Everybody knows you have to eat enough protein.
You need protein to build muscles. That’s why bodybuilders eat so much of it.
You can’t even follow many diets—Paleo, Atkins—without loading up on protein.
So order that steak and boil up some eggs.
And make sure your kids get protein at every meal to nourish those growing bodies.
That’s common wisdom. It makes sense to most of us.
But what if it’s all wrong?
No one but his patients listened to Dr. Ron Rosedale when he put forward the idea that too much protein could be a factor in diseases from type 2 diabetes to cancer.
It was the 1980s, and doctors were unified in condemning fat and split on whether high-carb or high-protein diets were best.
So when Dr. Rosedale’s patients were told to limit carbs and protein—and knock themselves out with healthy fats—they were startled.
Wasn’t fat bad? Wasn’t protein good?
Nearly forty years later, the research has finally come in to support Dr. Rosedale’s novel idea.
You do need protein in your diet, but too much is bad for you.
A 2014 study published in Cell Metabolism shocked the nutritional world by putting hard figures to the dangers of excess protein.
If you’re under the age of 65, you should limit your protein intake to no more than 10% of your total calories…
Or risk a 75% higher mortality rate.
The study found that even moderate meat consumption increases the risk of cancer threefold.
If you love your protein—defined as someone who gets 20% or more of her calories from protein—then you’re 4 times more likely to develop cancer compared to someone who eats little protein. You’re also 5 times more likely to develop diabetes.
Interestingly, that risk goes away if you’re getting your protein from plant sources.
That’s just one study, of course, but it was the tip of an iceberg.
Dr. Roberto Pili and his colleagues wanted to know if eating less protein could slow the growth of tumors in breast cancer and prostate cancer patients. So they carried out a study.
They discovered that not only does eating less protein slow tumor growth, but changing the source of that protein from animal sources to plant sources does, too.
How can that be?
The science is complex, but a simple explanation is that cancer cells are anaerobic. They prefer glucose as an energy source. Not only do carbs provide cancer cells with glucose, but protein does, too.
When you eat more protein than your body can process, the amino acids get converted to glucose. So cutting out sugar won’t starve cancer cells, not unless you limit protein, too.
Fat doesn’t feed cancer cells, and it’s a superior source of fuel according to Dr. Joseph Mercola.
Dr. Mercola was inspired by Dr. Rosedale’s work, and he expands on it in his book Fat for Fuel. He recommends a specific high-fat ketogenic diet for cancer patients, which he calls metabolic mitochondrial therapy.
It’s a story of hormones—insulin, leptin, and insulin-like growth factor—and the Holy Grail of arresting youth.
There’s even evidence to suggest that the only known diet proven to slow down the aging process, calorie restriction (also known as fasting), works by limiting protein.
The idea that there should be a cap on how much protein you consume isn’t as unconventional as you might think.
The Centers for Disease Control recommend just 46 grams of protein a day for women and 56 grams a day for men. Most Americans consume twice that.
So what do 46 grams of protein look like? According to Keck Medicine of USC:
If you eat meat of any kind (poultry, beef or pork) at lunch and dinner, chances are, you’re eating too much protein.”
But what if you exercise a lot? Don’t you need more protein?
The Academy of Nutrition and Dietetics agrees that athletes have higher protein needs, but not enough to justify the use of protein supplements.
If you’re not an athlete—you just work out a couple of times a week—then it’s unlikely you need more.
Dr. Rosedale recommends consuming 0.75 grams of protein per kilogram of lean body mass, which usually works out as between 40 and 70 grams.
There’s one exception to the rule:
If you’re 65 or over, then moderate to high protein consumption will be good for you.
That’s because seniors lose muscle mass as they age, and more protein helps them build it back.
If you’re still not convinced, I’m not surprised. American culture has been pro-protein for a long time. We worry about vegetarians getting enough protein. We worry about our kids getting enough protein. We assume we need protein shakes and protein bars.
But perhaps what we need is more fat.
For the full story, pick up Dr. Mercola’s book.