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9.3: Other Essential Micronutrients for Bone Health

  • Page ID
    21156
  • Learning Objectives

    • Identify additional nutrients that are vital in maintaining bone health and state their primary role.
    • Identify food sources for each nutrient.

    Bone tissue is greater than 70% inorganic material and as such, minerals are important for maintaining skeletal health. In addition to calcium, other minerals critical for bone health include phosphorus, magnesium, fluoride and vitamin K. But that is not all—iron, copper, zinc, and vitamin C are also essential for the synthesis of collagen. Consuming too much or too little vitamin A affects bone health too, as it plays a role in osteoclast and osteoblast activities. The fact that there are many bone-friendly nutrients provides us with one more reason why it is better to eat a diet rich in many nutrients than take one particular supplement. In Table \(\PageIndex{1}\), notice the important nutrients for bone health and good food sources for each.

    Table \(\PageIndex{1}\): Micronutrients and Bone Health
    Micronutrient Functional Role in Bone Health Food Sources
    Calcium
    • Component of mineralized bone
    • Provides structure and microarchitecture
    collards, mustard greens, kale, turnips, broccoli, beans, black molasses, fortified juices, milk
    Phosphorus
    • Component of mineralized bone
    • Provides structure and microarchitecture
    soy, legumes, whole grains, dairy, nuts, seeds
    Magnesium
    • Component of mineralized bone
    • Provides structure and microarchitecture
    whole grains, legumes, almonds, cashews, hazelnuts, beets, collards, kelp
    Fluoride
    • Component of mineralized bone
    • Provides structure and microarchitecture
    • Stimulates new bone growth
    fluoridated water (tap water), foods prepared in fluoridated water, seafood (because the ocean contains natural sodium fluoride)
    Vitamin D
    • Critical for maintaining calcium levels
    • Aids the absorption of calcium, promotes bone health
    salmon, rainbow trout, sardines, mushrooms, cod liver oil, egg yolks, fortified milk
    Vitamin K
    • Stimulates bone remodeling
    kale, spinach, turnip, dark leafy vegetables
    Boron
    • May enhance calcium absorption and estrogen metabolism
    avocado, nuts, peanut butter, green and orange vegetables, grapes, raisins
    Iron
    • Helps enzymes and regulators function properly so the body can form optimal bone structure for bone strength
    red meat, egg yolks, dark leafy vegetables, dried fruit, iron-fortified foods, beans, lentils, chick peas, liver, artichoke
    Vitamin C
    • Helps enzymes and regulators function properly so the body can form optimal bone structure for bone strength
    citrus fruits, tomatoes and tomato juice, potatoes, Brussel sprouts, cauliflower, broccoli, strawberries, cabbage, spinach
    Zinc
    • Helps enzymes and regulators function properly so the body can form optimal bone structure for bone strength
    oysters, wheat germ, pumpkin seeds, squash, watermelon seeds, beans, sesame seeds, tahini, beef, lamb

    Phosphorus

    Phosphorus is classified as a macromineral (major mineral). Macrominerals are those that the body requires in amounts of at least 100 mg per day.

    Functions of Phosphorus

    Phosphorus is the second most abundant mineral in the human body; 85% of it is housed in the skeleton. In addition to serving as a primary mineral in the skeleton, phosphorus in the form of phosphate is a component of RNA, DNA, adenosine triphosphate (ATP; the cell's energy storing molecule), and phospholipids. Because phosphorus is present with calcium in mineralized bone, it is somewhat regulated in parallel to calcium. PTH and calcitriol stimulate bone resorption, increasing not only blood levels of calcium, but also blood phosphate levels. However, in contrast to the effect of PTH on calcium reabsorption by the kidney, PTH stimulates the renal excretion of phosphate so that it does not accumulate to toxic levels.

    Recommendations for Phosphorus

    The Dietary Reference Intakes (DRIs) for phosphorus are listed in Table \(\PageIndex{2}\)1.

    Table \(\PageIndex{2}\): Dietary Reference Intakes for Phosphorus
    Age Group RDA (mg/day) UL (mg/day)
    Infants (0–6 months) 100* ND
    Infants (7–12 months) 275* ND
    Children (1–3 years) 460 3,000
    Children (4–8 years) 500 3,000
    Children (9–13 years) 1,250 4,000
    Adolescents (14–18 years) 1,250 4,000
    Adults (19–70 years) 700 4,000
    Adults (> 70 years) 700 3,000
    * denotes Adequate Intake; ND=not determined

    Dietary Sources of Phosphorus

    Most Americans are not at risk for having a phosphorus deficiency. Phosphate is present in many foods popular in the American diet including meat, fish, dairy products, and processed foods. Phosphate is also added to many foods because it acts as an emulsifying agent, prevents clumping, improves texture and taste, and extends shelf-life. The average intake of phosphorus in US adults ranges between 1,100 and 1,600 milligrams per day2, well above the RDA of 700 milligrams per day.

    Table \(\PageIndex{3}\): Dietary Sources of Phosphorus
    Food Phosphorus (mg) % Daily Value
    Yogurt, plain, low fat (6 ounces) 245 20
    2% milk (1 cup) 226 18
    Salmon (3 ounces) 214 17
    Chicken breast (3 ounces) 182 15
    Lentils (1/2 cup) 178 14
    Hamburger, 90% lean (3 ounces) 172 14

    Learn even more about this nutrient by reading the Phosphorus Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    Magnesium

    Magnesium is classified as a macromineral (major mineral).

    Functions of Magnesium

    Approximately 60% of magnesium in the human body is stored in the skeleton, making up about 1% of mineralized bone tissue. Magnesium is not an integral part of the hydroxyapatite crystal, but it does reside on the surface of the crystal and helps maximize bone structure. Observational studies link magnesium deficiency with an increased risk for osteoporosis. A magnesium-deficient diet is associated with decreased levels of parathyroid hormone and the activation of vitamin D, which may lead to an impairment of bone remodeling.

    In addition to participating in bone maintenance, magnesium has several other functions in the body. Every reaction that involves ATP requires magnesium. More than three hundred enzymatic reactions require magnesium. Magnesium plays a role in the synthesis of DNA and RNA, carbohydrates, and lipids, and is essential for nerve conduction and muscle contraction. Another health benefit of magnesium is that it may decrease blood pressure.

    Recommendations for Magnesium

    The DRIs for magnesium are listed in Table \(\PageIndex{4}\)1. It's important to note that the upper limit (UL) for magnesium applies only to magnesium supplements and is not a UL for magnesium intake from food and water.

    Table \(\PageIndex{4}\): Dietary Reference Intakes for Magnesium
    Age Group RDA (mg/day) UL (mg/day)
    Infants (0–6 months) 30* ND
    Infants (7–12 months) 75* ND
    Children (1–3 years) 80 65
    Children (4–8 years) 130 110
    Children (9–13 years) 240 350
    Adolescents (14–18 years) 410 (males), 360 (females) 350
    Adults (19–30 years) 400 (males), 310 (females) 350
    Adults (> 30 years) 420 (males), 320 (females) 350
    * denotes Adequate Intake

    Dietary Sources of Magnesium

    Magnesium is part of the green pigment, chlorophyll, which is vital for photosynthesis in plants; therefore green leafy vegetables are a good dietary source for magnesium (Table \(\PageIndex{5}\))3. Magnesium is also found in high concentrations in fish, dairy products, meats, whole grains, and nuts. Additionally chocolate, coffee, and hard water contain a good amount of magnesium. Most people in America do not fulfill the RDA for magnesium in their diets.

    Table \(\PageIndex{5}\): Dietary Sources of Magnesium
    Food Magnesium (mg) % Daily Value
    Almonds (1 ounce) 80 19
    Spinach, boiled (1/2 cup) 78 19
    Soy milk (1 cup) 61 15
    Black beans, cooked (1/2 cup) 60 14

    Learn even more about this nutrient by reading the Magnesium Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    Fluoride

    Fluoride is classified as a trace mineral. Trace minerals are nutrients that we need to consume in amounts less than 100 mg per day.

    Functions of Fluoride

    Fluoride is known mostly as the mineral that combats tooth decay. It assists in tooth and bone development and maintenance. Fluoride combats tooth decay (cavities) via three mechanisms:

    1. Blocking acid formation by bacteria
    2. Preventing demineralization of teeth
    3. Enhancing remineralization of destroyed enamel

    Recommendations for Fluoride

    The Institute of Medicine has given Adequate Intakes (AIs) for fluoride, but has not yet developed RDAs (Table \(\PageIndex{6}\))1. The AIs are based on the doses of fluoride shown to reduce the incidence of tooth decay, but not cause dental fluorosis which is the mottling and discoloring of the teeth (Figure \(\PageIndex{1}\)4).

    Table \(\PageIndex{6}\): Dietary Reference Intakes for Fluoride
    Age Group AI (mg/day) UL (mg/day)
    Infants (0–6 months) 0.01 0.7
    Infants (7–12 months) 0.50 0.9
    Children (1–3 years) 0.70 1.3
    Children (4–8 years) 1.00 2.2
    Children (9–13 years) 2.00 10.0
    Adolescents (14–18 years) 3.00 10.0
    Adults (> 19 years) 4.00 (males), 3.00 (females) 10.0
    fig-ch01_patchfile_01.jpg
    fig-ch01_patchfile_01.jpg
    fig-ch01_patchfile_01.jpg
    fig-ch01_patchfile_01.jpg
    Figure \(\PageIndex{1}\): Fluorosis Progression: normal teeth, mild fluorosis, moderate fluorosis, and severe fluorosis including pitted surfaces

    Dietary Sources of Fluoride

    More than 70% of a person’s fluoride intake comes from drinking fluoridated (tap) water when they live in a community that fluoridates the drinking water. Solid foods do not contain a large amount of fluoride. Fluoride content in foods depends on whether it was grown in soils and water that contained fluoride or cooked with fluoridated water. Canned meats and fish that contain bones do contain some fluoride. The Centers for Disease Control and Prevention (CDC) has reported that fluoridation of water reduces tooth decay by about 25% in children and adults5. Toothpaste that contains fluoride also reduces tooth decay. However, if fluoride toothpaste is swallowed by young children it can lead to fluorosis. This is why young children should be supervised while brushing their teeth and taught to spit out toothpaste instead of swallowing it.

    Vitamin K

    Vitamin K refers to a group of fat-soluble vitamins that are similar in chemical structure.

    Functions of Vitamin K

    Vitamin K acts as a coenzyme and plays an essential role in blood coagulation. Without vitamin K, blood would not clot. Vitamin K is also required for maintaining bone health; it modifies the protein osteocalcin, which is involved in the bone remodeling process.

    Recommendations for Vitamin K

    The Institute of Medicine has established Adequate Intakes (AIs) for vitamin K, but has not yet developed RDAs (Table \(\PageIndex{7}\))1. A Tolerable Upper Intake Level (UL) for vitamin K has not been set.

    Table \(\PageIndex{7}\): Dietary Reference Intakes for Vitamin K
    Age Group AI (mcg/day)
    Infants (0–6 months) 2.0
    Infants (7–12 months) 2.5
    Children (1–3 years) 30
    Children (4–8 years) 55
    Children (9–13 years) 60
    Adolescents (14–18 years) 75
    Adults (> 19 years) 120 (males), 90 (females)

    Dietary Sources of Vitamin K

    Vitamin K is present in many foods. It is found in highest concentrations in green vegetables such as broccoli, cabbage, kale, parsley, spinach, and lettuce (Table \(\PageIndex{8}\))6. Additionally, vitamin K can be synthesized via bacteria in the large intestine. The exact amount of vitamin K synthesized by bacteria that is actually absorbed in the lower intestine is not known, but likely contributes less than 10 percent of the recommended intake. Newborns have low vitamin K stores and it takes time for the sterile newborn gut to acquire the good bacteria it needs to produce vitamin K. So, it has become a routine practice to inject newborns with a single intramuscular dose of vitamin K. This practice has basically eliminated vitamin K-dependent bleeding disorders in babies.

    Table \(\PageIndex{8}\): Dietary Sources of Vitamin K
    Food Vitamin K (mcg) % Daily Value
    Natto (3 ounces) 850 708
    Collards, boiled (1/2 cup) 530 442
    Spinach, raw (1 cup) 145 121
    Broccoli, boiled (1/2 cup) 110 92
    Soybean oil (1 tablespoon) 25 21
    Pumpkin, canned (1/2 cup) 20 17

    Learn even more about this nutrient by reading the Vitamin K Fact Sheet from the National Institutes of Health, Office of Dietary Supplements.

    Key Takeaways

    • Phosphorous, a primary mineral component of bone, is regulated in parallel with calcium, and in high amounts is detrimental to bone health.
    • Magnesium helps keep bones strong. A deficiency in magnesium can compromise bone health.
    • Fluoride combats tooth decay and benefits teeth and bones when present in the diet at the recommended intake.
    • Vitamin K is a coenzyme that participates in the modification of proteins that act in bone tissues and promotes normal blood clotting.

    References

    1. Summary Report of the Dietary Reference Intakes. nationalacademies.org. https://www.nationalacademies.org/our-work/summary-report-of-the-dietary-reference-intakes. Accessed July 1, 2020.
    2. Phosphorus - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/Phosphorus-HealthProfessional/. Accessed July 1, 2020.
    3. Magnesium - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/. Accessed July 1, 2020.
    4. Fluorosis. cdc.gov. https://www.cdc.gov/fluoridation/faqs/dental_fluorosis/index.htm. Accessed July 1, 2020.
    5. Community Water Fluoridation. cdc.gov. https://www.cdc.gov/fluoridation/index.html. Accessed July 1, 2020.
    6. Vitamin K - Health Professional Fact Sheet. ods.od.nih.gov.https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/. Accessed July 1, 2020.