments of exposure – due largely to unreliable, self-reported dietary information– and far greater potential for confounding. Dietary choices are associated with subtle socio-economic, behavioral and lifestyle factors, all potentially explaining the observed associations, This is why epidemiologic associations have traditionally been considered suitable only for hypothesis generation and insufficient as rationale for establishing policy.
Despite the problematic track record of nutritional epidemiology for inferring causality, Drs. Mozaffarian and Forouhi assert that “it is appropriate to act” on ambiguous evidence, because “As in all fields, application cannot await flawless evidence or perfect understanding.” But dietary guidelines are a form of preventative medicine, not like “all fields” of science as the authors claim. If dietary guidelines are wrong, healthy people die prematurely, a point made in this very journal in 1981 by the epidemiologist Geoffrey Rose in his seminal article on the strategy of preventive medicine. Unlike medical interventions for the sick (i.e., interventional cardiology, an example elaborated upon by Drs. Mozaffarian and Forouhi), for whom risks might be worth the calculated benefits, dietary guidelines are prescribed to healthy populations with the goal of preventing disease: “This kind of population-wide preventive medicine is predicated on the assumption that it will do no harm,” wrote Rose, “and that the population following it will, at the very least on average, be healthier and live longer. It is a very different proposition than curative medicine.” It is therefore self-evident that such preventive guidelines must meet exceptional standards of evidence.
The authors’ argument closely echos the one used in 1977 to justify the U.S. Senate’s first Dietary Goals for the United States, prescribing an increase in carbohydrate consumption and decreases in total fat and cholesterol, based on much the same ambiguous trial data bolstered by epidemiologic associations. “There will undoubtedly be many people who will say we have not proven our point,” wrote Harvard nutritionist Mark Hegsted in the Senate report. Asking “what are the risks?” Hegsted answered, “There are none that can be identified and important benefits can be expected.”  A chorus of experts, including the president of the National Academies of Science and the director of the National Heart, Lung and Blood Institute, urged restraint, noting the potential for tragic unintended consequences. Indeed, the total fat and cholesterol caps have since had to be retracted, while obesity and diabetes prevalence has exploded coincident with promulgation of the guidelines.
We would like to revive that call for caution and humility. Despite methodological advances, nutritional epidemiology remains fundamentally limited by its observational nature. Guidelines relying on this circumstantial evidence can be little more than educated guesses. While public health emergencies such as the current “diabesity” epidemics compel experts to enact some, if imperfect, advice now, the risk of unintended consequences remain. Enacting prevention guidelines based on lesser evidence risks repeating what might be a tragic history of doing more harm than good.
 BMJ 2018;360:k822 doi: 10.1136/bmj.k822 (Published 16 March 2018)
 Ernst J. Schaefer et al., “Lack of Efficacy of a Food- Frequency Questionnaire in Assessing Dietary Macronutrient Intakes in Subjects Consuming Diets of Known Composition,” American Journal of Clinical Nutrition 71, no. 3 (2000): 746–751
 Alan R. Kristal, Ulrike Peters, and John D. Potter, “Is It Time to Abandon the Food Frequency Questionnaire?” Cancer Epidemiology, Biomarkers and Prevention 14, no. 12 (2005): 2826–2828
 Somdat Mahabir et al., “Calorie Intake Misreporting by Diet Record and Food Frequency Questionnaire Compared to Doubly Labeled Water among Postmenopausal Women,” European Journal of Clinical Nutrition 60, no. 4 (2005): 561–565
 Arthur Schatzkin et al., “A Comparison of a Food Frequency Questionnaire with a 24-Hour Recall for Use in an Epidemiological Cohort Study: Results from the Biomarker-Based Observing Protein and Energy Nutrition (OPEN) Study,” International Journal of Epidemiology 32, no. 6 (2003): 1054–1062.
 Rose G. Strategy of prevention. The BMJ 1981 282:1847-1851
 https://archive.org/details/CAT10527234 p.3
 Select Committee on Nutrition and Human Needs of the U.S. Senate. 1977. Cardiovascular Disease. Vol. 2, Pt 1 of Diet Related to Killer Diseases; hearings before the Select Committee on Nutrition and Human Needs of the United States Senate. Ninety-Fifth Congress. Feb 1 and 2, 1977. Washington, DC: U.S. Gov Printing Office, Washington D.C., pp. 8-33.
 Handler, P. 1980. On Bias: Does Where you Stand Really Depend on Where You Sit? In Issues and Current Studies, 1-15. Washington, DC: National Academies of Sciences.
Competing interests: No competing interests
Are Health Professionals and Tomorrow's Doctors up to the Task of Translating Nutrition Science to Practice?
Debates about the reliability of dietary guidelines sometimes evoke faint echoes of the frequent complaint that all the medical advances in the world have not conquered the common cold. We should come back to basics and remember all the important nutrition practices that truly work. Fundamental things like guiding pregnant women to achieve optimal weight, supporting breast feeding, ensuring that hospitalised and institutionalised people are not malnourished, and managing re-emerging micronutrient deficiencies, prevalent worldwide, often defying economic development. What’s more, this advice is beneficial not only for patients, but even more so for healthcare systems suffering from backlogs and unnecessary expenditure.
All this depends on health professionals receiving sufficient nutrition training, which for until now has been patchy at best. With better preparation they might just take a dramatic step forward and explain to their patients that nutrition standards now taken for granted, such as adequate vitamin C intake and avoidance of trans-fats, already shield them from health failures that shortened the lives of their parents and grandparents. They may also inform patients that given the evolution of the westernised, nutrient-poor diet, there has been a recent re-emergence of conditions previously thought to be largely eradicated, such as scurvy. Indeed, they could also ensure that women of childbearing age are not folate deficient, or not so many elderly people in the community suffer from the unmitigated effects of vitamin B12 deficiency, or that fewer patients in hospital have poor outcomes due to being underfed. We know enough already to prevent such nutrition failures and, yet, they occur far too frequently.
Having a doctor with solid foundations of nutrition knowledge does wonders for building trust, particularly for patients unsettled by rampant claims and counter-claims about defective nutrition guidelines. The emergence of ‘celebrity nutritionists’ and online forums has further blurred the lines between evidence-informed facts vs misinformed opinions being used for commercial gain. Doctors will prove themselves competent when they understand that nutrition science, like weather forecasting, has many elements of uncertainty and if they can explain to their patients in a minute or less the difference between settled knowledge and fanciful speculation. This takes practice and lifelong study, though no more than any other area of medical science. But this is our best bet in the long term, looking to medical and healthcare professionals to provide consistent guidance, rather than relying on the public to self-navigate what can seem to be an ever-changing jungle of nutrition evidence.
We can all get even better at this nutrition thing and we will with the help of good science. Truly open issues will be resolved, one irksome question at a time. Precision nutrition with the use of sophisticated diagnostic tools and integrative intervention algorithms will also imminently do their bit to bring us to the next level of quality health care.
Meanwhile, let’s make sure that we fully use the science and tools already in hand. The ever faster pace of nutrition science development will at times prove current practices right and sometimes wrong. This is inevitable. However, what will always be wrong, is a denial of the existing evidence. Education is the best food for better practice. The globally acting NNEdPro network is keenly focused on bringing nutrition education to health professionals to foster evidence-informed practice and ultimately to better health outcomes. Helping providers to give their patients up-to-date nutrition information will always be a good holding pattern until we know better.
We agree with Mozzafarian & Forouhi that modern nutrition science is up to the task, though always in need of improvement, which of course is an evolutionary trait needed for any cognate scientific discipline to remain fit for purpose. However, the nutrition education of health providers is less certain and still very much in need of essential support. On the brighter side, we now have well thought through nutrition curriculum standards in several countries as well as a body of evidence around what might work best to translate nutrition education to health providers, particularly medical professionals including tomorrow’s doctors i.e. our medical students. So really as the world heads towards the United Nations’ 2025 targets around Nutrition, it is a time for action rather than contemplation and perhaps there has never been quite so opportune a moment as there is now, for Nutrition Science to truly show its translational mettle!
Finally, the NNEdPro Global Centre for Nutrition and Health (www.nnedpro.org.uk) is poised and ready to do its bit, working in partnership with the BMJ Group, this year we launch a brand new journal: BMJ Nutrition, Prevention and Health (https://www.bmj.com/company/newsroom/bmj-to-launch-new-nutrition-journal/). We hope this will serve as an important vehicle that keeps us at the cutting edge of nutrition science on one hand whilst continuing to supply high quality evidence for both policy and practice.
Competing interests: No competing interests
Precision nutrition guidelines
There is little to argue with the tenor and key points of the valiant defense of Nutrition Science by Mozzafarian & Forouhi. What is missing, however, is a recognition of the diversity of responses to nutrition, using what we now tend to call precision nutrition. We have known for a long time that we are not all created equal when it comes to how we eat and drink, and what effects these intakes have on us. Some people can digest the lactose in milk, many others cannot. Many need much more folate than others, with optimal amounts probably being two- to threefold different between major groups. Energy utilization appears to vary by 20-30% between individuals of the same age, gender and body size, largely due to inherited differences. There is a rapidly growing list of such intrinsic diversities that are for now as unalterable as sex chromosomes.
Whether we like it or not, all dietary guidelines for a particular group implicitly state which principles and aims truly apply to nearly all members of that group. What they rarely do is to clearly tell the public that on a particular issue there is not one nutrition solution that is best for all of them. Controversies on some issues keep smoldering precisely because the evidence points in one direction for one group and in another direction for another group. Optimal salt intake is such a perennial controversy, not least because some people are predictably salt sensitive while others are not. Yet another sizeable group has also emerged that appears to respond paradoxically to very low salt intake and may have more harm than benefit with low intake guidance. This does not mean that everybody now needs to have their DNA analyzed. But it does mean that committees and agencies promulgating nutrition guidelines need to examine such known diversities and address them. They need to decide in each case whether the guidelines under consideration can be formulated broadly enough to encompass most people and still be useful. In some instances, they may come to the conclusion that a one-size-fits-all guideline for a particular nutrition issue is not feasible and should then say so. This is how precision nutrition can elevate the state of nutrition science in policy contexts.
Competing interests: No competing interests
In response to Rodney F. Cartocci's query about the authors' declaration of interests, we understand that Dariush Mozaffarian’s advisory role at Unilever ended in 2014 and is therefore outside the three year timeframe of The BMJ’s conflict of interest policy.
Competing interests: No competing interests
Nutrition science is not up to the task to provide dietary guidelines or optimal diets for health and different diseases because it relies primarily on empirical data instead of theoretical models of the biophysics of nutrition, systems design and “thought” experiments.
Nutrition science is methodologically inferior to other fields because it relies primarily on observation studies of hidden multidimensional factors without accurately measuring key variables, and extrapolating incorrectly.
Instead, nutrition science should mimic biophysics. It should identify the relevant variables, create mathematical models that describe the relevant variables. Then it can interpret the data and make recommendations. This task is difficult. It requires substantial expertise in mathematics, chemistry and physics. Researchers should apply statistical thermodynamics and differential equations (that take years of education and expertise) instead of statistical software that require hours of learning and minutes of computer time.
I disagree with the research approaches commonly used and cited by Dr. Frieden, see his Table 1; and Dr. Mozaffarian, which rely on empirical observations or clinical trials. Instead, nutrition science should use the methods of biophysics and systems analysis.
Nutrition science and clinical medicine does not need more interventional and observational studies. It needs more “thought” experiments, predictor models, a theory, or principle for the purpose of thinking through its consequences. https://en.wikipedia.org/wiki/Thought_experiment
We need to think of biophysics principles at play, what is being optimized by the system to reverse engineer how the system works. We look at a biological entity as a “system”, an ensemble or set of molecules. We know it works in a specific way not because of a will or intent, but because it is optimizing a physical property. If we identify its optimization purpose, then we can reverse engineer and figure out how the system works to accomplish its purpose.
How many MDs or PhDs in nutrition can write and solve differential equations? How many of the top journals in medicine and nutrition publish articles describing the equations of nutrient changes as a function of time, internal and external events (such as eating)? How many know that the equations for nutrients have solutions that oscillate over time, and thus measurements are intrinsically variable (with substantial implications for statistical analysis)?
We do not need to solve differential equations to tell people to eat fewer calories, eat foods closer to their natural state and avoid highly processed foods without PUFAs. Painters, plumbers, garbage collectors, sales clerks, artists, and many jobs do not need to solve equations. But we need differential equations and mathematical models to understand the complex relationships among the thousands of different molecules (probably 25K to 50K) that form the body. That ought to be the purpose of medical journals and conferences. Newspapers review restaurant food or ice cream flavors. Musicians play music. Scientific nutritionists ought to create math models.
What are the math scores of nutrition PhD or MD researchers? How many know how to create a math model, understand statistical thermodynamics (the field that describes the movement of molecules in the body and the basis for nutrition and medical research)? When I ask at meetings how many researchers took upper level or graduate level courses in thermodynamics and differential equations, the answer is usually . . . (can you guess?).
To have substantial advances in nutrition, schools and funding entities must change the nature of nutrition research. The nutritionists who help nursing homes or children eat better are unlikely to have the skills to understand the multidimensional relationships among biomarkers. We do not ask airplane pilots or taxi drivers to research the equations of planetary movement or optimize the movement of engine parts. We do require math knowhow from those who research engines or predict rocket paths.
“A core principle of good public health practice is to base all policy decisions on the highest-quality scientific data, openly and objectively derived.” “improve the use of multiple data sources for health decision making.” Frieden TR. Evidence for health decision making—beyond randomized, controlled trials[Review]. N Engl J Med 2017;377:465-75. doi:10.1056/NEJMra1614394 pmid:28767357
Seems to make sense? I disagree. Data are meaningless without a good theory or math model to interpret it. The fallacy that data are King, supreme decider, is embodied in the fallacy that randomized, controlled trials (RCTs) are the golden rule or best evidence to identify the best treatments (e.g., compare treatments). Without a good model, researchers are like blind men touching different parts of an elephant (and not knowing it). Every experiment is a tiny surface in the multidimensional space of nutrients and chemicals in the body. Without knowing where we are, we don’t know if the study is in the part of the space where increases in a nutrient lead to better or worse outcomes.
I propose that “thought” experiments and theories that identify relevant variables and make good predictions are essential (sine qua non) to interpret data and best methods to identify optimal treatments. This is particularly critical in situations that involve multiple variables that are similar across subjects, where the accumulation of life experience is critical to understand current outcomes, where a study cannot be run for years, and where the difference between treatment and control subjects cannot be made huge. It applies particularly to nutrition studies.
We, our bodies, are the result of a nutrition study we did on ourselves: we are the consequence of what we ate during our lives. There are about 30 to 60 essential nutrients. http://www.nutrientsreview.com/glossary/essential-nutrients. It is practically impossible to conduct nutrition studies lasting years, where every person eats the same amount of each essential nutrient except for one. Further, differences in quantities of nutrients between treatment and control groups must be small because it is impractical to make them huge. In contract, the treatment group in a drug experiment receives a drug in huge quantities (compared to control group), a drug that has not accumulated in the body. It is relatively easy to control the quantity of the drug taken by a subject. What is not feasible is to control the quantity of nutrients, exercise, environment (e.g., temperature, diet, humidity), genes, etc. These factors likely alter the experimental results in all trials, particularly nutrition trials. It means that it is essential to have a good mathematical theory that describes the relationship among all variables.
Clinical trials may be misleading if they omit major factors or evaluate results within a narrow range of critical factors. Unfortunately, most nutrition studies use empirical methods, measure a few variables and seek statistical relationships among them. Few involve biophysical predictor models (such as those used in physics). Further, measurements may have HUGE errors. This helps entities who design studies to obtain desirable results (or those that favor profit making entities or profitable diagnosis and treatment).
The relationship between most biomarkers and nutrition usually follows a U or inverted U curve. It means that outcomes are undesirable for high or low values of the nutrient. There is usually an optimal range for each nutrient (an optimal range in the body, an optimal range in different parts of the body, an optimal range for dietary intake). Increasing a nutrient may lead to desirable outcomes on one side of the U curve, and undesirable on the other side. If body levels of Fe are low, eating more Fe is usually desirable; if body levels of Fe are very high, eating more Fe is undesirable. Similarly, for all nutrients. But we rarely know the status of all nutrients in the body.
Further, the optimal values for each nutrient are not constant. They depend on the status of other nutrients, genes, environmental factors such as temperature, humidity, state of health or disease, etc. These issues are not adequately considered in nutrition research.
The relationships between biomarkers are represented by a system of differential equations. In its simplest form, with at least two biomarkers, it means the equation for one biomarker is at least a 2nd degree differential equation. Its solutions are oscillatory, values go up and down. With many biomarkers we can expect that the function of a biomarker over time and over different values of other biomarkers is likely to oscillate between two feasible ranges (upper and lower), so that values far below or far above the range are undesirable. Further, within the desirable range, there may be more than one optimal value, and many suboptimal but acceptable values in the sense that they do not cause substantial disease or clinically observable disease. In other words, the optimal value for one nutrient depends on the present values of other nutrients.
Given our body composition at a given time, the optimal intake of each nutrient depends on the body composition of all other nutrients, genes (that determine our biochemical reactions), environment, etc. Frequently, particularly in studies, researchers do not measure and do not know the biochemical values for all relevant nutrients, molecules, chemical reactions. Whatever results they find about a nutrient (except in extreme conditions such as those found in earlier studies of nutritional deficiencies), the results may not apply to the same or other person when conditions change (e.g., body concentrations of nutrients change, environment such as weather changes, etc.).
I propose that all empirical studies, based on observations of data or clinical trials, are likely to lead to misleading results and should be terminated. We need a different approach based on fundamental principles of biology. Physicists evaluated conservation principles and created the laws of momentum, energy, entropy, and others that lead to predictor models. Biologists and nutritionists need to identify similar principles that lead to predictor models.
For example, we know that the body conserves plasma K. It does so via complex regulatory processes. If we want to identify optimal K intake levels for one patient, we need to know if the body has whole deficits or excess of K. We cannot do that by measuring K in plasma because it is carefully regulated and it is usually within reference ranges. Instead, we can measure K in urine over 24 hours following a controlled intake of K and find if the body is conserving K or excreting K (which is a clue to deficit or excess of K) to guide therapy. This approach is useful to treat patients with K and determine optimal K intake levels, when they have a chronic disease that leads to K abnormalities (such as chronic diarrhea). But many physicians evaluate K via blood tests, missing chronic low K levels.
To me, nutrition topics in medical journals and conferences, are inadequate, the speakers are inadequate, the concepts are too simple. I believe speakers (often well-known, opinion makers) treat nutrition as an empirical, observation activity like botany used to be before atoms, thermodynamics, modern biophysics, DNA: a descriptive philosophy, akin to rating paintings and movies. There have been probably hundreds of meetings with similar topics reaching amazing conclusions such as “eat with moderation”, “there are relationships among nutrients”, “may be nutrient ZZ perhaps contributes to heart disease” (“may” is a common word using in writings instead of R squares or quantitative measures of relationships or mathematical equations). Why bother trying to solve differential equations and derive the function that predicts nutrient needs when “may” is more comprehensive, risk proof (nobody is wrong by using may)?
At forthcoming conferences and journal issues on nutrition, I would like answers to these questions:
What is the difference in biological activity of nutrients attached to different molecules (e.g., essential fatty acids in different phospholipids or triglycerides, Fe or Ca eaten with other foods)? What are the measurement errors? What are the best ways to measure nutrients in urine, fecal matter, nails, hair and other discarded tissues v. blood? What are the substantial measurement errors in epidemiologic and clinical trials? An expert in chromatography and mass spectrometry explaining state of the art methods to measure all nutrients, including their different shapes when attached to molecules.
What are the best approximate biophysical models of the interacting chemical reactions among different nutrients? We have a rough model of glucose and insulin. What are the equations relating insulin, glucose, glucagon, DNA, RNA and other key aspects of glucose regulation? These equations must explain glucose fluctuations, maximum and minimum achievable levels, urine excretion, response to glycogen loads, etc. Similar equations for all other nutrients.
What are the best biological matrices (e.g., food) to eat different nutrients? How do they relate to supplements? What factors influence absorption and biological utilization of nutrients? What are the absorption curves of each nutrient and why? Do absorption peaks occur at about the same time? When is the best time to eat supplements? (i.e., AM with high bile or night before sleep?). Ex: in IBD, some nutrients are poorly absorbed. Can we use absorption peaks or urine values to measure requirements and deficiencies (i.e., methyl malonic acid for B12)?
Did (USA) HHS/USDA, and other government agencies adequately consider the biological utilization of nutrients to determine daily allowances, maxima and minima? How? I could not find their mathematical models. Why? What math models were used by European countries to decide on nutritional requirements? Was it empirical guesses based on astrology, stomach feelings, good movies, pseudoscience, state of the art nonsense or valid, reliable, accurate scientific predictor models?
What are the best software and data to measure dietary intake over one week? How to make the task of keeping a diary easier with a cell phone and scale? What adjustment factors to use depending on how foods are cooked?
How to measure undesirable reactions to food intake in patients with IBD, perhaps using calprotectin or other measures in fecal matter?
Dietary guidelines and health—is nutrition science up to the task? (March 2018). BMJ 2018;360:k822. http://www.bmj.com/content/360/bmj.k822
Competing interests: Competing interests: I conduct many activities that influence my opinions (e.g., my research, write books or articles or patents, have websites, design foods, lecture about health and disease, health policies). I describe the types of fats to eat, exercise, stress management, diets, eating less, periodic fasting. I am developing a new theory of disease, including lipid metabolism and the cause of cardiovascular disease, cancer and other conditions, with new treatments. I intend to profit from my intellectual property (IP) (e.g., write articles, web sites, books, patents, lectures, ads, biomarker tests, seek financial support, venture capital, etc.). I wrote a patent to measure fatty acids. I wrote one book on essential and trans fatty acids. I gave talks to corporations, conferences and trade shows, for which I was paid (mostly on fats). I may receive compensation from food or other companies. This comment is an extract of books and articles either written or in progress (comment authorized by the author under the non-exclusive common license CC BY-NC 4.0 requested by BMJ). I criticized the value of the USDA nutrition guidelines, federal nutrition funding, and the National Cholesterol Education Program. I do not consider eggs harmful because they have cholesterol and fat, made my views public, received funding from egg industry. I tell my family to eat eggs and red meat, avoid processed fat. I do not follow the USDA nutrition guidelines. I proposed a different Food pyramid and nutrition guidelines. To me, nutrition is the most important factor in health and disease and I write that doctors should learn more about nutrition and spend more time with patients. I write that many blood, invasive, and diagnostic tests using energy (e.g., endoscopies, X-rays) are overutilized and harmful. Many of my writings are found via a search for Siguel and Fatty Acids or Siguel in BMJ.com responses.
This is a helpful article except I feel in the area of working with industry and vested interests. There is now abundant evidence that 'big'food and beverage companies and front organisations use a range of tactics, similar to those used by tobacco to undermine efforts to restrict sales and marketing of their unhealthy products. There should be firewalls around policy making at UN and government level and around prioritisation of the research agenda for all funders, to keep industry out. The place where industry can be involved is after policy and priorities have been agreed and in the implementation phase. There is clear evidence that if industry is involved in the formulation of policies and priorities these would favour voluntary codes and informed choice as the model for intervention, rather than fiscal and regulatory mechanisms that are shown to be most effective.
Conflicts of interests of nutrition researchers and their professional bodies is a major concern, and undermines the credibility of the evidence these conflicted researchers contribute to the evidence bas for actin. This has most recently been shown for the influence of Coca Cola on shifting attention away from diet to physical activity and the publication of these findings in industry funded journals ( see Serodio et al 2018 PHN doi:10.1017/S136898001700307X), and where many authors do not declare their industry funding.
Competing interests: No competing interests
In an analysis recently published in the British Medical Journal, Mozaffarian and Forouhi (1) argue that the basis of nutrition science is ‘reliable enough’ to improve the understanding of the impact of food on health and disease prevention. I agree with the authors’ statement, and share their view on how to move forward in the future. To overcome current criticism and controversy, the authors emphasise the need for more coherence in public messaging, too often jeopardized by people with vested interests. I would like to raise two additional points, specifically regarding research, that are also important to avoid public confusion in nutrition messages.
First, nutrition researchers should be proper nutrition experts. This means research teams should include academically trained nutritionists, and/or professionals with different backgrounds but solid training in nutrition. Although each researcher might have an opinion about nutrition and his/her own diet, research in nutritional epidemiology requires advanced specific knowledge and technical skills (2), together with both global and critical visions of food and nutrition.
Second, peer-reviewed journals have the responsibility to include nutrition experts in their editorial board and/or their pool of reviewers. This process may lead to more rejections of manuscripts with low quality nutrition data, weak discussion and/or biased conclusions. This is particularly true for high-ranked journals that have a large influence on health professionals’ opinion, and whose published studies often serve as media ‘buzz’. The wide diffusion of PURE study conclusions (3,4), not backed by strong evidence and criticised by nutrition experts (whose comments were unfortunately far less broadcasted), is a recent example of unnecessary exacerbation of scepticism and confusion about the dietary recommendations.
In conclusion, credibility in nutrition science relies on reinforcing coherence in the messages, particularly those conveyed by academic researchers and journals. Competent nutrition researchers should also invest more time in the public dissemination of dietary priorities in the prevention of cardio-metabolic disease (5) cited by the authors.
1. Mozaffarian D, Forouhi NG. Dietary guidelines and health-is nutrition science up to the task? BMJ 2018; 360: k822.
2. Willett W, editor. Nutritional Epidemiology. Third ed. New York: Oxford University Press 2012.
3. Dehghan M, Mente A, Zhang X, et al. Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study. Lancet 2017; 390(10107): 2050-62.
4. Miller V, Mente A, Dehghan M, et al. Fruit, vegetable, and legume intake, and cardiovascular disease and deaths in 18 countries (PURE): a prospective cohort study. Lancet 2017; 390(10107): 2037-49.
5. Mozaffarian D. Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity: A Comprehensive Review. Circulation 2016; 133(2): 187-225.
Competing interests: No competing interests
Mozaffarian and Forouhi’s long pledge for nutrition science deserves robust comment.(1) As a gastroenterologist, more than three decades ago my colleagues recommended eating wheat as if we were donkeys. Now as a public health advocate, my colleagues recommend eating fruits and vegetables as if we were chimps or, worse, pandas.
Considering the present recommendations, the possible relation between fruit and vegetable consumption with ischemic heart disease mortality is one example among too many. The relationship is characterized by uncertainty because studies are observational, in selected populations, with sophisticated but flawed methods. Eg. the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort surpassed 500 publications, seemingly torturing the data by multiplying post-hoc analysis and cherry-picking variables. This did not preclude hype as one study concluded that “participants consuming at least eight portions (80 g each) of fruits and vegetables a day had a 22% lower risk of fatal ischemic heart disease (IHD) compared with those consuming fewer than three portions a day.”(2) Neverthless, the number needed to diet to avoid 1 death from IHD during 8.4 years is 500 (6.7 deaths per 1000 persons consuming _3 portions of fruits and vegetables per day vs 4.7 deaths per 1000 persons consuming 8 portions per day). Last, adequate policies are still being sought for feasible changes in diet, even in the short-term. For vulnerable populations it remains a dream.
Meanwhile the reality is a nightmare. The Organisation for Economic Co-operation and Development just reported that in its 29 members but Denmark and UK self-reported overweight and obesity in children aged 15 years has been rising from 12.0 to 15.5 from 2001-2 to 2013-4. ( https://www.oecd.org/els/health-systems/Obesity-Update-2017.pdf )
Last, long term adverse effects of diets must not be overlooked. Indeed, recent molecular phylogenetic analyses support the placement of the Giant Panda as basal to the other bears.(3) Accordingly, I prefer to remain an omnivore who eats meat rather than becoming a vegetarian chewing bamboo sticks but sleeping all day long.
1 Mozaffarian D, Forouhi NG. Dietary guidelines and health-is nutrition science up to the task? BMJ 2018;360:k822.
2 Crowe FL, Roddam AW, Key TJ, et al; European Prospective Investigation into Cancer and Nutrition (EPIC)-Heart Study Collaborators. Fruit and vegetable intake and mortality from ischaemic heart disease: results from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Heart study. Eur Heart J 2011;32:1235-43.
3 Flynn JJ1, Finarelli JA, Zehr S, Hsu J, Nedbal MA. Molecular phylogeny of the Carnivora (Mammalia): Assessing the impact of increased sampling on resolving enigmatic relationships. Syst Biol 2005 ;54:317-37.
Competing interests: No competing interests