(This article previously appeared on Grandparents.com.)
Here's a new reason to join the Meatless Mondays (and maybe Tuesdays, Wednesdays, and Thursdays) bandwagon: A new study out from University of Southern California found that eating a diet rich in animal proteins (red meat, chicken, dairy — anything that comes from an animal) during middle age makes you four times more likely to die of cancer than someone on a low animal-protein diet. That's a mortality risk factor comparable to smoking.
There was also a comparable higher risk of overall mortality and diabetes. "Current smokers had a higher chance of dying than people on a high animal-protein diet; former smokers had a lower chance," says study author Valter Longo, the Edna M. Jones Professor of Biogerontology at the USC Davis School of Gerontology and director of the USC Longevity Institute.
The Protein-Age Connection
The reason may be due to a growth-promoting protein called Insulin-like Growth Factor 1 (IGF1), which is important when we are still developing as children, but has been linked to cancer susceptibility as we age. (Animal protein has been linked to the production of IGF1, one of the performance-enhancing drugs New York Yankee Alex Rodriguez is accused of taking.)
"When people consume animal protein — not plant protein — it seems to stimulate IGF1. It is involved in growth, and there are large amounts of it circulating in the blood of infants and teens. Normally that settles down in adulthood. But our data indicates that if you push it artificially through diet, you are increasing your cancer risk. If you mix IGF1 with cancer cells in test tubes, they grow like crazy," says Dr. Neal Barnard, president of the Physicians Committee for Responsible Medicine (PCRM) and an adjunct professor of medicine at the George Washington University School of Medicine and Health Sciences.
(MORE: Is Red Meat Killing You?)
In terms of cancer, the study found that eating less protein was associated with reduced risk of cancer and overall mortality in all people under age 65 and possibly in people over that age who have not lost weight or muscle mass.
Our bodies do need some amount of IGF1, which drops off dramatically after 65, leading to potential frailty and muscle loss. The study found that people over 65 who were losing weight or muscle mass were less susceptible to disease if they ate a moderate- or high-protein diet.
In another recent study, Barnard discovered that eating meat is consistently associated with an elevated diabetes risk, regardless of age. And if you need even more inspiration to cut back on the bacon and steak, a recent analysis of seven studies by PCRM demonstrates that a vegetarian diet reduces the risk of hypertension.
What about the low-carb, high-protein diet that some people swear will cut the pounds? "It may work for some people, but what happens to your health after 30 years? It is a very big risk," says Longo.
How Much Protein Is Enough
The USC study found that "people who received between ten to 20 percent of their calories from proteins were still three times more likely to die of cancer than those who ate a low-protein diet in middle age," says Longo.
Decreasing protein intake from moderate levels to low levels reduced likelihood of early death by 21 percent.
Longo advises eating 36 grams (which equals about 4 ounces) of protein per day per 100 pounds of body weight, which is in agreement with the U.S. Recommended Dietary Intake Allowance. This should be mostly from plant-based sources (so you aren't also getting animal fats), such as legumes (beans, peas, and lentils), whole grains and vegetables. Soy products, such as soymilk and tofu, are also healthy high-protein sources.
However, in agreement with Longo's new study and also with the recommendations of geriatricians, for people over 65, and particularly those who may have lost weight and are frail, the recommendation should rise to about 50 grams of proteins per day per 100 pounds. Most of the protein should be coming from plants, rather than animals; plant proteins were found to be less harmful to health than animal proteins.
Get Started with This Healthful Protein Recipe
One place you can start is looking for new recipes that are vegetarian and beginning to incorporate them into your diet. The recipe below is from the Physicians Committee for Responsible Medicine. Additional recipes can be found at NutritionMD.org.
Stuffed Peppers with Squash, Black Beans and Rice
If you have leftover rice and cooked black beans on hand, this recipe can be made in just a few minutes. Or you can slice up the red peppers, add some shredded lettuce, and make a salad out of it!
½ cup cooked brown rice
1 cup cooked black beans
2 Mexican gray squash or zucchini, diced
6 green onions, sliced
2 teaspoons pepitas (green pumpkin seeds)
2 cloves garlic, minced
1 tablespoon chopped fresh oregano
2 tablespoons apple cider vinegar
Juice of 1 lime
¼ teaspoon sea salt
½ teaspoon freshly ground black pepper
2 red bell peppers, cut in half, cored, and seeded.
Combine the rice, beans, squash, green onions, pepitas, garlic, oregano, vinegar, lime, salt, and pepper in a large bowl. Fill the pepper halves with the squash, rice, and bean mixture. Top with salsa, if using, and serve.
Serves 2 as a main dish or 4 as a side
Per serving: 187 calories, 16 g protein, 54 g carbohydrate, 13 g sugar, 3 g total fat, 14% calories from fat,
16 g fiber, 317 mg sodium
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