Minerals:   Ca  Mg  Na  K  Fe  I  Zn 

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Description and Use:

Minerals are inorganic (do not contain carbon) elements needed in minute amounts for normal health and growth. They, along with vitamins and phytochemicals, are therefore referred to as micronutrients. Minerals originate in the Earth and cannot be made by living organisms. Plants obtain minerals from the soil, and most of the minerals in our diets come directly from plants or indirectly from animal sources. Unlike vitamins which generally act as catalysts to chemical reactions but do not become part of bodily tissues, minerals can become structural components of bodily tissues and chemicals. Like calcium in bone, iron in hemoglobin etc. They are not broken down in digestion and unlike some vitamins; they are not affected by heat or light. They assist in maintaining fluid balance, producing energy, eliminating harmful by-products of metabolism, regulating heartbeat, making hormones and are essential for bone and blood health.

Minerals are divided into two categories, the major minerals, those with daily requirements of more than 100 mg/day and trace minerals, those with daily requirements below 100 mg/day.
There are 7 major minerals; calcium, phosphorus, potassium, sulfur, sodium, chlorine and magnesium.
There are 14 traces minerals; iron, selenium, iodine, chromium, zinc, fluoride, copper, manganese, molybdenum, boron, silicon, vanadium, nickel and strontium.

This document will review those minerals which require some consideration when planning a balanced diet. These include calcium, magnesium, sodium, potassium, iron, iodine and zinc. The other minerals are not generally a concern, especially if the diet is varied and includes fruits, vegetables and whole grains. For more information on any of these minerals, reference other sites using the links below.
Phosphorus   Sulfur   Chlorine   Selenium   Chromium   Fluoride   Copper   Manganese   Molybdenum   Boron

The National Institutes of Health do not have information pages for the following; Silicon, Vanadium, Nickel and Strontium.

Daily Reference Intakes:

DRIs, used in the U.S. are established by the Food and Nutrition Board, Institute of Medicine, National Academies. The DRIs for most nutrients include an RDA (Recommended Daily Allowance) or an AI (Adequate Intake) and a UL (Tolerable Upper Intake Limit). RDA is the intake level that meets the requirement of 98% of healthy individuals. AI is given if the RDA is unknown. UL is the highest intake level considered to be safe. Values are given for groups based on age, sex and pregnancy/lactation status. View DRI Tables. Nutrition labels on foods and supplements state the mineral content as a percent of daily value, DV, for the serving size indicated. The DVs used on labels are based on the RDA values established in 1968. They have been updated since then.

The mineral content of foods can be found at the USDA Nutrient Database.

Mineral Table:

Calcium Function: In addition to bone health, calcium has other important functions in the body. It is necessary for normal nerve transmission, muscle contraction, healthy blood pressure, blood clotting and maintaining a neutral acid-base balance in the blood. As such, the body strives at all costs to keep calcium levels in the blood within a normal range. If there is insufficient calcium absorbed from the diet, calcium will be drawn from the reserves in the bones.

Calcium is the most plentiful mineral in the human body. 99% of the body's calcium is stored in the bones. The remaining 1% is found in the blood and soft tissues. The primary concern for getting adequate calcium in the diet is to maintain healthy bones and teeth. Insufficient calcium intake over time is a contributing factor leading to osteoporosis, the most prevalent bone disorder. Osteoporosis is characterized by a decrease in bone density or porous bones which have a reduced ability to bear weight and are therefore more fragile and at risk for fracture. Worldwide, it affects one in three women and one in five men over the age of fifty. 20% of older adults who suffer a hip fracture, die within one year due to subsequent illness. This section will look at how bone density is built up, what causes bone loss and how to limit bone loss as we grow older.

It is important to build peak bone mass through proper nutrition and exercise while you are young. Bones reach their full length and 90% of their bone mass by age 18-21. Bone density can continue to increase through weigh bearing exercise like jogging, climbing stairs, tennis, resistance training etc. Peak bone mass is achieved before the age of 30. Bone mass remains stable in the 30's but by age 40 it starts its irreversible decline. During menopause when estrogen levels drop, the rate of bone loss can increase significantly. Men can also suffer bone loss due to age-related decreases in testosterone.

Adequate calcium intake alone is not sufficient to guard against bone loss. In some countries (U.S., U.K., Sweden, Norway, New Zealand ) calcium intake is high but the incidence of hip fractures is still relatively high also. In other countries, like China, (as pointed out in the "China Study" by Dr. Campbell ) calcium intakes are low but the incidence of osteoporosis is also very low. Other factors that affect calcium absorption and utilization include vitamin D, calcium loss in the urine and as mentioned before, exercise. Adequate vitamin D is needed to aid in absorption during digestion and later in the calcification of bone. Calcium is also lost in the urine. One's calcium balance can be calculated as the absorbed calcium minus the calcium excreted in urine. For example; you may consume 1000 mg, absorb 300 mg but excrete 350 mg. This would leave a negative -50 mg calcium balance. Some feel that this loss of calcium in the urine over time is the main cause of osteoporosis. High animal protein diets are a significant factor in calcium loss. It causes an acidic condition in the blood and calcium is then pulled from the bone to neutralize it. High animal protein intakes and low levels of vitamin D may be the main reason why countries with high calcium intake also have high incidences of hip fractures. This is another good reason for a vegetarian diet! A limited study found that lacto-ovo vegetarians are less prone to osteoporosis than omnivores. Smoking, alcohol, salt and caffeine (more than 3 cups per day) are other factors which contribute to calcium loss. More information on osteoporosis.

In summary, to maximize calcium utilization;
  • Get adequate calcium from multiple food sources. If intake is lower than the RDA, use a supplement. Assuming you are getting most your Ca from food, supplements need not be more than 50% of your RDA. Smaller doses throughout the day are better. 500 mg is the maximum that can be absorbed at one time. A Calcium-Magnesium-D supplement in the ratio of 333mg-133mg-200IU is well rounded. Avoid supplements made from bone meal, oyster shell or dolomite; they can have high levels of lead.
  • Get adequate vitamin D, approx. 600 IU per day either from diet, supplement or sunlight. Since there are only very small amounts of naturally-occurring vitamin D in plant foods, vegetarians should rely on foods fortified with vitamin D, including fortified soy/dairy milks, juices, and breakfast cereals. If you get adequate D or take a multivitamin with D, then it need not be included in the Calcium supplement.
  • Get regular weight-bearing exercise.
  • Soy protein can be a beneficial alternative to animal protein. Research has shown a positive relationship between soy protein and bone mineral density in postmenopausal women. This may be due to the isoflavones in soy which have estrogen-like properties.
  • Reduce sodium, do not smoke, be moderate in caffeine.
  • Do not take vitamin A in the retinol form. If using a supplement with vitamin A, use the beta-carotene form.
Requirements: For men and women aged 19-70 years, the RDA is set at 1,000 mg/day. After age 70 the RDA increases to 1,200 mg/day. These high levels take into consideration the bioavailability of the foods and absorption rate based on age. Absorption rates vary by age; children can absorb about 60%, pregnant/lactating women about 50%, young adults about 30% and older adults about 25%.
Food Sources: Milk and related dairy products, yogurt, cheese. Dark green leafy vegetables (except spinach which has a 5% absorption rate), broccoli, cauliflower, green cabbage, legumes, tofu and nuts. Fortified soy milk, cereals and orange juice. More
Deficiency: Deficiency over time can lead to osteoporosis.
Excess: The UL (Upper Limit) for calcium is set at 2,500 mg/ day up till age 50 then 2,000 mg per day after age 50. Large doses over a prolonged time can lead to kidney stones and an increase risk of prostate cancer. It can also affect the absorption of other minerals such as iron, magnesium and zinc. Top
Magnesium Function: Magnesium works together with calcium and vitamin D in maintaining bone health. 50-60% of the magnesium in the body is found in the bones. It also works with calcium to support normal muscle contraction. It is a cofactor for more than 300 enzyme systems and as such is involved in energy production, blood clotting and protein synthesis.

Because of its close association with calcium, it is often included in calcium supplements. Dosages are generally half that of the calcium reflecting the ratio set in the RDA's. If you use a calcium supplement, one that also includes magnesium is a good choice.
Requirements: For men aged 19-30, the RDA is 400 mg /day then after age 30, 420 mg/day. For women aged 19-30 the RDA is 310 mg /day then after age 30, 320 mg/day.
Food Sources: Green leafy vegetables, whole grains, brown rice, legumes, nuts and seeds. More
Deficiency: Low blood calcium levels, muscle cramps, spasms or seizures, nausea, weakness, irritability and confusion. Long-term deficiency can be associated with osteoporosis.
Excess: Toxicity does not occur from eating foods but can result from supplements or medicines (milk of magnesia). The UL for magnesium is set at 350 mg/day and this means from supplements or medicines not food. Excess can result in diarrhea, nausea and abdominal cramps. Top
Sodium Function: Sodium is essential to normal body function and its blood levels are closely regulated. It works together with potassium to maintain fluid balance, blood pressure and acid-base balance. It also assists with the transmission of nerve signals and muscle contraction. It should not be eliminated from the diet.
Requirements: There is no RDA for sodium. For adults, the AI ( Adequate Intake) is set between 1.2-1.5 g/day. The average American gets 3.3 g/day.
Food Sources: Table salt, soy sauce, miso and salt added in prepared foods. Buying the low-sodium version of some prepared foods can be a smart move. Soy sauce, tomato and mushroom soup, tomato juice etc. are some examples of traditionally high sodium foods that have low-sodium versions. More
Deficiency: Is rare since the American diet is so high in sodium. Generally, deficiency only occurs when salt is lost through excessive sweating and is not replaced. It can also be caused by drinking large volumes of water (hyponatremia) which can be very dangerous. Symptoms include becoming weak, faint and disoriented. In more extreme cases (marathon runners who sweat and drink excessive water) it can lead to nausea, vomiting, muscle cramps, seizures, coma and even death.
Excess: For healthy adults the UL (Upper Limit) for sodium is 2.3 g/day, about 1 tsp of salt. Those at risk for hypertension should not exceed 1.5 g/day. Sodium above the UL can lead to fluid retention and hypertension (high blood pressure) especially in older people and those with salt sensitivity. Top
Potassium Function: Potassium and sodium work together to maintain proper fluid balance, blood pressure and to regulate the contraction of muscles and transmission of nerve impulses. Unlike sodium, a diet high in potassium helps to maintain low blood pressure.

The body needs to maintain blood potassium levels in a narrow range. Levels that are too high or too low can result in heart failure and death. This is generally the result of a medical condition or medicines and not from diet.
Requirements: There is no RDA for potassium. For adults, the AI (Adequate Intake) is set at 4.7 g/day.
Food Sources: Tomatoes and tomato products, potato, sweet potato, legumes, green leaves, bananas, dates, raisins. More
Deficiency: Because potassium is in so many foods, deficiency is rare. Low levels of blood potassium are generally the result of a medical condition (kidney disease) or medications (certain diuretic medicines to treat blood pressure). Extreme dehydration, vomiting and diarrhea can also cause hypokalemia, low blood potassium. Symptoms include confusion, loss of appetite and muscle weakness. Extreme cases can lead to heart failure and death.
Athletes sometimes eat bananas, known to be high in potassium, to prevent muscle cramps.
Excess: There is no UL for potassium. People with healthy kidneys are able to excrete excess potassium effectively. Kidney disease may affect the ability to regulate potassium levels and hyperkalemia, high blood potassium, can result. This can result in heart attack and death. Top
Iron Function: : Iron is involved in energy production. It is a key component of hemoglobin and myoglobin, the proteins in blood and muscle used to transport oxygen throughout the body. It is a coenzyme involved in energy metabolism and part of the antioxidant system that fights free radicals.

There are two types of iron; heme iron (part of hemoglobin and myoglobin) only found in animal foods and non-heme iron found in both animal and plant foods. All iron in plants is non-heme. Heme iron is more absorbable than non-heme iron.

The absorption rate for iron varies depending on iron reserve levels, other nutrients in the meal and the type of iron. Typically absorption rates are 14-18% however if iron levels are low, the absorption rate can increase as high as 40%. Vitamin C enhances absorption. Adequate stomach acid is also needed for absorption. Soy protein, fiber, phytates, black tea and calcium inhibit absorption. The tannins in tea and coffee can reduce the absorption of non-heme iron in a meal by 60% and 40% respectively. It is estimated that the absorption rate for a vegan diet is about 10%.
Requirements: For men 19 or older the RDA is 8 mg /day. For women aged 19-50, the RDA is 18 mg /day and after age 50, 8 mg/day. The actual biological requirement is about 1 mg for men and 1.5 mg for women. The RDA values reflect the dietary intake required to compensate for the low absorption rate. Additionally, nutritionists recommend 1.8 times more for vegetarians since the source of their iron is non-heme. This would mean 18 mg for men, 32 mg for women 19-50 and 18 mg for women over 50. The IOM estimates that people who do regular intense exercise, like long distance running, need 30% more iron. This is to compensate for red blood cells destroyed in the feet and gastrointestinal blood loss.

Studies show that vegetarians usually consume more iron than non-vegetarians and that they are no more likely to be iron deficient than non-vegetarians. However, women in both groups often do not get the recommended amounts. If you are uncertain or are a premenopausal woman then taking a supplement can be a good idea. Most standard multivitamins include 100% of the daily value for iron. Do not take more than that. Choose a formula appropriate for your gender; men's formulas will has less iron, women's formulas will have more iron.
Food Sources: Fortified cereals, enriched flour/cornmeal, tofu, legumes, rice, green vegetables (broccoli, kale, collards) dried fruit (prunes, raisins, figs). Cooking foods in cast-iron pans significantly increases the iron content of a meal. More
Deficiency: According the World Health Organization, iron deficiency is the most common nutrient deficiency in the world. Women of child bearing years are the most susceptible due to losses in menstrual blood (8-10% are deficient). Rates are higher among athletes (especially endurance athletes). Besides inadequate dietary intake, iron deficiency can also result from diets high in fiber or phytates (which binds to iron), low stomach acid, poor intestinal health, high levels of calcium supplements and significant blood loss.

Deficiency results in microcytic anemia. Symptoms include fatigue, pale skin, shortness of breath, depressed immune system, impaired work performance, cognitive function and memory.
Excess: For adults, the UL (Upper Limit) for iron is 45 mg/day. Iron toxicity can cause nausea, vomiting, diarrhea, dizziness, confusion and rapid heart beat. If not treated quickly, toxicity can potentially cause death due to heart, nervous system, liver, and kidney damage. Iron toxicity is the most common cause of poisoning deaths in children under 6. This usually happens when they eat a number of adult vitamin supplements containing iron.

If you take a multivitamin, be careful not to double dose on iron. Some fortified foods like the breakfast cereals Product 19 or Total have 100% DV of iron. If you eat these cereals, skip the multivitamin. Top
Iodine Function: Iodine is used exclusively for the synthesis of thyroid hormones. Upon absorption, it is taken up by the thyroid gland. Thyroid hormones regulate body temperature, resting metabolic rate, macronutrient metabolism, reproduction and growth.

Few plant foods are a reliable sources of iodine since the amount of iodine in a food depends on the amount of iodine in the soil where it was grown. Large areas of farmlands in the US (Great Lakes and Pacific Northwest regions) are low in iodine. To address discrepancies between geographic regions, it was decided to add iodine to table salt in 1924. For many people this is the main source of iodine. Most developed countries fortify salt and this has reduced deficiency to < 2.8% within those populations.
Requirements: For adults the RDA is 150 mcg/day. ½ tsp of iodized salt meets the RDA. Using iodized salt is recommended. Iodine is also commonly found in multivitamins.
Food Sources: Iodized salt, seaweed (kelp, nori).
Deficiency: Insufficient iodine results in goiter, swelling at the base of the throat, where the thyroid gland enlarges to try to capture more iodine from the blood. A host of problems can result; growth and development disorders, mental deficiencies and decreased fertility.

Pregnant women who are deficient in iodine can have spontaneous abortions, stillbirths and babies suffering from birth defects, mental retardation (cretinism), stunted growth, deafness and muteness. The World Health Organization considers iodine deficiency to be the "greatest single cause of preventable brain damage and mental retardation" in the world.
Excess: For adults, the UL (Upper Limit) for iodine is 1,100 mcg/day. Excess iodine blocks the synthesis of thyroid hormones and results in goiter also. Top
Zinc Function: Zinc is involved in numerous aspects of cellular metabolism. It is required for the catalytic activity of approximately 100 enzymes and it plays a role in immune function, protein synthesis, wound healing, DNA synthesis and cell division. Zinc also supports normal growth and development during pregnancy, childhood, and adolescence. It is required for a proper sense of taste and smell. A daily intake of zinc is required to maintain a steady state because the body has no specialized zinc storage system

Zinc lozenges formulated to shorten the length or reduce the severity of a cold have not been shown to be effective.
Requirements: For adult men, the RDA is 11 mg/day. For adult women, the RDA is 8 mg /day.
Food Sources: Fortified cereals, legumes, nuts, whole grains including barley, buckwheat, wheat germ. More
Deficiency: Deficiency is uncommon in the US. Slow growth and growth retardation in children. Delayed sexual maturation and impotence, eye and skin lesions, hair loss and impaired appetite.
Excess: For adults, the UL (Upper Limit) for zinc is 40mg/day. Toxicity symptoms include intestinal pain and cramps, nausea, vomiting, loss of appetite, diarrhea and headaches. Top

Myths:

Lastly, a few myths about minerals;

  • It is not possible to get enough calcium in our diet without dairy products.
    Fact: Fortified soy products are an equivalent substitute. There are many plant-based sources that provide good calcium also. If the diet is not adequate in alternative sources, a supplement can make up the difference.
  • Vegetarians need less calcium than non-vegetarians.
    Fact: There have been insufficient studies on the specific calcium needs of vegetarians and nutritionists recommend vegetarians meet the established RDA.
  • Due to its protein content, milk actually drains our system of calcium.
    Fact: Milk has a good calcium to protein ratio. The ideal is 16mg:1g. One cup of milk has about 300mg: 8g or a 37:1 ratio and 32% of the calcium is absorbable. Milk is a good source of calcium.
  • Getting enough calcium ensures strong bones and teeth.
    Fact: Vitamin D is needed for absorption of calcium and calcification of bone. Weight-bearing exercise strengthens bones. Reduce calcium loss by not smoking and being moderate in sodium, alcohol and caffeine.
  • Most vegetarians end up with iron-deficiency anemia.
    Fact: Studies show that vegetarians consume as much iron as non-vegetarians and are no more likely to be deficient.

Summary:

  • There are 7 major minerals; calcium, phosphorus, potassium, sulfur, sodium, chlorine and magnesium. There are 14 traces minerals; iron, selenium, iodine, chromium, zinc, fluoride, copper, manganese, molybdenum, boron, silicon, vanadium, nickel and strontium.
  • Minerals usually mentioned as a concern for vegetarians are calcium, iron and zinc. This is because milk and dairy products are considered the main source of calcium and meat is generally considered the main source of iron and zinc. Lacto-vegetarians can easily consume adequate calcium. For vegans and those who avoid dairy products, fortified soy milk products are an equivalent substitute. For those who avoid dairy and soy, a Ca supplement can be used to reach the RDA. Iron and zinc can found in sufficient quantities from plant-based sources. Include legumes, green vegetables, nuts and seeds as part of your regular diet.
  • Calcium is needed in sufficient amounts over time to build strong bones during youth and to prevent or slow osteoporosis in later age. Calcium by itself is not enough. Adequate vitamin D is needed also to aid in the absorption of calcium and the calcification of bone. Regular weight-bearing exercise can help to maintain or even increase bone density.
  • Calcium loss is a major factor in osteoporosis. High animal protein diets, smoking, alcohol, high sodium intake and caffeine (more than 3 cups of coffee worth) contribute to calcium loss in the urine. Vegetarians have an advantage here because their diets contain little or none of the animal (sulphur-containing) proteins that cause calcium loss (meat, fish, poultry, eggs). It is best not to smoke and be moderate in sodium, alcohol and caffeine.
  • Magnesium works together with calcium to build strong bones and is also needed for more than 300 enzyme systems. It is found in green leafy vegetables, whole grains, nuts and seeds. Processing grains removes much of the magnesium and it is not added back during the enrichment process. For example; 1 cup of whole wheat flour has 164 mg, 1 cup of white flour, 28 mg. So, choosing whole grains is a smart choice to boost magnesium.
  • Sodium and potassium are electrolytes that regulate fluid balance, blood pressure, nerve transmissions and muscle contractions. The American diet is generally too high in sodium which can be a factor in high blood pressure, fluid retention and bone loss. Limit sodium intake to 2.3 g/day (about 1 tsp of salt) or 1.5 g/day if you are at risk for hypertension.
  • Iron is used in hemoglobin to transport oxygen throughout the body. Nutritionists recommend that vegetarians get 1.8 times the RDA since iron sourced from plants is non-heme. Vitamin C enhances absorption. Adequate stomach acid is also needed for absorption. Soy protein, fiber, phytates, tea, coffee and calcium inhibit absorption. To improve aborption, do not drink tea or coffee with meals. Adequate iron intake is generally not a concern for men but premenopausal women should take a supplement if they are unsure about their intake.
  • Iodine is found in thyroid hormones that regulate growth, metabolic rate and body temperature. Deficiency can lead to goiter and birth defects. Plants are not a reliable source of iodine since iodine content is dependent on the amount of iodine in the soil. Iodized salt provides a reliable source of iodine and has greatly reduced the incidence of goiter since its introduction in 1924.
  • A standard multivitamin is a simple way provide your daily iron, iodine and zinc requirement.
  • Calcium is generally too bulky to be included in significant amounts in a multivitamin so it is generally taken as a separate supplement. If you avoid dairy and other Ca fortified foods, a Ca supplement is recommended. A formula that includes magnesium and vitamin D is optimum. For example; 333mg Ca, 133mg Mg, 200 IU D is a good ratio. Assuming a good portion of your daily Ca comes from food, then supplements should probably not be more than 50% of the RDA. Ca supplements are absorbed better when taken between meals.

Disclaimer:

The contents of this Web site are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this Web site.

References:

  1. Thompson, Janice L., Melinda M. Manore and Linda A. Vaughn. "Nutrients Involved in Fluid and Electrolyte Balance", "Nutrients Involved in Bone Health", "Nutrients Involved in Blood Health and Immunity" The Science of Nutrition San Francisco, CA : Pearson Benjamin Cummings 2008
  2. Duyff, Roberta L. "Vitamins, Minerals and Phytonutrients", "Sodium and Potassium: A Salty Subject", "The Vegetarian Way", "Supplements: Use an Abuse" American Dietetic Association Complete Food and Nutrition Guide Hoboken, NJ : Wiley 2006
  3. Weil, Andrew. "The Micronutrients" Eating Well for Optimum Health New York : Quill 2001
  4. Willet, Walter C. "Calcium: No Emergency", "Take a Multivitamin for Insurance" Eat Drink and Be Healthy New York : Free Press 2001
  5. Melina, Vesanto, and Brenda Davis. "Power from Plants: Legumes, Nuts and Seeds", "Bone Boosters: Milks, Greens and Other Calcium Champions" Becoming Vegetarian Summertown, TN : BPC 2003
  6. Messina, Virginia, and Mark Messina. "Meeting Calcium Needs on a Plant-Based Diet", "Minerals in Vegetarian Diets" The Vegetarian Way New York : Three Rivers Press 1996
  7. Craig, Winston J. "Calcium: The Bare Bone Facts", "Majoring in the Minors", "Iron Status of Vegetarians" Nutrition and Wellness Berrien Springs, MI : Golden Harvest Books 2008
  8. Fuhrman, Joel. "The Dark Side of Animal Protein" Eat To Live New York, NY: Little, Brown and Company 2011
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