Who decides what we should eat? Usually Government departments advised by scientists and researchers. Here in the UK, that job was entrusted to the Food Standards Agency until recently. And what a mess this body made of giving us science-based information and advice. See here, here, here and here for some examples of the sort of dunder-headed advice the FSA has given the UK public over the years. And just see how the Chief Scientist of the FSA has his assertions about diet exposed as being a largely science-free area here.
In the US, dietary guidelines are set every few years in the form of Dietary Guidelines for Americans (DGA). A set was published earlier this year, and gave pretty much the same advice Americans (and many other nations) have had over the last few decades which is to keep the diet rich in carbohydrate, increase fibre and reduce fat (particularly saturated fat), salt and animal protein.
Anyone who knows anything about my views on diet will know that I wouldn’t sign up to these recommendations (unless, of course, weight gain and impaired health was the goal). And I’m not the only person to feel this way. Recently, a critique of the DGA was published in the journal Nutrition [1]. You can read a full test version of this critique here. The critique is an in-depth and, crucially, science-based take-down of the DGA and much nutritional nonsense spouted by health professionals.
I thought I’d summarise some of its main findings here. The authors of the critique make five broad criticisms of the DGA. Namely that:
1. Research questions are formulated in a way that precludes a thorough investigation of the scientific and medical literature.
2. Answers to research questions are based on an incomplete body of relevant science; relevant science is frequently excluded due to the nature of the question.
3. Science is inaccurately represented, interpreted, and/or summarized.
4. Conclusions do not reflect the quantity and/or quality of relevant science.
5. Recommendations do not reflect the limitations, controversies, and uncertainties existing in the science.
The authors go into plenty of specifics though, with the authors skewering the report’s take on a wide variety of issues including the relevance of saturated fat and carbohydrate in the diet. The DGA recommendations, as expected, demonise saturated fat and exalt the value of a high-carb diet. In fact, the authors of the DGA are down on low-carb diets, and put forward the notion that such diets are likely to be hazardous to our health. The authors of the critique, however, point to the quite-voluminous evidence from intervention studies (studies where the effects of diets are tested in real people) that show that low-carb diets generally out-perform higher-carb, perhaps lower fat diets in terms of their effects on weight and disease markers.
The authors of the critique also draw our attention to the following facts:
1. Standard nutritional recommendations, including those of the DGA, have consistently over the last 30 years urged us to increase our carbohydrate consumption while reducing intake of fat (especially saturated fat and cholesterol).
2. Official statistics show that, over the last 30 years, consumption of total fat, saturated fat and cholesterol has decreased to around or below recommended levels.
3. Carbohydrate intake has increased during this time period, and appears to account for most if not all of the calorie intake increase seen in the US over the last 30 years.
4. Over the last 30 years, rates of overweight and obesity, as well as the rates of type 2 diabetes, have increased dramatically
Perhaps the explanation for all this is to be found in our exercise habits. But the data suggest otherwise: levels of activity have actually increased over the last 30 years too.
So, in summary, here’s what we know:
There is an association between following conventional nutritional ‘wisdom’, specifically the low-fat, high-carb paradigm, and much-enhanced rates of chronic disease including obesity and type 2 diabetes.
The low-fat, high-carb paradigm was never based on any good evidence. 30 years later, though, we have a stack of epidemiological evidence and many intervention studies that this approach does not work, and is likely to be detrimental to health. This recent review reveals conventional nutritional recommendations for what they are: unscientific and ineffective. This critique should be, in my opinion, required reading by all those interested in giving individuals science-based, trustworthy information advice about what to eat.
References:
1. Hite AH, et al. In the face of contradictory evidence: Report of the Dietary Guidelines for Americans Committee. Nutrition. 2010;26:915-924
There is an implicit assumption here that the low-fat message has manifested in low-fat eating behaviours.
This is not borne out in the evidence. To the contrary, the evidence suggests that people have largely ignored the low-fat message, and have simply added additional calories (mostly from carbs).
Under the assumption that macro-nutrition is the locus of the problem, the causative agent here (in terms of obesity, Type2 diabetes) cannot be fats (they have not increased)…but neither can it be low-fats (they have not decreased either). By a process of elimination, this just leaves calories and/or carbohydrates as the causative agents.
Hello Dr Briffa,
The fifth of those links from within your first paragraph references a broken url and fails to find the target.
Did you mean to hyperlink to an external site and if so was it this thread here?
I’ve noticed from my own bookmarks that older links to the blog of the FSA Chief Scientist are returning ‘page not found errors’. Part of the filname has been dropped; it’s the “/roller” part I think.
So;
http://blogs.food.gov.uk/roller/science/entry/lose_lbs_not_s
has become;
http://blogs.food.gov.uk/science/entry/lose_lbs_not_s
Your second link is to your own blog of 6 February 2008 and I remember the thread quite well, particularly the sentiments of ‘Ashley’ who chanced upon the thread while researching a school project.
My own son has just completed some ‘Science in the News’, mock, GCSE coursework, and resit. The whole year perfomed badly and resat! THe students were poorly prepared by their own science department.
I conversed with the teacher and have since placed five concerns firmly in a letter. One concern conscience, enterprising and contemporary research seems not to be rewarded in the marking scheme. Another concern dovetailed with ‘Ashleys’ experience and I cited the thread.
Astronomer Royal, Martin Rees, delivered this years Reith Lecture Series. I’ve been catching up with the podcasts available from BBC Radio 4. In a Q&A session the issue of MPs being generally poorly informed upon contemporary science and it was felt this was a failing. Seemingly to the list of Chief Scientists, we can add examiners, teachers and politicians as those in want of a more contemporary grasp of matters pertaining to ‘science’.
In the present times of austerity I can’t help thinking that if only the consensus upon nutritional advice was better founded then the NHS treatment bill could be so much less.
Henry, in the US, fat consumption as a percentage of calories in the diet has decreased. For the period from 1965 to 1995, the percentage of calories from fat in the typical American diet has decreased from 45% of the total to “about 34%”. (http://www.cnpp.usda.gov/Publications/NutritionInsights/insight5.pdf)
Yet, Americans have also increased total caloric intake, and more are obese. Why? My personal experience is that a high carbohydrate diet increases hunger due to blood sugar spikes, leading to insulin being released to do its job, and a subsequent low blood sugar “crash” that prompts more eating. Perhaps that situation happens with more people.
Good post. Just want add what Walter Willett, Dariush Mozaffarian et al told to dieticians about fats a couple of weeks ago in Boston (in ADA’s conference 2010). “Great Fat Debate” http://bit.ly/gLMLN1
Chris
Thanks for that – link fixed now.
To Frank: Insulin certainly plays role here. Still, I think this is more complicated. There is evidence that some of the major appetite regulating peptides CCK, grehlin and PYY are less supressed by carbohydrates than by protein. It practise, this means that you feel hungrier sooner after high carbohydrate meal than high protein. Then it’s another story if much protein is good for your overall health.
I follow the logic that high carb diets can be disruptive in insulin and I note Barry Sears proposition that glucagon acts in some way like a partner hormone to insulin and balances or assists to regulate its’ effects. (Glucagon is to ingestion and digestion of protein that insulin is to ingn. & dign.of carbohydrate).
I also take the point made in registering the observation that overall fat consumption has decreased yet obesity has risen.
The ‘Ethnographic Atlas’ supports the notion that humans are a species that seem able to adapt to diets of some variance. We thrive in a range of habitats on diets that can vary quite markedly. Some are rich in animal products and rare in vegetable matter, and some are the converse, being wholly or largely vegetarian in nature.
But increasingly large numbers of our species do not live in natural habitats, instead the majority of our species now live in predominantly urban habitats largely of our own making. It is in the habitats of the developed western world that incidence of chronic weight gain and chronic disease seem problematical and resistant to the prescribed remedies.
Are we in danger of missing something? I think Michael Pollan, journalist and author of ‘In Defence of Food’, projects a similar concern. For all that the macro nutrient composition of the diet may be revealing are there other less well debated attributes of the modern diet that could be revealing in the realms of cause and effect?
The quite distinguished human capacity for pre-consumptive process is something that may have determined the evolution of distinctly human attributes during the course of our evolution from australopithecines over 4 or more million years. The long view is of co-evolution with an evolving diet that constituted a slow but incrementally improving energy economy. Our guts could shrink over the course of time and our brains, an energy hungry organ, could grow. There’s a feedback circuit established. Bigger brain; improving capacity for pre-consumptive process, consumption of ‘novel’ and more energy dense foods made possible, improving survival rates, perhaps, and growing brain size. The use of fire for cooking is one big ratchet point in a long and incremental succession of improvements and Prof Richard Wrangham, author of ‘Catching Fire’ Did Cooking Make us Human’, takes up with this aspect. The origins of mechanical (pre-consumptive) process and cooking as applied to the human diet can be traced back over millennia and until recently the basis of our industrial economies relied most predominantly upon mechanical process and heat morphology to produce maost of the goods for trade. The observation, I find, dents slightly the notion that humans are sophisticates.
What distinguishes humans living in urbanised and industrial societies as compared to the peoples living more a traditionally based existence and reported in the Ethnographic Atlas is the extent to which the diet relies upon pre-consumptive process. Moreover, modern urban people do not preserve sufficient mutuality to the way pre-consumptive process is applied. Instead it is often trusted to outside ‘troupes’ or ‘groups’ who have organised themselves into business ventures intent on using process as a means to return a profit. Does it seem that the ability for pre-consumptive process has been taken too far?
Compared to more traditional peoples, I feel, modern peoples are exposed to foods and diets that are:
* too heavily dependent upon starchy ‘roots’ and or cereal derived foods,
* subject to too much process in which important micro nutrients are denuded or removed,
* too low in fibre, particularly soluble fibre,
* do not contain a sufficient component of truly ‘fresh’ foods.
* rely too heavily on foods with shelf lives extended by process,
* and contain fats from the wrong sources that have in turn been subjected to ‘bad’ process.
I particularly feel that the decline of soluble fibre content in modern diets deserves more consideration. I also think that the type and properties of fats is significant, that these have changed over time, and are putting bodily functions under stress. The particular combination of refined sugar, and/or high fructose cereal derived sugars, with refined vegetable oils from seed or cereal sources, seems particularly ‘novel’ in the long succession of human dietary evolution. I find I have not suffered the muscle lethargy associated with my type 2 diabetes, since I ceased consuming ‘healthy’ margarine and have taken more care over the choice of other oils some two years ago.
Nature discourages hoarding. Energy and nutrients must be highly perishable to justify the competition, yet retain adequate horizontal and vertical mutuality that prevails within ecologies. Everything has to be cycled and re-cycled. The best of nutrients are therefore highly perishable. Perishability, however, is an impediment to profit, which is why the food industry is intent upon refining important micro nutrients out of our food.
Hoarding has become somewhat of a problem for humans. The facet is currently highly detrimental to the workings of our economies. And progressing with a read of Chris Harmans’ ‘Peoples History of the World’ I note how he places the arrival of class and social distinctions firmly as a consequence of the arrival of agriculturalist practice based upon harvesting the domesticated grass seeds we now call cereals. Agricultural surplus not only paved the way for the diversification of craft based activities and our developing wider economies but it also permitted the custodians of the stock of grain to become an elitist minority, in some ways similar to todays’ bankers and for similar reasons. Agriculturalism created the opportunity for whole new markets. Dentistry, the market for drugs to manage diabetes, banking, financialism, casino capitalism, and poor quality state sponsored nutritionism come to mind.
Yes the low fat high carb experiment can be considered a big fail!!!! just too bad it impacts so much on people’s lives….and yet they continue to bleat about it on the radio an tv ….feed your kids anything but artery clogging saturated fat..blah blah blah blah..but the real artery clogger sugar gets a free ride.