Prevention of Osteoporosis


Children and adolescents

Calcium (daily)

Vitamin D (daily)

1 through 3 years

500 mg

200 IUa

4 through 8 years

800 mg

200 IUa

9 through 18 years

1300 mg

200 IUa

Adult women and men

Calcium (daily)

Vitamin D 3 (daily) b

19 through 49 years

1000 mg

400–800 IU

50 years and over

1200 mg

800–1000 IU

Pregnant and breastfeeding women

Calcium (daily)

Vitamin D 3 (daily)b

18 years and under

1300 mg

400–800 IU

19 years and over

1000 mg

400–800 IU


Source: Adapted from National Osteoporosis Foundation [10]

Vitamin D3 is also known as cholecalciferol; vitamin D2 is also known as ergocalciferol

aThe National Osteoporosis Foundation does not have specific vitamin D recommendations for these groups. These suggestions are from the Institutes of Medicine of the National Academies and National Institutes of Health, Office of Dietary Supplements

bWhen available, a supplement of vitamin D3 is recommended over vitamin D2



The IOM RDA for calcium varies according to age group [7]. Children under the age of nine should be consuming at least 700–1000 mg/day. For adolescents 9–18, levels as high as 1300 mg/day are advocated because this is a crucial time for bone remodeling, impacting bone structure throughout adulthood. Based upon IOM guidelines, adults under the age of 50 should consume 1000 mg/day. Males age 50–70 should aim for 1200 mg/day with 2000 mg/day age 71 and over. Females require 1200 mg/day from age 50–70. These numbers have been questioned by several experts in the field who maintain that the vitamin D RDA is too low, whereas the calcium RDA may be too high; the IOM itself indicates that more data is needed regarding the interaction of vitamin D and calcium on bone health [11].


Vitamin D


Vitamin D plays a crucial role in calcium homeostasis, bone metabolism, and balance and risk of falling. Low vitamin D levels are linked to impaired calcium absorption and an increase in parathyroid hormone (PTH) which can result in excessive bone resorption. Without sufficient vitamin D, calcium absorption fails to satisfy the body’s requirements, even when calcium intake is adequate.

Serum 25(OH)D levels, reflecting vitamin D levels produced cutaneously as well as those obtained from food, are the most effective measure of vitamin D. The principal sources of vitamin D are sunlight, food, and supplements. The skin synthesizes vitamin D from the ultraviolet rays (UVB) of the sun which vary depending on time of day, season, skin pigmentation, and other factors; in some areas, vitamin D production may not occur at all in winter. In addition, the use of sunscreen can severely limit the skin’s ability to make vitamin D [12]. The pathway of absorption of vitamin D from sunlight and dietary sources is illustrated in Figs. 1 and 2. Sources of vitamin D in naturally occurring foods are extremely limited and are primarily restricted to fatty fish (salmon, swordfish, tuna), fish liver oil, and egg yolks. Most of the vitamin D in American diets comes from fortified foods such as fluid milk (400 IU per quart), ready-to-eat breakfast cereals, yogurt, cheese, and juices [13]. Since it is difficult to obtain the recommended level of vitamin D from sunlight and food, supplements in the form of vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) may be recommended. Whereas the two forms were once regarded as equivalent, recent studies indicate that vitamin D3 is more effective at raising serum 25(OH)D concentrations than is vitamin D2 [14]. Manufacturers appear to be producing more vitamin D3 than vitamin D2 as well as increasing the levels in multivitamin supplements from the former 400 IU per daily dose to as much as 1000–1500 IU/day. Adequate oral intake of vitamin D is also a factor in preventing falls because it addresses several components of the fall-fracture construct including strength, balance, bone density, lower extremity function, and risk of hip and non-vertebral fractures [5, 6]. Table 2 summarizes the vitamin D content in common food group [15].

A334322_1_En_4_Fig1_HTML.jpg


Fig. 1
The photolysis of ergosterol and 7-dehydrocholesterol to vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). An intermediate is formed after photolysis, which then undergoes a thermally activated isomerization to create the final form of vitamin D. The rotation of the A-ring positions the 3β-hydroxyl group into a different orientation with respect to the plane of the A-ring during production of vitamin D. (Source: Bikle et al. [59]. Used with permission)


A334322_1_En_4_Fig2_HTML.jpg


Fig. 2
Interaction of vitamin D with other hormones. 1,25(OH)2D interacts with other hormones, in particular FGF23 and PTH, to regulate calcium and phosphate homeostasis. FGF23 inhibits whereas PTH stimulates, 1,25(OH)2D production by the kidney. In turn, 1,25(OH)2D inhibits PTH production but stimulates that of FGF23. (Source: Bikle et al. [59]. Used with permission)



Table 2
Vitamin D content of foods






































































Food item

Serving size

Estimated vitamin D content in international units (IUs)

Dairy

Whole, nonfat, reduced fat (fortified with vitamin D)

8 oz. (1 cup)

115–124

Yogurt (fortified with 20 % of the DV for vitamin D)

6 oz.

80

Margarine (fortified)

1 tbsp.

60

Egg (vitamin D in yolk)

1 large

41

Cheese, Swiss

1 oz.

6

Meat

Liver oil, cod

3 oz.

1360

Swordfish (cooked)

3 oz

566

Salmon, sockeye (cooked)

3 oz.

447

Tuna (canned in water and drained)

3 oz.

154

Sardines (canned in oil and drained)

2 sardines

46

Liver, beef (cooked)

3 oz.

42

Cereal and fruit juice

Orange juice (fortified with vitamin D)

8 oz. (1 cup)

137

Cereal (fortified with 10 % of the DV for vitamin D)

8 oz. (1 cup)

40


Source: Adapted from National Institutes of Health [15]

DV percent daily value


Calcium


Calcium is the most abundant mineral in the body, and 99 % of it is stored in bones and teeth. A number of nutrients play a role in bone health, but calcium is accorded special attention not only because it is essential in bone composition but also because the average American’s intake of calcium is far below the amount recommended for optimal bone health, in part because food preferences such as soda have led to reduced consumption of dairy products [16]. Only 30 % of calcium intake is absorbed by the body; factors influencing calcium absorption include vitamin D intake, age, and, to an extent, the amount of phytic acid and oxalic acid in food. Some absorbed calcium is eliminated in the form of urine, feces, and sweat [17]. When calcium intake is insufficient, bone tissue is resorbed, bone mass is reduced, and bone strength is diminished. Bone resorption is controlled by PTH in response to extracellular fluid calcium ion homeostasis rather than to a structural need for bone mass. PTH is also implicated as a cause of bone fragility through its stimulation of bone resorption [18]. “Optimal” calcium intake is defined as the level of calcium consumption required to maximize peak adult bone mass, to maintain that mass, and to minimize bone loss later in life. In this sense, calcium serves as a “threshold” nutrient meaning that below a critical level, the effect of calcium on bone mass is limited by the amount of available calcium, whereas above that level, increased calcium intake provides no added benefit [19].

Calcium-rich foods include dairy products such as low-fat and nonfat milk, cheese, and yogurt; vegetables including kale and broccoli; fish such as sardines and salmon; and calcium fortified foods, particularly fruit juices, cereal, bread, and bottled water. Table 3 gives the calcium content of several of the most common foods [10]. To ensure bone health, the dairy group is most important, providing 20–75 % of recommended calcium, protein, phosphorus, magnesium, and potassium. As Weaver and Heaney point out, the rising consumption of soft drinks and the growing recognition of lactose intolerance have occurred concurrently with a significant decline in milk intake in the United States; alternative foods containing milk’s nutrients are not consumed in sufficient amounts to replace what milk can provide [18]. Recommended calcium levels for healthy individuals vary according to age group, as discussed above. If calcium intake through food is insufficient, two common forms of supplements may be advised. Calcium carbonate is inexpensive, available in several over-the-counter antacids, and absorbed most effectively when taken with food. Calcium citrate is easier to absorb, can be taken with or without food, and causes less constipation than the carbonate form [17]. Whether calcium is obtained from foods or from supplements, it is best absorbed in amounts of 500–600 mg or less. People with osteoporosis or those at risk are often referred to a registered dietician for nutrition counseling.


Table 3
Calcium content of foods










































































































































Food item

Serving size

Estimated calcium content in milligrams (mg)

Milk

Whole

8 oz. (1 cup)

275

Low-fat

8 oz. (1 cup)

290

Skim

8 oz. (1 cup)

305

Yogurt

Plain yogurt, fat-free or low-fat

8 oz. (1 cup)

415

Fruit yogurt, low-fat

8 oz. (1 cup)

245–385

Frozen yogurt, vanilla, soft-serve

8 oz. (1 cup)

205

Ice cream, low-fat or high-fat

8 oz. (1 cup)

70–90

Cheese

American

1 oz.

175

Cheddar, shredded

1 oz.

205

Cottage cheese, 1 % milk fat

1 cup

140

Mozzarella, part skim

1 oz.

145–205

Parmesan, grated

1 tbsp.

70

Ricotta, part skim

4 oz. (½ cup)

335

Swiss

1 oz.

220–270

Fish and shellfish (canned)

Sardines, in oil with bones

3 oz.

325

Salmon, pink with bones

3 oz.

180

Shrimp

3 oz.

50

Vegetables

Bok choy (Chinese cabbage), raw

8 oz. (1 cup)

75

Broccoli, cooked and drained

8 oz. (1 cup)

60

Kale, cooked

8 oz. (1 cup)

95

Soybeans, mature, cooked, and drained

8 oz. (1 cup)

175

Turnip greens, fresh, cooked, and drained

8 oz. (1 cup)

200

Fruits

Oranges

1 whole

50

Dried figs

2 figs

55

Fortified foods

Fruit juice with added calcium

6 oz.

200–260

Cereal with added calcium (without milk)

1 cup

100–1000

Tofu prepared with calcium

4 oz. (½ cup)

205

Soy milk with added calcium

8 oz. (1 cup)

80–500


The calcium content listed for most foods is estimated and may vary due to multiple factors such as fortification and fat content

Source: Adapted from National Osteoporosis Foundation [10]



Other Dietary and Lifestyle Factors



Sodium Intake


On average, Americans consume about 3400 mg of sodium per day as opposed to the recommended 2300 mg [20]. Over the past quarter century, studies have shown a correlation between sodium intake and urinary calcium excretion, some of which comes directly from bones. Researchers led by R. Todd Alexander at the University of Alberta have demonstrated a molecular link between sodium and calcium loss, observing that the epithelial sodium/proton exchanger, NHE3, which is responsible for sodium absorption also regulates calcium loss. The greater the intake of sodium, the greater the loss of calcium through the urine [21]. In another study, Nordin et al. have shown that with sodium as the determining factor, 100 mmol of sodium removes approximately 1 mmol of calcium in the urine, which is the equivalent of 1 % extra bone loss each year. Moreover, sodium-dependent calcium loss can continue indefinitely [22]. Adhering to the recommended guidelines of 2300 mg/day, with 1500 mg over age 50 is critical to good bone health.


Alcohol Consumption


Avoidance of excessive alcohol intake, particularly during adolescence and young adulthood, also prevents general bone deterioration and risk of falls. Hormones, vitamins, and growth factors act together to regulate the distribution of calcium between bone and blood. Chronic heavy drinking disrupts that interaction by affecting the substances that regulate calcium metabolism, including PTH, calcitonin, and vitamin D. In addition, alcohol causes men to generate less testosterone, a hormone linked to the production of osteoblasts that promote bone formation. Similarly alcohol leads to irregular menstrual cycles in women, reducing estrogen production and leading to osteoporosis [23]. The effect of alcohol on balance and gait leads to an increased number of falls and particularly hip fractures.

Current dietary guidelines for Americans define heavy drinking as seven drinks or more per week for women and 14 drinks or more per week for men. Moderate drinking is defined as one drink per day for women and two drinks per day for men [20]. A few recent studies have indicated that moderate drinking may be linked with decreased fracture risk in postmenopausal women, most notably, a study of 14,000 subjects by Naves Diaz et al. found that women age 65 and over who drank alcohol on more than five days per week had a reduced risk vertebral deformity compared with those who consumed alcohol less than once a week [23]. Other studies show no beneficial results. Further research is needed to clarify these findings.

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Aug 17, 2017 | Posted by in PHYSICAL MEDICINE & REHABILITATION | Comments Off on Prevention of Osteoporosis
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