Are You Getting Enough Protein? Too Much?
How obsessing over protein could be harmful to your health
If you’re like me, you often find yourself confused by how many health headlines contradict one another. Lately, I’ve found this to be true where protein is concerned, particularly the protein needs of adults aged 50 and over.
In one study, published Jan. 1, 2015 in the American Journal of Physiology’s Endocrinology and Metabolism, scientists split 20 adults aged 52 to 75 into one group that consumed the U.S. RDA recommended level of protein, and another group that consumed double that amount, measuring levels of whole body protein at the beginning and end of the trial. While both groups maintained a positive protein balance (their bodies synthesized more protein than they broke down), the higher protein group ended up with a higher overall protein balance than the lower protein group. The news media jumped all over this, proclaiming that older adults should double their protein intake if they want to live long, healthy lives.
This caught my attention because it ran rather contrary to the findings from a study published in the March 4, 2014 issue of the journal Cell Metabolism. In this study, scientists found that higher animal protein consumption was linked with higher rates of cancer, diabetes and all-cause mortality — but only for those aged 50 to 65. For adults 66 and over, the trend reversed itself, with a higher protein diet (whether from plant or animal sources) seeming to offer some protection. Despite these split results, the media proclaimed that meat was as dangerous as smoking.
Muddying the Waters
Finally, last month I picked up a copy of Proteinaholic: How Our Obsession With Meat Is Killing Us and What We Can Do About It, by Howard Jacobsen and Dr. Garth Davis, a top weight-loss surgeon and co-star of the 2007-'08 reality medical series Big Medicine.
As he relates in the book, Davis used to count himself among the high-protein, low-carb advocates — he even encouraged a high-protein diet in his first book, The Expert’s Guide to Weight Loss Surgery. But over time, the ill effects of that high protein diet on his health and that of his weight-loss patients forced him to re-examine his beliefs. Looking for answers, he spent the next several years scouring the scientific literature. The summary of what he learned became the book, Proteinaholic.
But I still wanted clarity about all the seemingly conflicting research.
Hashing It Out
I asked Davis about the other two studies. He said the first merely showed that if you eat more protein, your body will process more protein, but that means nothing in the real world. “Other studies show no functional difference between adequate protein intake and higher protein intake for either strength or muscle retention,” he said.
Study author Il-young Kim conceded that no direct correlation could be drawn between the higher protein diet and improved muscular function. However, he referred me to a 2015 cross-sectional study which examined data gathered between 1995 and 2001. In that study, older adults who consumed the most protein had greater leg muscle mass and strength than those who consumed the least protein.
Davis said that exercise is, in fact, the real key to maintaining strength, muscle mass and healthy function as we age. In other words, sedentary individuals should not expect to avoid the effects of age-related sarcopenia (loss of muscle mass) just by eating a diet higher in protein.
Indeed, research by Purdue University scientists and others have demonstrated that in adults over 50 who exercise, consuming protein above the U.S. RDA values offers no significant benefit.
More Beneficial for Those Over 65?
What about the study that showed a correlation between higher protein consumption and decreased mortality rates later in life? Davis said the findings for both age groups were only correlational, and didn’t show a true cause-and-effect relationship between protein consumption and mortality. He explained that many variables could have affected mortality rates in either group, and that direct levels of protein consumption weren’t measured; rather, estimates were made based on 24-hour dietary recall.
Study author Valter Longo confirmed that was the case, but stressed that insulin-like growth factor (IGF-1) levels were also measured, which would have helped to more accurately estimate protein consumption. He also said the study did control for many of the other variables that could have affected mortality rates.
But why would protein be detrimental to health up to a certain age and then become protective?
General malnourishment and frailty may be the culprits, Longo said. Beyond age 65, Longo noted, people typically begin to lose a little of their body weight every year, increasing the risk for malnourishment and illness. In the study, low protein in the diets of those 66 and older may have simply been indicative of malnourishment in general. Longo also said that sick, frail people may not feel like eating or not be likely to pay attention to their diet, so the low protein consumption could have been the result of illness, and not the other way around.
He acknowledged the limitations of correlational epidemiological studies (such as this one) to pinpoint exact causes. Longo noted, however, that he and his colleagues were convinced that adults over 65 need to focus on eating a diet meeting all of their nutritional needs and that getting adequate protein is essential.
But What Does “Adequate” Mean?
When I asked Davis how much protein is optimal for 50+ adults he said, “I hate that question!”
He urges his patients to eat the way he does, focusing on healthy whole foods rather than getting bogged down in the individual nutrients.
“Each person’s case is different,” Davis said. He added that the U.S. RDA guideline for protein consumption — 0.8 grams of protein per kilogram of bodyweight per day — has been well tested, and the totality of the science shows those amounts to be more than adequate for 97 percent of the population, regardless of age. As long as you’re getting enough calories to maintain weight, you’re almost certainly getting enough protein, he said. Most people get more than enough. (Calculate your own approximate protein needs with this online tool.)
Can Too Much Protein Be Harmful?
The subtitle of Davis’ book, How Our Obsession with Meat Is Killing Us and What We Can Do About It, suggests that we should be as worried about protein overconsumption as we are about potential deficiencies. He spends 91 pages citing hundreds of studies that have shown a correlation between meat-heavy diets and obesity, diabetes, hypertension, cardiovascular disease, cancer and all-cause mortality.
The evidence was enough to convince me that prioritizing protein in the diet probably is harmful. This was a reversal for me; I even wrote a section about higher protein diets in my own weight loss book.
While I’m not convinced that it’s necessarily the protein itself that is harmful, when we consume more protein than we need, we do so at the expense of, or in addition to, other nutrients. When we crowd out healthy fruits, vegetables and whole grains by loading up on protein-heavy foods, we lose out on the well-documented protective benefits those foods have to offer. And when those protein sources come from animals, we are often getting as many or more calories from fat as protein.
By over-focusing on protein, we may simply end up consuming more total calories, which leads to weight gain.
The great myth of all diets is that swapping out calories from one source for those from another will somehow magically rev our metabolism and help our bodies burn more fat. But numerous studies have shown that it’s the number of calories we eat — and not whether those calories come from protein, carbohydrates or fat — that matters.