I first heard about bone broth a couple months ago when I stumbled upon an osteoporosis-themed Twitter chat. The question:

The answer:

As you can see above, I tried futilely to refute this claim but the damage had already been done – some had retweeted his tweet, and many replied with comments like “Makes sense!” or “Good to know!”, while no one even made a peep at mine.

Since then, I’ve learned that bone broth is slowly (but steadily) becoming a thing. Fuelled equal parts by the Paleo movement and Kobe Bryant, bone broth is becoming so popular that Brodo, a takeout window that doles out hot cups of broth, recently opened in New York! You have to admit, it’s definitely appealing to sip on a hot cup of broth than a cold juice or smoothie in the dead of winter, right?

What makes bone broth different from say, regular broth or stock?

The difference between bone broth, broth and stock is not just semantics. According to Nourished Kitchen, bone broth is made with minimal meat, and simmered for much longer than stocks or broths – up to 1-2 days. The goal is to simmer it for so long that the “minerals have leached from the bones” and the bones themselves become brittle. Often vinegar is added to bone broths so that the acid can help leach the minerals from the bones.

Is bone broth rich in calcium and minerals?

Although broth is a food as old as time, the idea of it being a superfood is relatively new, so there are few studies of its contents. Even the Canadian Nutrient File only has nutrient analyses of commercial broths. I only boldly made my claim on that Twitter chat because I remember in my early days as a dietitian, I used to give out this handout which says that the amount of calcium in “boiled bone soup” is “negligible”.

In this recent blog post by Kaayla T. Daniel, the co-author of a book called Nourishing Broth: An Old-Fashioned Remedy for the Modern World, she states that she had to go as far back as 1934 to find a thorough review of the calcium content of bone broth, and the results were abysmal – about 12.3-67.7 mg per cup. In other words, you would have to drink 5-26 cups of broth to equal the same amount of calcium in a cup of milk (322 mg calcium per cup)! Interestingly, Daniel notes that the study found that the broths with the highest calcium also included vegetables. Dissatisfied with the technology of the Dirty 30’s, Daniel and lead author Sally Fallon Morell ran their own experiments, and found even worse results – a chicken bone broth had only 2.3 mg of calcium per cup, and a bone broth made with vegetables contained 6.1 mg per cup.

What about the other minerals? Lawrence Dubois, manager of Salt Spring Natureworks and reader of Alive, a natural health magazine, recently did his own analysis by preparing several varieties of bone broths (plus a nettle and dandelion broth) and sending them off to a lab for analysis. He found that his bone broths contained about 1.6-21.6 mg per cup. Other minerals that bone broth is purportedly high in, like magnesium, phosphorus and potassium, clocked in quite low as well, as illustrated by this table I made below:

OK, what about collagen?

One thing that Dubois did find was that the bone broths all contained a good amount of protein – about 12-30 g per cup. It’s assumed that most of this protein comes in the form of collagen. Collagen is the most abundant form of protein in our bodies; it is the main component of connective tissue and makes up about 25-35% of our total protein mass. The terms collagen and gelatin are sometimes used interchangeably – gelatin is a hydrolyzed form of collagen, meaning that the original bonds between the components in the collagen molecule are broken down and reformed into a slightly different structure. Otherwise, their chemical structure is similar, and commercial gelatin is generally made from the same stuff that people would make bone broth out of.

So, is this why they serve so much Jello at old folks’ homes and hospitals? It’s not as simple as more dietary collagen = more body collagen (just like less dietary cholesterol does not always equal lower blood cholesterol). Our stomach acid denatures (i.e. deactivates) all proteins and our bodies break them down to their individual amino acids. As a protein, collagen/gelatin is not considered a good source, as it does not contain all of the essential amino acids (i.e. the amino acids that we can only get from diet). The two amino acids collagen is known for, proline and glycine, are both non-essential amino acids that our bodies can make as long as it is getting adequate, complete protein. Most other animal sources, like whey (dairy) and eggs, are considered complete proteins as they contain all of the essential amino acids. Some plant sources, like soy, are also complete proteins.

Vitamin C is another major player in collagen production. Scurvy (vitamin C deficiency) often leads to bleeding gums due to the breakdown of collagen.

Most of the research available on collagen has to do with its effect on joint health and skin health. There are some studies that supplementing with type II collagen, a type mainly found in cartilage, may have some benefits in reducing joint pain, increasing range of motion and increasing collagen content in the skin. When it comes to “bone building”, however, according to Examine.com:

“As a general statement, the immunological effects of CII [type II collagen] do not appear to apply much to bone health and the role of CII supplementation in bone density pertain to it simply being a protein source. It might be able to increase bone mass mildly when high doses (estimated 10g in a human) paired with a low protein diet, but when the overall protein intake is increased this benefit is lost and it performs equally to other protein sources”

Bottom Line

This is not a hate on to food cultures where broth has played a huge role – most Chinese soups are broth-based, and I remember growing up we had to have a bowl before and after our dinner meal. There is even an oft-quoted South American proverb that “Good broth will resurrect the dead.” Still, based on the weak evidence behind its current claims, I’m not convinced that bone broth deserves all this superfood buzz.