T Nation

High Protein Diet & Cancer Risk


Sorry, if this has been posted before. I couldn't find a thread.

THURSDAY, Dec. 7 (HealthDay News) -- Eating a low-protein diet may protect against certain cancers, while a diet high in protein may increase the risk for malignancies, a new study suggests.

The results of this preliminary study show that lean people on a long-term, low-protein, low-calorie diet or who participate in regular endurance exercise training have lower levels of plasma growth factors and certain hormones such as insulin-like growth factor 1 (IGF-1). These substances have been linked to an increased cancer risk, especially premenopausal breast cancer, prostate cancer and certain types of colon cancer.

"We know there is a link between nutrition and cancer," said lead author Dr. Luigi Fontana, an assistant professor of medicine at Washington University in St. Louis. "There are certain cancers that are linked with levels of IGF-1, which is an important growth factor that stimulates the proliferation of cells."

If there are high levels of IGF-1, there's a greater chance that mutated cells will become cancer cells, said Fontana, who's also an investigator at Istituto Superiore di Sanita, in Rome, Italy. "We found that people following a low-calorie, low-protein diet have lower IGF-1 than lean athletes who eat a Western diet. This suggests that low protein intake may reduce IGF-1, independent of body weight," he said.

The study is published in the December issue of the American Journal of Clinical Nutrition.

For the study, Fontana's team looked at three groups of people. The first, made up of 21 lean men and women, ate a low-protein, low-calorie, raw food, vegetarian diet. The second group of 21 people did regular endurance running, averaging about 48 miles a week. These runners ate a standard Western diet that included more calories and protein than the first group. The third group included 21 sedentary people who also consumed a standard Western diet, higher in sugars, processed refined grains and animal products.

People in the first group averaged a daily intake of 0.73 grams of protein per kilogram of body weight. The runners ate 1.6 grams, and sedentary people ate 1.23 grams of protein a day. The recommended daily allowance for protein intake is 0.8 grams, Fontana said. That's about three ounces of protein per day for a 220-pound man.

The researchers found that people in the first group had significantly lower blood levels of IGF-1 compared with the runners or the sedentary people. High levels of IGF-1 have been linked to premenopausal breast cancer, prostate cancer and certain types of colon cancer.

In addition, lower IGF-1 levels are associated with increased life span in animals, Fontana noted.

Fontana thinks that if people ate more whole grains, beans, fruits and vegetables and far fewer animal products, they would be healthier. He recommends fish, low-fat dairy products and, occasionally, some red meat. This type of diet reduces total calories and the amount of protein consumed, and it also might result in lower levels of IGF-1.

"Many people in the United States and Italy are eating 50 percent more protein than what is recommended," Fontana said. "If we eat 50 percent more calories than recommended, we become overweight and obese. What happens if you eat 50 percent more protein than required -- we don't know."

He speculated that eating too much protein increases the risk for cancer and also accelerates aging, "but we need more studies to see if my hypothesis is true or false."

One expert also thinks that a high-protein diet increases the risk for certain cancers.

"We recently published a paper that also shows that a high-protein diet is bad for you. It reduces survival; it increases the risk of cancer," said Dr. Dimitrios Trichopoulos, the Vincent L. Gregory Professor of Cancer Prevention at the Harvard School of Public Health's Department of Epidemiology.

In that study, published online in the Nov. 29 issue of the European Journal of Clinical Nutrition, the researchers collected data on the diets of 22,944 healthy adults and found that eating diets low in carbohydrates and high in protein was associated with increased mortality.

Trichopoulos thinks that levels of IGF-1 may be the reason for the increased cancer risk. However, other factors may be at work, he added.

Despite his and Fontana's findings, Trichopoulos isn't ready to recommend a low-protein diet to reduce the risk of cancer or to live longer. Another recent study contradicted this finding, Trichopoulos said. "At this stage, we should wait for clarification," he said.

From Yahoo news

Abstract of study here http://www.ajcn.org/cgi/content/abstract/84/6/1456


Did they do anything to rule out whether it was the fat sources chosen by those they studied considering they were on low-carb diets?

I bet more than half of these people are eating frankenmeats for their protein source.


Oh christ.... I'm thinking that everything but vegetables causes cancer these days.... that is until they do the study that says we can get cancer from vegetables... lol


Did you copy the text below directly or is it your summary? I found a lot of inconsistencies and errors.

First off the logic here is off. If one were to say eating high protein may increase the risk (regardless if this is true or not), you cannot automatically assume eating low protein actually may [i]protect against[/i] cancer. That's a pretty big quantum leap.

Linking a certain level of substances to cancer is one thing, but you need to look at why those levels are high in people to draw any meaningful correlation. For someone who eats a lot of protein, but also eats a lot of junk food and doesn't exercise, then yes the risk may be increased. High protein alone is not enough of a connection.

Not exactly an appropriate set of study groups. How is one to compare protein intake as a link to cancer when the study groups are so varied. All three should have been very similar groups with the dependent variable being protein intake, and maybe activity level. Say the first group be low protein, second be high protein, third be low protein high activity, fourth being high protein high activity.

0.8 grams?? Per pound is what it should say. 3oz a day for a 220lb man? A DAY???? This can't be right.

This sounds less like a protein study and more like a personal vegetarian quest. Plus the results of the study groups are worthless.

"We don't know?" Yes we do. Isn't he supposed to be a doctor?

I can save him time and money. It's false.

What a retarded ridiculous factless study based on hype.

That's all I have to say.


this is retarded. the two major problems with this cluster fuck are:

  1. they are trying to say that higher protein intake increases growth factor levels, which in turn CAUSE cancer. IGF-1 can make cancerous cells proliferate. great. the problem in the train of logic is that they did not show that IGF-1 makes normal cells cancerous. it has been long known that IGF-1 (and other growth factors) make cancerous cells grow, but it hasn't been shown that these growth factors cause cancerous cells.

  2. the experiment with the exercise and diet didn't even come close to try to prove their hypothesis. it reinforced what was already known: that less protein and more endurance exercise lowers growth factors. so what? it didn't show that growth factors cause cancer. either this is a distraction technique by these scientists who have a hidden agenda, or they are some of the least logical people in the world.

oh, and forget the fact that all of these growth factors are actually needed to live.


LOL. Yep.


I copied it directly. altough I'm guessing someone else has done that summary. The full study is available with the link I posted but you have to pay for it.


My sentiments exactly.


I would not worry about one study. If one is eating lean meats, vegetables, whole wheat, using fish oil and regularly doing cardio (basically what is advised on this site) they are probably better off than 90% of the US population in regards to cancer risk from diet even if consuming more protein and higher calories.

If you want to be in the lowest few percentiles for cancer risk and highest few for life expectancy you want to have the physique of a marathon runner, and eat mainly vegetables with little meat.


I think this is a correlation, not a cause and effect situation. Many high protein diets are also very low in fruits and veggies, and thereby lower in antioxidants. Also, heavily cooked meat is higher in carcinogens. So you have a potential double whammy of more carcinogens and fewer antioxidants in high protein diets.

Rather than changing macros radically, eat a wide variety of fibrous veggies, cycle in carbs (since certain fruits and veggies that are higher in sugar/starch are also very high in antioxidants), and taking a daily antioxidant supp.

Oh and of course ensure to get a healthy balance of fat and keep trans fat out of your diet.


These people seem to be overlooking obvious correlations in order to support the viewpoints that the article shows them to have. Mainly, they already believe protein is bad and are trying to show it.

For example, in what I have quoted above, you'll note that most quality carbohydrates are associated with high levels of nutrients and fiber. They are in fruits and vegetables.

Removing those from the diet is likely to be harmful... and it doesn't have to be related to the protein consumption at all.

Then, across various studies, you need to look at the sedentary versus active as well as whether or not the individuals are consuming excess calories to the point of being fat. Being fat is an independent risk factor, for example.

I'll consider believing this type of information when well designed studies show some real causation and not just easy to spot underlying nutritional correlations (which the studies ignore).


Oops, looks like I should have read the whole thread before jumping in, as this has already been pointed out.


I was about to post this. I just read it on MSN.

Personally I feel as if someone in authority hates meatheads and fitness enthusiasts. They are putting out study after study of unfounded bs to try and sway people away from this lifestyle. Perhaps I'm one of those conspiracy paranoid guys, but can you show me one study published on a mass media source helping what we believe?


Let's just assume for a minute that this study is true. Would any T-Nationers give up their high protein diets because of a SLIGHTLY elevated cancer risk. HELL NO, we wouldn't. I know it's been said on this site before, but if we wanted to be just healthy then we would all be vegetarians and walk several hours a day.


You don't even have to eat "lean". Just make sure you eat beef, and lots of it. If you're worried about a heart attack, high cholesterol, or constipation just have a large (2 cups) bowl of oatmeal everyday. It works great at keeping everything in working order for me.


There is credible information that diets low in fruits and veggies are cancer-promoting. Or at least, that fruits and veggies are highly protective against cancer. A high[er] protein diet need not skimp on fruits and veggies. This study here is flawed for the reasons people have stated.


No. Because being vegetarians and just walking several hours a day instead of my current lifestyle would make me less healthy. But I probably wouldn't eat a lower-protein diet because of a SLIGHTLY elevated cancer risk.


Whoever funds these studies needs to be hung.
Here they are doing studies on diets high in protein.
I have seen people who eat high protein diets not eat enough produce.
Maybe that alone will increase their risk of cancer,but it doesn't mean higher protein diets themselves cause cancer.
I'm sure there are more important things to do studies on,like trans fat.


"stress" the silent killer. i agree, you hit the nail etc.

a book titled "the china study" also has much to say about too much protien, with plenty of research behind it. at 59, i'm looking to go soemwhere in the middle, eat less protien than would recommended BUT high quality protien, free range, grass fed, etc. since i'll be consuming less the cost should balance out. also will get protien from whey and some home made protien bars.
could i get some input on store bought protien bars. some of the ingredients look not so healthy to me.


I agree - I think most protein bars are basically crap - full of artificial ingredients, modified/hydrogenated oils, soy protein concentrate (which is hard to digest and not terribly bioavailable)... Real food's always better imo. But that's just me.