How to Optimize Your Diet for Bone Health

The heart, the lungs, the brain and organs of the body are all made of soft tissue that can easily be damaged. Fortunately for us, they’re protected by hard tissue called bone. Strong bones are built in childhood and, depending on one’s lifestyle, either remain strong or weaken throughout adulthood. Fragile and brittle bones can fracture more easily, increasing the risk for spinal and mobility issues.

Every 20 seconds, an American breaks a bone as a result of osteoporosis, a condition caused by low calcium levels that weakens the bones. That means in one year alone, two million Americans will suffer a broken bone due to osteoporosis. Low bone mass and osteoporosis threaten 44 million women and men aged 50 and older(1).

Unfortunately, osteoporosis remains under-diagnosed and under-treated. Only nine percent of Medicare beneficiaries were screened for osteoporosis within six months of sustaining a bone fracture. In 2018, the total cost of care associated with fractures was $57 billion and is expected to rise to $95 billion in 2040(2). Thankfully, healthy lifestyle choices can help to preserve the strength of your bones as you age. Chief among them is nutrition.

What is bone?

There are206 bones in the human body that perform several functions: support, movement, protection, storage and the formation of blood cells. Bones are a composite of the crystalized minerals calcium and phosphate bound to a protein which gives them both strength and flexibility. The dense outer layer called cortical bone makes up about 75 percent of the skeleton. Inside the cortical bone is a spongy inner structure called the trabecular bone that makes up the remaining 25 percent of the skeleton. Cortical bone provides strength and surface area for tendons to connect muscle to bone. The trabecular bone helps maintain bone integrity and strength while providing surface area for mineral exchange.

Remodeling

Bone is the storehouse for the essential minerals calcium and phosphorus as well as fat, sodium and potassium. The cyclical breakdown of bones releases these minerals and other substances into the bloodstream. Bones are also under continuous stress from motion and weight-bearing. As a result, throughout life, bones are constantly being broken down and restored in a process called remodeling.

In most adults, the skeleton is replaced almost every 10 years(3). This remodeling process is also responsible for the reshaping of bones. According to Wolff’s law, changes in bone structure coincide with changes in bone function. For example, bone responds to the stressfulforces of exercise by laying down more bone tissue, thereby increasing its density. On the other hand, prolonged periods of bed rest and inactivity due to illness or injury result in reduced mineral deposits, ultimately reducing bone density.

Bone marrow

In the center of some bones, especially the hip and thigh bones, is a soft tissue called bone marrow. The bone marrow contains immature cells called stem cells. Red bone marrow contains the stem cells that produce 200 billion new red blood cells every day, along with white blood cells and platelets. Yellow bone marrow contains the stem cells that produce fat, cartilage and bone(4). With red blood cells transporting oxygen and white blood cells helping to fight infections, bone marrow is critical for producing the blood cells that keep the body going.

Bone health

There are two kinds of bone cells. Osteoblasts are the cells that produce bone and osteoclasts are the cells that dissolve and remove old bone. Once bone is dissolved by osteoclasts, osteoblasts attach to the exposed sites of the bone to form osteocytes which combine with calcium and other minerals to form new bone.

Bone health, therefore, depends on the balanced efforts of these two types of cells(5). The key to healthy bones is maintaining maximum bone density and blood cell production. This is achieved through the following three principles:

• Physical activity, which stimulates your bones to increase strength
• Nutrition, which supplies the body with key ingredients to develop bone
• Prevention, or avoiding habits that decrease bone strength

Nutrition for bone health

Bone loss in osteoporosis is accelerated by nutrient deficiencies and increases the likelihood of falls. These are major causes of hip fractures, especially among the elderly.

The bone-building osteoblast cells use calcium to build the collagen-calcium-phosphate matrix of new bone. The calcium is drawn into the bone matrix by proteins that require vitamin K2. To absorb the calcium, vitamin D is required. Thus, optimal nutrition for bone health begins with calcium, vitamin D and K2, as well as sufficient protein.

Red blood cell production in the bone marrow also depends on protein, iron, folic acid, vitamin B-12 and vitamin B-6 to help form hemoglobin that binds with oxygen allowing its transport via the blood. Finally, vitamin A plays a vital role in promoting healthy development and maturation of stem cells in the bone marrow(6).

Nutrition for bone health, therefore, depends onconsuming and absorbing the proper amount of the right nutrients, especially calcium, vitamin D, magnesium, collagen, vitamin K2, iron, folic acid and vitamin A.

Calcium

Bones make up 99.5 percent of all the calcium in your body, comprising 60 percent of the weight of bone(7,8). Thus, a steady supply of calcium is necessary for bone growth, bone repair and maintenance of bone density. Food sources of calcium include:

• Milk (particularly reduced-fat or skim)
• Yogurt (low-fat or plain)
• Cheese, especially Parmesan, Swiss and cottage
• Seeds, especially poppy, sesame, celery and chia
• Sardines
• Canned salmon
• White beans
• Almonds
• Leafy greens: especially kale, collard and spinach
• Edamame and tofu
• Foods fortified with calcium

Vitamin D

Consuming the right amount of calcium is not enough to maintain healthy bones. In order for the body to absorb calcium, it requires vitamin D. If you are deficient in vitamin D, your calcium levels may be deficient as a result.

Vitamin D is produced in the body when cholesterol in the skin is exposed to UV-B radiation from the sun. Thus, getting daily exposure to sunlight is essential for maintaining bone health. If you’re not spending enough time in the sun, good dietary sources of vitamin D include:

• Egg yolks
• Fatty fish
• Vitamin D-fortified milk

The daily recommended dietary intake of calcium and vitamin D varies by age, sex and hormone status. See the table below for a reference of these values, adapted from the Surgeon General's Report on Bone Health and Osteoporosis.

Magnesium

Magnesium keeps calcium flowing in the blood and is required to convert vitamin D into its active form. This, in turn, allows vitamin D to activate calcium absorption. Taking high doses of vitamin D when you are deficient in magnesium can drain the magnesium from muscles, contributing to twitches and cramps. Thus, magnesium is also important for bone health(9). Food sources of magnesium include:

• Dark chocolate
• Avocados
• Nuts, especially cashew, Brazil, and almonds
• Legumes, especially black beans, chickpeas, and soybeans
• Seeds, especially pumpkin, flax and chia
• Whole grains, especially barley, wheat, and oats
• Fatty fish, especially salmon, mackerel and halibut
• Bananas
• Tamarind
• Okra
• Oysters

Collagen

In order for calcium to form into bone, a matrix or scaffolding is required for the calcium to bind to. As much as 90 percent of the matrix is formed from collagen, the most abundant protein in the body, and binds with water to provide matrix flexibility(10). Thus, consuming foods with collagen-building nutrients is important for maintaining bone health.

Not surprisingly, bone broth made from bones and connective tissue contains calcium, magnesium, phosphorus, collagen, glucosamine, chondroitin, amino acids and other nutrients, making it a great choice for bone health. Vitamin C is also an important precursor to collagen production. Other food sources for boosting collagen production include:

• Chicken
• Fish and shellfish, especially the less desirable parts like the head and eyes
• Egg whites
• Citrus fruits, especially oranges, grapefruit, lemons and limes
• Berries

Vitamin K2

As stated above, calcium is drawn into the bone matrix by proteins that require vitamin K2. As a result, low bone mass, osteoporosis and fracture risk are all associated with low vitamin K levels(11,12,13).

Vitamin K comes in two forms, K1 and K2. Vitamin K2 appears to protect bones more than K1 because of its role in synthesizing osteocalcin which regulates bone mineral accumulation (14) and inhibiting the deposits of calcium in blood vessel walls(15). Food sources of vitamin K1 include:

• Leafy greens, especially spinach, kale, lettuce, mustard greens and Swiss chard
• Broccoli
• Brussels sprouts
• Vegetable oils

Food sources of vitamin K2 include:

• Hard cheeses, especially Gouda and Swiss
• Blue cheese
• Chicken
• Pork
• Eggs
• Natto (Japanese specialty food)

Iron

Iron plays a role in collagen synthesis and vitamin D metabolism. In addition, 73 percent of the body’s iron is in the circulating hemoglobin of red blood cells. For this reason, iron is important for bone health. Both excess iron and iron deficiency can be risk factors for osteoporosis, so a simpleblood test from your doctor can help you understand where your iron levels are at(16). If you need a boost to your iron levels, good dietary sources include:

• Red meat
• Turkey
• Legumes, especially lentils and peas
• Green vegetables and tomatoes, whose vitamin C facilitates absorption of iron
• Pumpkin seeds
• Broccoli
• Quinoa
• Spirulina
• Dark chocolate

Folic acid

Folic acid, also referred to as folate or vitamin B9, promotes bone health by detoxifying homocysteine, an amino acid that increases the risk of fractures and osteoporosis. When homocysteine levels increase, especially in women under the age of 50, bone mineral density of the lumbar spine and femur is decreased because it interferes with bone remodeling(17). Food sources of folic acid include:

• Chickpeas
• Liver
• Brussel Sprouts
• Lentils
• Spinach
• Asparagus
• Avocado
• Beets

Vitamin A

Retinoic acid, which the body makes from vitamin A, stimulates osteoclast cells that initiate the remodeling process by breaking down the bone and releasing calcium into the bloodstream. Vitamin A also suppresses the osteoblasts from releasing collagen to repair lost bone material. As a result, excess vitamin A intake is linked to increased risks of fractures(18). Therefore, it’s important to make sure you’re getting the right amount of this nutrient.

A four-year study of 958 men and women found that an average daily consumption of 2,000 to 3,000 IU per day (600 to 900 mcg) was associated with the highest bone mineral densities(19). The current recommended daily intake is 3,000 IU (900 mcg) for men and 2,330 IU (700 mcg) for women. The top 10 food sources for vitamin A include(20):

• Carrots
• Tuna
• Butternut squash
• Sweet potato
• Spinach
• Cantaloupe
• Lettuce
• Red bell pepper
• Pink grapefruit
• Broccoli

Nutritional supplements

In most cases, it’s recommended to get your nutrients from real food. The ultimate goal is to increase the amount of nutrients that are actually absorbed and used in the body, which can be affected by the way food is prepared. While raw foods often contain the most nutrients, the body can absorb more nutrition from cooked foods. This is because the process of cooking pre-digests the food, minimizing the effort required by the body for digestion.

Similarly, the processing of nutritional supplements can reduce the absorption of the nutrients. In addition, absorption can be increased or decreased depending on the presence of other nutrients. When it comes to bone health, the most important combinations are calcium, vitamin D and magnesium.

Supplements aren’t intended to replace food because they can’t replicate all the benefits of real food. However, if you’re not getting enough nutrients from the food in your diet, nutritional supplements play a very important role.

According to a national survey of 16,444 participants in the United States, many Americans are deficient in key nutrients:

• 94.3% of Americans did not meet daily requirements for vitamin D
• 44.1% of Americans did not meet daily requirements for calcium
• 43% of Americans did not meet daily requirements for vitamin A
• 52.2% of Americans did not meet daily requirements for magnesium(21)

The Center for Disease Control and Preventions (CDC) also states that more than half of the general population is deficient invitamin D, regardless of age. Thus, when it comes to bone health, most Americans would most likely benefit from supplementing calcium, vitamin D, vitamin A and magnesium.

In summary

Since bones perform the functions of support, movement, protection, storage and the formation of blood cells, bone health is essential. Getting the right nutrients—especially calcium, vitamin D, vitamin K2,collagen, magnesium, folic acid, iron and vitamin A—will ensure the body has all the ingredients it needs to both break down old bone as well as repair bone to keep it hard, flexible and strong. This remodeling process ensures that bones do not become brittle and weak, leading to fractures and osteoporosis.

Siphiwe Baleka - Contributing Writer Physician's Choice