We were wrong about cholesterol

It seems we have been wrong in regards to saturated fat and high cholesterol increasing our risk of heart disease. We have been advised to eat carbohydrate and reduce our intake of saturated fats for over 50 years- and yet Cardiovascular diseases (CVD) are the number 1 cause of death globally. More people die annually from CVDs than from any other cause and an estimated 17.7 million people died from CVDs in 2015, representing 31% of all global deaths. Of these deaths, an estimated 7.4 million were due to coronary heart disease and 6.7 million were due to stroke. Only recently are we starting to see studies that are raising the question of whether the current dietary guidelines are optimal for population health. Below are just a few of the recent studies that indicate that a high carbohydrate diet is not optimal for cardiovascular health.

A recent study investigating the mean consumption of 62 food items from the FAOSTAT database (1993–2008) and compared them with the actual statistics of five CVD indicators in 42 European countries. It was reported in this study that the common denominators of high stroke mortality were cereals, sunflower oil, distilled beverages, and carbohydrate alcohol energy. The common predictors of low stroke mortality in all the examined years were bananas, oranges and mandarins, coffee, dairy, animal protein, and total fat and animal protein. Stroke mortality correlated highly negatively with life expectancy and GDP per capita. (1) The most interesting finding of this study is that the highest CVD prevalence can be found in countries with the highest carbohydrate consumption, whereas the lowest CVD prevalence is typical of countries with the highest intake of fat and protein. In addition a 2012, a meta- analysis on 23 studies reported that low carbohydrate diets had favourable effects on weight loss and also cardiovascular disease risk factors (2).

A small 2014 study had 16 participants put on a tightly controlled diet of fats and carbohydrate. The participants were on their own high-carb, low-fat diets before entering the study. For the first three weeks of the study, they doubled or tripled their saturated-fat intake, consuming 84 grams of saturated fats, and 47 grams of carbs per day. Researchers found no jump in the levels of saturated fat in the blood during this phase. After the initial phase participants decreased the fat and increased their carb intake every 3 weeks, ending the study on a diet of 32 grams of saturated fat and 346 grams of carbs per day. The final phase of the study modelled U.S. dietary recommendations for carbs and included whole grains. The purpose was to assess whether carbohydrate was being turned to saturated fats. Although saturated fats did not increase; one type of fatty acid, palmitoleic acid, did increase over time. Palmitoleic acid in blood or adipose tissue is detrimental and associated with obesity, inflammation, metabolic syndrome, type 2 diabetes, coronary disease, heart failure, and some types of cancer. It would seem that results from this study indicate that a high carbohydrate intake is associated with the accumulation of Palmitoleic acid in the blood, a driver for an increased risk of heart disease (3).

It may be argued that a high fat, low carbohydrate diet has been associated with increased LDL cholesterol levels. Whilst this is true it would seem that most people consuming a low carbohydrate, high fat diet, report that LDL levels tend to go up, triglyceride levels tend to go down and total and HDL cholesterol tend to remain the same or rise slightly. LDL particle size tends to increase and LDL particle numbers tend to decrease. However there are a small number of people who consume low carb, high fat diets that will experience increased cholesterol levels, including increases in Total and LDL cholesterol as well as increases LDL particle number. We believe that high LDL cholesterol is associated with increased risk of CVD for a number of reasons and there is evidence of a correlation between high cholesterol/LDL levels and heart disease. The Framingham Study, a large cohort study published a paper in the late 70’s reporting that higher HDL levels and lower LDL levels were associated with a reduced risk of coronary heart disease (4).  However a follow-up from the initial Framingham study suggested that there was only an increase in mortality, by heart disease or other causes, in people with higher cholesterol levels under the age of 50 years (5).  This is significant and should not be excluded if we want to offer medication or lifestyle advice about preventing heart disease to those over 50 years old. Also of interest is a 2016 systematic review concluding that those over 60 years lived longer if they had higher LDL levels (6).

The whole cholesterol/ heart disease connection has been over simplified and total cholesterol is a very crude outdated measurement according to cardiologist Dr William Davis. Small LDL particles are present in the blood for 7 days and are prone to oxidation. Small LDL particles are what we want to avoid as they are adherent to artery walls and form atherosclerotic plaque. Large LDL particles, in comparison, are more benign, persist for a much shorter period of time and are less oxidation-prone, less adherent. What is more interesting is that smaller LDL particles are produced by carbohydrate intake and larger LDL particles from consumption of fats.  Furthermore it is now known that LDL cholesterol is a poor marker of CVD risk. For example a large 2009 study analysed data from 136,905 patients hospitalised for a heart attack nationwide between 2000 and 2006, whose lipid levels upon hospital admission were documented. This accounted for 59 percent of total hospital admissions for heart attack at participating hospitals during the study period. Among individuals without any prior cardiovascular disease or diabetes, 72 percent had admission LDL levels less than 130 mg/dL, which is the current LDL cholesterol target for this population (7).

I find it interesting that the predominant  argument against low carbohydrate, high-fat diets are concerns regarding saturated fats and cholesterol, yet randomised clinical trials don’t strongly support any adverse effects. In fact, reducing carbohydrate intake has shown beneficial effects in numerous studies, and often outperform other diets when comparisons are made. It is another reminder that we should always question the advice of medical practitioners as they are rarely trained in nutrition, and are informed by dietary guidelines. These same guidelines should be formulated based on recent research, however this is not always the case.