Is Milk Bad for Your Bones?
There’s a rumor going around that dairy products contribute to osteroporosis by acidifying the body. Nutrition Diva gets to the bottom of the controversy.
Nutrition Diva listener Rona writes:
“My health coach says that I should avoid milk because it is acidic and, contrary to common belief, will actually deplete the calcium in my bones. I have always believed that milk was a good source of calcium. In fact, I insist that my children have at least 2 servings of milk a day! Does milk really deplete calcium from bones? Should I stop giving it to my kids?”
The idea that milk and dairy products weaken bones has been steadily gaining traction in alternative health communities. Of course, this runs contrary to the conventional wisdom that dairy products help build strong bones by providing calcium. Is the conventional wisdom wrong? Let’s take a closer look at the evidence.
Sponsor: Squarespace, the all-in-one platform that makes it fast and easy to create your own professional website, e-commerce site, or online portfolio. For a free trial and 10% off, go to Squarespace.com/diva and use offer code Diva1.
Do Dairy Products Cause Osteoporosis?
People who are suspicious of milk’s role in bone health like to point out that the countries with the highest consumption of dairy products also have the highest incidence of osteoporosis. Is this convincing proof that dairy products cause osteoporosis? Not even remotely.
There are many things that affect bone health, including genetics, physical activity, body weight, smoking or exposure to second hand smoke, alcohol use, hormone levels, and medications. Ifany of those risk factors are more common in countries that have higher dairy consumption, then the link between dairy and osteoporosis may be nothing more than a coincidence.
See also; How the Media Sensationalizes Science
If we’re going to take this hypothesis — that dairy products cause osteoporosis — seriously, we need more than just a correlation. We need a plausible mechanism — an explanation for how dairy products might weaken your bones.
Is Your Diet Too Acidic?
Like Rona’s health coach, some people have argued that milk weakens your bones because it is an “acid-forming” food. The idea is that milk leaves an acidic residue in your body after digestion. This supposedly causes your body to pull calcium from the bones to keep your body from becoming too acidic.
I talked about acid- and alkaline-forming foods in my episode on pH-balancing diets. It’s true that some foods do leave behind acid residues, while others have alkaline residues. And it is true that eating more acid-forming foods causes your urine to become more acidic. But this is not evidence that these foods are “acidifying” your body. In fact, it is evidence of exactly the opposite. One of the ways that your body maintains its optimal pH is by excreting extra acid in your urine.
In other words, the acid-load of your diet does not have any meaningful impact on the pH of your blood.
Do Acidic Foods Weaken Bones?
What’s going on in your urine is not always a very good indication of what’s going on in your body.
OK, so maybe your body doesn’t actually become acidic when you eat acid-forming food. But is this at the expense of your bones, as many have said? After all, it’s true that eating more acid-forming foods can increase the amount of calcium that is excreted in urine. But once again, what’s going on in the urine is not always a good indication of what’s going on in the body.
Studies demonstrate that the acid residue of the diet does not affect the overall calcium status of the body. It appears that your body compensates for these calcium losses by increasing the amount of calcium it extracts from your food. In any case, although acid-forming foods may increase calcium in your urine, this calcium is not coming from your bones. The whole calcium balance thing is being handled in the digestive system and kidneys.
See also: Are You Getting Enough Calcium? (Or Are You Getting Too Much?)
Bottom line: As long as you are getting a reasonable amount of calcium from your diet, your body will handle the rest.
Is Dairy Even an Acid-Forming Food?
Now that we’ve got all that settled, there’s one more thing: Turns out that dairy is not an acid-forming food after all.
That’s right: milk produces an alkaline residue when digested. So even if there were evidence to uphold this theory about acid-forming foods stealing calcium from the bones, it would not appear to apply to dairy products anyway.
Should You Drink Milk?
And, finally, back to Rona’s question: Should she and her kids continue to drink milk? As I discussed in my episode on the Pros and Cons of Dairy, for those who don’t have a lactose intolerance, milk can be a very good source of absorbable calcium and vitamin D. But it’s certainly not the only source.
See also: What Are the Best Sources of Calcium?
And let’s not let calcium steal the show here. There are a lot of other nutrients and lifestyle factors involved in building healthy bones. Maybe that’s why the positive correlation between dairy consumption and bone density isn’t stronger. It’s not that dairy is weakening our skeleton. It’s just that dairy alone doesn’t guarantee strong healthy bones.
For more on all the ways to build healthy bone density for life, please see my episode on Diet for Healthy Bones.
Additional Research
Milk and acid-base balance: proposed hypothesis versus scientific evidence.
About the Author
Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes’ most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation’s leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.
