Is Dietary Protein Dangerous?

A currently popular diet is a low-carbohydrate diet, often high fat with normal amounts of protein. But some people call low-carb diets high-protein diets. So recent headlines disparaging high-protein diets may cause worry to people on low-carb diets even if they're not eating an especially high amount of protein.

Two examples of such headlines are

High-protein diets boost artery-clogging plaque, mouse study shows.

And Lower-protein diet may lessen risk for cardiovascular disease.

If you just read headlines like this, you might worry that you're eating too much protein.

But we need protein. And as we get older, we need more protein because our muscles tend to lose strength and the dietary protein helps to slow this decline.

So how much protein do we need? A rule of thumb is 0.8 grams of protein per kilogram of body weight, or 0.36 grams per pound. An ounce of meat has about 7 grams of protein.

If you're math-phobic, Jenny Ruhl has a calculator that will estimate how much protein you need on the basis of size and age, and you can find other calculators online. Some use lean body mass, rather than weight, for the calculations because it's muscle mass, not fat, that determines how much protein  you need.

Note that all these calculations refer to a minimum amount needed for good health. Especially if you're getting older, you should eat a little more than the minimum, and recommendations increase to 1.2 to 1.5 grams per kilogram weight or lean body mass. I weigh about 50 kg, and different calculators say I need from 31 to 71 grams of protein a day, so don't take the results as totally accurate.

When I was first diagnosed in 1996, I was told to follow the ADA low-fat diet, which prescribed an average of less than 2 ounces of meat per meal. I felt very deprived and not satisfied. I now try to eat 3 or 4 ounces of meat or other protein per meal, and that satisfies me.

But the real question here is what the authors of the papers I've cited mean by "high protein" or "low protein." The mice in the first study were fed 46% protein. This is indeed high. Normal protein intake in humans is 12% to 20% of calories from protein. And except for people on the Carnivore Diet (nothing but meat), I doubt that many people, even those on low-carb diets, are eating 46% of calories as protein. 

However, with protein, the amounts rather than the percentages are the important factors, because as you reduce one nutrient, like carbohydrate, the percentages of the other nutrients go up even if the amounts stay the same.


In addition, this study was done in mice, and mouse results often don't translate to  human results. In the wild mice eat mostly seeds, grains, and small fruit, although they'll eat almost anything they can get their paws on.

However, people seeing "high protein" and "artery clogging" linked in the headline might cut back on their protein intake and end up protein deficient.

The second study, citing "lower protein diet," focussed on sulfur-containing proteins, and their intake is difficult for the average person to estimate. But again, the headline is misleading. It doesn't refer to sulfur-containing proteins but proteins in general.

And just to confuse patients even more, a 2015 study was titled "High protein foods boost cardiovascular health, as much as quitting smoking or getting exercise."


Nutrition is a very fuzzy science. Many studies are done with food-frequency questionnaires. I sometimes can't remember what I had for lunch, much less how many chicken legs I ate last month. Sometimes people don't mention foods they think are unhealthy. Or they'll overestimate or underestimate the amounts they ate.

So when you see headlines like the ones cited here, take them with a grain of salt (unless, of course, you're on a low-salt diet). If they worry you, try to read the papers themselves to find out what they mean by fuzzy terms like "high protein," and ask your doctor for another opinion.

If you eat real foods, not fast foods or boxed foods, in reasonable portions, you probably have a healthy diet. If your blood glucose and hemoglobin A1c levels are good, you're following a diet that is good for your diabetes. Keep it up and don't obsess about sensational headlines.