1. Chapter 11 MAJOR MINERALS AND BONE HEALTH

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Minerals in the Body
Minerals are elements needed by the body in small amounts for health and maintenance.
Major minerals are needed in the diet in amounts greater than 100 mg per day or are present in the body in amounts greater than 0.01% of body weight.
Trace minerals are required in the diet in amounts less than 100 mg per day or are present in the body in amounts less than 0.01% of body weight.
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Minerals
Figure 11.1 Major and trace minerals in the periodic table
The major minerals are shown in purple, and the trace elements are shown in blue.
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Minerals in the Diet
Figure 11.2 Minerals in Canada’s Food Guide food groups
Minerals are found in all food groups, but some groups are particularly good sources of specific ones.
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5. Calcium, Magnesium and Phosphorus Intake of Canadians
Source: Health Canada. Canadian Community Health Survey, Cycle 2.2, Nutrition (2004) - Nutrient Intakes from Food: Provincial, Regional and National Summary Data Tables, Volume 1,2 and 3. Cat No
Note: At press time, Health Canada had not yet modified CCHS calcium data to reflect 2010 DRIs for calcium; values shown here were estimated by the author (D.G) and should be considered no more than an approximate assessment of Canadian intakes.
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Mineral Talk
Minerals are available in unprocessed foods, some processed foods and dietary supplements.
To maintain health, minerals must be consumed in the correct proportions.
Bioavailability is very important. For example, phytates can limit the body’s ability to absorb calcium, zinc and iron.
DRIs for minerals are expressed as RDAs, EARs or AIs.
Because certain minerals can be toxic if taken in too high an amount, ULs have been established.
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Minerals as Cofactors
1 The mineral cofactor combines with the incomplete enzyme to form the active enzyme.
2 The active enzyme binds to the molecules involved in the chemical reaction (compounds A and B) and accelerates
their transformation into the final products (products A and B).
3 The final products are released, while the enzyme remains unchanged.
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Calcium in the Diet
Figure 11.5 Calcium content of Canada’s Food Guide food groups
Calcium is provided by many different foods, but milk and alternative products and fish consumed with bones are the best sources; the
dashed lines represent the RDA for adults ages and for adults over age 50.
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9. Calcium in the Diet (continued)
Intake of soft drinks is affecting the calcium intake of teenagers. Canadian adolescent males (14–18 years) consume an average of 376 ml/day of regular soft drinks and adolescent girls consume 179 ml/day.
Milk intake declines with age.
Teenage boys consume 323 ml/day; girls, 222 ml /day.
Young men (19–30 years) consume 201 ml/day; young women, 178 ml/day.
Men over 70 consume 136 ml/day; women, 136 ml/day.
Canada’s Food Guide recommends 3 servings of milk or milk products/day to ensure adequate calcium intake. (Intake as milk would be 750 ml/day).
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10. Calcium in the Diet (continued)
Soft drinks are replacing milk, have no calcium and are higher in sugar.
Low calcium intake early in life increases the risk of osteoporosis and increases the number of overweight and obese individuals.
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11. Calcium in the Diet (continued)
You can determine if a packaged food is a good source of calcium by looking at the label.
The Nutrition Facts panel lists the amount of calcium in mg and as % of Daily Value.
The product label may have a nutrient content claim.
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12. Calcium in the Diet (continued)
A multivitamin and mineral supplement will not provide enough calcium to meet your needs.
Read labels to find a supplement that contains calcium alone or calcium with Vitamin D (which aids in absorption of calcium).
The form of calcium is also important. Calcium carbonate should be taken with a meal, whereas calcium citrate can be taken at any time.
Antacids that contain aluminum and magnesium may actually increase calcium loss.
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Calcium Talk
Calcium is the most abundant mineral in the body.
Calcium provides the structure to bones and teeth and has important regulatory roles.
Calcium is absorbed by active transport and passive diffusion, depending on the availability of the active form of vitamin D.
Bioavailability of calcium is decreased in the presence of tannins, fiber, phytates and oxalates.
Calcium accounts for 1–2% of adult body weight.
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14. Calcium’s Role in the Body
99% of calcium in the body is found in solid mineral deposits in the bones and teeth.
The remaining 1% is found in intracellular fluid, blood and extracellular fluid.
Calcium found in the body’s fluid plays a role in nerve transmission, muscle contractions, blood pressure regulation and the release of hormones.
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15. Regulation of Blood Calcium
Figure 11.7 Regulation of blood calcium levels
Levels of calcium in the blood are very tightly regulated by parathyroid hormone and calcitonin.
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16. Calcium and Bone Health
Figure 11.9 Bone remodelling
During bone remodelling, osteoclasts (pink) break down bone, and osteoblasts (blue) build bone.
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Figure 11.8 Types of bone
Cortical bone is compact bone that forms the dense outer layer; the spongy interior is referred to as trabecular bone.
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18. Risk Factors for Osteoporosis
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Osteoporosis
Osteoporosis is a major public health problem in Canada.
Two million Canadians over age 50 have osteoporosis. Twice as many women as men have the condition.
Osteoporosis is responsible for 80% of fractures in people over 60 years of age.
Osteoporosis and fractures cost the Canadian health care system $1.9 billion annually to treat.
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Osteoporosis Risk
Figure Effects of osteoporosis
Osteoporosis of the spine leads to a stooped posture and decreased stature. (Larry Mulvehill/Photo Researchers)
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Gender and Bone Mass
Figure Bone mass by gender and age
Although both men and women lose bone after about age 35, women have a lower bone mineral density than men and experience accelerated bone loss after menopause.
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Phosphorus in the Diet
Figure Phosphorus content of Canada’s Food Guide food groups
Adults can obtain their RDA of phosphorus (dashed line) by consuming foods in all the food groups.
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Phosphorus Talk
Phosphorus makes up about 1% of an adult’s body. 85% of phosphorus in the body is found in the bones and teeth.
Phosphorus is more readily absorbed than calcium.
Phosphorus is an important component of molecules with structural or regulatory roles.
Phosphorus deficiency can lead to bone loss, weakness and loss of appetite.
Phosphorus toxicity is rare, but can lead to bone resorption.
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Magnesium in the Diet
Figure Magnesium content of Canada’s Food Guide food groups
Magnesium is found in nuts, seeds, legumes, and leafy greens; the dashed lines represent the RDA for adult men and women over age 30.
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Magnesium Talk
About 50-60% of magnesium in the body is found in bone, where it is essential for the maintenance of structure.
Most of the remaining magnesium is present inside cells, where it is the second most abundant intracellular ion, after potassium.
Magnesium is a cofactor for over 300 enzymes. It is necessary for the generation of energy from carbohydrate, lipid and protein.
Magnesium deficiency is rare. When it does occur, especially in individuals with alcoholism, malnutrition, kidney and GI disease or in people taking diuretics, it may cause nausea, muscle weakness and cramping, mental derangement and changes in blood pressure and heartbeat.
Magnesium toxicity is rare. The UL for adults has been set at 350 mg from nonfood sources of magnesium.
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Sulfur Talk
Dietary sulfur is found in protein foods and sulfur-containing amino acids in vitamins.
Dietary sulfur is also found in nonfood additives, such as sulfur dioxide, sodium sulfite and sodium bisulfite.
Sulfur-containing amino acids, such as methionine and cysteine, are needed for protein synthesis.
The vitamins thiamin and biotin contain sulfur.
There is no recommended daily intake for sulfur.
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27. Summary of Calcium, Phosphorus, Magnesium and Sulfur
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