By Keir Watson of Rosemary Cottage Clinic
A study of 42 European countries found lower cardiovascular disease and mortality among countries that consumed more fats and animal protein. Higher cardiovascular mortality was linked to carbohydrate consumption. Another nail in the coffin for the diet-heart hypothesis?
Read time Key points: 4 minutes (700 words plus several tasty graphs); Additional analysis: +4 minutes (+700 words)
Controversy over the diet-heart hypothesis rages on: the role of saturated fat, animal products, LdL vs HdL cholesterol levels, statin drugs, low-carb vs low-fat diets… So here is another piece of the jigsaw puzzle that reveals some pretty striking correlations.
The study by a researchers in the Czech Republic was published in Food and Nutrition Research last year but gained little media attention so few in the nutrition community seem to have heard of it. It examined the mean consumption of 62 food items from the FAOSTAT database (1993–2008) and compared these with the actual statistics of five cardio-vascular disease (CVD) indicators across 42 European countries.
The FAOSTAT database compiles the total food consumption by category at a national level. Although it tells us noting about any individuals consumption this data is a robust and reliable method of assessing each countries consumption over all. Its use in this study provides a pretty objective picture and avoids the pitfalls and bias involved in most epidemiological studies which rely on participants accurately recalling personal food consumption over a given period – a notoriously inaccurate affair. So what did they find?
- Cholesterol levels were tightly correlated to the consumption of animal fats and proteins – Countries consuming more fat and protein from animal sources had higher incidence of raised cholesterol
- Raised cholesterol correlated negatively with CVD risk – Countries with higher levels of raised cholesterol had fewer cases of CVD deaths and a lower incidence of CVD risk factors
- Carbohydrates correlated positively with CVD risk – the more carbohydrates consumed (and especially those with high GI such as starches) the more CVD
- Fat and Protein correlated negatively with CVD risk – Countries consuming more fat and protein from animal and plant sources had less CVD. The authors speculate that this is because increasing fat and protein in the diet generally displaces carbohydrates.
The study includes a huge amount of data analysis, which for a sub set of countries spanned three decades, allowing tracking of these correlations over time. Interestingly, in the 1980s there was a brief period when CVD rates correlated positively with fat intake, which the authors speculate may have led to the reinforcing of the saturated fat and heart disease hypothesis, but these trends have long since reversed.
The strongest predictor of raised cholesterol that came from this analysis was consumption of animal fat and animal protein – which includes cheese and meat. (Only graph for men shown, but graph for women is similar)
Note, how closely the points lie along the line. A correlation (r value) of 0.92 indicates that 85% of the variation in raised cholesterol (in men) can be predicted by their consumption of animal fat and protein (primarily meat and cheese)
On the other hand, carbohydrates from cereals and potatoes (i.e. starches) were inversely correlated with raised cholesterol.
The authors state that these results are expected, based on previous studies:
This is in accordance with the meta-analyses of clinical trials, which show that saturated animal fat is the major trigger of raised cholesterol
So far, so good. But how do these correlations translate into cardiovascular health?
CVD Mortality and Raised Cholesterol
As the graph below shows, and contrary to received wisdom, the higher the cholesterol, the lower the CVD mortality:
Whilst many people would find this surprising, being the exact opposite of what we are all told, the authors explain:
The negative relationship between raised cholesterol and CVD may seem counterintuitive, but it is not at variance with the available evidence. The largest of the recent worldwide meta-analyses dealing with cholesterol and CVD risk observed a positive relationship between raised cholesterol and CVD mortality at younger ages, but this association gradually started to reverse in seniors, where the number of deaths is the highest. . .