Download Orange sweet potatoes are an excellent source of vitamin A

Peer-reviewed scientific article
Orange sweet potatoes
are an excellent source of
vitamin A
TAMI TURNER, BETTY J. BURRI*
Betty J. Burri
*Corresponding author
United States Department of Agriculture (USDA), Agricultural Research Service
Western Human Nutrition Research Center, 430 West Health Sciences Drive, Davis, CA 95616, USA
AgroFOOD industry hi-tech - July/August 2011 - vol 22 n 4
Functional food
ABSTRACT: Vitamin A is an essential nutrient required for proper growth and development, vision, red blood cell production,
and immune function. An estimated 208 million women and children suffer from vitamin A deficiency worldwide, making
vitamin A deficiency a public health problem in numerous countries. Several carotenoids, including beta-carotene, can
convert to vitamin A in the body. Orange-fleshed sweet potatoes contain high concentrations of beta-carotene, and have
succeeded in improving human vitamin A status in several small-scale food-based interventions. We estimated the amounts
of orange sweet potatoes needed to provide sufficient vitamin A for individuals and at the international level. The amounts
required can reasonably be provided by orange sweet potato making it an excellent source of vitamin A.
VITAMIN A
VITAMIN A DEFICIENCY
Vitamin A (VA) is an umbrella term for compounds that have
VA activity in the body (1). VA is an essential nutrient needed
for proper growth and development, vision, red blood cell
production, immune function, and numerous roles in genetic
regulation (1-3). Rich sources of dietary VA are found in animal
products which contain preformed retinol, that is ready to use
in the body. Thus, liver, fish oils, and organ meats are excellent
sources of VA (4) but are often expensive and inaccessible
to much of the world’s population. The amount of dietary VA
needed by an individual depends on their age, gender, life
stage (i.e. pregnant, lactating), and presumably on genetics,
lifestyle, and immune system status. Recommended VA
intakes are shown in Table 1.
Vitamin A deficiency (VAD) is a public health problem in
numerous countries, affecting approximately 208 million
people (3, 6, 7). The highest burden of VAD is in women
and children often in Sub-Saharan Africa and South East
Asia. Providing VA to at risk people decreases the severity
of diarrhoea, influenza, and measles (3). VAD is also the
leading cause of preventable blindness (3, 6-9). Child
mortality decreased by 23 percent (3) and maternal
mortality decreased by about 30 percent with VA
supplementation (10, 11). VAD prevention and intervention
has included large-scale supplementation programs, foodfortification, bio-fortification, and food-based programs.
Large-scale, synthetic VA capsule programs have provided
a cost-effective way to alleviate and prevent VAD in
many countries (e.g. Bangladesh, Nepal). However, these
programs are usually funded by national governments and
international organizations. Funding issues mean these
programs can be difficult to sustain and can fail to cover
some of the population at risk, especially the rural poor
(12). There are also potential toxic effects in some infants
receiving more than one high-dose supplement (13). Highdose capsules are also contraindicated in reproductiveaged women, and due to potential teratogenic effects,
they can only be given within 6-8 weeks postpartum (3).
Fortifying food with VA could reach more people, since it
is often done at the national level, but there are inherent
problems in fortifying food: 1) the type of food chosen
should be consumed and available by most, including
those at highest risk for deficiency, 2) the food needs
to be compatible with the nutrient added, 3) the dose
must be safe but also provide enough VA to prevent
deficiency in both children and adults, and 4) monitoring
must be on-going for safety and effectiveness. Bio-fortified
or genetically engineered foods also have common
issues, such as the amount of VA actually provided to
the consumer, consumer acceptance, and underlying
environmental issues.
Using fruits and vegetables rich in PVA compounds in
prevention and treatment of VAD is a good alternative
to supplements or food fortification (14, 15). Not only
can it provide income to farmers but also it offers longterm sustainable ways to improve VA status. Fruits and
vegetables also provide a variety of nutrients along with
VA. Many small-scale food-based interventions to improve
VA status have been successful (16-20).
Table 1. Recommended intake of vitamin A.
Carotenoids are orange, red, and yellow pigments; over
700 naturally occurring carotenoids have been described.
There are three primary carotenoids in the human diet that
can be converted to VA: β-carotene (BC), α-carotene (AC),
and β-cryptoxanthin (CX). These are termed provitamin A
(PVA) carotenoids. Orange-fleshed sweet potatoes (OFSP),
tangerines, carrots and mangoes, as well as dark-leafy
green vegetables such as kale and mustard greens are
excellent sources of VA. The conversion of carotenoids to
VA can be poor, so the amount of VA provided by these
carotenoids is controversial. Conversion ratios range from
2:1 to over 24:1 (carotenoid: VA) (1) due to food factors
(e.g. species, growing conditions, food matrix, cooking,
storage) and host factors (i.e. digestive health, VA status,
dietary fat).
14
ORANGE-FLESHED SWEET POTATOES IN VITAMIN A DEFICIENCY
PREVENTION AND INTERVENTION
OFSP are well-suited for VA interventions since they contain
large amounts of BC. They are low in fat and protein, high in
antioxidants (21), fibre, some B vitamins, many minerals, and
have been efficacious VAD interventions (16, 18, 20). They
grow well in hot, humid climates generally from root cuttings
and are a high yielding crop. OFSP store well and retain most
of their carotenoids for at least 50 days (22). The amount of BC
depends heavily on the species grown and ranges anywhere
from trace amounts to 31450 µg BC/100 g (OFSP having
higher BC than yellow, cream, and purple varieties). Cooking
can cause loss of BC, but also may help soften the food matrix
allowing carotenoids to be released with a general trend of
higher temperatures and longer time causing more loss of BC
(Table 2). Bioaccessibility of BC from OFSP is also influenced by
dietary fibre and fat concurrently consumed.
Functional food
Table 2. The effects of variety and processing on the amount of betacarotene measured in 100 grams of sweet potato.
AgroFOOD industry hi-tech - July/August 2011 - vol 22 n 4
Amount of sweet potatoes needed to provide vitamin A
The VA requirement of individuals varies by age and life
stage (Table 1). We calculated the amount of OFSP needed
to provide 100 percent VA per day, assuming a range of BC
in OFSP (4-23mg/100g), loss from storage and cooking of
10 percent, a bioaccessibility fraction (0.25), a conversion
of BC to VA of 3:1 for deficient and 12:1 for adequately
nourished people, and the weight of one cup of sweet
potatoes (255g/cup) (25). Figure 1 shows the amounts
of OFSP needed to meet the dietary VA requirement at
different life stages. The results show that OFSP provide an
excellent source of VA. A person can reasonably consume
100 percent of their VA from OFSP.
Figure 1. The amount of orange sweet potatoes needed per day to meet
vitamin A requirement.
15
Functional food
AgroFOOD industry hi-tech - July/August 2011 - vol 22 n 4
Overall, the effectiveness of OFSP in food-based nutritional
interventions to improve VA status in populations is
mainly based upon the variety of the potato, since BC
concentrations vary greatly. Smaller factors that improve
the effectiveness of BC-rich OFSP to provide VA include
as ranked: the presence of fat in the meal consumed with
the potato > growing, harvesting > cooking and storage >
consumer preference (25).
To estimate the amount of OFSP needed to supply VA
worldwide for the 190 million children and 19.1 million pregnant
and lactating women at risk for VAD, we assumed 75 percent
of preschoolers were 1-3 years old, and 20 percent pregnant
women were also lactating. The smallest amount of OFSP
needed to supply these people was 2.083 million metric tons
per year whereas a higher, and maybe more realistic amount,
was 11.681 million metric tons. Current production worldwide is
approximately 106.5 million metric tons (26). Surprisingly, most
sweet potatoes are produced in low-income, food-insecure
countries with populations that have moderate VAD (6, 8,
9, 11). However, many sweet potato growing countries eat
cream or white sweet potatoes, and much of the crop is used
for animal feed. Although production and consumption values
do not separate the different varieties of sweet potatoes,
worldwide production is much higher than our estimated
amounts needed to supply VA to VAD people worldwide.
Feasibility of orange sweet potatoes to improve vitamin A
status
The distribution and consumption data of sweet potatoes
suggest they are accepted and available among many VAD
populations. Studies assessing switching to OFSP have shown
low resistance with only a small impact of 5-10 percent on
consumer preference (26, 27). There is also little evidence of
especially unfavourable environmental impacts if one were to
increase the production of sweet potatoes (28, 29). Although
growing large quantities of any single crop may have
ecological, societal, or economic impacts that must be taken
into account, this indicates that encouraging farmers and
consumers to substitute OFSP for other varieties, or to increase
OFSP production, may be successful in preventing VAD.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
CONCLUSION
Orange sweet potatoes are excellent sources of VA. VAD is
a public health problem in numerous developing countries.
Providing foods naturally rich in VA to alleviate VAD can
improve the health of millions of people. In low-income
countries, approximately 82 percent of total dietary VA intake
is via the consumption of carotenoid-rich plants (7). OFSP
varieties commonly grown provide high amounts of BC which
can provide a considerable amount of VA and thus, are
excellent sources of this essential nutrient. Production of sweet
potatoes for human consumption is encouraging, since these
could be a considerable nutritious and sustainable source of
VA. Improvement in agricultural practices in developing
countries to increase yields and the replacement of
other varieties of sweet potatoes as white-fleshed,
yellow, or purple potatoes with OFSP could allow
further improvements in nutrition, especially in
VAD-insecure countries.
REFERENCES AND NOTES
1.
16
2.
Dietary reference intakes for vitamin A, vitamin
K, arsenic, boron, chromium, copper, iodine,
iron, manganese, molybdenum, nickel, silicon,
vanadium, and zinc, eds. U.S. Institute of Medicine,
Food and Nutrition Board, National Academy Press (2000).
22.
23.
24.
25.
26.
27.
28.
29.
R. Blomhoff, H.K. Blomhoff, J of Neurobiol., 66, pp. 606-630
(2006).
Vitamin A Supplementation, World Health Organization,
online:
http://www.who.int/vaccines/en/vitamina.shtml,
accessed April 20, 2011.
National nutrient database for standard reference, release
22, U.S. Department of Agriculture, online: www.nal.usda.
gov/fnic/foodcomp/search, accessed August 20, 2010.
Vitamin and mineral requirements in human nutrition, 2nd
edition, World Health Organization and Food and Agriculture
Organization of the United Nations (2004), online: http://
whqlibdoc.who.int/publications/2004/9241546123.pdf,
accessed August 30, 2010.
Global prevalence of vitamin A deficiency, Micronutrient
Deficiency Information System (MDIS), World Health
Organization
(1995),
online:
www.wholint/nutrition/
publications/vad_global_prevalence/en/index.html,
accessed August 6, 2010.
Global prevalence of vitamin A deficiency in populations
at risk 1995-2005, WHO global database on vitamin a
deficiency, World Health Organization (2009), online: http://
whqlibdoc.who.int/publications/2009/9789241598019_eng.
pdf, accessed August 19, 2010.
K.P. West, J Nutr., 132, 2857S-66S (2002).
Micronutrient Initiative Vitamin and mineral deficiency, a
global progress report, United Nations Children’s Fund (2004),
online:
www.micronutrient.org/CMFiles/PubLib/VMd-GPREnglish1KWW-3242008-4681.pdf, accessed October 20, 2009.
A. Sommer, F.R. Davidson, J Nutr., 132, 2845S-50S (2002).
R.E. Black, R.H. Allen et al., Lancet, 371, pp. 243-260 (2008).
R.D. Semba, S. de Pee et al., J Health Popul Nutr., 128, pp.
143-148 (2010).
G. Murdur, Brit Med J., 323, p. 1206 (2001).
S.A. Tanumahardjo, Comp Rev Food Sci Food Safety, 7, pp.
373-381 (2008).
C.U. Loechl, C. Hotz et al., Ann Nutr Metab., 55, p. 376 (2009).
M.J. Haskell, K.M. Jamil et al., Am J Clin Nutr., 80, pp. 705-714
(2004).
M.J. Haskell, P. Pandey et al., Am J Clin Nutr., 81, pp. 461-471
(2005).
P.J. van Jaarsveld, M. Faber et al., Am J Clin Nutr., 81, pp.
1080-1087 (2005).
J.W. Low, M. Arimond et al., F Nutr Bull, 28, pp. S258-270
(2007a).
J.W. Low, M. Arimond et al., J Nutr, 137, pp. 1320-1327 (2007b).
C.C. Teow, V.D. Truong et al., F Chem., 103, pp. 829-838
(2007).
K. Wantanabe, T. Toki et al., J Jap Soc Hort Sci., 68, pp. 10441046 (1999).
U. Kidmose, L.P. Christensen et al., Inn Food Sci Emer Tech., 8,
pp. 399-406 (2007).
A. Bengtsson, A. Namutebi et al., J Food Comp Anal., 21, pp.
134-143 (2008).
B.J. Burri, Comp Rev Food Sci Safety, 10, pp. 118-129 (2011).
J.W. Low, P.J. van Jaarsveld et al., Food Nutr Bull., 29, pp. 98107 (2008).
A.T.A. Naico, J.L. Lusk, J African Econ., 19, pp. 536-558 (2010).
A.C. Bovell-Benjamin, Adv Food Nutr Res., 52, pp. 1-59 (2007).
A.W. Wood, P N G Med J., 45, pp. 15-43 (2002).