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Table 21-1.
Daily protein requirements for selected age groups. |
| Body_ID: None |
| Daily protein requirements for selected age groups |
| Body_ID: T021001.50 |
| Age | g/day
males | g/day
females |
| Body_ID: T021001.100 |
| 0-3 months | 12.5 | 12.5 |
| Body_ID: T021001.150 |
| 10-12 months | 14.9 | 14.9 |
| Body_ID: T021001.200 |
| 4-6 years | 19.7 | 19.7 |
| Body_ID: T021001.250 |
| 15-18 years | 55.2 | 45 |
| Body_ID: T021001.300 |
| 19-50 years | 55.5 | 45 |
| Body_ID: T021001.350 |
| 50+ years | 53.3 | 46.5 |
| Body_ID: T021001.400 |
|
| Body_ID: T021001.450 |
Protein requirements are age- and sex-dependent. Here we show the reference nutrient intakes (RNI) for selected age groups. Data from Dietary Reference Values for Food Energy and Nutrients for the United Kingdom; Report of the Panel on Dietary Reference Values of the Committee on Medical Aspects of Food Policy, London: TSO 2003.
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| Fats are the main nutrient used for energy storage. Lipids are also essential components of biological membranes and serve as substrates for the synthesis of glycolipids and glycoproteins, and also phospholipids, prostaglandins, leukotrienes, and thromboxane. Lipid-derived molecules have many signaling functions and affect gene transcription. Lipids provide
thermal insulation for the body. They are particularly important for the development of brain and retina. Fats are classified into saturated and unsaturated (and within the latter category there is a subdivision into mono-and polyunsaturated fats: see below).
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| Long-chain fatty acids are not souble in water but medium-chain fatty acids are. The most common saturated fatty acid is the palmitic acid (C16). Other are stearic (C18), myristic (C14), and lauric (C12) acids. Medium chain saturated fats (C8-C10) are water-soluble and are transported between the tissues in plasma rather than in chylomicrons. All animal fats (beef fat, butterfat, lard) are highly saturated. Saturated fats are also present in palm oil, cocoa butter and coconut oil.
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| Oleic acid (ω-9) is the only significant dietary monounsaturated fatty acid
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| Monounsaturated fatty acids are present in all animal and vegetable fats. Olive oil is a particularly rich source of monounsaturated fats. Monounsaturated trans-fatty acids (Fig. 21.4), the isomers of the cis-oleic acid are by-products of the hydrogenation process of liquid vegetable oils.
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| Polyunsaturated fatty acids include ω-6 and ω-3 acids
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| page 302 |  | | page 303 |
| Figure 21.4 The example of cis- and transform of a monounsaturated fatty acid (18-carbon oleic acid). Trans fatty acids are produced during the hydrogenation process of liquid vegetable oils. |
| The ω-6 acids are arachidonic acid (ω-6, C-20:4, Δ5,8,11,14) and its precursor linoleic acid (C-18:2, Δ9,12). They are present in vegetable seed oils. The ω-6 fatty acids are present in soybean
and canola oils and in fish oils (particularly in fatty fish such as salmon, sardines, and pilchards).
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| The ω3 fatty acids are α-linolenic (ω-3, C-18:3, Δ9,12,15), eicosapentaenoic (ω-3, C-20:5, Δ5,8,11,14,17), and docosahexaenoic (ω-3, C-22:6, Δ4,7,10,13,16,19) acids. They are present primarily in fish, shellfish, and phytoplankton and also in some vegetable oils such as olive, safflower, corn, sunflower, and soybean and leafy vegetables.
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