Background

Cardiometabolic disease risk is complex and diet is one of the key modifiable risk factors that can influence its development and progression. Reductions in the concentrations of TC, LDL-C, triglycerides, and total apolipoprotein B, and an increase in the concentration of HDL are common markers for improved cardiometabolic health.

The traditional Western-style dietary pattern, which is often characterized by higher intake of red and processed meat, along with other dietary components, has been associated with increased risk for cardiometabolic disease in observational studies. However, randomized clinical trials assessing the role of red meat consumption, specifically unprocessed beef, within healthy dietary patterns (e.g., Mediterranean-style and DASH-style patterns) have shown that beef can have a beneficial effect on blood lipid profiles and other markers of cardiovascular health.^1,2,3,4 Beef is a nutrient-dense source of high-quality protein and numerous essential vitamins and minerals, including heme iron, zinc and vitamins B6 and B12. Over the past decade, diet quality and micronutrient intake in the United States (U.S.) have declined or remained below recommended levels, with many Americans failing to meet key nutritional guidelines. Combined with dietary recommendations to decrease the consumption of nutrient-dense animal source-foods, like beef, these declines in diet quality and micronutrient intakes may have unintended health consequences. With a focus on improving nutrient intakes and overall health of Americans, the U.S. Departments of Agriculture and Human and Health Services developed the U.S.-style healthy dietary pattern (HDP), presented in the 2020 Dietary Guidelines for Americans, to encourage a flexible approach to enjoy a variety of nutrient-dense foods. Several previous studies have examined the effects of varying amounts of animal-source proteins within the U.S.-style HDP on markers of cardiometabolic health, yet fewer studies have been conducted to compare healthy omnivorous to healthy “plant-forward” lacto-ovo or vegetarian dietary patterns.

Objective

To assess the effects of a omnivorous U.S-style HDP including two daily servings of lean, unprocessed beef (about 6 ounces) as compared to a lacto-ovo vegetarian U.S.-style HDP (no meat) on short-term changes in cardiometabolic disease risk factors in adults with overweight or obesity.

Study Design

In a 16-week randomized, crossover-controlled feeding trial, 41 adult study participants with overweight or obesity, started with one week of baseline testing (without dietary control), followed by two five-week long controlled feeding periods (either VEG HDP or BEEF HDP in random order), separated by washout period (unrestricted self-selected (i.e., habitual) dietary pattern for five weeks. All meals were provided for study participants for the BEEF HDP or VEG HDP and no food or beverages were provided during the washout period. The BEEF HDP contained two, 3-oz cooked servings of lean, unprocessed beef per day (about 168 g or 6 oz/d) while the VEG HDP substituted the two servings of lean beef for predominantly starchy vegetables and refined grains, such as white potatoes, corn, green peas, green lima beans, plantains, and cassava. Adjustments were primarily made in the dairy and fat intake to match the energy and fat content in both dietary patterns. The researchers chose this approach because refined grains and starchy vegetables, similar to red meat, are generally recommended to be consumed less frequently as part of a HDP.

Both BEEF HDP or VEG HDP provided similar total calories, total fat, potassium, and added sugars. VEG HDP was higher in total carbohydrate, total dietary fiber, vegetable protein, polyunsaturated fatty acids, and sodium, while BEEF HDP was higher in total protein, animal protein, cholesterol, saturated fatty acids, and monounsaturated fatty acids (See Table 1 in publication).

Participants came to the lab a total of 8 times for standardized testing visits: two visits in the week before each intervention (total of 4 visits for the study) and two visits during the last week of each intervention (total of 4 visits for the study). Participants were weighed weekly to monitor weight maintenance. Dietary adherence was assessed by documenting any deviations from the prescribed dietary intervention based on the self-reported menu check-off lists.

Participants completed a dietary satisfaction questionnaire after completing each 5-week dietary intervention. There were 23 questions using a Likert scale, with responses ranging from ‘Strongly Disagree’ to ‘Strongly Agree’ (See Supplementary Table S2 in publication).

• Adopting an omnivorous U.S.-style dietary pattern, with two daily servings of lean beef (BEEF HDP), or a lacto-ovo vegetarian U.S.-style dietary pattern (void of meat, VEG HDP), resulted in a wide variety of improvements in markers of cardiometabolic health in adults who were overweight or obese.
• Both dietary patterns (BEEF HDP and VEG HDP) reduced total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), total LDL particles, dense LDL IV, high-density lipoprotein-cholesterol (HDL), total HDL particles, buoyant HDL2b, apolipoprotein A1, and systolic blood pressure from baseline to the end of the intervention.
• The VEG HDP decreased LDL, glucose, and insulin significantly greater than the BEEF HDP.
• There were no differences between diets or over time for dense LDL III, apolipoprotein B, triglycerides, HOMA-IR, or diastolic blood pressure.
  

• Dietary adherence was high for both HDPs and averaged 89% with no significant difference between the BEEF HDP and VEG HDP.
• The participants’ total diet satisfaction did not differ after consuming the BEEF or VEG HDP interventions.
  
• Blood urea nitrogen was higher, yet still well within normal range, following BEEF HDP compared to VEG HDP, which is consistent with the higher protein intake by the BEEF HDP group.
  

Study Implications

• The overall diet quality is important in defining the healthful of a dietary pattern that supports cardiometabolic health, rather than the absence or presence of individual foods.
• This study demonstrates the inclusion of two servings of lean beef as part of a healthy omnivorous diet can support cardiometabolic health, such as reduced total cholesterol, dense LDL and systolic blood pressure.