Discussion
stroke, Heart Disease, OMNI
CVD, STROKE, HEART DISEASE, HEART
In GET-READI, a randomized controlled cross-over feeding trial among 166 African Americans, a reduction in dietary saturated fat intake from 16% to 6%, replaced primarily with carbohydrates, resulted in significant reductions in systolic and diastolic blood pressure and LDL-C concentrations. In contrast, a reduction in dietary saturated fat intake led to a significant 24% increase in Lp(a) concentrations. Therefore, the replacement of dietary saturated fats with carbohydrates generated a discordant response in two highly atherogenic lipoproteins in African Americans. Furthermore, these opposing changes in LDL-C and Lp(a) concentrations were accompanied by small but significant changes in HDL-C (decrease) and triglyceride (increase) concentrations.Plasma Lp(a) levels are mostly genetically determined (The Optimal Macronutrient Intake Trial to Prevent Heart Disease (OMNI Heart) controlled dietary trial was one of the largest studies investigating racial/ethnic differences in Lp(a) response to dietary changes (Effect of replacement of dietary saturated fats with other nutrients on Lp(a) concentrations in randomized controlled metabolic feeding trials. Data are shown as mean percent (%) change in Lp(a) concentration from the average American diet (DELTA 1, DELTA 2 and GET-READI) or the baseline habitual diet (OMNI Heart) to the respective healthy diets that replaced saturated fats with another macronutrient. Percentages under macronutrient names indicate the % replacement of SFA with the corresponding nutrient. Data are from all participants in the DELTA 1 (n = 103, including 26 African Americans) (In the DELTA (In individuals with low Lp(a) levels, a reduction in LDL-C remains an important goal for risk reduction. However, in individuals with very high Lp(a) levels and minor-to-modestly elevated LDL-C levels, an increase in Lp(a) level due to SFA reduction could become an important risk determinant. Under such conditions, more informed and individualized dietary advice would be necessary. Given the high prevalence of elevated Lp(a) (∼20–25% of the population, i.e., ∼1.4 B people worldwide) (A study by Faghihnia The study has some strengths and limitations. We studied a large number of African American men and women recruited in a single geographical location. In the U.S., and particularly in the South, African American individuals disproportionately suffer from CVD and stroke, warranting detailed investigations into risk factors and their responses to treatment modalities. The present study contributes to addressing this issue. The diets tested are based on common food-based eating patterns and are representative of the current guidelines for CVD prevention and management. The findings, therefore, are relevant to the free-living U.S. population. Notably, nearly half of the meals during the entire study period were consumed on-site at the PBRC, which has extensive experience conducting such studies (In conclusion, controlled feeding of a healthy DASH-type diet with a lower SFA and a higher carbohydrate content increased Lp(a) levels by 24% (when compared with the AAD diet) in African Americans. This atherogenic response in Lp(a) levels to dietary SFA reduction is in sharp contrast to the well-known LDL-C lowering effect of dietary SFA reduction. The findings suggest that dietary SFA reduction exerts an opposing effect on the circulating levels of two highly-atherogenic lipoproteins. Future studies are warranted to elucidate the mechanism(s) underlying the SFA reduction-induced increase in Lp(a) levels, responses in Lp(a) atherogenic properties (e.g., cholesterol and/or oxidized phospholipids) to dietary changes, and their roles in cardiovascular outcomes across population groups.