Is Eating High Amounts of Animal Protein Really as Bad as Smoking?

A new study suggest that eating high amounts of animal protein in middle age can in some senses be as bad for your health as smoking, but why is this and how should we react to this research?

The study, published this month in the journal Cell Metabolism, is making headlines for purporting to show that people who consume a lot of protein between the ages of 50-65 are almost 74% more likely to die as a result of cancer, diabetes and other such health problems. However, the risk was significantly less if study participants consumed plant protein rather than animal protein.

As with all studies of this nature, this finding is proving controversial — yet, to understand it properly, let’s delve into the research.

What Did the Researchers Find Out About Age and Protein Consumption?

Conducted by researchers from the University of Southern California, scientists monitored 6,381 adults over the age of 50 years old, with an average age of 65, by analyzing data from the National Health and Nutrition Examination Survey (NHANES) III, a nationally representative US health and diet study.

To understand the study, it’s important to know how much protein researchers classed as a high amount. The study says that high protein levels would be about 20% of someone’s daily calorie intake. A moderate diet would be about 10-19% protein, and a low protein diet would be under 10%.

Researchers found that eating a so-called high-protein diet during your 50s appears to make you four times more likely to die from cancer or diabetes. The data suggests high animal protein consumption also doubles general disease mortality rates over the next 18 years of a person’s life. Even moderate consumption of protein seemed to predict a three fold chance of dying of cancer.

Crucially though, those numbers were all virtually wiped out if the protein source was plant based (soy in this study) rather than animal based.

Another interesting aspect to this study was that the researchers found that in older age participants, mortality rates decreased among those with high (animal/plant) protein intake. In those aged 65 and over, high protein intake resulted in a 60% reduced risk of mortality from cancer. It also reduced the overall mortality risk by about 28%. Moderate protein intake gave similar results. The exception was in diabetes risk where a low protein diet appears to be beneficial throughout middle to old age.

Why Might Animal Protein Cause This Problem, and Why are the Effects Different as we Age?

The researchers speculate that the negative health impact of a high protein diet may be the fact that animal protein carries amino acids and growth hormones that, other research has shown, can make us more prone to cancers and certain other diseases, but that’s controversial and by no means is this research conclusive.

However, the researchers believe they can explain the seeming discrepancy between protein impact at middle age and old age.

While in our 50s, our bodies can still usually process protein fairly well. but as we age our bodies can’t process protein properly, meaning we have to eat higher amounts in order to fulfill our protein needs and stay healthy. This might explain why a high protein diet in old age might be beneficial. The researchers believe this points to the fact that while, for instance, low-carb diets can give quick weight loss results, we may have to think about our longer-term management dietary needs and even that we should be prepared to change our diets as we get older.

“There’s a misconception that because we all eat, understanding nutrition is simple,” study author Valter Longo, a professor of gerontology and biological sciences at the University of Southern California, is quoted as saying. “But the question is not whether a certain diet allows you to do well for three days, but can it help you survive to be 100?”

So is Eating Meat Really as Bad for You as Smoking?

Here’s where the sensational headlines come in: if the high animal protein and high mortality link does hold up under further research, it would mean a diet high in animal meat would carry roughly the same cancer risk as smoking. However, while in pure numbers that might be true, these kinds of comparisons don’t work because smoking and actual food consumption are very different things. We can say with nearly complete certainty that smoking in and of itself is a very harmful thing to do, whereas eating meat cannot be maligned in that way because very few people, if any, solely subsist on meat.

It’s also important to know that this study has some fairly serious limitations.

For instance, it appears from the data that “animal protein” is a catch-all and that the research doesn’t distinguish between, for instance, intake of red meat over white meats, or particular meat sources like beef or pork. We’ve known for a long time that for the average person reducing red meat consumption can provide real health benefits, whereas white meat, and particularly fish, has been associated with a healthy diet. This research does not chip away at that.

Technical aspects like that aside,  this is the first observational study on this issue and therefore it creates a hypothesis that needs to be tested in the future. Therefore, radically changing our eating habits on this basis alone isn’t recommended.

However, as pointed out above, general medical advice does suggest that reducing red meat consumption can be beneficial and a varied diet is more likely to give you a complete nutritional profile. With that in mind, if you are looking for alternative protein sources, Care2 has some great options for you to try. You might want to skip the quinoa, though.

Photo credit: Thinkstock.


Jim Ven
Jim Ven3 months ago

thanks for the article.

Carrie-Anne Brown

thanks for sharing :)

Oleg Kobetz
Oleg Kobetz2 years ago

Thank you

Greg Blome
Greg Blome2 years ago

Here is my breakdown of the study:

Rainbow W.
.2 years ago

IGF-1 deficiencies are well known. Laron syndrome is a rare genetic disorder affecting approximately 300 people in the world, a third reside in the remote mountainside villages of southern Ecuador. This is a very small population and we are unsure WHY they have low rates of diabetes and cancer.

There is also an ethical violation. The lead researcher is Valter Longo. He created a company called L-Nutra. []”Valter Longo (Professor of Gerontology) is the founder of L-Nutra and serves as the Chairman of the Scientific Advisory Board. L-Nutra's first diet to nutritionally manage disease stems from 15 years of research by Prof. Longo at USC.”

Just more snake oil salesmen.

Rainbow W.
.2 years ago

High IGF-1 is not associated with cancer risk. The PCRM would like to make us think it is. “From the data presented for the cancers associated with IGF-1, this is clearly not the case. For prostate cancer, the odds ratio for all cohort studies was 2•43, whereas for all case-control studies it was 1•43; corresponding odds ratios for premenopausal breast cancer were 2•08 and 1•68, respectively (no case-control studies were included for colorectal cancer). The conclusion that stronger associations were found in case-control studies seems to have been derived from an analysis that included cancers not associated with IGF-1 concentrations. There is little compelling evidence that tumour-derived IGF-1 can increase circulating concentrations as suggested. However, the progressively deteriorating nutritional and metabolic status of patients with cancer results in declining IGF-1 concentrations, which could attenuate any associations with cancer risk in case-control studies.”

Basically they are seeing a correlation when there is none.

Rainbow W.
.2 years ago

AnnieLaurie B. is correct. But I’ll elaborate.

I have long since disregarded questionnaires in studies. This was the NHANES III, a very flawed one. []” Across the 39-year history of the NHANES, EI data on the majority of respondents (67.3% of women and 58.7% of men) were not physiologically plausible. The confluence of these results and other methodological limitations suggest that the ability to estimate population trends in caloric intake and generate empirically supported public policy relevant to diet-health relationships from U.S. nutritional surveillance is extremely limited.”

Another problem with questionnaires is the assumption that the individual understands the questions and has no cognitive or developmental disabilities. Considering that a number of individuals who volunteer for research need the money they will tell the researcher what they want to hear. And then you have those odd ones who are “addicted” to studies and travel to participate in them. This really throws a monkey wrench into the validity of questionnaires.

While Cox Proportional Hazard models have become the standard, many do not know how to use them properly or use them in the wrong setting. Using the model with data generated from questionnaires is useless.

Christine W.
Christine W.2 years ago

Thanks for sharing :)

Rhonda B.
Rhonda B.2 years ago


Rhonda B.
Rhonda B.2 years ago