Advances in Food and Nutrition Research, Volume 71

171 Pages·2014·2.413 MB·English

by  Jeyakumar Henry (Eds.)

ADVISORY BOARDS
KEN BUCKLE
University ofNew South Wales, Australia
MARY ELLEN CAMIRE
University ofMaine, USA
ROGER CLEMENS
University ofSouthern California, USA
HILDEGARDE HEYMANN
University ofCalifornia, Davis, USA
ROBERT HUTKINS
University ofNebraska, USA
RONALD JACKSON
BrockUniversity, Canada
HUUB LELIEVELD
Global Harmonization Initiative, The Netherlands
DARYL B. LUND
University ofWisconsin, USA
CONNIE WEAVER
Purdue University, USA
RONALD WROLSTAD
Oregon State University, USA
SERIES EDITORS
GEORGE F. STEWART (1948–1982)
EMIL M. MRAK (1948–1987)
C. O. CHICHESTER (1959–1988)
BERNARD S. SCHWEIGERT (1984–1988)
JOHN E. KINSELLA (1989–1993)
STEVE L. TAYLOR (1995–2011)
JEYAKUMAR HENRY (2011– )
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CONTRIBUTORS
IrisF.F.Benzie
DepartmentofHealthTechnologyandInformatics,TheHongKongPolytechnic
University,Kowloon,HongKong
RuthS.M.Chan
DepartmentofMedicineandTherapeutics,TheChineseUniversityofHongKong,Shatin,
HongKong
BerniceH.K.Cheung
DepartmentofMedicineandTherapeutics,TheChineseUniversityofHongKong,Shatin,
HongKong
Siu-WaiChoi
DepartmentofHealthTechnologyandInformatics,TheHongKongPolytechnic
University,Kowloon,HongKong
ChiaraGori
DepartmentofClinicalMedicine,SapienzaUniversity,Rome,Italy
JeyakumarHenry
ClinicalNutritionResearchCentre,SingaporeInstituteforClinicalSciences,Singapore,
Singapore
IvanC.H.Ho
DepartmentofMedicineandTherapeutics,TheChineseUniversityofHongKong,Shatin,
HongKong
BhupinderKaur
ClinicalNutritionResearchCentre,SingaporeInstituteforClinicalSciences,Singapore,
Singapore
AlessandroLaviano
DepartmentofClinicalMedicine,SapienzaUniversity,Rome,Italy
SerenaRianda
DepartmentofClinicalMedicine,SapienzaUniversity,Rome,Italy
MandyM.M.Sea
DepartmentofMedicineandTherapeutics,TheChineseUniversityofHongKong,Shatin,
HongKong
JeanWoo
DepartmentofMedicineandTherapeutics,TheChineseUniversityofHongKong,Shatin,
HongKong
vii
PREFACE
The8thWorldCongressonDevelopmentalOriginsofHealthandDisease
hasjustendedinSingapore(November2013).Itattractednearly1000sci-
entistsfrom52countries.Thediversityandnumberofparticipantssignifies
theimportanceofthistopic.The“fetaloriginshypothesis”wasproposedin
1989 by Prof. David Barker, working at the University of Southampton.
The fetal origins hypothesis suggests that fetal undernutrition in the first
andsecondtrimesterofgestationleadstodisproportionategrowthandpro-
grams later coronary heart disease in adulthood. In 1995, British Medical
Journalcoinedtheterm“Barkerhypothesis.”Thenotionthatprepregnancy
dietandfetalandpostnatalgrowth(allinfluencedbynutrition)cancontrib-
ute to long-term health outcomes is a major shift in nutritional paradigm.
The Barker hypothesis may bethe single most important medical observa-
tionofthetwenty-firstcentury.Thatadultdiseasemayhaveitsrootsinearly
life, particularly related to the diet consumed and nutrition, enables us to
potentially shape our health destiny by dietary interventions. Here is an
example of close synergy between food, nutrition, and health. It testifies
the need to better understand the mechanistic, metabolic, physiological,
and nutritional consequences of early programming. Advances in Food and
Nutrition Research is at the forefront of publishing papers on the interface
offoodandnutrition.Intheyearstocome,wewillseehowdietarymanip-
ulation early in life can imprint and shape our health trajectory.
C. J. HENRY
Singapore and Oxford
ix
CHAPTER ONE
Antioxidants in Food: Content,
Measurement, Significance,
Action, Cautions, Caveats, and
Research Needs
Iris F.F. Benzie1, Siu-Wai Choi
DepartmentofHealthTechnologyandInformatics,TheHongKongPolytechnicUniversity,Kowloon,
HongKong
1Correspondingauthor:e-mailaddress:[email protected]
Contents
1. Introduction:AntioxidantsinFood—TheirRoleandImportance 2
1.1 Basicconceptsofoxidationandtheroleofantioxidants 2
1.2 Antioxidants:Typesandaction 3
1.3 Acloserlookatascorbicacid:Akeyantioxidant 4
1.4 Humanantioxidantdefenseanddietaryinfluences 6
2. Measuring“TotalAntioxidantContent”ofFood 9
2.1 Basicprinciples,notesoncalibration,units,andconfusion 9
2.2 Limitationsofthe“totalantioxidantcontent”approach:Cautions
andcaveats 11
3. TheFRAPAssayandItsModifiedForm(FRASC)forAscorbicAcid 13
3.1 Basicprinciples 13
3.2 TheFRAPassay—Procedureinbrief 14
3.3 ApplicationoftheFRAPassayinfoodscience 16
3.4 Anoteonthe“nonuricacidFRAPvalue”ofbloodplasmaanditsrelevance
tonutritionalscience 16
3.5 ThemodifiedFRAPassay(FRASC)fortotalantioxidantandascorbicacid
measurement 32
4. WhyIstheAntioxidantContentofFoodofInterest? 33
4.1 Basicconcepts 33
4.2 Antioxidantsandhealth:Theevidenceandpotentialimpact 34
5. AntioxidantsinFood:EnigmasandEvolutionaryAspects 36
6. MechanismsofAction:RedoxIssues,Phytohormesis,andColonicMicrobiota 38
6.1 Redoxtonechangesasadrivingforceforcytoprotectionandthebiological
senseofrestrictedbioavailabilityofdietaryantioxidants:Theredox-sensitive
KEAP-1–Nrf2signalingpathway 39
6.2 Colonicmicrofloraandmetabolismoffoodantioxidants:Movingintonew
territoryofthemicrobiome 42
AdvancesinFoodandNutritionResearch,Volume71 #2014ElsevierInc. 1
ISSN1043-4526 Allrightsreserved.
http://dx.doi.org/10.1016/B978-0-12-800270-4.00001-8
2 IrisF.F.BenzieandSiu-WaiChoi
7. TheStorySoFar 43
8. ConcludingRemarksandResearchNeeds 46
Acknowledgments 46
References 47
Abstract
Thereareamultitudeofantioxidantsinfoods,especiallyinfoodsofplantorigin.Higher
intakeofantioxidant-richfoodsisclearlyassociatedwithbetterhealthandfunctional
longevity.Thespecificagentsandmechanismsresponsiblearenotyetclear,butthere
isconvincingevidencethatincludingmoreplant-based,antioxidant-richfoods,herbs,
andbeveragesinthedietiseffectiveinpromotinghealthandloweringriskofvarious
age-relateddiseases.Thecontentofsomeindividualantioxidants,suchasvitaminC,in
foodcanbemeasured,butitisnotfeasibletoattempttomeasureeachantioxidant
separately,andmethodshavebeendevelopedtoassessthe“totalantioxidantcontent”
offoods.Oneofthemostwidelyusedmethodsistheferricreducing/antioxidantpower
(FRAP) assay, which is relatively simple, quick, sensitive, and inexpensive to perform.
TherearemanypublishedstudiesthathaveusedtheFRAPassay,andthesehavegen-
eratedaverylargedatabaseoftotalantioxidantcontentoffoodsthatcanhelpguide
foodchoices forincreased antioxidant intake. TheFRAP assay hasalsobeen used to
assessthebioavailabilityofantioxidantsinfoodsandtoinvestigatetheeffectsofgrow-
ingconditions,storage,processing,andcookingmethodonthetotalantioxidantcon-
tentoffood.Thetestcanbeemployedasaqualitycontrolcheckdevice,andtodetect
adulterationoffood.Furthermore,inamodifiedform(FRASC),theassaycanmeasure
ascorbicacidcontentalmostsimultaneouslywiththetotalantioxidantcontentofthe
sample.Inthischapter,basicconceptsofoxidationandtheroleofantioxidants,aswell
asthetypesandactionofdifferentantioxidantsinfoodswillbereviewedbriefly,andthe
underpinningconceptsandevidenceforhealthbenefitsofincreasedintakeofdietary
antioxidantswillbediscussed,withsomefocusonvitaminC,andalsointhecontextof
ourevolutionarydevelopment.Thebasicconceptsandlimitationsofmeasuring“total
antioxidantcontent”offoodwillbepresented.TheFRAPassayandthemodifiedversion
FRASCwillbedescribed,andthetotalantioxidantcontent(astheFRAPvalue)ofarange
offoods willbe presented. Finally,issues ofbioavailability and redox balance willbe
discussedinrelationtothebiologicalsignificanceandmolecularactionofantioxidants
infoods,somecautionandcaveatsarepresentedaboutovercomingbiologicalbarriers
toabsorptionofantioxidantphytochemicals,andresearchneedstofurtherourunder-
standingintheimportantareaoffood,antioxidants,andhealthwillbehighlighted.
1. INTRODUCTION: ANTIOXIDANTS IN FOOD—THEIR
ROLE AND IMPORTANCE
1.1. Basic concepts of oxidation and the role
of antioxidants
Inchemicalterms,oxidationistheadditionofoxygentoortheremovalof
hydrogen or an electron from a molecule. A biological antioxidant can be
AntioxidantsinFood 3
defined as a substance that prevents the oxidation of an important biomol-
ecule, such as afatty acid, DNA, or a protein, by areactive oxygen species
(ROS) (Ames, 1998; Halliwell & Gutteridge, 2007). ROS are partially
reduced or “energized” forms of oxygen (Table 1.1). Some ROS contain
anunpairedelectroninanorbitalandaresometimesreferredtoas“freerad-
icals”;others,suchashydrogenperoxideandsingletoxygen,arenonradical
species,buttheirreactivity isnonethelessgreater thanground-state molec-
ular oxygen, allowing them to oxidize biomolecules they interact with.
Some ROS have important physiological functions (Ames, 1998;
Halliwell & Gutteridge, 2007). For example, nitric oxide is a vasodilator,
hydrogenperoxideisakeyintracellularsignalingmolecule,andsuperoxide
andhydrochlorousacidplayanimportantroleinourinnateimmunedefense
(Winketal.,2011).However,anexcessofROScanleadtouncontrolledor
indiscriminate oxidation of important biomolecules. This deleteriously
affects their structure and function and is known as “oxidative stress”
(Ames, 1998; Halliwell & Gutteridge, 2007). The imbalance that results
in oxidative stress can be caused by excessive production of ROS, or to a
deficit in the antioxidants that oppose ROS and their damaging oxidative
effects (Fig. 1.1).
1.2. Antioxidants: Types and action
Inanoxygenicenvironment,thethreatofoxidativestressisubiquitousand
continuousforallorganisms,butthephotosensitizingplantsthatarerespon-
sible for our oxygenic environment are exposed to particularly high
Table1.1 TypesofROSandrelativereactivity
ROS Redoxcouple E(cid:1)0 (mV)
Hydroxyl radical HO%,Hþ/H O þ2310
2
Alkoxyl radical RO%,Hþ/ROH þ1600
Peroxylradical ROO%, Hþ/ROOH þ1000
Glutathiyl radical GS%/GS(cid:3) þ920
Tocopheroxyl radical TO%,Hþ/TOH þ480
Hydrogen peroxide H O , Hþ/H O, HO% þ320
2 2 2
Ascorbate radical Asc%(cid:3),Hþ/AscH(cid:3) þ282
Superoxide radical O /O%_ (cid:3)330
2 2
One-electronreductionpotentialsatpH7.0.
Source:HalliwellandGutteridge(2007).
4 IrisF.F.BenzieandSiu-WaiChoi
Figure 1.1 The concept of antioxidant/oxidant imbalance and the development of
oxidativestress.
intracellularlevelsofoxygenandROSandhaveevolvedspecializeddefense
factors to deal with the high oxidant challenge and protect plant structures
and tissues (Benzie, 2000). These factors are referred to as antioxidants.
The best-known antioxidant is vitamin C (ascorbic acid), but there are
various others, and many are unique to the plant kingdom. These include
“vitamin E,” a group of eight tocopherols and tocotrienols, and the very
large families of flavonoids and carotenoids (Benzie, 2005; Buettner,
1993;Gey,1998;Tametal.,2005).Indeed,therearethousandsofdifferent
antioxidants in plants, and they work in different ways (Table 1.2). Some
antioxidantspreventthegenerationofROS,someareenzymesthatdestroy
ROS,somearesmallwater-solublemoleculesthatactasreducing(hydrogen
or electron-donating) agents to “neutralize” free radicals, and some absorb
electrons or excess energy from ROS and “dissipate” this within their
complex lipophilic structure (Ames, 1998; Halliwell & Gutteridge, 2007).
Overall, the effect is to oppose ROS action and limit oxidative stress.
1.3. A closer look at ascorbic acid: A key antioxidant
Vitamin C (ascorbic acid) is present in high concentration in many plants
(Benzie & Wachtel-Galor, 2009; Frei et al., 1989; Gey, 1998;
Halliwell & Gutteridge, 2007; Halvorsen et al., 2002). The content of this
water-solubleantioxidantisparticularlyhighinfruits,butitisfoundinvar-
iousplantpartsandaidsrepairandgrowthofplantsandtheripeningofseeds.
AntioxidantsinFood 5
Table1.2 Plant-derivedantioxidanttypes,action,andsources
Antioxidant Action Mechanism Sources
Ascorbicacid Scavenging Sacrificial interaction Fruits and vegetables,
(vitaminC) of ROS byreplaceable or particularly
recyclable substrates to strawberries, citrus,
scavenge and destroy kiwi, Brussels sprouts,
ROS cauliflower,some
Chinesegreen
vegetables
“VitaminE”(a,b, Quenching Absorptionofelectrons Green leafy vegetables
d, g)isomers of ofROSand and/orenergy (e.g., spinach); nuts,
tocopherols and chain seeds, especially wheat
tocotrienols breaking germ; vegetable oils,
especially sunflower
Carotenoids Chain Chainbreaking atlow Orange/redfruitsand
(hundreds) breaking partialpressures of vegetables (e.g., carrot,
oxygen,complements tomato,apricot,melon,
action of vitamin E pumpkin),green leafy
vegetables, peppers
Flavonoids (large Scavenging Sacrificial interaction Berries, apples, onions,
range of different of ROS tea,red wine, some
types) herbs (parsley,thyme)
citrus fruits,grapes,
cherries
Source:HalliwellandGutteridge(2007).
Mostanimals,fish,andreptilescansynthesizevitaminCinliverorkidney,
buthumanshavelosttheabilitytomakeascorbicacid,eventhoughwehave
retained an absolute requirement for it (Benzie, 2000, 2003; Benzie &
Strain,2005;Freietal.,1989).Ascorbicacidisknowntobeneededforcol-
lagen synthesis in humans, and severe deficiency results in scurvy, which is
nowadaysrarebutcasesarenonethelessstillreported(Doll&Ricou,2013).
Humans must obtain a regular and adequate dietary supply to maintain
plasmaandtissuelevels,andthebestdietarysourcesarefruitsandvegetables
(Frei et al., 1989). In the past, the daily recommended intake of vitamin
C was set at a level ((cid:4)30mg/day) that would prevent overt deficiency
(Newton et al., 1983). However, accumulated epidemiological and exper-
imentalevidenceindicatesthattheroleofascorbicacidinthehumanbodyis
notrestrictedtocollagensynthesisandthatithasanimportantroleinhealth
maintenance overall (Benzie,1999). Ascorbic acid is recognized as a major
6 IrisF.F.BenzieandSiu-WaiChoi
playerinhumanantioxidantdefense(Benzie,1999,2000).Currentdietary
recommendations are for at least 70mg/day for women, 100mg/day for
men, with higher levels advised in pregnancy and for smokers (Carr &
Frei,1999).Theselevelsofintakearerecommendedtoattain“optimal”sta-
tusforhealth,thoughthishasnotbeenclearlydefined.Humancells,espe-
cially white blood cells, and some organs, most notably the eye, contain
millimolarconcentrationsofascorbicacid(Choyetal.,2001,2003).Plasma
ascorbic acid concentrations in the fasting state range quite widely, from
<10 (worryingly low) to (cid:4)100mmol/l in apparently healthy adults (Choi
etal.,2004).Tissueandplasmalevelsaremaintainedby,andsoreflect,die-
taryintakeofvitaminC,andtheplasmaconcentrationofascorbicacidcan
act as a marker of fruit and vegetable intake (provided no supplements are
used) (Choi et al., 2004). A concentration <10mmol/l indicates very low
intake and severe deficiency, even if signs of scurvy are not clearly present
(Levineetal.,2011).Plasmalevelsat1–2hafteringestionofalargedose(1g
ormore)ofvitaminCcanapproach200mmol/l,butpeaklevelsarelimited
byrestrictedgastrointestinalabsorptionofalargedoseandbyurinarylossof
ascorbicacidwhentheplasmaconcentrationexceedstherenalthresholdof
(cid:4)100mmol/l(Levineetal.,2011).Therefore,mostofasingle,largedoseis
notretainedinthebody,andregular,modestdoses(500mgorless)arelikely
to be more effective in enhancing the ascorbic acid status of the body. In
large prospective trials, it has been shown that healthy people with higher
fasting plasma concentrations of food-derived ascorbic acid (i.e., not from
supplements) have significantly lower risk of incident diabetes, cancer,
stroke, heart failure, and all cause mortality in the ensuing years (Fig. 1.2;
Hardingetal.,2008;Pfisteretal.,2011).Ithasbeenestimatedthatforevery
20mmol/l increase in fasting plasma ascorbic acid concentration, there is a
9%relativereductioninriskofincidentheartfailureanda29%decreasein
risk of incident type 2 diabetes (Harding et al., 2008; Pfister et al., 2011).
Plant-based food is the primary source of ascorbic acid in human plasma.
However, it must be noted that the protective agent may not be vitamin
C itself. It could be something very closely associated with vitamin C in
plant-basedfoods,oritcouldbethatthehealthbenefitsareduetotheinter-
active effects of the various antioxidants present in plant-based foods.
1.4. Human antioxidant defense and dietary influences
ThehumanbodyisexposedtoROSonacontinuousbasis,andwehavean
effective antioxidant defense system that has evolved to help deal with the