Bacon at breakfast, ham and cheese at lunch and steak for dinner aren’t all that uncommon in the American diet.
Coupled with the enduring popularity of lower-carb diets, which many mistakenly think to mean all protein, all the time, it seems our consumption of meat and cheese continues to increase.
But if you’ve reached mid-life and want to live longer, it’s time to retreat from the meat.
A recent study published in the journal Cell Metabolism found that eating a high-protein diet in middle age could increase the risk of diabetes and cancer.
“Middle-age adults who ate a high protein diet were four times as likely to die from cancer during the 18-year follow-up period.”
Researchers used data from 6,381 U.S. men and women aged 50 and up, participants in the National Health and Nutrition Examination Survey, to analyze the relationship between protein intake, disease, and mortality.
Participants were categorized into three groups:
- High-protein group: 20% or more of daily calories from proteins
- Moderate-protein group: 10 to 19% of their calories from proteins
- Low-protein group: less than 10% of their daily calories from proteins
Results showed that individuals between the ages of 50 and 65 who ate a high-protein diet had a 74% increase in overall mortality compared to those in the low-protein group. They were also more than four times as likely to die from cancer during the 18-year follow-up period.
However, only those who consumed high amounts of animal-based proteins such as meat, cheese, and eggs were affected; those who got their protein from plant-based sources such as beans, nuts, and seeds did not see the increased risk.
Surprisingly, high-protein diets had an opposite effect on those over the age of 65, as older individuals saw a 28% decrease in mortality and a reduced risk for death from cancer.
But regardless of age, the risk of death from diabetes was five times greater for all who ate diets high in protein.
As part of the data for the study, researchers also collected insulin-like growth factor 1 (IGF-1) levels from more than 2,200 participants.
IGF-1 is a hormone in the body associated with growth and development, and high levels of IGF-1have been linked to age-related diseases including cancer, in other studies.
Research has shown that reducing protein intake can lower IGF-1 levels in the body, prompting scientists to believe that incidence of disease and death could be connected to protein consumption.
Analyzing the data showed that for every IGF-1 increase of 10 ng/ml, people on a high-protein diet were nine percent more likely to die from cancer than those on a low-protein diet.
A second investigation was also included in the study where mice were fed either a high-protein or low-protein diet over a period of six weeks.
Despite being implanted with 20,000 melanoma cells, the mice given a low-protein diet showed a lower cancer rate than those on a high-protein diet. The average size of the tumors they developed also tended to be smaller than those of the high-protein mice.
However, when the high-protein mice were changed to a low-protein diet, their IGF-1 levels were lowered by 30%.
Given the results, lead study author Valter Longo of the University of Southern California noted, “Almost everyone is going to have a cancer cell or pre-cancer cell in them at some point. The question is: Does it progress?” [It] turns out, one of the major factors in determining if it does is protein intake.”
He further stated, “The majority of Americans are eating about twice as much protein as they should. It seems that the best change would be to lower their daily intake of all proteins, but especially animal-derived proteins.”
The Bottom Line
There’s no denying that protein is an important part of the diet, but population and clinical studies point to the benefit of eating a mostly plant-based diet.
Interestingly, Dr. Michael Mosley who is credited for the popular 5:2 diet talks about the issue of elevated IGF-1 levels and chronic disease in his book The Fast Diet (see our review here: Will Intermittent Fasting Help Me Lose 15 Pounds & Keep It Off?).
High levels of protein, like the amounts found in a typical western diet, help keep IGF-1 levels high. High protein diets are associated with chronic inflammation and IGF-1, which are in turn associated with increased risk of heart disease and cancer. One of the benefits of intermittent fasting is that it lowers IGF-1 levels.
In what might be the worst timing for a new product launch, this past week, Oscar Meyer launched the P3 Portable Protein Pack. Each pack contains cheese, meat (turkey, ham or chicken) and nuts. Many nutritionists are pointing out that this new snack is just Lunchables for adults. With 20% of your daily sodium and 15-18% of your saturated fat intake, P3 is not the best snack choice. In light of the current study, the combination of meat and cheese is not ideal.
Getting public health officials to convince Americans to eat less meat and dairy is going to be a political challenge. With the issuance of the most recent 2010 Dietary Guidelines for Americans, jointly created by the USDA and Department of Health & Human Services (HHS), the guidelines were criticized because the authors recommended that Americans “choose a variety of protein foods including seafood, lean meat and poultry, eggs, beans and peas, soy products and unsalted nuts and seeds” and “replace protein foods that are higher in solid fats with choices that are lower in solid fats/calories.”
As always, we recommend that your diet feature plenty of fruits and vegetables. Add lean protein sources, but make this the smallest portion of your plate. Choose from a wide variety of protein sources including nuts, beans, fish and poultry. On occasion, enjoy a good steak, but keep your protein intake to well below 20% (e.g., 12% to 15%) of your caloric intake (or about 0.8 grams per kilogram of body weight) and make animal protein a smaller portion of the total. For a 130 pound woman, the target would be around 45 to 47 grams of protein daily.
Here’s the math (to determine kilograms, divide weight by 2.2) for a 130 pound woman targeting 1,500 calories a day:
59 kilograms weight x 0.80 = 47 grams of protein per day
Protein intake of 12% of 1,500 daily calories = 180 calories or 45 grams of protein (180 calories divided by 4)