Agriculture Reference
In-Depth Information
Table 18.1.
Daily intake recommendations for
vitamins B
1
, B
2
, B
3
, B
5
, B
6
, B
7
, and B
9
in adults
aged
18
and older. (From USDA National Nutrient
Database for Standard Reference, Release
17,
and
National Institute of Health.)
enhance content in potatoes. An additional rea-
son to enhance B
2
content in plants is given by
recent findings from work on another night-
shade, tobacco (Wu
et al
., 2010). Transgenic to-
bacco plants overexpressing the riboflavin bio-
synthesis enzyme, lumazine synthase, had
increased FMN and FAD levels. The correspond-
ing tobacco plants grew better, had higher
amounts of jasmonic acid, and showed upregu-
lation of defense responses, leading to tobacco
that was less susceptible to pathogen infection
(Wu
et al
., 2010). These findings point out that
elevating riboflavin levels is technically feasible,
and potentially may lead to superior plants with
improved phytonutrient content, better growth,
and enhanced performance when exposed to
pathogens. Considering this, transgenic ap-
proaches or breeding efforts to increase B
2
con-
tent in potato are appealing. Unfortunately, no
data about vitamin B
2
variation among a wider
variety of potato germplasm are available, which
clearly is a critical gap in knowledge.
EAR
RDA
AI
UL
Vitamin B
1
(thiamine)
Women
0.9
1. 1
-
-
Men
1
1. 2
-
-
Vitamin B
2
(riboflavin)
Women
0.9
1. 1
-
-
Men
1. 1
1. 3
-
-
Vitamin B
3
(niacin)
Women
11
14
-
35
Men
12
16
-
35
Vitamin B
5
(pantothenate)
Women
-
-
5
-
Men
-
-
5
-
Vitamin B
6
(pyridoxine)
Women
1.1-1.3
1.3-1.5
-
100
Men
1.1-1.4
1.3-1.7
-
100
Vitamin B
7
(biotin)
Women
-
-
0.03
-
Men
-
-
0.03
-
Vitamin B
9
(folate)
Women
0.32
0.4
-
1
Vitamin B
3
(niacin)
Men
0.32
0.4
-
1
Notes
: EAR = estimated adequate intake; RDA =
recommended dietary allowance; AI = adequate intake;
UL = upper limit; - = no data available; all values given
in [mg day
-
1
].
The term “niacin” includes nicotinamide or
nicotinic acid, two pyridine derivatives that
carry either a carboxamide or carboxyl group at
the pyridine
3¢-
position
(Fig. 18.3c
)
. Both are
precursors for the enzymatic cofactors NAD
+
and NADP
+
that are required for various redox
reactions in context with carbohydrate and fatty
acid metabolism (Wahlberg
et al
., 2000). Niacin
also plays roles in cellular signaling reactions,
ADP-ribosylation, Ca signaling, or cell-cycle
control (Lepiniec
et al
., 1995; Doucet-Chabeaud
et al
., 2001; Virag and Szabo, 2002; Hassa
et al
.,
2006; Monks
et al
., 2006; Shiotani
et al
., 2006;
Pollak
et al
., 2007; Adams-Phillips
et al
., 2008;
Lamb
et al
., 2011). Consequently, deficiencies
in humans have broad health implications, in-
cluding mental disorders (poor concentration,
apathy, depression) (Lanska, 2010), and pellagra,
a disease where patients suffer from dementia,
dermatitis, and diarrhea (Kohn, 1938). Niacin
deficiencies can be severe in regions where
people rely on a maize-based diet, which requires
an elaborate processing known as “nixtamaliza-
tion” before stored vitamins, amino acids, and
proteins are accessible to the body.
Shortages are common among developing coun-
tries, but are rare in Western societies, which
have good access to riboflavin-fortified foods
(Bates and Powers, 1985; Boisvert
et al
., 1993;
Hoey
et al
., 2009).
Little is known about riboflavin content
variation in different potato cultivars. A study on
Australian retail potatoes and their nutrient con-
tent over a period of 12 months reported average
riboflavin content in the two potato varieties,
Pontiac and Sebago, was comparable and consist-
ently measured at 0.3 mg
100
g
-
1
edible portion,
which the authors defined as 85% of purchase
weight (Wills
et al
., 1984). Processed potato ap-
peared to be a poor source for this vitamin, as
100
g of cooked or baked potatoes contained
only around
2-
4% (~0.02-0.04 mg
100
g
-1
) of
the recommended daily intake, suggesting a sig-
nificant amount was lost through cooking.
Because the overall amount of riboflavin is com-
parably low, breeding efforts may be desirable to