Poultry’s status as a presumed “healthier” meat could be coming to an end. People have long assumed that poultry, with lower levels of saturated fatty acids compared with most red meats, would contribute less to cholesterol levels and other factors associated with cardiovascular disease (CVD).
Research results have challenged those assumptions though, and results of a recent clinical trial from researchers at the Lawrence Berkeley National Laboratory, and the Children's Hospital Oakland Research Institute indicates no significant differences between the effects of dietary red meat and chicken on most measures of risk for CVD.
The report, titled “Effects of red meat, white meat, and nonmeat protein sources on atherogenic lipoprotein measures in the context of low compared with high saturated fat intake: a randomized controlled trial,” is published in the American Journal of Clinical Nutrition.
In this trial, the researchers compared the effects of red meat, chicken and vegetable proteins in diets containing high or low total saturated fatty acids (SFA). They randomly selected study 177 participants and divided them into the high- and low-SFA groups. Most of the dietary SFA came from high-fat dairy products, with a smaller portion coming from the meats or vegetable sources.
Within each group (high versus low SFA), participants spent four weeks eating each of the three diets, with blood tests and a two- to seven-week “washout” period between each study period.
The primary outcomes the researchers measured were LDL cholesterol, apolipoprotein B (apoB), small and medium LDL particles, and total/high-density lipoprotein cholesterol.
In this study, LDL cholesterol and apoB were higher with red and white meat than with nonmeat, independent of SFA content. The authors note this was due primarily to increases in large LDL particles, whereas small and medium LDL and total/high-density lipoprotein cholesterol were unaffected by protein source. These outcomes did not differ significantly between red and white meat. Independent of protein source, high SFA compared with low SFA increased LDL cholesterol.
Other key findings include:
- Over the course of the study, there were no significant changes in body weight across protein diets in either the low-SFA groups or high-SFA groups.
- There were significant effects of both dietary protein source and SFA content on total cholesterol, LDL cholesterol, non-HDL cholesterol, and apoB concentrations, whereas the ratio of total/HDL cholesterol was unaffected by these dietary modifications.
- There was a relatively small effect of protein source on HDL cholesterol (“good cholesterol”) with concentrations slightly higher on the red and white meat diets, particularly in the high-SFA arm.
- The cholesterol-raising effect of the meat diets was associated with increases in large LDL whereas small and medium LDL and LDL peak particle diameter were unaffected by dietary protein source. Lipid, lipoprotein, and apolipoprotein concentrations, together with concentrations of large, medium, and small LDL particles, did not differ significantly between the red meat and white meat diets. The authors note that large LDL particles have not been associated with CVD in multiple population cohorts in contrast to the associations observed for concentrations of medium, small, and/or very small LDL
- There were no significant effects of protein source or SFA level on blood pressure, plasma glucose, or endothelial reactivity as assessed by endothelial peripheral arterial tone.
- Importantly, the authors note that “the weaker association with CVD risk of large LDL than of small LDL suggests that the impact of high intakes of red and white meat, as well as SFA from dairy sources, which selectively raised large LDL subfractions, may be overestimated by reliance on LDL cholesterol, as is the case in current dietary guidelines.”
The Researchers note their findings are consistent with previous studies indicating that intake of neither lean red meat nor poultry results in increases in plasma lipid concentrations in a diet low in overall SFA.
The news isn’t all good though. The authors say their results support earlier findings that plant-based, lacto-ovo-vegetarian, or vegan dietary patterns are associated with lower total, LDL (But also lower HDL) cholesterol concentrations than diets including animal protein. This study, though, is the first to show that both categories of meat protein result in LDL concentrations that are higher than those resulting from vegetable protein sources in otherwise comparable diets, and that these effects are independent of dietary SFA level.
Finally, the researchers point out that CVD risk factors outside of the scope of this study could be associated with red meat versus white meat or vegetable proteins, and that processed red meats probably contribute to CVD risk for reasons other than SFA or cholesterol content.
See the full report from American Journal of Clinical Nutrition.
For more information on meat’s role in human nutrition, see these articles from BovineVetOnline: