HOW TO BUILD STRONGER BONES

BY JAMIE SHEAHAN, M.S., M.D.

Got milk? If you lived through the 1990s you’re all too familiar with that question splashed across ads with images of athletes, celebrities, and even politicians sporting the now-iconic milk mustache. The importance of milk for building strong bones and teeth was the focal message of the dairy industry’s hugely successful ad campaign during that time period.

These days the response to “got milk” is far more complicated. Are we talking soy milk? Oat milk? Hemp milk? The definition of milk has changed quite a bit since “got milk” posters covered the walls of seemingly every school cafeteria. What hasn’t changed is the importance of strong bones, especially for athletes.

Considering the constant pounding we athletes put our bodies through, you’d think we would give a little more time and thought to supporting the structures that literally support us. Stronger than concrete or even steel, the 206 bones that make up the human body provide structure and make movement possible.

Despite that strength, bones are not immune to injury. Stress fractures are the most common bone injury sustained by athletes. Commonly described as an “overuse” injury, they begin as a stress reaction in response to repetitive force. If activity is not discontinued or modified to reduce stress on that bone then eventually a tiny crack forms, resulting in a stress fracture. Recovery can include everything from avoiding impact and weight-bearing activities to immobilization in a cast or splint depending on the location and severity of the injury.

Stress fractures account for up to 20% of all sports medicine clinic injuries, but overuse isn’t always entirely to blame. Poor bone health increases the risk for developing stress fractures even from everyday activities, let alone from regular exercise. Therefore, a top priority for athletes should be to optimize bone health, to prevent both stress fractures and the potential long-term complications of poor bone health in the form of osteopenia and osteoporosis.

Perhaps the most frustrating aspect of bone health is how much is already determined by the time we reach adulthood. I think many of us may not have made the smartest decisions in our childhood and adolescence. Fortunately, many of our daily habits at that age don’t have long-terms consequences. That’s not the case for bone health. That’s because bone is a dynamic tissue: as new bone is being made, old bone is being broken down constantly. Peak bone mineral density, or the maximum density bone can attain, is established at a relatively young age since during these years new bone is made faster than it is broken down.

By age 20 to 30 our ability to increase bone mineral density is gone and bone loss begins to occur. Bone is made up of a matrix of protein and minerals like calcium and the denser a bone is, the better able it is to handle every step, jump, and impact we put it through. How to build and maintain these dense bones is not as simple as Serena Williams rocking a milk mustache would lead you to believe.

A Recipe For Good Bones

There are factors that influence bone density that aren’t under our control. Genetics, body size, gender, ethnicity and age, all play a role in establishing peak bone mineral density. While we may not have much of a say in those things, when it comes to bone health it’s not all just luck of the draw. Diet and exercise are the two most significant modifiable factors in building and maintaining strong bones.

Calcium is often the first thing that springs to mind when thinking about diet and bone health. But the interplay between the calcium in the foods we eat and the calcium in bone is rather complex.

This is because calcium is needed throughout the body for numerous vital functions and structures other than just bone. Bones serve as a proverbial calcium bank storing 98% of the calcium in the human body. So when levels of calcium in the blood fall too low, the body has no choice but to “withdraw” calcium from bone. Without adequate consumption of calcium, these continuous withdrawals cause bone to become less dense and consequently weaker over time.

This can be exacerbated in athletes due to losses of calcium in sweat. To prevent this, it is recommended that adult men and women consume 1,000 mg of calcium per day. That increases to 1,200 mg per day for women over age 50 and men over age 70.

This might seem like a lot, but look no further than our “A Better-Bone Diet” chart on the following page to see how much calcium even non-dairy foods pack in.

Of course, a calcium supplement can help meet your needs. But more isn’t necessarily better when it comes to calcium supplementation. There may even be a link between high-dose calcium supplementation and risk of heart attack and prostate cancer. There is no definitive ruling on either because evidence is mixed; however, it is advisable to avoid exceeding the recommended daily intake of calcium from supplements alone.

JUST ADD…. SUNSHINE?

There’s far more to eating a bunch of calcium-rich foods to optimize bone health. Chugging a gallon of milk would have little impact on our bones were it not for vitamin D. Vitamin D is a fat-soluble vitamin that is necessary for calcium to be absorbed, making it a major player in bone health. Vitamin D isn’t naturally found in many foods, but it can be made in the human body when the skin is exposed to direct sunlight. Although that sounds simple, ask anyone in the northern hemisphere in January and they will tell you that the idea of getting significant daily exposure to sunlight is laughable. Even on the sunniest of days, UV light from the sun is too weak to allow for the conversion of vitamin D. Trying to catch some rays in a bathing suit in the winter in Vermont is a surefire way to get frost bite, but not vitamin D. Getting vitamin D from the stronger sunlight in the summer months can prove just as challenging considering that sunscreen can reduce vitamin D absorption by more than 90%. It is also more difficult for the elderly and those with darker skin pigmentation to make vitamin D from the sun, putting them at a higher risk for deficiency. Fortunately, we aren’t totally reliant on the sun to meet our vitamin D needs.

Trout, salmon, sardines, mushrooms exposed to UV light, and egg yolks all contain vitamin D. However, fortified foods provide the majority of vitamin D in American diets. Dairy milk, plant-based milks, ready-to-eat cereals, and orange juice are commonly fortified with vitamin D. Raw milk, however, does not have it.

The RDA of 600 IU of vitamin D for adults can be met through a combination of whole foods, fortified foods, and supplementation. IA serving of milk delivers 100 IU, for instance. But it is important to mention that the Tolerable Upper Intake Level (UL), or the maximum amount unlikely to cause negative health effects, is 4,000 IU per day. So, if you are relying on fortified foods or supplements, be cautious not to exceed this amount.

While other vitamins and minerals play a less significant, albeit still important role in building and maintaining healthy bones, there are two other dietary factors that are of the upmost importance for athletes in particular: protein and energy intake.

Protein And Power

Athletes tend to think about the need to consume protein purely for building and repairing skeletal muscle; however, its structural functions extend to bone as well. Protein comprises about 50% of bone volume and forms the framework that gives bones their strength.

How much protein is needed to build and maintain this framework though, has been an area of major debate. The acid-ash hypothesis states that a diet high in acidic foods prompts the body to degrade bone in order to release calcium to help buffer this acidity. Animal proteins just so happen to be one of these “acidic” foods. Considering that the recommended protein intake for athletes is higher than for sedentary individuals, if the acid-ash hypothesis is correct, then athletes would have to walk a tightrope to give their body enough protein to support skeletal muscle growth and recovery without having so much that it could compromise bone health.

Fortunately, recent studies indicate that higher protein diets are unlikely to negatively impact bones and, in fact, could be a boon for bone health. Higher protein intake has been shown to increase the amount of calcium absorbed from foods, offsetting any potential calcium loss from bone.

Additionally, protein intake

Try A Betterbone Diet

When it comes to meeting the daily recommended intake for calcium of 1,000 mg, a glass of dairy milk is a good place to start, especially since it has 7 grams of protein and is fortified with 100 IU of vitamin D. However, it’s not the only good source. You can also try fortified milk alternatives or orange juice. Also consider adding these foods to your meals.

raw, 1 cup a lot of energy and if enough energy isn’t supplied by the diet to meet those demands then serious complications can arise. These complications are most commonly known as the Female Athlete Triad.

Low Energy Availability

The Female Athlete Triad describes the relationship among decreased bone density, menstrual dysfunction, and low energy availability (LEA). LEA can be due to disordered eating or due to individuals unknowingly failing to consume adequate calories to support their level of activity. Clinicians still aren’t entirely sure how these components interrelate, but it seems that LEA affects hormones that regulate menstruation and bone metabolism.

Which brings us back to how paradoxical exercise is when it comes to bone health. Even with the wellestablished benefits weight bearing exercise exerts on bone, those benefits are negated when LEA is present. Studies estimate anywhere from 22% to 50% of high-level female athletes have osteopenia and up to 50% have osteoporosis. Compare that to just 12% and 2.3% in the average population respectively. This isn’t just a “female problem” either. Only recently it has come to light that male athletes are not immune to the negative effects of LEA.

increases levels of certain hormones that facilitate bone formation. Therefore, it appears that consuming protein in the recommended amounts for athletes is just as important for bones as it is for muscle. You can also opt for plant-based proteins or consume higher amounts of calcium.

The most impactful dietary factor when it comes to bone health is energy availability. Energy availability is defined as the amount of energy left over and available for the body’s physiological functions after subtracting the energy used for exercise. Essentially, how many calories are left over after we run, bike, hike and engage in all of the other activities we do as part of competition, training, and enjoyment.

This can make exercise a bit of a Catch-22 for bone health. Highimpact, weight-bearing exercise as well as resistance training has long been established as osteogenic, or bone building. Activities like walking, hiking, running, jumping rope, tennis, dancing, and lifting weights all stimulate more calcium to be deposited and prompt new bone to be formed.

Although non-weight-bearing activities like cycling and swimming are great for cardiovascular health, they do not have the same osteogenic effect. In fact, athletes participating in high-impact sports have a 5% - 30% higher bone mineral density compared to sedentary individuals and those who participate primarily in non-weight bearing sports.

However, all that movement requires

Relative energy deficiency in sport (RED-S) is a relatively newer term that recognizes the broader impact LEA has on health and functionality in both male and female athletes. Although studies on the prevalence and impact of LEA on bone health in males is limited, there is evidence that LEA results in hormonal changes that negatively impact bone mineral density in male athletes. Male endurance cyclists, in particular, appear to be at a much higher risk of developing low bone mineral density due to LEA combined with the non-weight bearing nature of the sport. Thus, regardless of gender, the importance of consuming adequate calories to support bone health cannot be underscored enough.

Building strong bones may not be as simple as those “Got Milk” posters led us to believe, but they did get one thing right; much of our bone health is up to us. Consuming adequate calcium, vitamin D, and protein as part of a balanced diet that provides sufficient calories along with engaging in weightbearing and resistance exercise is crucial for athletes to build bones that can withstand whatever we put them through now