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This report discusses the challenges of setting future Dietary Reference Intakes (DRIs) for both healthy and "non-healthy" individuals and populations. It explores factors such as nutrient-environment interactions, nutrient deficiencies, and the impact of irregular periods of dietary excesses and wants. It also addresses questions about the appropriateness of DRIs for estimating the needs of unhealthy populations, considering undesirable characteristics, and accounting for multiple factors. The report also examines the estimation of Upper Limits (ULs) for free living populations in low and middle-income countries.
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Targeting Healthy and “non-Healthy” Individuals and Populations Future Dietary Reference Intakes* *EA Yetley, AJ MacFarlane,LS Greene-Finestone, C Garza, JD Ard, SA Atkinson, DM Bier, AL Carriquiry, WR Harlan D Hattis, JC King, D Krewski, DL O’Connor, RL Prentice, JV Rodricks, and GA Wells. Options for basing Dietary Reference Intakes (DRIs) on chronic disease endpoints: report from a joint US-/Canadian-sponsored working group. Am J ClinNutr. 105:249S-285S, 2017.
Demographic Shift Source: U.S. Census Bureau,
Changes in the Landscape of Nutrition and Health • 1988 Surgeon General’s Report • 1989 Diet and Health Report • 1994 How Should the RDAs be Revised? “As problems of nutritional deficiency have diminished in the U.S., they have been replaced by problems of dietary imbalance and excess”. No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% Prevalence of Obesity: 2010 1986
Challenges in Setting Future DRIs for Healthy and “non-Healthy” Individuals and Populations • Outcomes of interest are unlikely to be nutrient-specific • Absolute risks of targeted preventable conditions are not 100% in any population group • Uncertainty in magnitude of risk reduction effectiveness remains difficult to estimate • Multi-factorial nature of likely outcomes of interest
Growth Reference Study Prescriptive Approach: Reference v Standard • Optimal Nutrition • Breastfed infants • Appropriate complementary feeding • Optimal Environment • No microbiological contamination • No smoking • Optimal Health Care • Immunization • Pediatric routines Optimal Growth
Mothers' heights – Longitudinal study cm Source: WHO Multicentre Growth Reference Study Group. Enrolment and baseline characteristics in the WHO Multicentre Growth Reference Study. Acta PaediatrSuppl 2006;450:7-15.
Fathers' heights – Longitudinal study cm Source: WHO Multicentre Growth Reference Study Group. Enrolment and baseline characteristics in the WHO Multicentre Growth Reference Study. Acta PaediatrSuppl 2006;450:7-15.
Length at Birth cm Source: WHO Multicentre Growth Reference Study Group. Enrolment and baseline characteristics in the WHO Multicentre Growth Reference Study. ActaPaediatrSuppl 2006;450:7-15.
Brazil Ghana India Norway 80 Oman USA Mean of Length (cm) 70 60 50 0 200 400 600 Age Mean Lengths from Birth to 24 Months at Each of the MGRS Sites
Projected Adult Heights Means (points) and standard deviations (bars) of the difference between 2 times the height of the child at two years and the mid-parental height by site.
Key Messages Mid-parental height consistently explained a greater proportion of observed variability in attained child length than either paternal or maternal height alone Doubling a child’s height at two years matched mid parental height when parental stature was likeliest to reflect genetic potential and their children’s care approximated international recommendations Meeting international care recommendations also resulted in predicted adult statures of the children that approximate international norms notwithstanding shortfalls in parental heights.
Nutrient-environment interactions:Not New to DRI Discussions • Smoking (vitamin C) • Sun exposure (vitamin D) • Epigenetics - phenotypic flexibility • Secular trends in food supply such as: • Fibre • Salt • Omega-3 fatty acids • Fortificants • Use of dietary supplements – nutrients and natural health products
Key Questions To Be Addressed in Deriving DRIs for Low and Middle Income Countries/Regions • When are DRI’s for healthy populations/individuals appropriate baselines for estimating needs of unhealthy populations/ individuals? • How and when does one account for undesirable characteristics such as the occurrence of LBW, excessive energy intakes, specific morbidities, poor baseline diets, polluted environments, etc? • How and when does one consider other variables such as the non-continuous nature of human growth, simultaneous consideration of multiple factors many possibly having small effects (some synergistic; others antagonistic) on targeted outcomes? • What are impacts of irregular periods of dietary excesses and want?
Estimating ULs for Free Living Populations In Low and Middle Income Countries • The pathophysiology of macro- and micronutrient excesses in healthy individuals is usually understood poorly at all life stages, adding to extrapolation difficulties. • Nutrients that are deficient but required to maintain homeostatic mechanisms that counter responses to other nutrient excess(es) often are inadequately considered.