Dietary cholesterol consumption and its association with low-density lipoprotein levels: a secondary analysis of the DIETFITS weight loss diet study

Background: For decades, advocates for heart health, such as the American Heart Association, have recommended that dietary cholesterol intake be limited in all populations (less than 300 mg/day) due to its supposed association to elevated blood cholesterol levels, especially low-density-lipoprotein (LDL-C). However, while there is a historical basis of evidence for the relationship between dietary and blood cholesterol levels, more recent studies have concluded that the relationship is so weak as to be negligible. This secondary analysis of the DIETFITS study explores the effects of increasing dietary cholesterol intake well above the 300 mg/day cut-point on LDL-C levels. The DIETFITS study was a randomized controlled weight loss diet trial that randomized 609 overweight, otherwise healthy participants into either the Healthy Low Fat (HLF) or Healthy Low Carbohydrate (HLC) diet arms. Participants were followed for 12 months and provided both diet and lipid data at baseline, 3, 6, and 12 months. A secondary analysis was conducted on those participants in the HLC arm to examine whether 12-month change in dietary cholesterol intake had an association with 12-month change in LDL-C levels. Objective: The primary aim of this analysis is to evaluate whether there exists an association between changes in intake of dietary cholesterol and changes in LDL-C levels when dietary cholesterol intake is increased greatly in excess of the historical recommended limit of 300 mg/day. Methods: This secondary analysis included only HLC participants, as they increased dietary cholesterol intake most as they reduced carbohydrate intake. Only participants with complete diet and plasma lipid data at baseline and 12 months (n=208) were included. Descriptive statistics were used to summarize baseline characteristics. 12-month change in dietary cholesterol intake was calculated using diet data collected by three unannounced 24-hour recalls at baseline and 12 months. Lipid data was collected and analyzed at all study time-points. A linear regression model was used to determine the association between 12-month change in LDL-C levels and 12-month change in dietary cholesterol intake (per 100 mg), both unadjusted and adjusted for 12-month change in both saturated fat intake and weight. For descriptive illustration of the data, the 208 HLC participants were also divided into tertiles of 12-month change in dietary cholesterol intake. Results: Without adjustment, for every 100 mg per day increase in dietary cholesterol consumption, LDL-C increased a non-significant 0.36 mg/dL (95% CI: -0.14 to 6.22). After adjustment for 12-month change in saturated fat intake and weight, the association with LDL-C was further diminished to a non-significant increase of 0.014 mg/dL (95% CI: -1.42 to 1.45) for every 100 mg per day increase in dietary cholesterol intake. From a qualitative analysis of the data, those who increased their dietary cholesterol intake most (the highest tertile of 12-month change in dietary cholesterol intake) were accomplishing this via increased consumption of eggs, with a concomitant decrease in consumption of refined grains and sugars. All tertiles, on average, were consuming at or above the previously recommended 300 mg/day limit at 12-months. Conclusion: In the context of a healthy-low-carbohydrate weight-loss diet, increased consumption of dietary cholesterol was not associated with a negative impact on LDL-C over 12 months. Those who increased their dietary cholesterol intake the most ate more eggs and less refined grain and sugars at 12 months. This secondary analysis of DIETFITS provides some guidance for clinicians in advising overweight but otherwise healthy, non-diabetic patients following a healthy low-carbohydrate diet. It informs clinicians that the consumption of over 300 mg of dietary cholesterol per day or consumption of eggs is not likely to be a blood lipid concern for non-diabetic patients in the context of an overall healthy low-carb diet.

Keywords: diet
cholesterol
low-density-lipoprotein
epidemiology
dietary cholesterol
cardiovascular disease
health research and policy
Thesis
Advisor: Gardner Christopher
Luby Stephen