Haskell nutrition vit a

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Haskell nutrition vit a

  1. 1. Research gaps and constraints to mainstreaming biofortification as a public health and nutrition intervention Marjorie Haskell Program in International and Community Nutrition University of California, Davis
  2. 2. Biofortification as a strategy for improving vitamin A status in populations at risk of vitamin A deficiency – Biofortification increases the provitamin A (PVA) carotenoid content of staple crops – Dietary intake of PVA-carotenoids increases in populations consuming biofortified staple foods – Vitamin A status improves in populations consuming biofortified staple foods
  3. 3. Biofortified staple foods for improving vitamin A status Traditional breeding techniques: High provitamin A sweet potatoes ~100 µg/g High provitamin A maize ~ 15 µg/g (target level) High provitamin A cassava ~ 15.5 µg/g (target level) Transgenic techniques: High provitamin A rice Golden rice ~37 µg/g
  4. 4. Populations at risk of vitamin A deficiency Low-income populations in developing countries: – Infants and young children 6-24 months of age – Preschool-age children (2-5 y of age) – Pregnant women – Lactating women
  5. 5. Can PVA-carotenoid biofortified staple foods improve vitamin A status in populations at risk of vitamin A deficiency?
  6. 6. Efficacy/Effectiveness of biofortified foods for improving vitamin A status in populations at risk of vitamin A deficiency Groups at high-risk of Evidence of VA deficiency: Efficacy/Effectiveness Infants and young children No data Preschool-age children OFSP Effective Pregnant women No data Lactating women No data
  7. 7. Assessing efficacy of PVA-biofortified staple foods for improving vitamin A status Initial vitamin A status Intervention -biofortified food group -negative control group Final vitamin A status Outcome: mean change in vitamin A status Intervention effect: Mean change in vitamin A status in biofortified food group vs. Mean change in vitamin A status in negative control group
  8. 8. Challenges in evaluating the efficacy of biofortified foods for improving vitamin A status 1. Biofortified staple foods tend to provide small to moderate amounts of provitamin A carotenoids 2. Which target groups are most likely to demonstrate a measureable change in vitamin A status in response to consumption of biofortified foods? – infants/young children have small gastric capacity; limits intake – initial vitamin A status is important; marginally deficient individuals more likely to respond
  9. 9. Challenges in evaluating efficacy of food-based interventions for improving vitamin A status 3. What is the expected impact on vitamin A status in the selected target group? – infection may reduce the expected impact; reduced absorption of PVA-carotenoids/increased utilization of vitamin A; infection rates tend to be high 4. Which vitamin A status indicator(s) can detect the expected impact on vitamin A status?
  10. 10. Serum retinol concentration Olson, 1981 Serum retinol concentration homeostatically controlled; not an optimal indicator of change in vitamin A status Serum retinol concentration declines transiently in infection; difficult to interpret; high infection rates in target populations
  11. 11. Relative dose response tests Relative dose response tests assess adequacy of liver vitamin A stores: – more sensitive than serum retinol concentration – dichotomous outcome (adequate/inadequate) – do not provide information on magnitude of change in vitamin A status in response to an intervention
  12. 12. Stable isotope dilution technique Stable isotope dilution technique provides a quantitative estimate of total body vitamin A stores – provides a quantitative estimate of change in total body vitamin A stores in response to an intervention – method is not validated in pregnant or lactating women or infants – costly, requires analysis by mass spectrometry
  13. 13. Breastmilk retinol concentration Breastmilk retinol concentration provides information on the mother’s vitamin A status – may also be useful for assessing adequacy of vitamin A intake in breastfed infants – milk vitamin A reflects maternal dietary vitamin A intake; recently absorbed dietary vitamin A is taken-up directly by the mammary gland – milk vitamin A is not under homeostatic control; likely to be more sensitive than serum retinol
  14. 14. Dietary vitamin A rapidly affects milk vitamin A Akohoue SA, Green JB and Green MH, J Nutr. 136:128-132, 2006 days of lactation Dietary treatments – Pregnancy/Lactation:
  15. 15. Plasma and liver vitamin A concentrations of pups of dams fed different levels of vitamin A during pregnancy and lactation -VA/-VA -VA/+VA +VA/+VA +VA/-VA Plasma, µmol/L 0.78 0.08c 1.02 0.14b 1.15 0.15a 1.02 0.12b Liver, nmol/g 38.3 7.29d 143 16b 204 24a 63.6 11.7c Means SD, means in a row without a common letter differ, P<0.001 Akohoue SA, Green JB and Green MH, J Nutr. 136:128-132, 2006
  16. 16. Breastmilk vitamin A response to vitamin A fortified MSG in lactating Indonesian women Muhilal, AJCN, 1988
  17. 17. Dark adaptation as a functional indicator of vitamin A status – Nightblindness (impaired dark adaptation) is prevalent in areas where vitamin A deficiency is endemic – Dark adaptation can be measured objectively using the pupillary threshold test – Nightblindness (impaired dark adaptation) responds to treatment with small daily amounts of vitamin A
  18. 18. Initial and final pupillary thresholds of pregnant Nepali women initially reporting nightblindness = proposed cut-off for abnormal dark adaptation (>-1.11 log cd/m2) = mean value for non-pregnant US women (-1.35 log cd/m2) = mean value for non-nightblind Nepali women (-1.42 log cd/m2) Final means with different superscript letters are different, p<0.02, n=353 Hi Vi t A Lo Vi t A Ul tra-ri ce Li ver Greens Carrots -2.50 -2.25 -2.00 -1.75 -1.50 -1.25 -1.00 -0.75 -0.50 -0.25 0.00 Logcandela/m2 Initial Final a,b a,b a,b a,b b a
  19. 19. 0.00 0.03 0.06 0.08 0.11 0.14 0.17 0.19 0.22 Initial Final HiVA LoVA Ultra-rice Liver Greens Carrots Mean value for comparison women (0.087 µmol/L) Final means with different superscript letters are different, p<0.02, n=353 Initial and final plasma β-carotene in pregnant Nepali women initially reporting night blindness Plasmaβ-caroteneµmol/L Haskell et al., AJCN, 2005
  20. 20. Initial and final plasma retinol in pregnant Nepali women initially reporting night blindness = mean value for comparison women (1.03 mol/L) Final means with different superscript letters are different, p<0.05, n=353 Hi Vi t A Lo Vi t A Ul tra-ri ce Li ver Greens Carrots 0.00 0.30 0.60 0.90 1.20 1.50 Plasmaretinol,µmol/L Initial Final a b,c a a,b c a a Haskell et al., AJCN, 2005
  21. 21. Summary 1. The effectiveness of OFSP for improving vitamin A status in preschool children has been demonstrated. 2. Further evidence on efficacy and effectiveness of the other biofortified staple crops (maize, cassava, golden rice) is needed in populations at risk of deficiency. 3. Target groups and indicators of vitamin A status should be chosen carefully to optimize chances of demonstrating efficacy or effectiveness.
  22. 22. Summary 4. Targeting lactating women may be advantageous because milk vitamin A is likely to be responsive to consumption of biofortified staple foods; and their breastfed infants are likely to benefit from increased milk vitamin A. 5. Dark adaptation is a functional indicator of vitamin A status that is likely to be useful for evaluating the efficacy/effectiveness of biofortified foods.
  23. 23. Thank you
  24. 24. Biofortification is a complementary strategy for improving vitamin A status Existing strategies for improving vitamin A status: – supplementation – high-dose vitamin A capsules – children 6 mo to 5 y of age – women in first 8 wk post-partum – food fortification – universal vitamin A fortification of cooking oil, sugar – targeted vitamin A fortification (infant foods) – diet diversification; other food-based interventions Evaluate biofortified staple foods in the context of other intervention strategies in selected target population

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