Editor’s note: Michael Roussell, Ph.D., the author of this story, is an adjunct assistant professor of nutrition at Penn State University. He is coauthor of a new study, “Type and Amount of Dietary Protein in the Treatment of Metabolic Syndrome: a Randomized Controlled Trial,” published on September 9, 2015 in the American Journal of Clinical Nutrition.
Pursuit of a healthy heart and a fit body are often seen as separate journeys—at least.
For example, if your focus is a healthy heart, most medical and health professionals will advise you to eat a diet that’s low in saturated fat. Specifically, they’ll recommend that you limit your intake of beef and other red meats while telling you to eat lots of whole grains and to enjoy an occasional glass of red wine.
But if you’re in search of a fit-looking body, you’re likely to be told by your personal trainer or ripped gym buddy to eat “meat and vegetables,” and avoid starchy and grain-based carbs—whether they’re whole grain or not. They’re also likely to tell you to swear off liquid calories, save for a whey protein shake after training.
Put simply, one message is to consume less saturated fat by any means necessary, while the other places an emphasis on eating more animal protein.
Interestingly, when it comes to your heart, protein has always been an afterthought, if not a liability. For instance, in 2003, one of the most widely cited nutrition meta-analyses was published.
It looked at the effects of differing amounts and types of carbohydrates and fats on cardiovascular disease risk, across all the previous research that had been done. Protein, however, was never mentioned, except to say that it wasn’t included because there was no information on the impact of protein on heart health.
How could there be no information? Because the previous studies manipulated carbohydrate and fat intake, but always set protein at the same level. That level was the Recommended Daily Allowance, or RDA, which is the minimum amount needed to prevent protein malnutrition—not the optimal intake needed to improve health and reduce body weight.
Protein was simply seen a requirement that you need to hit, like vitamin C intake, and it wasn’t considered that consuming more of the nutrient might have a physiological benefit.
The result: Since protein intake was almost always the same in these studies, researchers couldn’t determine what happened when people ate more protein.
If anything, the medical community has pushed back against fitness world for their love of protein, often by falsely touting the dangers of high protein diets on your liver, bones, and kidneys. (These are all myths fabricated out of rudimentary interpretations of normal processes in your body.) In fact, it wasn’t until the last decade that protein has really even entered the conversation about playing a role in promoting heart health.
The Power of Protein for Your Heart
The focus has started to shift. Population-based studies in the 2000s started finding beneficial associations between protein and blood pressure. The link suggested that plant protein—protein from beans, legumes, and grains—was the driver here.
Unfortunately, it is all too common in the media storm that is now nutrition news to confuse association with cause and effect. So despite what was being reported, there was no actual clinical evidence that plant protein was superior to animal protein for improving heart health.
But at least there was now an incentive to seriously investigate the overall benefits of protein on heart health. So researchers at Johns Hopkins created the OmniHeart study, which pitted the darling of heart-healthy diets—the DASH diet—against modifications of that approach which included a significantly higher consumption of unsaturated fats or protein.
The result: Taking the gold standard of heart healthy diets and adding more protein to it—at the expense of carbohydrates—led to the greatest reduction in estimated 10-year risk of heart disease.
But even though the higher protein diet in the OmniHeart study was a mix of plant and animal protein—eggs, poultry, beans, dairy, seafood, and a small amount of beef/ham—plant protein was still touted as the superior protein choice for a healthy heart. And that’s still the case today, despite more and more clinical studies suggesting that it was total protein—and not the source of protein—that has the greatest effect.
Protein Type: Does it Matter?
Under the guidance of world-renown scientist Penny Kris-Etherton, PhD, RD, FAHA, I ran a feeding study at Penn State University that began to look more closely at the question of protein source. I asked the question: Does the protein source matter if the total amounts of protein, carbohydrate, and fat are the same?
The research group that I was a member of published two papers from this study, which we called the BOLD study (Beef in an Optimal Lean Diet). We found that your heart health improved whether you ate a more traditional heart healthy diet—with poultry as a primary protein source—or a BOLD diet with lean beef as a primary protein source.
The message from this research: You can eat the beef you enjoy most, even daily, if you hit your macronutrient targets. (Our diets were low in saturated fat and high in fiber.) We also found that bumping up your protein from a variety of sources—beef, cottage cheese, turkey, edamame—yielded a greater reduction in blood pressure.
Even with this new research bringing lean beef to the table as an acceptable and equal protein option in a heart healthy diet, it still didn’t answer the question, Is plant protein a superior source of protein for your heart?
And another unanswered question centered on weight loss. All the studies that I have mentioned above were designed to ensure that study participants didn’t lose any weight. That’s because the beneficial effects of weight loss on heart health can cloud the effects of diet on heart health. But would nutritional minutia like plant or animal protein even matter as long as you were losing weight?
Recently, my colleagues and I at Penn State, this time led by Dr. Alison Hill, set out to examine if in fact the origin of a protein—plant or animal—did indeed impact heart health. This time we chose to work with an ever-growing population of people with metabolic syndrome. (Metabolic syndrome is essentially the unholy marriage of heart disease and pre-diabetes.)
Participants in the study were placed on one of the following heart healthy diets: 1) a plant protein diet; 2) an animal protein diet; or 3) an animal protein diet that provided significantly more protein than those in the other two groups.
The plant protein diet contained two-thirds plant protein (soy, beans, legumes, nuts, seeds, and grains) and one-third animal protein (beef, poultry, dairy). The animal proteins diets contained the reverse, one-third plant and two-thirds animal proteins. Counter to most heart healthy diets, the animal protein diets were rich in lean beef, as was the case with our previous BOLD study.
In this new study, the participants traversed 3 different phases of the study over the course of 6 months. These phases included: (1) a rigorously controlled weight maintenance phase; (2) a weight loss phase; and 3) a free-living phase.
During the first two phases, we weighed, measured, and provided the study participants with everything they ate and drank—not including water—for the duration of those phases.
But as the title of the final “free-living phase” suggests, we cut the participants free from the world of weighed and measured food, gave them advice and educational materials on how to maintain the diet they had been eating, and asked them to try their best to stick to the diet and continue their weight loss.
When the last participant had stepped on scale for a final time, and the last vial of blood had been centrifuged and analyzed by the lab, the main finding from this study was very clear: Weight loss is a very powerful factor in fighting metabolic syndrome.
Our study found that as long as you’re hitting key targets such as a moderate calorie deficit (minus 500 calories) and fiber (more than 35 grams a day), eating ample fruits and vegetables (more than 8 cups a day) and losing weight, it doesn’t matter whether your lunch is beef chili or a spinach salad with edamame.
Our findings suggest that, despite beans being the magical fruit, the protein they contain doesn’t have any more heart healthy magic than the protein found in a lean piece of top sirloin.
There are lots of ways to eat a healthy diet and the best one for you is going to be the one that you follow day in and day out.
Personally, I could never survive more than a couple days on a diet that relies on edamame beans and lentils as primary protein sources. I much prefer eggs, lean ground beef, and Greek yogurt. So I embrace my preferences and make them work in a moderate-calorie, nutrient-rich diet.
I recommend you do the same, whatever your protein preferences are.
MENS HEALTH
