1. Taking Stock of the Evidence on
Biofortification of Food Crops with
Provitamin A Carotenoids: Situation
Analysis of What We Know
Sherry A. Tanumihardjo
Associate Professor
University of Wisconsin-Madison, USA
Department of Nutritional Sciences
3. Definitions
Bioaccessibility: how much carotenoid is released
from the food matrix and available for
absorption.
Bioavailability: fraction of ingested nutrient
available for utilization or storage.
Bioconversion: proportion of bioavailable
carotene converted to retinol.
Bioefficacy: efficiency ingested carotenoids are
absorbed and converted to retinol.
5. SLAMENGHI - 1996
Species of carotenoids
molecular Linkage
Amount of carotenoids consumed in a meal
Matrix in which the carotenoid is incorporated
Effectors of absorption and bioconversion
Nutrient status of the host
Genetic factors
Host-related factors
mathematical Interactions
6. Advantages of Biofortification:
Enhancing micronutrients in crops
Targets the poor: eat high levels of food
staples
Rural-based: complements fortification
and supplementation
Cost-effective: research at a central
location can be multiplied across countries
and time
Sustainable: investments are front-loaded,
low recurrent costs
7. The Sherry Factors!!!
S – Species of carotenoid
H – Host related factors
E – Effectors of absorption
R – Relative amounts of carotenoids
R – Resistant starch
Y – Yet to be determined
11. Bioconversion for
b-cryptoxanthin
was 2.8 mg to 1 mg
retinol and almost
identical to b-
carotene.
a
ab
bc
c
ab
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Base Ctl bC bCX VA
µmolRE/gliver
ab
c
bc
a
a
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Base Ctl bC bCX VA
µmolRE/liver
Davis et al., BJN, 2008
13. Bioefficacy of biofortified b-carotene maize
High-b-carotene maize did not differ from b-carotene .
Bioconversion: ~3 mg b-carotene to 1 mg retinol.
0.0
0.5
1.0
1.5
2.0
Control Maize BC VA
Treatment
LiverVA(mmol)
a
bb
c
14. What about bioconversion
factors in human studies?
Li et al. Am J Clin Nutr 2010
• 6.48 ± 3.51 mg bC:1 mg retinol in 6 young
women in Iowa
Muzhingi et al. FASEB J. 2009
• 3.0 ± 1.5 mg bC:1 mg retinol in 9 healthy
Zimbabwean men
16. Cassava:
Comparable to
b-carotene supplement
even with substantial
cis-b-carotene
a
bb
c
bc
0
0∙2
0∙4
0∙6
0∙8
1
1∙2
1∙4
1∙6
1∙8
Base Control BC Cassava VA
Treatments
mmolVitaminA/liver
A
a
bcb
c
bc
0
0∙1
0∙2
0∙3
0∙4
0∙5
0∙6
0∙7
0∙8
Base Control BC Cassava VA
Treatments
mmolVitaminA/gliver
B
c c c
a b
b b
a
a
b
0
1
2
3
4
5
6
7
8
9
Base Control BC Cassava VA
Treatments
nmolb-Carotene/liver
trans
cis
C
17. Erdman’s group
All-trans b-carotene appears to be more
bioavailable than 9-cis or 13-cis b-carotene in
gerbils given single oral doses of each isomer
• Deming et al., J. Nutr. 132: 2700-8, 2002.
The relative vitamin A value of 9-cis b-carotene
is less and that of 13-cis b-carotene may be
greater than the accepted 50% that of all trans-
b-carotene in gerbils
Deming et al., J. Nutr. 132: 2709-12, 2002.
20. Polymorphisms
Single nucleotide polymorphisms in the
human BCMO1 gene have been
discovered causing observably reduced
BCMO1 activity.
We do not know how this will influence
biofortification efforts at the population
level.
Lietz et al., Arch Biochem Biophys, 2010
21. R = 0.885
0
5
10
15
20
25
0 0.5 1 1.5 2
Conversionfactor(mg:mg)
Total vitamin A liver reserves (mmol)
Vitamin A status of the host
High b-carotene
orange carrots
Orange and
purple carrots
Kale, spinach,
and brussels
sprouts
Sweet Potato
Red carrots and Cassava
Maize
Total vitamin A liver reserves (mmol)
Conversionfactor(mg:mg)
22. H – Host related factors
Other nutrient status
23. How are iron and vitamin A related?
Hematopoiesis and erythropoiesis: formation
of red blood cells
Modulation in the anemia of infection
Iron absorption and metabolism: iron
mobilization and transport
Immune modulation: Reduced morbidity and
mortality of some infectious diseases
26. Ribaya-Mercado et al. AJCN
2007;85:1041-9
Schoolchildren fed 4.2 mg provitamin A
carotenoids in the form of vegetables for
9 weeks with 2.4, 5 or 10 g fat/meal.
Low liver reserves (< 0.07 mmol/g) fell
from 35% to 7% and the amount of fat
did not influence the results.
27. Influence of fat on bioconversion
Mills et al. J. Nutr. 139: 44-50, 2009
mgb-carotenetoretinol
28. Emerging data: Type of fat
Dietary fats with increased unsaturated
to saturated fat enhance absorption of
carotenoids by increasing efficiency of
micellarization and lipoprotein secretion
Unsaturated fat enhances carotenoid
bioavailability
• Chitchumroonchokchai et al., FASEB J.
2010; Abstract 539.3.
30. Conversion factors
ranged from 9 to 11
mg b-carotene to 1 mg
retinol for typical
orange and 23 mg b-
carotene to 1 mg
retinol for biofortified
carrots.
0
50
100
150
200
250
300
350
high orange orange purple white
Totalliverb-carotene(nmol)
a
b
b
c
(A)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
high orange orange purple white
TotallivervitaminA(mmol)
a
b b
c
(B)
Dosti et al., BJN. 2006
31. Cassava:
Varying the level
of cassava
a
abab
b
a
a
0
0∙3
0∙6
0∙9
Base Control 15% #2 17% #1 35% #2 40% #1Treatments
mmolVitaminA/liver
A
abab
ab
b
ab a
0
0∙1
0∙2
0∙3
Base Control 15% #2 17% #1 35% #2 40% #1Treatments
mmolVitaminA/gliver
B
b
b a
bb
a
a
b
b
cc
a
0
1
2
3
4
5
6
7
8
Base Control 15% #2 17% #1 35% #2 40% #1
Treatments
nmolb-Carotene/liver
trans
cis
C
33. VA status with increasing b-carotene. Liver
VA from orange maize was greater than
yellow, regardless of % (P < 0.05).
0
0.2
0.4
0.6
0.8
30% typical 60% typical 30% high BC 60% high BC
Maize Treatment
LiverVA(mmol)
ab
bc
c
a
35. Conclusions:
Not all provitamin A carotenoids are equivalent,
one conversion factor does not fit all foods and is
related to vitamin A status.
Biofortified maize not only maintained vitamin A
status, but was as efficacious as b-carotene
supplements.
In populations consuming maize, using orange
instead of white maize may impact vitamin A
status.
48. • Using the paired isotope dilution test, final
vitamin A was higher in the spinach, vitamin A and
b-carotene groups compared to the control group.
• Vitamin A equivalency factors were estimated:
~13:1 for sweet potato
~10:1 for Indian spinach
~6:1 for b-carotene
Vitamin A provided with meals
Haskell et al. Am J Clin Nutr. 2004;80:705-14
49. Mills et al. J. Nutr. 139: 44-50, 2009
Influence of dry matter on bioconversion
mgb-carotenetoretinol
50. South African Trial
Supervised feeding; 125 g x 5 d/wk for 10.5 wk; 1030 mg RAE OFSP
vs 0 mg RAE WFSP; 90% compliance; 250% RDA
53. Sweet potato in Mozambique
Effectiveness study using an integrated
agricultural and nutrition intervention
2 year intervention covering 2 agricultural
cycles
90% of intervention households produced
sweet potato
Intervention children (n = 498) ate more sweet
potato and had higher serum retinol than
controls (n = 243)
Low et al. J Nutr. 2007;137:1320-7.
54. .
Towards Sustainable Nutrition Improvement
in Rural Mozambique
Taste tests were conducted at every adaptive trial
harvest to determine preferences of local consumers.
55. .
Towards Sustainable Nutrition Improvement
in Rural Mozambique
Sweet potato bread maker making his bread at home and
selling it in the nearby market of Lualua. Bread is marketed
under the name of Golden Bread.
56. Orange sweet potato
in Africa – a Success Story
Active behavior change
Agronomic ‘equality’ crucial
Assistance to understanding and
overcoming constraints to adoption
crucial
• Farmer participation in breeding
and varietal selection
• Seeds systems, product, and market
development
59. Bioconversion factor:
The conversion factor for Golden Rice
was 3.8 + 1.7 mg to 1 mg with a range of
1.9–6.4:1 in 5 healthy adults
• Tang et al. Am J Clin Nutr 2009;89:1776–83
Pure βC, GR βC, and spinach βC to
retinol were 2.0, 2.1, and 7.3 mg to 1 mg,
respectively
• Tang et al. FASEB J 2010 Abstract
63. What do the numbers predict?
6 mg/g X 0.75 retention factor
4.5 mg/g X158 g/day
711 mg with an optimistic 3:1
conversion
237 mg with a 275 mg/d EAR = - 38 mg
Potential loss during the trial is 28
mg/g liver with maize feeding
65. BN MN OR TN PP VA
VitaminA(μmol/liver)VitaminA(μmol/gliver)
Values are means + SD; n = 10. Means with different letters are
different, P < 0.05. ND, not detected
VA Concentration
Total Liver VA
All fruits maintained
baseline liver VA
concentrations.
All fruits prevented VA
depletion as compared to
control, except banana.
Liver carotenoids
present in respective
groups.
Arscott et al., Exp. Biol. Med, 2009
Fruit – Banana?
66. r = 0.88
Banana r = 0.44 with banana
Dark orange carrot
Orange and
purple carrots
Kale, spinach
brussels Red carrots
sprouts Maize
Mango, orange, tangerine, papaya
Conversion efficiency improves as VA status declines
71. Another
reason to feed
whole foods!
Mills et al. J. Nutr.
2008.;138:1692-8
c
a
ababab
bc
d
0
2
4
6
8
10
12
B
aselineC
ontrol
PO
O
O
R
PO
R
VA
mmolTEAC/g
Hydrophilic Extracts Lipophilic Extracts
b
a a a a a a
0
1
2
3
4
5
6
B
aselineC
ontrol
PO
O
O
R
PO
R
VA
mmolTEAC/L
75. The Current VAAL Team
Sara Arscott
Kara Bresnahan
Ashley Valentine
Emily Nuss
Chris Davis
Harold Furr
David Liu
Napaporn Riabroy
Margertha McLean
Sammie Schmalzle
Jacob Tanumihardjo
Collaborators:
Philipp Simon
Torbert Rocheford
Kevin Pixley
Natalia Palacios
Past members whose
work was cited:
Mandy Porter Dosti
Hua Jing
Julie Howe
Jordan Mills
