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
