Food Consumption and the Actual Statistics of Cardiovascular Diseases

This 2016 paper analyzes the relationship between 62 different food items and cardiovascular risk. The data for the study came from the WHO’s FAOSTAT database, which offers “free access to food and agriculture data for over 245 countries and territories.”

The relationship between nutrition and heart disease remains a subject of debate. Recent meta-analyses challenge the role of saturated fat as a driver of cardiovascular risk (1). The results across various studies are highly varied, at least in part due to fundamental flaws in the methodologies used to study the relationship between diet and disease. Randomized controlled trials are generally too short to directly assess the impact of dietary factors on heart disease and therefore can only track the impact of diet on biomarkers (such as cholesterol levels) that may or may not accurately predict disease risk. Observational trials generally rely on survey-based methods, which, as previously discussed on CrossFit.com, fail to accurately assess what individuals actually eat. Thus, neither trial design provides an accurate assessment of the direct relationship between dietary intakes and disease incidence.

The group behind this study instead used economic data, drawn from the FAOSTAT database (2). This database tracks food production, imports, exports, and nonfood uses across 42 European countries; the sum of production plus imports minus exports and nonfood uses provides an estimate of food consumption. The surveyed countries varied dramatically in diet and socioeconomic status, with annual per capita health-care expenditure ranging from less than $500 (Moldova, Azerbaijan, Armenia) to over $5,000 (Norway, Luxembourg). Cardiovascular disease and risk factor statistics were drawn from two large surveys (3), also drawn primarily from WHO databases.

Many of the relationships between dietary factors and specific biomarkers were in line with mainstream dietary beliefs. The dietary factors most strongly correlated with elevated total cholesterol levels were animal fat and animal protein; the dietary factors most strongly correlated with lower total cholesterol levels were cereals. Cholesterol was significantly higher among countries where a larger share of calories came from animal sources and lower among countries where a larger share of calories came from plants. Higher cholesterol was also associated with higher total calorie intake.

Significantly, the relationship between these same factors and either heart disease mortality or total cardiovascular mortality (i.e., including stroke) was reversed. Total fat and animal protein were strongly associated with reduced cardiovascular mortality in both men and women. Conversely, the share of energy from plants and/or carbohydrates was associated with increased cardiovascular mortality. The magnitude of the protective effect of increased animal fat and protein consumption on cardiovascular mortality was similar to that of the association between increased health-care expenditure and cardiovascular mortality.

Total animal fat and protein were similarly correlated with both reduced blood pressure and reduced fasting blood glucose in both men and women.

Taken together, these results are at once consistent and inconsistent with widespread dietary guidelines related to diet and heart disease. This economic data suggests increased intake of animal fat and animal protein is associated with increased cholesterol. However, this increase in cholesterol does not translate to an increase in heart disease risk. Conversely, increased consumption of plant foods and cereals is associated with lower cholesterol levels, but this change does not protect against cardiovascular disease.

The results of this study are consistent with the hypothesis that total cholesterol fails to predict heart disease risk. They also suggest foods that increase blood glucose levels may increase heart disease risk. Diets that reduce total cholesterol levels, such as plant-based, low-fat diets, tend to increase plasma triglyceride levels and reduce both LDL and HDL cholesterol levels. These changes correlate with a more atherogenic lipid profile characterized by smaller, denser LDL particles (4).

It is important to note many of the usual caveats governing observational research apply to this study. For example, the relationship between increased animal fat and protein intake and reduced cardiovascular risk may not represent a true direct relationship; it could instead be the result of a confounder associated with both variables (and vice versa for the relationship between carbohydrate intake and increased cardiovascular risk). It is possible that in this study, increased animal fat and protein intake correlated with increased health-care expenditure, suggesting both markers are indicators of national economic development. The authors note, however, that the relationship between intake of animal foods and reduced cardiovascular risk was present throughout the sample; conversely, low health-care expenditure was only associated with increased cardiovascular risk when per capita spending was below US$2,000, above which increased spending conferred no further benefit.

Due to potential confounders, this study cannot be used as evidence to directly argue increased consumption of animal protein and animal fat is protective against heart disease, or that increased consumption of plant foods increases heart disease risk.

These results do, however, bring into question the value of public health guidelines that claim a reduction in animal fat and protein intake will reduce heart disease risk. At minimum, the direct association between increased intake of animal foods and increased heart disease risk argued in previous studies may result from confounders rather than a true association. Alternatively, these results are consistent with the hypothesis that animal foods increase cholesterol levels without increasing heart disease risk, which undermines one of the fundamental pillars of the diet-heart hypothesis.

Figure 1: Relationship between animal fat and protein consumption and prevalence of elevated cholesterol levels in men

Figure 2: Relationship between total fat and animal protein intake and total cardiovascular mortality in women

Figure 3: Relationship between per capita health-care expenditure and total cardiovascular mortality in women

Notes

1. A systematic review of the evidence supporting a causal link between dietary factors and coronary heart disease; Dietary fat and coronary heart disease: summary of evidence from prospective cohort and randomised controlled trials; Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease; Association of dietary, circulating, and supplement fatty acids with coronary risk; Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies; Effect of the amount and type of dietary fat on cardiometabolic risk factors and risk of developing type 2 diabetes, cardiovascular diseases, and cancer: A systematic review
2. Major correlates of male height: A study of 105 countries
3. European cardiovascular disease statistics 2012; Cardiovascular disease in Europe: epidemiological update
4. Low-density lipoprotein size and cardiovascular risk assessment; Effects of low-carbohydrate diets versus low-fat diets on metabolic risk factors: a meta-analysis of randomized controlled clinical trials; Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: A meta-analysis of randomised controlled trials