Bone is a dynamic, living organ that plays structural, protective, and functional roles in the body. It is made up of a protein matrix and mineral deposits. The matrix provides a framework, and the mineral deposits provide hardness and strength. Remodeling is a process of removing old bone and rebuilding new. Remodeling is ongoing throughout life, continually working to maintain bone homeostasis and responding to injury, inflammation, and mechanical load. The process is regulated by several hormones, cytokines, and growth factors, and it requires many nutrients for building and maintenance.
Protein for Bone Health: Collagen
Collagen is the most abundant protein in the body and is important for building the protein framework necessary for bone formation. It is synthesized from a set of specific amino acids and forms a triple helix structure. The body’s production of collagen depends on sufficient dietary intake of protein to provide amino acids, as well as zinc, copper, iron, manganese, and vitamin C as cofactors of required enzymes.1
Minerals for Bone Health
Calcium plays a role in providing strength and hardness to bone, but because of its importance in other biological processes, bone also serves as a storage location for easy access to calcium when required. If serum calcium levels start to fall too low, the body can release calcium from bone storage and maintain necessary blood levels. By providing adequate calcium in the diet bone can be prevented from being excavated for other bodily needs. The Recommended Dietary Allowance (RDA) for calcium ranges from 1,000 to 1,200 milligrams (mg) per day for healthy adults, depending on age and gender, and 1,300 mg per day for ages nine to 18.2
While calcium is the nutrient that seems to get the most attention in the context of bone health, nutritional support for building and maintaining healthy bones goes well beyond this important mineral. Phosphorus is another bone health superstar and, along with calcium, makes up hydroxyapatite – the mineral complex that hardens the protein matrix. Phosphorus and calcium need to be consumed in a balanced way for optimum bone health. Studies suggest that low calcium and/or high phosphorus diets can adversely affect bone homeostasis.3 Phosphorus can be found in a variety of foods, but excess intake is generally associated with overconsuming convenience foods due to the extensive use of phosphorus-containing additives in food processing.4 The RDA for adults over age 18 is 700 mg per day, and phosphorus additives are estimated to contribute 300 to 1,000 mg to daily intake.5
Magnesium plays both direct and indirect roles in bone health. Directly, magnesium takes part in mineralizing the protein matrix. When serum magnesium levels fall too low, magnesium from the bone is mobilized to buffer the effect. Indirectly, magnesium deficiency leads to inflammation and oxidative stress – both associated with bone loss. Magnesium deficiency also impacts parathyroid hormone (PTH) secretion and activity, which leads to reduced vitamin D activation and low serum calcium levels.7 Magnesium is found in green leafy vegetables, legumes, nuts, seeds, and whole grains. The RDA for magnesium is 400 mg per day for healthy males ages 19 to 30 and 310 mg per day for healthy females in that age range. The RDA for adult males and females age 31 and older is 420 mg and 320 mg respectively.7
One particular mineral that gets very little attention is manganese. Manganese acts as a cofactor in several enzymatic reactions involved in the synthesis of collagen, cartilage, and the mineralization of bone itself.10 One study reported that those with osteoporosis had low serum manganese levels, and another study found that a supplement containing a combination of manganese, copper, and zinc, along with calcium, prevented bone loss more effectively than supplementing calcium alone.10 Manganese is found in cereals, nuts, pineapple, beans, certain shellfish, chocolate, cinnamon, and tea. AI levels based on healthy populations are set at 1.8 mg per day for females and 2.3 mg per day for males. The AI during pregnancy is two mg per day and lactation 2.6 mg per day. AI for children varies based on age.
Additional Minerals for Healthy Bones
The minerals boron, selenium, and silicon have also been associated with healthy bone, though their mechanisms of action are not clear. All have been associated with effects on bone composition, function, and mineralization.10 And while the exact mechanism of boron’s actions is still being elucidated, the role of selenium seems related to the antioxidant capacity of selenium-containing proteins. This ability to reduce free radicals has an effect on enhancing bone-building osteoblast activity.10 Silicon appears to activate osteoblasts and play a role in collagen synthesis.10
Boron is abundant in prunes, raisins, dried apricots, and avocadoes; selenium is found in wheat, red meat, and seafood, and silicon is found in cereals, wheat, carrots, and green beans. RDAs for boron and silicon have not been established. The RDA for selenium is 55 mcg for adults with varying recommendations for children depending on age.
Vitamins for Bone Health
In recent years, research into the various roles of vitamin D has exploded. The National Institutes of Health Office of Dietary Supplements reports at least seven areas of wellness in which vitamin D might play a role, but the importance of vitamin D for bone health has been known for decades.6 Vitamin D is a fat soluble vitamin that acts as a signaling molecule to stimulate the absorption of calcium and regulation of phosphorus. It is also required for the proper functioning of bone cells involved in remodeling – osteoclasts and osteoblasts. Vitamin D is synthesized in the skin when exposed to ultraviolet (UV) radiation from the sun. Natural food sources of vitamin D are few (fatty fish is a good source; egg yolks and cheese contain a small amount), but fortified foods include milk, ready-to-eat cereals, some orange juices, and some yogurts. The RDA for vitamin D is 15 micrograms (mcg) for adults between ages 19 and 50 and 20 mcg for adults over age 70. The RDA is only based on the ability to maintain bone health and normal calcium metabolism in healthy people.6
Vitamin K is most widely known for its role in blood clotting but is often overlooked when it comes to bone health. It is a major player in calcium transportation, being important for both bone mineralization and blood clotting. Vitamin K activates a series of bone remodeling proteins through a process called carboxylation. This process allows bone remodeling proteins to bind calcium, carrying it for deposition via the bone matrix. Data collected from 72,000 participants of the Nurses’ Health Study showed that those who consumed the most vitamin K were about one-third less likely to fracture their hip. In addition, those who had high vitamin D intake but a low vitamin K intake doubled their risk of hip fracture.8 Vitamin K is fat soluble and comes in a few different forms: Phylloquinone (K1) – found primarily in leafy greens – and various forms of menaquinones (K2), designated by the length of their side chains (MK4 – MK-13). The menaquinone MK7 has been shown to be the most bioavailable and the form that induces the most complete carboxylation of bone remodeling proteins. K2 is synthesized by gut bacteria and is found in a fermented soybean product called natto. Small amounts can also be found in meat, dairy, and eggs. Based on the amount of vitamin K consumed by healthy population groups, the adequate intake (AI) levels have been established at 120 mcg for adult males and 90 mcg for adult females. The RDA for children varies based on age.9
Herbs for Bone Health
Dietary herbs and herbal extracts can be a supportive addition for promoting healthy bones. Isoflavones from herbs such as black cohosh, red clover, and kudzu are being studied for their potential association with lower rates of osteoporosis.12,13,14 One double-blind placebo-controlled study using black cohosh (Cimicifuga racemosa) in osteoporotic, post-menopausal women found it to be just as effective as treatment with conjugated estrogens, though working through a different mechanism. Black cohosh acted through activation of osteoblasts (which build bone tissue), and estrogen worked by inhibiting osteoclasts (which break down bone tissue).15 A 12-week, randomized, double-blinded, placebo-controlled trial that studied red clover isoflavones in menopausal women found that red clover had positive effects on bone status as confirmed by bone mineral density and bone resorption markers.13 And, studies on the use of kudzu for bone health have shown its effects on preventing cartilage degradation and increasing bone mineral density.14
The herb Epimedium (also known as horny goat weed) appears to affect bone health through a different mode of action than the above effect of isoflavones. Epimedium has been used in Chinese medicine as a tonic for fatigue, sexual dysfunction, and bone related conditions, but little has been known about its mechanism of action until recently. A 2011 study that looked at the effects of flavonoids extracted from Epimedium found that treatment in ovariectomy mice increased renal reabsorption of calcium, activated osteoblast formation, and suppressed osteoclast activity.16 And, a 2017 cell study found that Epimedium treatment induced differentiation of specialized stem cells associated with bone growth.17
Building healthy bone starts during childhood and adolescence when mineral deposition is at its peak. In fact, it is estimated that more than half of an individual’s peak bone density is acquired during the teenage years.11 With proper care and attention, the ongoing process of bone remodeling throughout one’s life can favor bone growth and maintenance. And with proper dietary intake, nutritional support, and an active lifestyle the skeletal structure may last a lifetime.