Visit any natural-history museum and you’ll find your fair share of bones. Looking at these cold, lifeless objects under glass, it might be easy to conclude that our own bones are much the same: static objects that simply provide scaffolding for the living parts of the body, such as the heart and brain.
The truth is, as long as we’re alive, so are our bones — and they’re working hard. “Bones are our inner armor,” explains orthopedic surgeon Brian Gruber, MD.
They contain nerves, blood vessels, proteins, and minerals. A strong outer layer called cortical bone contains a flexible, spongelike inner layer known as trabecular bone.
Dense and rigid, the cortical layer makes up about 80 percent of the bone mass in an adult, providing skeletal support, protecting organs, and storing and releasing calcium. Trabecular bone accounts for the remaining 20 percent. It contains red bone marrow, which produces our supply of red blood cells.
Bones are also mineral reserves, storing up to 99 percent of the body’s calcium and 85 percent of its phosphorus. They help the body maintain a healthy pH balance by releasing calcium to process excess acid in the bloodstream.
Recent research even suggests that bones are critical players in the fight-or-flight response, producing the stress hormone osteocalcin, which stimulates muscle function. (For more on this, see “The Stress Response May Start In Your Bones”.)
In short, our bones are far more dynamic than those objects on display at the museum. They do a lot for us — and we can do a lot for them.
After our bones grow to adult size, our entire skeletons are renewed roughly every 10 years. Up to 90 percent of our lifetime bone mass develops before age 18 for women and 20 for men. It generally peaks around age 30, and that peak is usually later in men than women.
Our bones are maintained and remodeled by an army of specialized cells. Osteoclast cells dissolve and digest old bone, while osteoblast cells produce proteins that harden into new bone.
“Bones are a very active organ in the body,” explains functional-medicine practitioner and arthritis expert Susan Blum, MD, founder of the Blum Center for Health in Rye Brook, N.Y. “They’re not inert, sitting there doing nothing. They’re metabolically active — osteoclasts and osteoblasts are always chewing up and rebuilding bone like little Pac-Men.”
Osteocytes are a third kind of cell: inactive osteoblasts buried in the bone they helped create. These cells control a dense network that signals work orders to the other two bone-cell types. Osteocytes, osteoclasts, and osteoblasts are like the project manager, demolition crew, and construction crew, respectively, at work on the bone-remodeling project that is constantly underway in our bodies.
When we’re children, our bodies make new bone faster than old bone breaks down, leading to increases in bone mass. This is why a broken bone that may take at least six weeks to heal in an adult might take as little as two weeks to heal in a child, notes Gruber. As we age, this process shifts.
For most people, bone development follows an arc that rises slowly during childhood, peaks in the late teen years, and then begins sloping downward after age 35. That’s why it’s important to maximize the deposits we make in our “bone bank” during our early years. Once we reach middle age, many of us will lose bone faster than we’re able to build new bone. It becomes much more difficult to build as we grow older.
We will all lose some bone density over time, but when bones lose substantial mass, it can lead to osteoporosis, a condition in which bones become porous, brittle, and fracture-prone. Osteoporosis is often undetected until it’s revealed by a fracture or break.
Yet we need not resign ourselves to frailty as we age. Even those who didn’t maximize their deposits in those early years can still ensure they have enough bone mass to retire on.
Diane Schneider, MD, author of The Complete Book of Bone Health, compares our bones to a 401(k) from which we start making mandatory withdrawals in adulthood. The key, she advises, is to limit the withdrawals as much as possible.
Maintaining a bone-healthy diet and lifestyle can help ensure that your “retirement account” stays robust for years to come.
We can slow or even reverse secondary bone loss — the result of conditions such as type 1 diabetes, eating disorders, and thyroid conditions, as well as the use of certain medications — by addressing the underlying health issues.
And it pays to attend to another surprising factor that contributes to bone density: hormone regulation.
Bones and Hormones
“All hormones in the body either build up or break down muscles and bone,” Blum explains. “Estrogen and testosterone are builders, while cortisol is a breakdown hormone. If you live in the land of high cortisol for too long, your body is being told to break down structural protein — that’s how stress has a big influence on breaking down bone.”
Long-term use of glucocorticoids, such as prednisone, can also reduce bone density by boosting cortisol levels in the body. Blum recommends practicing relaxation techniques to support a healthy balance between anabolic (building-up) and catabolic (breaking-down) hormones.
For women, estrogen plays a significant role: It acts as a check on the cells that break down bone and stimulates the cells that build it. Menopause takes its toll on that delicate balance, as declining estrogen levels cause women to lose as much as 3 percent of their bone mass annually during the menopausal years. Men experience the same pattern as their testosterone production flags.
Thyroid hormones also affect bone health. The thyroid gland produces calcitonin, which regulates the body’s calcium supply, as well as T3 and T4, which aid control of growth and metabolism.
Hypothyroid (underactive) and hyperthyroid (overactive) conditions are both associated with a higher risk of osteoporosis, but hyperthyroid conditions pose the greater risk of the two because too much thyroid hormone speeds the rate of bone loss.
Experts recommend bone-density DXA tests — for women, ideally before menopause — to determine if any lifestyle changes are needed to protect your bones. (For more on this, see “Testing Bone Density” below.)
And while it may sound overly simplistic, doing what you can to cultivate a peaceful and relaxed state of mind will help keep bone-stressing cortisol in check.
Bones and Nutrition
Nutrition is another essential factor in bone health. “The bones are a big buffering system to keep our bloodstream’s pH level perfect,” explains Blum, noting that we require a controlled blood pH level of about 7.4 to survive and thrive.
Eating a diet full of processed foods, sugar, dairy, meat, and alcohol produces acid in our bloodstream that the body must clear — and calcium is the primary tool for the job.
“The bones release that reservoir of calcium to the kidneys to buffer the acid load,” says Blum. “And losing that calcium from bone reduces bone density.”
In her work with patients displaying low bone density, Blum prescribes home-testing strips to assess their urine’s pH. “The more acidic your urine, the more likely you’re losing calcium from your bones to buffer that acid,” she notes. To balance your pH, Blum encourages restricting acid-producing foods.
Experts generally recommend between 1,000 and 1,200 mg of calcium daily for a healthy adult — a guideline that typically points to sources like milk and cheese, as well as calcium supplements, to reach this goal. But this advice fails to consider the acid-producing aspect of dairy, and how the body buffers it with its own calcium reserves.
“Limiting dairy to increase bone health goes against the dogma,” Blum admits. But there’s a reason for it: “When you get calcium from dairy you’re getting it in an acidic vehicle.”
It’s also important to consider how calcium is absorbed and transmitted to the bones. “Calcium cannot act alone,” writes Laura Kelly, MD, and Helen Bryman Kelly in The Healthy Bones Nutrition Plan and Cookbook. They explain that vitamins D and K2 and minerals magnesium and phosphorus all help ensure that calcium is deposited into the bones.
Vitamin D increases the intestine’s absorption of calcium, and magnesium is helpful both in converting vitamin D into its active form and in transporting minerals across cell membranes. “Vitamin K2 helps the calcium get to the right place,” explains Blum. (Note: While calcium needs help to do its job, calcium supplements are best taken on their own, because calcium binds to other minerals, such as zinc and magnesium, so they can’t be absorbed.)
Blum recommends an alkaline diet in which at least 70 percent of daily food intake is plant-based; the remaining 25 to 30 percent can comprise acid-forming foods, in moderation. Greens, nuts, and seeds are all good calcium sources; a cup of cooked collard greens, for instance, contains a whopping 266 mg.
Choose calcium-rich greens low in oxalic acid, such as collards, arugula, and alfalfa sprouts. When you eat other alkalizing greens like spinach and kale, enjoy them cooked — to reduce their higher oxalic acid content — and pair them with another calcium-rich food, like crushed almonds or grated Parmesan cheese, for bone support.
As far as dairy goes, says Blum, full-fat yogurt is the best choice: It’s high in calcium but less acid-producing than milk and cheese thanks to fermentation. Dairy from goats, she adds, creates less acid than that from cows. When you want to enjoy cheese, consider choosing gouda, which contains bone-health-boosting vitamin K2. (For more calcium-rich foods, see “20 Calcium-Rich Foods”.)
In addition to limiting acid-forming foods, Lani Simpson, DC, CCD, recommends eating an abundance of alkaline-forming foods to help keep calcium in the bones. These include kale, broccoli, parsley, kelp, lemons, and limes. The nutrients in grains, legumes, and nuts that have been soaked and sprouted are more bioavailable, and these traditional preparation methods also weaken chemicals like phytic acid that can inhibit mineral absorption.
Include plenty of raw foods in your diet, as well. Eating a salad loaded with raw veggies each day is a good way to start. Adding apple-cider vinegar to your salad dressing can also release calcium and other minerals from leafy greens.
If you plan to supplement calcium, Blum suggests limiting that intake to 600 mg daily, because excess calcium can land in unwanted places, such as joints and blood vessels. Supplementing with vitamins D and K2, trace minerals, and digestive enzymes may also be helpful, depending on your base levels and digestive health.
Digestion is key: Beefing up nutrition is helpful only if we’re able to absorb what we’re consuming.
Bones and Exercise
When NASA scientists studied astronauts in outer space, they found that prolonged weightlessness resulted in bone deterioration. This finding supports other research suggesting that weight-bearing exercise is a key lifestyle intervention for building and sustaining healthy bones here on Earth.
“Bones want weight,” explains Gruber. “You don’t want to do just 20 minutes of riding a bike: For strong bones you really need to stress them with weighted exercise.”
“Tension against the bone keeps it strong and growing,” adds Blum. “When there’s stress on the bone, the body responds by laying more down.”
Both high- and low-impact weight-bearing exercise is essential for bone health. High-impact options include team sports like basketball, as well as strength training, running, jumping rope, jumping jacks, or a vigorous yoga practice. Some low-impact options are walking, elliptical machines, and stairclimbing.
Strength training, in particular, is helpful for building sturdier bones. As they get older, women especially lose upper-body muscle mass, and challenging the muscles counteracts that loss.
Gruber notes the difference in bone health between a triathlon runner who doesn’t strength train and one who does. “You expect them both to be healthy, but adding strength training makes a big difference to the bones and muscles,” he observes. “Cardiovascular health is distinct from musculoskeletal health.”
Most health clubs and gyms have an array of free weights and machines that make it easy to include strength training in your exercise routine. If you’re fracture-prone, work with a personal trainer to design a program that’s biomechanically correct. (For an at-home, no-equipment workout, see “The Minimalist Workout”.)
And if you have a diagnosis of osteoporosis, take heart: It doesn’t have to mean a fracture is in your future.
Bone health can be positively influenced at any time of life when we make choices that truly support us.
Testing Bone Density
Some of the risk factors for fractures and osteoporosis are out of your control. These include Caucasian or Asian ethnicity, older age, thinness or small bones in women, a history of fractures, low body weight, primary relatives with osteoporosis, early menopause, rheumatoid arthritis, gastric- or intestinal-bypass surgery, hysterectomy with ovary removal, and thyroidectomy.
Factors that are within your control include smoking, alcohol consumption, a sedentary lifestyle, poor diet, and the long-term use of certain symptom-controlling medications, such as proton pump inhibitors, or PPIs.
Several tools can help you determine your personal risk of fracture, and they can motivate you to make nutrition and lifestyle adjustments. A bone-density test — also known as a dual energy x-ray absorptiometry (DXA) test — uses two low-dose beams of radiation to assess bone-mineral density. It’s the gold standard for diagnosing osteoporosis.
The International Society for Clinical Densitometry recommends DXA testing for women over 65, men over 70, anyone who has sustained a fracture after age 50, and anyone with a condition or who is on a medication associated with osteoporosis. The test is noninvasive and painless and usually takes less than 15 minutes.
If you’re at risk for osteoporosis, testing can go a long way in helping you take steps that can prevent the condition and the needless fractures it often produces. A low bone-density score is no reason to panic: Consider it a great motivator to increase weight-bearing exercises and eat more alkalizing foods.
This article originally appeared in Experience Life, Life Time’s whole-life health and fitness magazine.