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least 30 essential vitamins and minerals and a vast array of important bioactive compounds in the human diet, so a detailed discussion is beyond the scope of this chapter. For more information, see summaries about the roles of vitamins and minerals in health and disease available from the US National Institutes of Health, Office of Dietary Supplements,⁵ US Department of Agriculture,⁶ and Dietary Guidelines for Americans.⁷ The Fact Sheets for Health Professionals may be particularly useful for clinicians.⁵

      The essential vitamins include vitamins A, C, D, E, and K, choline, thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9), and cobalamin (B12). Essential minerals include calcium, phosphorus, potassium, sulfur, sodium, chloride, magnesium, iron, zinc, copper, manganese, iodine, selenium, molybdenum, chromium, and fluoride. A succinct summary of the characteristics of several key micronutrients, including their functions, deficiency diseases or symptoms, age‐related changes in metabolism, public health concerns, and sources from foods and supplements, is provided in Table 16.3.

Micronutrients of special concern for older adults

      Because of low intakes in the US and many other countries, nutrients of public health concern have been identified for older adults. These include several vitamins (choline, riboflavin, thiamin, and vitamins A, C, D, and E) and minerals (calcium, magnesium, potassium, and selenium) (Table 16.3).^7,8 In the US, several of these nutrients are added to foods, especially riboflavin, thiamin, vitamin A, vitamin D, vitamin E, and iron, while selenium is added to foods (and fertilizers) in some countries with low selenium in the soil (e.g. Finland⁹). With the exception of choline and potassium, these nutrients of concern are typically found in nutritionally significant amounts in multivitamin‐mineral (MVM) supplements (Table 16.3).

      Calcium and vitamin D are widely recognized for their roles in bone health and have many other functions such as differentiation, growth, immunity, insulin secretion, blood pressure, and neuromuscular function.⁵ Menopause leads to bone loss through decreased oestrogen that increases bone resorption and decreases calcium absorption. Adequate calcium and vitamin D intake throughout life protects skeletal health. Recommended daily intakes after age 50 are 1000–1200 mg for calcium and 800 IU (20 μg) (AI) for vitamin D.³ The UL for calcium after age 51 is 2000 mg daily, and the UL for vitamin D after age 9 is 4000 IU (100 μg) daily.³ Although there is no clinical biomarker for calcium status, vitamin D status can be assessed through serum/plasma 25‐hydroxyvitamin D.¹⁰ At a minimum, 25‐hydroxyvitamin D concentrations less than 25–30 nmol/L (10–12 ng/ml) should be treated. There is no clear consensus as to what constitutes adequacy, although a concentration of 50 or more nmol/L is often used.¹⁰

      Vitamin B12 (cobalamin) malabsorption is common in older adults and is often associated with atrophic gastritis.^3,5,11 About 10 to 30% of older adults malabsorb food‐bound vitamin B12, so it is recommended that those age 50 and older meet the RDA mainly by consuming foods fortified with vitamin B12 or a supplement containing B12. Pernicious anaemia is characterized by a lack of intrinsic factor and occurs in 1 to 2% of older adults. Loss of intrinsic factor markedly decreases vitamin B12 absorption in the gastrointestinal tract. Although pernicious anaemia is usually treated with intramuscular vitamin B12, oral doses are also effective.^3,5,11 Vitamin B12 deficiency is usually thought of as mainly causing anaemia (macrocytic anaemia). However, other common signs of vitamin B12 deficiency are fatigue, weakness, loss of appetite, weight loss, and neurological symptoms such as numbness and tingling in hands and feet, balance problems, depression, confusion, dementia, poor memory, and/or soreness of the mouth or tongue.

Iron deficiency is less prevalent in older people than in younger age groups.⁵ Iron deficiency can cause microcytic anaemia and should not be confused with the microcytic anaemia of chronic disease; standard laboratory tests can distinguish these two conditions (serum ferritin, C‐reactive protein). Iron‐deficiency anaemia is associated with gastrointestinal disturbances, weakness, and fatigue as well as impaired concentration, cognitive function, immune function, exercise or work performance, and temperature regulation. Atrophic gastritis, some medications, and other conditions that cause achlorhydria can impair intestinal iron absorption. For health reasons, older people may decide to avoid red meat, which contains the most bioavailable form of iron as heme iron in haemoglobin and myoglobin. Individuals of any age who follow vegetarian and vegan dietary patterns have a higher requirement for iron because of low availability and absorbability of iron from plant‐based diets. Also, MVM supplements marketed to older adults typically contain very little iron to address the lower requirement for iron among postmenopausal women, as well as hereditary hemochromatosis that involves life‐long accumulation of iron,⁵ and thus do not provide repletion for iron deficiency. In the choice of iron supplements for treatment of deficiency, the more bioavailable form, which is ferrous iron (+2), should be selected rather than ferric iron (+3).

Table 16.3 Function, deficiency, age‐related changes, food sources, and supplements.

Nutrient	Function	Deficiency diseases or symptoms	Age‐related changes in metabolism	Low intakes so of public health concern	Primary food sources	Commonly fortified or enriched foods (US)	Types of supplements (US)	Chemical forms or methods of exposure of interest
Calcium	Major mineral in bones and teeth; circulating calcium tightly regulated by parathyroid hormone (PTH)	Very low bone density (osteoporosis) and increased risk of fractures	AI increases for women at age 50 and increases for men after age 70; ageing decreases intestinal absorption	Yesa, b	Milk products, some green leafy vegetables	Milk products, most fluid milk, some yoghurts, some cereals	Single or with vitamin D, some MVMs	Calcium‐citrate better absorbed than calcium‐carbonate; calcium‐carbonate in some antacids (e.g. Tums)
Chromium	Enhances insulin action; role in metabolism and storage of carbohydrate, fat, and protein in the body	Some rare reports of chromium deficiency in hospitalized patients who were fed intravenously	AI decreases at age 51 for men and women; ageing‐associated decrease in chromium in hair, sweat, and blood		Meat, whole grains, some fruits and vegetables	Some meal‐replacement beverages (e.g. Boost Plus, Ensure Plus)	MVMs, single, complex with selected vitamins or minerals	Chromium+3 is biologically available; chromium picolinate is biologically available; but chromium+6 is toxic and not used in foods or supplements
Choline	Source of methyl groups for metabolism, phospholipids, acetylcholine, gene expression, cell signalling; liver production in liver not sufficient to meet human needs	Muscle damage, liver damage, and nonalcoholic fatty liver disease (NAFLD or hepatosteatosis)	AI does not change after age 19	Yesa	In plant and animal foods; in US, main sources are meats, poultry, fish, milk products, and eggs Скачать книгу В начало < 175 176 177 178 179 180 181 182 183 184 > В конец