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By Kevin L. Boyd, M.Sc., DDS

DARWINIANDENTISTRYPART 2:

DARWINIANDENTISTRYPART 2:Early Childhood Nutrition, Dentofacial Development and Chronic Disease

As was discussed in DarwinianDentistry part 1: An Evolu-tionary Perspective on theEtiology of Malocclusion1,

the concept of a genome-environ-ment mismatch is one explanationfor the high rates of systemic diseasesof civilization (DC’s) now seen inindustrialized populations that wereseldom, if ever, present in ancestralpopulations. Evidencefrom various academicdisciplines suggests acorrelation between riskfor chronic systemic DC’slike type 2 diabetes,obstructive sleep apneaand cardiovasculardisease, and changeddietary practices associ-ated with industrializa-tion. The mismatchhypothesis can also helpexplain the relativelyrecent increasing preva-lences of certain chronicDC’s of oral origin; dentalcaries, periodontal diseaseand malocclusion are oralinfirmities that have plaguedmankind since the advent of agri-culture some 10-12,000 years ago,but have only begun increasing infrequency over the past 250-300years, and mainly in culturesconsuming an industrial-type diet.Human fossil and pre-Industrialskeletal evidence suggest that therelatively recent secular trend inincreasing worldwide prevalence ofhuman malocclusion seems toclosely coincide with changeddietary practices since the IndustrialRevolution of the late 18th-mid/late19th centuries.

Infant and Early-ChildhoodFeeding (IECF): Then and Now

It is well established by anthro-pologists that modern human andarchaic human mothers have beenbreastfeeding their offspring forthousands of generations. Through-out their evolutionary history foodhad commonly been relativelyscarce for our human and pre-human ancestors and the possibility

of hunger and starvation was aharsh reality of everyday pre-historicexistance; and breastmilk was theonly source of infant nutrition for atleast their first 6 months of life. Toprecisely determine at what age achild would have been completelyweaned from a mother’s milk, fossilstudies designed to detect isotopicmarkers in teeth and bones haveconsistently verified that through-out human history nearly all babiescontinued to (non-exclusively)breastfeed for well into their 3rdyear of life since long beforeanatomically modern humans

(AMH’s) first appear in the fossilrecord some 200,000+ years ago; thepattern is remarkably consistent.Furthermore, many present-daycultures who remain unexposed totypically Western diets, includingextant foraging and hunter-gathererpeoples like Australian Aborigines2

and !Kung bushmen3, also nurse andwean their young, typically withfirm-textured and fibrous complimen-

tary foods, according to anancestral-type*, vs. modern-type** pattern of IECF behav-iors. After the Agricultural Revo-lution spread out of the FertileCrescent in roughly the9th/8th-century BCE, thepersistant threat of starvationwas gradually lessened aspeople throughout the worldgradually gained more controlover their feeding environ-ment. Over the next severalmillennia humans also learnedto domesticate animals as anadditional food source.Advances in agriculture andanimal husbandry gave way tobetter food supplies, increased

population growth and eventuallyled to the invention of the mecha-nized factories and industry thatultimately began to flourish inmid/late 18th-century England,North America and Western Europe.

*ancestral-type IECF- typically characterizedby exclusive breastfeeding for approximately4-8 months, followed by a weaning periodwith firm-textured complementary foodscontinuing well into the 3rd year of life.

**modern-type IECF- typically character-ized by 4-6 months of exclusive bottle-feeding with commercial infant formu-las and artificial nipples, followed by aweaning period with soft pureed andoverly-processed commercial baby foodswell into the 2nd year of life.

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Fig. 1

Then: The Long 19th-Century -Women, Infants and Children

With the coming of the IndustrialAge, many women began to leavetheir traditional agrarian and cottageindustry domestic lifestyles for workin textile mills and as domestic work-ers for middle- and upper-class urbanfamilies. The historical eracommonly referred to as the Long19th-Century (1750-1914)4 is used todescribe this period that featuredboth the emergence of the IndustrialRevolution and the consequential Riseof the West. The Long 19th-Centurynot only brought sweeping changesin agriculture and manufacturingtechnology, but also ushered inimproved transportation and naturalresource management that would alleventually, as did the much earlierAgricultural Revolution, spread to therest of the world. The transition froma manual labor to the new machine-based manufacturing economy seenduring this era eventually led to massmigration of human populationsfrom agrarian life to cities; increasedincome opportunities and generalimprovements in overall standards ofliving also contributed to the explo-sive post-Industrial populationgrowth. Affordable and easily accessi-ble highly-processed and calorically-dense foods also contributed toincreased standard of living andpopulation density.

The traditional roles of women andchildren were drastically changed bythe Long 19th-Century. Prior to theIndustrial Revolution, the primary roleof children raised in agrarian settingshad been as active participants infamilial efforts geared towards suste-nance. When urbanized industrybecame the prevailing way of life,young children were expected towork, usually malnourished, longhours in factories under deplorableconditions. For many European andNorth American women of the Long19th-Century, their traditional role infarmhouse and/or domestic cottageindustry settings, which was generallyconducive to ancestral-type child rear-ing and IECF practices within thehome (Fig. 1), was often exchangedfor greater income opportunities awayfrom their homes and children. Oneof the biggest tradeoffs for women

who sought better wages away fromthe home was in having to give upthe ability to breastfeed and tradition-ally wean their young beyond thestages of early infancy. Prior to theIndustrial Revolution, and usually onlyduring extenuating circumstances likematernal death during childbirth andfamine, occasionally newborns had tobe fed emergency foods that usuallyconsisted of being wet-nursed and/orfed nutritionally-inferior animal milkand weaned with low-nutrient cereal-based gruels; wet-nursing usuallyinvolved the employment of a lactat-ing woman other than the child’sown biological mother. Seeminglysuperior to other forms of artificialfeeding, wet nursing is considered asomewhat inferior substitute as wetnurses did not usually feed childrenaccording to an ancestral-type pattern(i.e., ‘on-demand’ and in to the 3rdyear of life).

As the Industrial Revolutionencouraged the employment ofwomen away from their homes andhearths, the newly available highly-processed, calorie-rich and inexpen-sive soft starchy foods were oftenviewed as a modern miracle. By themiddle to end of the 19th-centurythe trend away from traditionalancestral-type IECF practices wasaccompanied and graduallyreplaced by a trend towards feedingbabies according to a modern-typeIECF regimen that primarilyconsisted of manufactured animalmilk-substitute formulas, newlyinvented artificial rubber nipples5

and highly-processed soft-texturedgruels. These new commercial babyfood products were also oftenaggressively marketed, not so muchas emergency food alternatives forcertain babies who couldn’t betraditionally fed according to anancestral-type IECF regimen, butmore often as superior sources ofnutrition for all babies; the earliestcommercial infant formulas werealso marketed as being ideal forindividuals of all ages who sufferedfrom chewing disabilities (Fig. 2).Artificial methods of IECF is by nomeans a recent development inhuman history. Archaeological sitesin the Nile Delta have containedspecimens of wooden baby bottles,

and references to artificial feedingare seen in ancient Roman literatureand also in the Old Testament.

Now: Infant Nutrition…...Breast is Best?

While formula-feeding can beuseful and beneficial in terms ofconvenience and under certain exten-uating circumstances that mightpreclude breastfeeding, scientificevidence is overwhelming regardingthe health advantages of breastmilk incomparison to feeding babies with arti-ficial formulas. According to the WorldHealth Organization (Appendix 1):

Breastfeeding is an unequalled wayof providing ideal food for thehealthy growth and developmentof infants; it is also an integralpart of the reproductive processwith important implications forthe health of mothers. As a globalpublic health recommendation,infants should be exclusivelybreastfed for the first six monthsof life to achieve optimal growth,development and health. There-after, to meet their evolving nutri-tional requirements, infants shouldreceive nutritionally adequate andsafe complementary foods whilebreastfeeding continues for up totwo years of age or beyond. Exclu-sive breastfeeding from birth ispossible except for a few medicalconditions, and unrestricted exclu-sive breastfeeding results in amplemilk production. Even though it isa natural act, breastfeeding is alsoa learned behavior. Virtually allmothers can breastfeed providedthey have accurate information,and support within their familiesand communities and from thehealth care system. They shouldalso have access to skilled practicalhelp from, for example, trainedhealth workers, lay and peer coun-selors, and certified lactationconsultants, who can help to buildmothers’ confidence, improve feed-ing technique, and prevent orresolve breastfeeding problems.When discussing issues related to

modes of infant feeding and potentialhealth outcomes, it is important to bemindful that there are primarily two

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Fig. 2

different components to consider: 1.)the chemical composition of artificialformulas when compared to chemicalcomposition of breastmilk as the idealstandard; and 2.) the mechanical modeof delivery of infant formulas and/orpumped breastmilk from artificiallynippled-bottles, in comparison to theideal standard of breastmilk directlysuckled from the breast. And whendiscussing infant feeding with regardto potential health risks vs. potentialhealth advantages, it is also importantto consider that it may be difficult todetermine whether a particular healthoutcome is directly related to aspecific mode of infant feeding; forexample, prolonged bottle-feeding hasbeen shown to positively correlatewith recurrent ear infections6, butdoes this necessarily imply that breast-feeding is somehow inherently protec-tive against developing recurrent earinfections? Breastfeeding is indeedassociated with reduced risk for manydiseases in infants and mothers; incontrast, the following deleterioussystemic health issues have been posi-tively linked to prolonged formulafeeding: acute otitis media, non-specific gastroenteritis, severe lowerrespiratory tract infections, atopicdermatitis, asthma (young children),obesity, type 1 and 2 diabetes, child-

hood leukemia, sudden infant deathsyndrome (SIDS), and necrotizingenterocolitis. (Appendix 2).

In addition to the well-recognizednutritional, immunological andpsychological benefits, breastfeedingalso promotes adequate developmentof the dental and oral myofunctionalstructures7. Two primary oral healthissues associated with mode of infantfeeding include risk for dental cariesand/or malocclusion. Whencompared to formula-feeding, due tothe presence in breastmilk of caries-inhibiting lactoferrin, combined withthe fact that lactose (the only sugar inbreastmilk), is not an optimal energysubstrate for Mutans streptoccus,breastfeeding seems to be highlyprotective against the development ofearly childhood caries (ECC). In termsof malocclusion, when compared tobottle-fed (with human or commer-cial formula) children, breastfeedinghas been shown to be protectiveagainst development of anterioropen-bite8 and posterior cross-bite9 inthe primary dentition.

Wolff’s Law and Moss’Functional Matrix

Wolff's Law, which was establishedin the late 19th-century, essentiallystates that a bone’s form will follow

it’s function: “Remodeling of bone…occurs in response to physicalstresses—or to the lack of them—inthat bone is deposited in sitessubjected to stress and is resorbedfrom sites where there is little stress.In essence, a bone's form follows itsfunction.”10 According to Pottenger11,“In accordance with Wolff's law, thevigor of the nursing infant and theresistance of the nipple to his effortdetermine how strong the importantmuscles of mastication will be. Thepull of the muscles acts on theirattachments and develops theaccompanying bones of the skull andmandible in proportion to the forceexerted.” Complementary to Wolff’sLaw is Moss’ Functional MatrixTheory (FMT) of bone growth; in the1960’s Professor Melvin Moss, aColumbia anatomy professor, intro-duced his FMT12 which describes howbones are essentially grown by inter-capsular pressures at ‘growth centers’rather than grow independently (ofapplied force) at ‘growth sites’.

The example most commonlyused to illustrate the Moss FMTconcept is that of how an expandingand encapsulated infant brainapplies internal force against thecranial sutures/fontanelles and thusstimulates interstitial bone growthacross the sutures, and in turn, willultimately determine the finalcranial vault volume.

Breastfeeding MechanismPrevious thinking regarding the

mechanism by which babies extractmilk from their mother’s breast wasprimarily predicated upon the percep-tion that a baby’s sucking wouldstretch the nipple to the junction ofthe hard and soft palate and then thetongue would massage milk expressedfrom the nipple during nursing (Fig.3); it has only recently been deter-mined through ultrasound imagingdata (Appendix 3) that the actualmechanism by which babies removemilk from their mother’s breast isprimarily due to a vacuum actionproduced by a lowering of the baby’stongue from the roof of the mouth13.

After the expressed milk is swal-lowed, the child then re-elevates themiddle portion of the tongue firmlyagainst the roof of the mouth with

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Fig. 3

Fig. 4

simultaneous pushing of themother’s nipple against the inside ofthe pre-maxillary/incisive suturejunction (Fig. 4). This has a widen-ing, flattening and lengthening effecton the palatal-facial sutural complex(i.e., mid-palatal, transverse-palataland incisive sutures) (Fig. 5) that isconsistent with, not only the bonegrowth theories of Wolff and Moss,but also with the good dentofacialdevelopment that is seen in typicallyancestral fed versus non-ancestral-fedindividuals (Fig.8). Given what isobserved about how the expandinginfant brain essentially grows thecranial vault, it seems reasonable tosuggest that the initial volume of thepalatal-facial sutural complex isprimarily determined by the pressureof a breastfeeding baby'stongue/mother's nipple against the(still patent) mid-palatal, incisive,and to a lesser extent, transverse-palatal sutures. Worth noting, theincisive suture (IS) (Fig. 6) separatesthe hard palate into two separatebones, a pre-maxillary section andmid/posterior section; the pre-maxil-lary section provides the foundationfor the development of the mid-face,and interestingly, the IS disappears atabout 3 years old in most children….on about the same time that pre-Industrial humans and modern dayhunter-gatherers usually stop breast-feeding their babies.

Sleep-Disordered Breathing,Attention Disorders and Malocclusion

Malocclusion, and someorthodontic treatment options (e.g.,bicuspid extraction and incisorretraction)14 is seldom discussed as apossible predisposing risk factor forlater development of certain chronicsystemic diseases that were likelynever suffered by our ancestors.Additionally, certain orthodontictreatment strategies that aredesigned to encourage very earlydevelopment of a child’s palate andairway, such as Biobloc-Orthotrop-ics15 and myofunctional therapy16,are also seldom discussed, and onmany occasions even disparaged, asa possible options for decreasingsusceptibility to later developmentof chronic systemic disease.

One such disease that is indeedoften associated with some forms ofmalocclusion is adult obstructivesleep apnea (OSA), a potentially life-threatening respiratory condition.OSA is a particularly severe form ofsleep disordered breathing (SDB) that isnow being more frequently seen inchildren. Due in part to the inferiorquality of orally-versus nasally-inspired environmental air (Fig. 8),pediatric OSA is often characterizedby early viral infections and associ-ated enlarged lymphadenoid tissues(tonsils, adenoids); high palates,narrow dental arches and retrog-nathic jaws are also associated riskfactors for OSA16. In a recentlypublished study on palatal vaultchanges and treatment efficiencyimplications in growing subjects17,the authors’ conclusions providedefinitive support for decisions thatare sometimes made by allied pedi-atric health professionals to recom-mend addressing malocclusion inthe primary- and/or early to middle-mixed dentitions when certainairway-impairment risk factors, such

as a narrow/V-shaped dental archand/or a deeply vaulted palate,might be present.

According to a 2007 reportpublished in the journal Pediatrics17,childhood SDB can have an adverseimpact on cognitive development,behavior, quality of life, and use ofhealth care resources. In response to arecent New York Times article18 aboutan alarming national shortage ofADHD medications, Bronx otolaryn-gologist and sleep medicine specialistDr. Steven Park commented(Appendix 4), “There’s no doubt thatADHD medications can be lifesavingfor millions of Americans, but there’sanother dimension to this issue that’sbeing ignored by the mainstreammedia and the general public, despitegrowing evidence in published stud-ies. It’s a general consensus in sleepmedicine that sleep deprived adultsget drowsy, whereas children becomefidgety and hyperactive. Not only aretodays’ children sleep deprived(homework, TV, etc.), many are notable to breathe properly at night, dueto narrowed airways.” Dr. Park goeson to say, “in a study published in

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Fig. 5

Fig. 6: Course of the incisive suture (SI) from the palatal to the facial surface of the maxilla. The incisive suture is often still evident until age 5.

Pediatrics in 2006, 28% of childrenscheduled for tonsillectomy werefound to have undiagnosed ADHD,compared to 7% in controls. Aftertonsillectomy, 50% of the ADHDgroup were cured. Another studyshowed that children with ADHD aremore likely to snore, and that about25% of children with ADHD could betreated effectively by treating theirsleep apnea. Notice all the typicalfindings in a child with sleep-breath-ing problems that are also found withADHD: inability to sleep supine, snor-ing, nasal congestion, mouth-breath-ing, snoring parents, unrefreshingsleep, frequent urination, inability tofocus or concentrate, history of need-ing braces, and bottle-feeding. Youdon’t have to be obese or snore tohave sleep apnea. It’s clear that insome children with ADHD, stimulantslike Ritalin or Adderall work becausethey’re sleepy. My feeling is that all

children with ADHD should bescreened for obstructive sleep apnea.“

Future ConsiderationsChronic diseases of civilization that

result from a genome-environmentmaladaptedness were likely seldomexperienced by our pre-Paleolithicancestors and only began to appearsignificantly in humans following theIndustrial Revolution of the middle18th to late 19th centuries. Similar towhat is now understood with regardsto adult immuno-competence devel-opment through having beenexposed to adequate antigen-expo-sure challenge in early childhood (i.e.,Hygiene Hypothesis)20, early growthof the infant and early childhoodpalatal-facial sutural complex is likelyresponsive to tongue and masticatorychallenges in much the same manneras the developing neurocranium’ssutural-fontanelle complex is respon-sive to the challenges imposed of the

expanding brain. In accordance withWolff’s Law and Moss’s FunctionalMatrix theory, it seems reasonable tosuggest that an ancestral-type IECFregimen would be conducive to opti-mal palatal-facial development. Opti-mally growing palates and open nasalairways can confer resistance to laterSDB/OSA in children. Encouragingmothers to breastfeed and wean theirinfants with minimally-processedcomplementary foods wheneverpossible, can only be seen as a goodthing from an oral-systemic healthperspective. Regardless of how riskfactors for SDB/OSA are acquired,very early non-surgical/non-invasiveefforts to decrease nasal airway resis-tance, including early palatal expan-sion and/or other efforts aimed atimproving tongue posture (e.g.,myofunctional therapy and/orBiobloc-Orthtropic treatment), shouldalso be considered. Whether ofsystemic or oral origin, chronicdiseases of civilization (DC’s) all seemto follow a predictable pattern ofprogression: first, if a susceptible indi-vidual is identified early, DC’s canoften be prevented; second, if signsand symptoms are not too advanced,DC’s can often be successfully reversedand/or treated; and third, if notprevented, reversed and/or appropri-ately treated, systemic and/or oralDC’s can seriously threaten well-beingand survival.

Increasing U.S. prevalences of diag-nosed, and likely many more undiag-nosed, cases of pediatric SDB andOSA, should serve as a call to actionfor all pediatric health professionalsto screen their patients for SDB/OSArisk factors….especially when thosepatients are growing children. Orofa-cial myologists, pediatricians, sleep-medicine specialists, lactation consul-tants, otolaryngologists and dentists,need to work together in collectiveefforts to compile solid evidence insupport of how an inter-disciplinaryapproach to treatment can vastlyimprove pediatric nasal airwaycompetence, and thus, facial andsomatic growth potential and overall(lifelong) systemic health.

Editor’s Note: Article references are availableupon request or for download in the digitalversion at www.orthodontics.com.

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Fig. 7

Fig. 8: During nasal respiration the paranasal sinus complex has 4 main functions: 1.) filtering oflarge particulate matter (e.g., dust mites, fungi, bacteria, industrial pollutants); 2.) warming ofinspired environmental air to body temperature; 3.) humidification of drier environmental air; and4.) release of nitric oxide (N-O); N-O is a powerful anti-microbial, anti-oxidant and smooth musclerelaxant which acts to facilitate diffusion of oxygen from the alveoli to the bloodstream and alsodecrease vascular resistance.

High and narrow palatal vault and V-shapedarchcommon in Western-exposed children.

Shallow/flat and broad palatal vault and U-shapedarch of a pre-Industrial (16th-century) child.