2. Taking Stock of Evidence
on Biofortification of Food
Crops with Iron and Zinc:
Analysis of what we know
so far
BIOFORTIFICATION
Washington, DC
K. Michael Hambidge MD ScD
3. Progress to date
1. Genetic variation for nutrients exists.
2. Micronutrients can be bred into staple foods.
3. Iron and zinc are inherited together.
4. It is easier to breed for Vit A than Zinc/Iron
5. Neither yield nor farmer preferred traits are
compromised by breeding for micronutrients.
6. Micronutrient traits are NOT difficult to breed in.
7. Novel methods, protocols, and equipment for low-
cost, high throughput measurement (to the
microgram) had to be developed and implemented
by HarvestPlus.
2004 2010
HarvestPlus has established:
4. Taking Stock of Evidence
on Biofortification of Food
Crops with Iron and Zinc:
Analysis of what we know
so far
BIOFORTIFICATION
Washington, DC
K. Michael Hambidge MD ScD
7. DEVELOPMENT
Estimate targets for Zn
and Fe so that
biofortified staple food
provides a meaningful
amount of these
micronutrients.
8. CONTRIBUTING GOALS TO
ASSESSMENT OF TARGET
• ESTIMATE USUAL INTAKE OF STABLE
CROP.
• RETENTION OF IRON & ZINC DURING
PROCESSING.
• BIOAVAILABILITY OF BIOFORTIFIED
IRON & ZINC.
• RELIABLE ESTIMATES OF
PHYSIOLOGICAL REQUIREMENTS
Modified from Hotz & McClafferty, 2007
9. Estimate usual intake
of staple food
Challenge: availability of
representative dietary
intake data for target
populations
10. Examples of quantities of staple
crops consumeda
CROPa CHILDRENb WOMENc
Polished rice 120g 400g
Cassava 150g 500g
a. expressed as dry wt equivalents for rice and fresh wt for
cassava. Derived from mutlticountry composite of
household food expenditure data & estimated on basis of
consumer equivalence
b. 4-6 yrs c young. Not pregnant or lactating
(Hotz & McClafferty Food & Nutr Bulletin 28 [2] S271-279)
11. FOOTNOTE
HUMAN NUTRITION RESEARCH 0F
HARVESTPLUS AND COLLABORATING
INSTITUTIONS MADE MORE ARDUOUS
BY LACK OF ESSENTIAL DATA THAT
MIGHT REASONABLY BE AVAILABLE
OR IN PROGRESS WITH SUPPORT
FROM OTHER SOURCES.
12. Zn and Fe
RETENTION
Amount of micronutrient [or
increase in amount of
micronutrient] in the biofortified
food in ready-to-eat form.
13. About 25% loss
G. Barry, IRRI 2009
Effect of polishing on grain zinc content (3 varieties)
14
16
18
20
22
24
26
28
30
32
Brown
rice
10 20 30 40 50 60
Polishing time (sec)
Zinccontent(ppm) Areumbyeo IR 68144-2B-2-2-3-1-120 PSB Rc28
14. Pearl Millet
Zn & Fe content before cooking
μg Zn/g μg Fe/g
Whole
grain
27.7 110.5
Coarse
grind
30.0 110.0
Fine
grind
24.3 108.0
15. Zinc retention in wheat
converted to tortillas
(μg Zn/g sample)
High Extraction Low Extraction
Whole grain Flour Tortilla* Flour Tortilla
High Zn 41.3 40.5 39.5 20.4 18.5
Control 23.6 23.0 21.8 10.6 10.0
*Tortillas made from flour, water, lard, salt
16. BIOAVAILABILITY
Definition: Proportion of micronutrient absorbed
into the body and potentially available for
biological function.
Challenges:
Zinc: now relatively simple to estimate effect of
factor[s] inhibiting absorption.
Iron: complex with multiple inhibitors and
facilitators.
17. Study
Serum
ferritin2
Bean
meal1
Fractional iron
absorption2
Absorption
Ratio3 p4
µg/L %
Low vs
High Iron
9.3
(4.2- 20.6)
SER 16 6.8 (3.2; 14.2)
1.59
<0.00
1
MIB465 4.3 (1.8; 10.1)
Low vs
High PP
10.3 (5.4-
19.6)
SER 16 7.5 (4; 14.1)
0.96 0.71
MIB 497 7.7 (4; 15.2)
1all A meals contained 0.4 mg Fe57 or 0.4 mg Fe58
2 values are geometric means; range in parentheses
3 absorption ratio study 1 (SER16/ MIB465) and study 2 (SER16/ MIB497)
4 paired Student’s t-test was used to compare differences in absorption on logarithmically transformed data
5-day % Fe absorption from test meals
(beans + rice or potatoes) by healthy
Rwandan university students
18. Combined Effects of Polyphenols
& Phytic Acid in Common Beans
Reduction of polyphenols in low
phytate beans or selection of beans
with low levels of polyphenols and
phytic acid necessary to achieve
substantial increase in fractional
absorption of iron.
(Perry N, et al, J. Nutr. 2010)
19. Dose dependent effect of phytic
acid on Fe absorption in humans
Adapted from Hallberg, et al. Am J Clin Nutr 1989
21. Zn absorbed versus predicted at
actual phytate intakes
0 3 6 9 12 15
0
1
2
3
4
5
phytate
0 mg/d
600
800
2300
2500
80% High Zn
80% Control Zn
95% High Zn
95% Control Zn
Total Dietary Zn (mg/d)
TotalAbsorbedZn(mg/d)
22. Low-Phytate Cereal and Legume Germplasm and Breeding
“1st Generation Breeding”=Simply Crossing in Alleles or Introducing Genes
“2nd Generation Breeding”=1st Generation Followed by Selection for Performance, Emergence, Yield
Species
Current Genetic
Technologies Identification
Mature Seed
Phytic Acid/Phytase Status of Breeding and Comments
Maize Recessive Alleles lpa1, lpa2, lpa3 50% to 95% Phytate
Reduction
1st Generation Only, No 2nd Generation Selection;
Yields Range from Greatly Reduced to 95% of Control
Transgenic MRP4/ABC
Transporter
30% to 90% Phytate
Reduction
1st Generation Only, No 2nd Generation Selection;
Embryo-targeted Expression; Lack of Extensive Yield Data
Transgenic Fungal Phytase High Phytase and Normal to
~25% Phytate Reduction
Either Embryo or Endosperm Targeted Expression;
Lack of Extensive Yield Data
Barley Recessive Alleles lpa1, lpa2, lpa3,
lpa-M593
50% to 90% Phytate
Reduction
1st and 2nd Generation Breeding; Cultivars Available;
Yields Range From Greatly Reduced to Excellent, Depending on
Line and Environment
Wheat Recessive Alleles Js-12-LPA 35% Phytate Reduction 1st and 2nd Generation Breeding; Yields 80% to 100% of Control
Rice Recessive Alleles lpa1, lpaN15-186,
lpa-XS110-1
40% to 70% Phytate
Reduction
1st Generation Breeding Only;
Reduced Yields Indicated but Lack of Extensive Yield Data
Soybean Recessive Alleles pha1::pha2
lpa-ZC-2
LR 33-MIPS
50% to 80% Phytate
Reduction
For pha1::pha2: 1st and 2nd Generation Breeding, Yield Up To >90%
of Control; Germination/Emergence General Problem;
Lpa-ZC-2: Good Emergence
Transgenic “CAPPA: Bacterial
Phytase
High Phytase: 90% Phytate
Reduction
1st Generation Only; Lack of Extensive Yield Data
Common
Bean
Recessive Allele lpa-28-10 80% Phytate Reduction 1st Generation Only; Apparently Very Good Yield and
Germination/Emergence, But More Extensive Yield Data Needed
For most references, please see Cichy and Raboy. 2008. Pp. 177-200 in: “Modification of Seed Composition to Promote Health and Nutrition”. Agronomy
Monograph Series, American Society of Agronomy and Crop Science Society of America. Also see: Campion et al. 2009, Theor Appl Gene 118:1211;
Drakakaki et al. 2005, Plant Mol Bio 59: 869; Chen et al. 2007, Transgenic Res DOI 10.1007/s11248-007-9138-3.
23. HarvestPlus minimum target levels
for Zn
“An additional amount of
bioavailable Zn in the food supply
that is equivalent to 40% of the
physiological requirements for
absorbed Zn for non-pregnant
women and children of 4-6 yrs of
age”
C Hotz. Food Nutr Bull 2009:30(1);172-8
24. Zn Physiological Requirements:
Roles in Biofortification
• Establishing target goals.
• Interpretation of bioavailability of zinc
increment achieved with biofortification.
• Providing reference data for interpretation
of bioavailability of zinc from biofortified
crops
• First of 2 major steps in determining
dietary requirements of target populations.
25. • Determine the biological impact of biofortified foods
on micronutrient status and health conditions under
controlled conditions.
• Challenges:
• Identify adequate & sensitive biomarkers and other
indices of host status that are dependent on iron or
zinc status.
• Difficulkt to control for al environmental factors
EVALUATION:
EFFICACY
26. Hass JD, Beard JL, et al
IRON-BIOFORTIFIED RICE IMPROVES
THE IRON STORES 0F NON-ANEMIC
FILIPINO WOMEN.
(J. Nutr 135: 2823-2830, 2005)
27.
28. 1
1.5
2
2.5
3
3.5
4
4.5
Finalferritin(lnug/L)
1 2 3
Plasma ferritin after 9 months of consuming
high iron (IR68144) or control (C4) rice
non-anemic at baseline (n=137)
C4 IR68144
1
1.5
2
2.5
3
3.5
4
4.5
Finalferritin(lnug/L)
1 2 3
Plasma ferritin after 9 months of consuming
high iron (IR68144) or control (C4) rice
non-anemic at baseline (n=137 )
C4 IR68144
p=.01 p=.02 p=.13
Iron
deficiency
(<12ug/L)
30. CONCLUSIONS
A LONG-TERM PROJECT WITH
ENCOURAGING PROGRESS AND
PLENTY OF WORK AHEAD WITH
BREEDING, HUMAN STUDIES &
DISSEMINATION, BUT WITH
EMINENTLY WORTHWHILE GOALS
ESPECIALLY FOR THIS PLANET’S
RURAL POOR.
