by Amy Blaszyk, The Salt at NPR Food (2/10/15)
How did bone broth become the magic elixir du jour?
We're not sure, but in the last three months, breathless stories about its umami depth and super nutrition have ricocheted through food media. Meanwhile, restaurants like New York's Brodo, Portland's JoLa Café and Red Apron in Washington, D.C., have begun selling it, to much fanfare.
To be clear, there's nothing all that new about bone broth (sometimes called stock). Around the world, chefs and home cooks have been using the feet, knuckles, tendons and bones of all sizes from poultry, beef, pig and fish to make rich, nourishing broths practically forever. There's seolleongtang in Korea, sopa de lima in the Yucatán and "Jewish penicillin" (chicken soup with matzo balls), to name a few.
"Broth has always been considered a healing food, especially if you consider the tradition of eating chicken soup when you're sick with a cold," says Jennifer McGruther, author of The Nourished Kitchen.
But lately, the list of bone broth's rumored healing and restorative properties seems to be getting longer and longer.
In their book Nourishing Broth, authors Sally Fallon Morell and Kaayla T. Daniel assert that bone broth can help with a variety of ailments — from improving joint function and helping wounds heal faster, to modulating the immune system and rebuilding bones with collagen.
The problem is that there are precious few scientific studies of the specific healthful properties of bone broth. What's more, there is no one bone broth recipe. It can be made with different animal bones (some with fatty marrow, some without), with different added flavors (like onions and herbs) and with different cooking methods (five hours of simmering versus 24 hours or more). All of those variables impact the nutritional properties and will give you a different broth.
Still, Daniel and Fallon Morell suggest that by boiling down animal and fish bones, skin, cartilage, tendons and ligaments, we create gelatin-rich liquid that provides the amino acids necessary to make collagen, or "the glue that holds the body together." And, they add, "We need collagen to build the structure for a bone."
Scientists agree that bone broth's so-called ability to heal and restore collagen is probably overblown.
William Percy, an associate professor at the University of South Dakota's Sanford School of Medicine, isn't convinced that the collagen in the bones and joints that go into bone broth will do much for your skeletal system.
"Since we don't absorb collagen whole, the idea that eating collagen somehow promotes bone growth is just wishful thinking," Percy says. Instead, he says, the digestive system will break down the collagen into amino acids, and the body will use these building blocks wherever they're needed.
Kantha Shelke has a different take. She's a food scientist and spokesperson for the Institute of Food Technologists, and a principal with the food science and research firm, Corvus Blue LLC.
She says that if you want to build collagen, you'll need more than bone broth.
"Eating a diet rich in leafy green vegetables is ideal," she says. "Plants offer richer sources in collagen building blocks and, in addition, provide nutrients not found in sufficient quantities in meats or broth."
What's more, bone broth may provide vitamins and enzymes, but they get denatured from heat as the broth cooks, rendering them less useful to the body, according to Shelke.
But there are two health claims about bone broth that do seem to have a little more science behind them. This first is that bone broth may bolster the immune system — at least if it's made from chicken bones.
According to a study published in 2000 in the medical journal Chest, "chicken soup may contain a number of substances with beneficial medicinal activity." The researchers observed that people eating chicken soup seemed to experience a mild reduction in inflammation that helped reduce symptoms of an upper respiratory tract infection.
The second is bone broth's use as a sports recovery drink, which Kobe Bryant and members of the Los Angeles Lakers have been hyping lately.
Rebecca Mohning, a registered dietician and certified sports dietician, works with endurance athletes though her Washington, D.C.-based practice, Expert Nutrition.
Mohning says bone broth or soups made with it could help replace electrolytes after intense exercise and aid in post-workout recovery.
"It's a nice way to rehydrate the body, because of the liquid, and then replenish the sodium — that electrolyte — that was lost through sweat during exercise," she said. The amino acids may also provide the body with the building blocks it needs to rebuild muscle.
But, she adds, "There's a little too much focus on one aspect of a person's diet. There's not that one magic food or that one magic ingredient that is going to do everything."
"Bone broth as part of a well-balanced and nutritionally sound diet is probably harmless, but it is not some type of 'miracle food source' with the ability to cure a multitude of aches, pains and diseases all by itself," he says.
Both McGruther and Sally Fallon Morell say bone broth may help lead people to being more thoughtful about what they put in their bodies.
"I think the real benefit of bone broth is that people are returning to the kitchen, to prepare homemade, whole foods from scratch," McGruther says. "There's always benefits to cooking foods from home, and that's exactly what we're seeing with bone broth."