Does a High Protein Diet Weaken Your Bones?



“Ever since my wife heard your episode on the benefits of protein for preventing muscle loss as you get older, she’s eating more eggs, meat, and fish, especially at breakfast and lunch. But doesn’t a high protein diet weaken your bones? Do we have to choose between strong muscles and strong bones once we get past middle age?”

Actually, it’s just the opposite, Ely: Protein contributes to strong muscles AND strong bones.

Does Protein Cause Bone Loss?

The concern about protein and bone health may stem from the fact that when you increase your protein intake—especially from animal sources—the amount of calcium in your urine goes up. The assumption has always been that this urinary calcium was being taken from the bones in order to buffer the acid residue that remains after digestion of meat and other animal products.

Obviously, if something you are eating is regularly causing the calcium to leach out of your bones and into the toilet, over time this is going to be very bad news for your bones. However, this is not at all what is happening.

As I’ve talked about in previous episodes, only a fraction of the calcium from foods is absorbed by the body. You may absorb as little as 5% of the calcium in spinach or as much as 60% of the calcium in your broccoli. But most of the calcium in the foods you eat passes through your system unabsorbed. When you increase your protein intake, something very interesting happens:  Your body starts absorbing more calcium from your food.

It turns out that almost all of the extra calcium in the urine when you increase your protein intake is due to increased intestinal absorption of calcium. Very little is coming from your bones. And this probably explains why people with higher protein diets do not, in fact, have higher fracture rates or lower bone mineral density.

Eat More Protein for Stronger Bones

Just this month, a group of researchers from Harvard published data from more than 100,000 men and women that were followed over the course of more than 30 years. Among the men, the risk of fracture went down as protein intake (from any source) went up. Among the women, total protein intake didn’t seem to affect risk positively or negatively. But higher intakes of plant-based and dairy proteins reduced the risk of hip fracture. Earlier this year, researchers assessed a group of 750 women in their 60s and found that higher protein intakes were associated with increased bone strength.

And most recently, researchers writing in the American Journal of Clinical Nutrition compiled the results from 36 different studies looking at the effect of protein intake on bone health. This meta-analysis also found no evidence that higher protein diets endanger bones and some evidence that higher protein diets actually protect against bone loss.

A diet that is too low in protein actually appears to be a much bigger threat to bone health than one that higher in protein.

How Much Protein Do You Need?

A diet that is too low in protein actually appears to be a much bigger threat to bone health than one that higher in protein. The recommended daily allowance for protein is 50 grams per day. However, there is a growing chorus of scientists calling for increasing that recommendation to 75 or even 100 grams per day in light of recent evidence—especially for people over 50.

The good news is that most Americans are already getting between 75 and 100 grams of protein per day. And, as I talked about in a previous episode, you can get more benefit without actually increasing the amount of protein you’re eating simply by spreading it out more evenly throughout the day, rather than eating most of it at dinner time.

Want Strong Bones? Eat Your Vegetables

Of course, there are many things besides protein that affect bone health. In addition to adequate protein, healthy bones require a variety of vitamins and minerals, including vitamin D and K, calcium, and magnesium. And that’s why my nutrition prescription for healthy bones isn’t just about getting more protein (or calcium) but also encourages eating plenty of vegetables! Also, because vitamin D is not terribly well-distributed in the food supply, a vitamin D supplement may be a good idea.

Exercise also plays an important role in bone health, in two important ways. 1) Strong muscles help maintain strong bones. Strength training exercise with weight machines, stretchy bands, free weights, or even your own body weight helps to maintain muscle strength throughout life.  2) Impact also helps strengthen bones. Walking gives your bones some low impact stimulation, but if you can manage a bit of jogging, jumping, bouncing, or other higher impact activities, so much the better.