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					Nutrition & ageing

   Dr Petula Nurse
      Lecture 3


                     1
            Life expectancy
• Can be extended by restricting food intake
• Not known whether the ageing process in
  humans can be altered by nutrition




                                               2
             The ageing process
• Wear & tear, number of theories postulated
• Programmed ageing theory
   – pre-determined, presumably genetic, age- related
     alteration in cellular function
      • leads to a susceptibility to disease and death
• Genomic instability theory
   – errors in transcription & translation
   – resulting in impaired protein synthesis, deterioration in
     cell function as age increase

                                                                 3
           Free radical theory
• Highly reactive molecules
  – no longer metabolised rapidly
     • accumulation occurs
     • leading to irreversible cell damage
• Random genetic errors
  – an accumulation of errors over time
     • impaired protein synthesis
     • decrease in cellular function

                                             4
  Nutritional requirements in the
              elderly
• Qualitatively similar to the requirements of
  younger adults
  – energy expenditure is less
  – a lower energy requirement
• Maintaining physical activity
  – required for overall health of elderly



                                                 5
     Daily energy requirement
• ‘Elderly people’ (60 +)
  – 1.5 x BMR
• BMR is reduced
  – due to a fall in fat-free mass
     • from 60 to 50 kg men
     • from 40 to 35 kg women
  – diet should contain same proportions of
    nutrients
  – essential nutrients still required        6
          Nutritional deficits
• Dental problems
• lack of cooking skills
• depression
• lack of motivation
• significant malnourishment - social
  problems or disease
• vitamin D supplements required
• high prevalence of osteoporosis, daily Ca   7
           Food & nutrition
• Income & expenditure on food 1998
• Average household UK
  – devoted ~17% income on food
• Lower income - 23%
• Higher income - 14%
• Composition of diet varies substantially
  between different income groups
                                             8
      Programming hypothesis
      (Barker hypothesis 1999)
• Inadequate maternal nutrition during
  pregnancy
• adversely affects the development of fetal
  blood vessels
  – increases the risk of coronary heart disease and
    stroke when the baby reaches late middle-age
• Maternal nutrition is adversely affected by
  low income increase morbidity, mortality
                                                       9
 Inadequate nutrition in early life
• Have long lasting effects
• Infants growth & development are restricted
  by a prolonged shortage of food
  – they are more prone to infection
  – may never reach their full height potential




                                                  10
         Critical periods (CP)
• Growth is affected by any environmental
  stress (including lack of nutrients)
  – during the later stages of intra-uterine life &
  – in the first two years of life (weaning)
• During CP there is a capacity to ‘catch-up’
  on any lost growth
  – provided the stress is reversed

                                                      11
       As the end of the CP is
            approached
• Ability to recover fully is reduced
• A child who suffers repeated episodes of
  stress through & beyond second year of life
  – has an accumulated short-fall in
     • height & weight which is permanent
  – This deficit is carried over to affect the final
    adult size
• These effects cannot be reversed after 2yr
                                                       12
  Intrauterine growth retardation
               IUGR
• IUGR is poor fetal growth during the antenatal
  period
   – Resulting infants are described as being
      • ‘small for gestational age’ (SGA) or
      • ‘small for dates’ (SFD)
• Brain growth is maximal in the
   – 2nd half of pregnancy &
   – 1st year of extrauterine life
      • the ‘period of critical brain growth’
                     Aetiology
• Fetal size is determined by gestational age
• Other factors influence fetal growth
  – Disturbances of these conditions eg:
     •   Environmental
     •   maternal
     •   Placental
     •   Fetal
          – May lead to IUGR
        Environmental factors
• Protein –& calorie- deficient diet
  – Commonest cause of mild IUGR in developing
    countries (poverty & infection)
     • Pre-conceptional maternal weight &
     • Weight gain during pregnancy both related to birth
       weight
• Malnutrition
  – Affect growth at any stage
     • Has most effect during 3rd trimester
                 Maternal factors
• Maternal vascular disease
   – Commonest cause of IUGR (developed countries)
       • Chronic hypertension, pre-eclampsia, chronic renal disease
       • Diabetes mellitus & lupus
   – A reduction if the O2 carrying capacity of maternal
     blood
       • Limit fetal growth
           – Haemoglobinopathies: sickle cell disease
   – Heavy cigarette smoking, fetal alcohol syndrome,
     altitude, nutrition, climate, genetic racial differences,
     size of parents (maternal weight)
                Placental factors
• Close correlation between placental weight & fetal
  size
   – Infarctions associated with reduction in area of
     placental exchange (maternal disease)
   – Haemangioma
      • Rare condition of placenta or cord
          – Causing mechanical interference with placental circulation
   – Placenta praevia (placenta lies wholly or partially in
     lower uterine segment – vaginal bleeding)
      • May cause IUGR
                 Fetal factors
• Growth failure occurs with a chromosomal
  abnormality
  – Placental weight & morphology may be normal
  – IUGR can be due to intrauterine infections
     • Causes damage to vascular epithelium
     • Fetal viraemia arrests metabolic activity in fetal cells
     • IUGR more pronounced the earlier in pregnancy an
       infection occurs
 Symmetrical growth retardation
• Occurs early in fetal life
   – At the time that cells are dividing
      • Body will contain fewer cells all over
          – And be symmetrically growth retarded
• Babies are small, may be perfectly normal or have
  gross chromosomal abnormalities
   – Down’s syndrome, Trisomy 13, 18
• Congenital malformations should be looked for
   – & lab investigations performed
      • To inform the management of these babies
Asymmetrical growth retardation
• The uneven growth retardation that occurs
  – Late in fetal life
• In times of shortage of oxygen or nutrients
  – The fetus protects his brain and structures close
    to the head
     • growth retardation is less likely to occur in the brain
       than other structures
         – E.g. liver, legs, trunk
• Babies subjected to a hostile environment
  – Because of placental problems
• Small bodies, disproportionately large heads
  – Thin, wasted, loose folds of skin
  – Active, feed hungrily
  – Do not develop RDS
     • Intrauterine stress leads to
         – increased production of surfactant

				
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posted:5/9/2008
language:French
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