So this was in the news today, what are your thoughts?
Looks like Bro Science of the worst order… how many times can he fit in “carbs are essential”
Ask @Dread1840 or follow him on facebook at Carnivore Muscle
There is some degree of truth to the article. It’s true that our bodies prefer glucose for high intensity activities but those energy demands are short term. In the long run our body prefers ketones because it’s more efficient.
The two deceptive studies the author uses to bash LCHF made me roll my eyes. They are classic examples of Big Food, Big Pharma and/or Vegan groups manipulating and/or exaggerating data to better their image.
I think it’s possible of course to build a super body on carbs, at the same time you’re f-ing up your underlying health.
Not related to body building but I trust Dr. Westman’s opinion in his letter to Oxford about carbohydrate, nobody ever accused the Inuit of being fragile weak people. I wonder what they would have looked like after hitting the gym for a while.
Bigger question what kind of carbs are they talking about?
Empty calories? (purely refined sugars (inc. grains/simple carbohydrates), fats or oils made in bulk (extracted with hexane then hydrogenated) for animal and human consumption - not natural)
The other problem; no actual reliable long-term research study concerning longevity has ever been done on a 20/30/50/100 or more gram carb restriction?
”…Can you remember what you ate last year? How standard were your portions? Did you have 5-6 ‘pats’ of butter a week or did it tip over to 1 a day? What’s a pat anyway? Did your diet then stay the same for 20-25 years?..” - Dr. Zoe Harcombe PhD
 Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis: “…Scientists concluded that a 50-year-old person who consumes less than 30% carbs has a life expectancy of 79.1 years, but this rises to 82 years for someone who eats more than 65% carbs…” …More “…There was a U-shaped relationship between carbohydrate intake and mortality in the Atherosclerosis Risk in Communities cohort, a finding that was consistent in the meta-analysis combining these data with those from the other cohorts. When assessing total carbohydrate without regard to specific food source, diets with high (>70%) or low (<40%) percentage of energy from carbohydrates were associated with increased mortality, with minimal risk observed between 50–55%. Low carbohydrate dietary patterns that replaced carbohydrate with animal-derived protein or fat were associated with greater mortality risk, whereas this association was inverse when energy from carbohydrate was replaced with plant-derived protein or fat. These findings were also corroborated in the meta-analysis. …” Source: page 2 of 10
 Low carb diets could shorten life (really?!) - Dr. Zoe Harcombe PhD “…The findings: The findings from Part 1, the ARIC study, were that there were 6,283 deaths during the 25 year follow-up. The conclusion from this part of the study was that 50-55% of energy from carbohydrate was associated with the lowest risk of mortality. The average intake of carbohydrate in the ARIC study was 49%. The paper presented a U-shaped curve to indicate that carbohydrate intake below 30% and above 65% was associated with the highest risk of mortality.
In Part 2, when the meta-analysis pooled together the results from ARIC with seven other population studies, the U-shaped association was observed again. Both lower carbohydrate intake (<40%) and higher carbohydrate consumption (>70%) were associated with higher mortality than ‘moderate’ carbohydrate intake.
Part 3 reported that the results varied depending on the source of macronutrients. It was claimed that mortality increased when carbohydrates were exchanged for animal-derived fat or protein and mortality decreased when the substitutions were plant-based.
The headline that generated so much media attention was a purely statistical calculation in the paper, which resulted in the claim “we estimated that a 50-year-old participant with intake of less than 30% of energy from carbohydrate would have a projected life expectancy of 29·1 years, compared with 33·1 years for a participant who consumed 50–55% of energy from carbohydrate… Similarly, we estimated that a 50-year-old participant with high carbohydrate intake (>65% of energy from carbohydrate) would have a projected life expectancy of 32·0 years, compared with 33·1 years for a participant who consumed 50–55% of energy from carbohydrate .”
I’ll show below how this claim was generated – when we address the biggest issue with the paper.
10 things wrong with this article:
There are a number of issues with all epidemiological studies. The two most important generic limitations are:
- Association does not mean causation; and
- Relative risk is presented when absolute risk is invariably tiny.
All dietary epidemiological studies also suffer from three further limitations:
- The Food Frequency Questionnaire.
- Incomplete adjustment of the data.
- The healthy person confounder.
This particular study then additionally suffers from the following limitations:
- Failure to adjust for a serious confounder (alcohol).
- The small comparator group issue.
- The selection of the reference group.
- The meta-analysis.
- The claims related to food ‘exchanges.’
I’m going to go through each of these issues, with particular reference to this Lancet Public Health paper, to show why the findings of this paper and the headlines can’t be trusted:
1) Association does not mean causation.
Population studies enable us to observe that people who, for example, eat broccoli die older than people who don’t. They cannot conclude that eating broccoli causes you to die older. Equally possible is that people who tend to eat broccoli tend to be generally healthy and therefore tend to die older.
If association is observed, the association should be subjected to The Bradford Hill Criteria to test association (Ref 6). The first test is “strength of the association” – if this isn’t double, or greater, there’s little point looking at any of the other criteria – you aren’t going to be able to claim causation. This brings us to…
2) Relative risk is presented when absolute risk is invariably tiny.
This study didn’t present its claims in the usual way “37% greater chance of dying” – which is a measure of relative risk. It is as if the world has become immune to such headlines. This paper chose a new way of trying to shock the world: “ You’ll die 4 years earlier unless you eat the ‘perfect’ intake of carbohydrate .”
The main paper didn’t present the relative risk numbers. The appendix did, however. The following data are extracted from Supplementary Table 1 from the appendix:
The table below shows: the carb ranges subjectively selected by the researchers (we’ll come back to this); the number of people that ended up in each range; and the deaths that occurred in that carb range during the 25 year follow-up. I have then included the Hazard (risk) Ratio (HR) for the most adjusted model (Model 2). Model 2 adjusted for age, race, gender, which test center the person attended, total energy consumption, diabetes, cigarette smoking, physical activity, income level and education. Please note that Model 2 – the most adjusted model – didn’t adjust for BMI. (It didn’t adjust for something else either, as point 6 will cover).
The Hazard Ratios give us the relative risks. It is claimed that, relative to the group chosen as the reference group (50-55% carbohydrate intake), a carb intake <30% gives a relative risk of 1.37 (37% greater) and a carb intake of >65% gives a relative risk of 1.16 (16% greater). Neither of these “strengths of association” come anywhere close to double and so the possibility of carbohydrate intake being causal in these relative risks can be discounted. We could stop here. However, there are many more issues to note…
The numbers are always reported as relative risk; the absolute numbers are usually not worth getting excited about. In the ARIC study, there were 6,283 deaths among 15,428 adults who were studied for 25 years having been recruited between the ages of 45-64 years. The average age was 54, so an average person would have been 80 at the end of the follow-up period, so survivors did pretty well. The overall death rate in this study was 40%. The annual death rate was 1.63%.
A 37% difference on an annual death rate of 1.63% is the difference between a death rate of 1.38% and 1.88% (Ref 7). That’s the absolute difference and that’s in middle aged people followed for 25 years.
3) The Food Frequency Questionnaire.
Each population study relies for dietary information on a self-reported recall of what one ate some time ago. The paper reported that the ARIC study used the Harvard Food Frequency Questionnaire (FFQ), which was developed by Walter Willett – one of the paper authors – and colleagues. This questionnaire involved asking people how often, on average, over the previous year , they consumed ‘standard portion sizes’ of each of 66 items. Credit to Nina Teicholz for getting hold of the precise questionnaire used in the ARIC study (Ref 8). If you only look at one reference, please let it be this one – there’s nothing like seeing a FFQ first hand. As you can see, there were nine possible responses, ranging from “never” to “six or more times a day.”
Can you remember what you ate last year? How standard were your portions? Did you have 5-6 ‘pats’ of butter a week or did it tip over to 1 a day? What’s a pat anyway? Did your diet then stay the same for 20-25 years? …” …More
I need Help to Rebut a Canadian Nutritionist