modeling the level of fortification and post-fortification assessments: u.s. experience

June 2004: (II)S50–S59

Modeling the Level of Fortification and Post-FortificationAssessments: U.S. ExperienceElizabeth A Yetley, Ph.D., and Jeanne I. Rader, Ph.D.

Mandatory fortification of enriched cereal-grainproducts became effective in the United Stateson January 1, 1998. This fortification was under-taken to assist women of child-bearing age inincreasing their intake of folic acid to reduce theirrisk of having a pregnancy affected by a neuraltube birth defect. The process by which the Foodand Drug Administration modeled the level offortification with folic acid illustrates the complexissues and general principles that emerge whenfortification of a nation’s food supply is evaluatedas a means of addressing a public health con-cern. The effectiveness of fortification for a targetpopulation and safety for the much larger generalpopulation impose conflicting challenges thatmust be considered concurrently when makingdecisions regarding fortification. Recent datashow improved folate status and apparent de-creases in risk of neural tube birth defects in theU.S. Much about the long-term effects of thefortification program remains unknown and care-ful monitoring over time will be necessary toensure that the program functions as intended.Key words: fortification, folic acid, post-fortifica-tion assessments, vitamin B12

© 2004 International Life Sciences Institute

doi: 10.1301/nr.2004.jun.S50–S59

Modeling the Level of Fortification

In 1992, the United States Public Health Service (PHS)issued a recommendation that all women of childbearingage consume 0.4 mg of folic acid daily to reduce theirrisk of having a pregnancy affected with spina bifida orother neural tube birth defects (NTD).1 The U.S. Foodand Drug Administration (FDA) had several options thatwould assist the Public Health Service in implementingthis recommendation. These options included (a) autho-rization of the use of a health claim on labels and in

labeling of foods that characterizes the relationship be-tween a nutrient (e.g., folate) and a health-related con-dition (e.g., NTDs) and (b) fortification of cereal-grainproducts with folic acid. The fortification option had thepotential for reaching most women of childbearing agewithout requiring them to change their food selectionpatterns. The agency’s responsibility for the safety offoods required it to consider effects of fortification on theentire U.S. population. A description of how the agencymodeled the level of fortification to be implemented inthe U.S. and a consideration of post-fortification findingsare the subjects of this presentation.

General ConsiderationsThe addition of nutrients to foods has been an effectiveway to maintain and improve the overall nutritionalquality of the U.S. food supply. During the 1940s and1950s, the FDA established standards of identity forseveral enriched cereal-grain products (e.g., enrichedbread, rolls and buns, enriched flour, enriched corn gritsand corn meal, enriched rice, and enriched macaroni andnoodle products). These standards required fortificationat specified levels with thiamin, riboflavin, niacin andiron. Addition of the nutrients at the levels specifiedserved to replace losses that occurred during milling andto supplement inadequate dietary intakes. In the U.S.,cereal-grain products are excellent vehicles for fortifica-tion because they are consumed by most of the popula-tion on a daily basis and provide a significant percentageof daily energy intake.2,3

In developing its fortification proposals in 1993, theagency followed the general guidelines for fortificationset forth in its regulations.4 These guidelines include theprinciples that: (a) a nutrient may appropriately be addedto a food to correct a dietary insufficiency recognized bythe scientific community if sufficient information isavailable to identify the nutritional problem and theaffected population; (b) the food used to supply thenutrient is likely to be consumed in quantities that willmake a significant contribution to the diet of the popu-lation in need; (c) the nutrient added to a food is stable inthe food under customary conditions of storage, distri-bution, and use; (d) the addition of the nutrient is not

Drs. Yetley and Rader are with the Center for FoodSafety and Applied Nutrition, U.S. Food and DrugAdministration, College Park, MD 20740, USA.

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likely to create an imbalance of essential nutrients; (e)the nutrient is physiologically available from the food;and (f) there is reasonable assurance that consumption ofthe fortified food will not result in an excessive intake ofthe nutrient, considering cumulative amounts from othersources of the nutrient in the diet.

Potential Adverse Effects of High FolateIntakesThe agency had extensive discussions with its Folic AcidAdvisory Committee and its Food Advisory Committeeon potential risks attendant on excessive intakes of fo-late. While the primary concern was for persons withvitamin B12–related conditions, there was recognitionthat there may also be risks created for pregnant women,persons with epilepsy (i.e., those on anti-seizure (i.e.,antiepileptic) medications that alter folate metabolism)and those on anti-folate medications for a range of otherconditions. With respect to the vitamin B12–related is-sues, the agency evaluated all of the then-available in-formation regarding vitamin B12 deficiency in the U.S.,including evaluation of vitamin B12 status and uncertain-ties regarding the number of persons potentially at riskfrom high intakes of folate.

Safe Upper Limit of Daily IntakeIn developing its fortification options, the agency used 1mg/day of total folate as the safe upper limit of intake.This decision was based on the scientific evidence anddiscussions with experts that there were no data to ensurethat adverse effects were not likely to occur at intakesabove 1 mg; the PHS recommendation that women ofchildbearing age should not exceed intakes of 1 mgfolate/day; the support by FDA’s Folic Acid Subcom-mittee of the agency’s use of 1 mg of total folate/day asthe safe upper limit guide for fortification; the uncertain-ties in food intake estimates and the difficulty in correct-ing for bioavailability; and the need for some margin ofsafety between estimates of intakes and the safe upperlimit of intake.

Following extensive discussions and a review of allavailable data, FDA concluded that for those with vita-min B12 deficiency, there was little likelihood of prob-lems if daily folate intakes are 1 mg or less. In addition,no data were submitted in response to FDA’s proposedrules that long-term intakes of greater than 1 mg weresafe, and this lack of documentation was and continues tobe a major factor in assessing safety of intakes greaterthan 1 mg/day.

Consequently, in its process of developing fortifica-tion plans, the agency focused its review on ensuring safeintakes for all age-gender groups at the high end of theirintake distribution curves, while increasing intakes bythe target population of women of childbearing age at thelow end of their intake distribution curves.

Goal: Safety for the Entire PopulationBecause of its passive nature, food fortification has theadvantage of reaching most of a target population (in thisinstance, women of child-bearing age) without requiringa change in their food selection patterns. However, theremust also be an assurance that a mandate to add specifiedamounts of a nutrient to a staple food in the general foodsupply is safe for the more than 290 million Americanswho will be exposed to the added amounts throughouttheir lifetimes. Thus, in setting fortification with folate toa level that is safe for the general population, the agencyrecognized that it may be difficult for some women in thetarget population to reach their folate intake goals with-out changes in their dietary patterns. In order to workwithin the competing considerations of safety for thegeneral population and increasing intakes by the targetpopulation, FDA concluded that its overriding responsi-bility in developing the folic acid fortification policy wasto establish a safe range of intake for all populationgroups and then to maximize folate intakes for the targetgroup of women within this safe range.

Resolution of Safety ConcernsFDA concluded that its overriding responsibility in seek-ing to ensure that there is adequate folate in the foodsupply is to ensure that even with the fortification offoods that it proposed to provide for, the amount of folatethat people are reasonably expected to consume is withinthe safe upper limit of consumption. The resolution ofsafety concerns was made possible by the agency’sauthority to limit the addition of folic acid to foodthrough its authority to regulate the use of food additives.In the U.S., folic acid is a substance that is regulated bothas a drug for the treatment of megaloblastic anemia offolate insufficiency and as a food additive. Specificsections of the Food, Drug and Cosmetic Act establishthat the use of a substance in food must be safe. Thus, theprobable consumption of a food additive and the cumu-lative effect of the additive in the diet of humans may beconsidered in determining whether a proposed use of afood additive is safe. The original food additive regula-tion for folic acid dated from 1973. The 1973 regulationlacked the necessary detailed guidance to enable vendorsof foods to decide which foods were appropriate forfortification and the levels at which folic acid should beadded. In the course of finalizing the folic acid fortifica-tion regulation and health claim regulation in 1996, theagency also amended the food additive regulation forfolic acid to set limits on the use of folic acid on a perserving basis, to allow for the addition of folic acid tocertain foods for which there exists a standard of identity,and to make breakfast cereals and dietary supplementsthe only non-standardized foods to which folic acid maybe added.5–8

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Methods Used in Modeling the ProposedFortificationThe modeling process FDA used in developing its forti-fication proposals has been described in detail else-where.2,3,9 The general approach involved use of theUSDA 1987–1988 Nationwide Food Consumption Sur-vey to estimate current total daily folate intakes andpotential total daily intakes with simulated fortifications,updating of food composition files to correct for morerecent folate values, and incorporation of estimations ofthe contribution of folate from dietary supplements intototal folate intake. In examining options for providingincreased folate to women of childbearing age, theagency also considered various options including forti-fication of cereal-grains, fruit juices and dairy products.Particular attention was paid to current practices withrespect to consumption of fortified breakfast cereals anddietary supplements because of their wide use in the U.S.In examining potential intakes that might result fromfortification of cereal-grain products, a unique data filewas created that contained recipes for products thatincluded cereal-grain components. Using this unique file,simulated fortification levels could be applied to flourconsumed in foods such as breads and cake as well asflour consumed from, for example, an entree such as tunanoodle casserole (e.g., noodles, bread crumbs, and whitesauce). Daily folate intakes from all sources could thenbe estimated. Means and distributions of total daily folateintakes for eight age-gender groups were calculated us-ing procedures of the SAS system (release 6.08). Resultswere weighted using factors supplied with the data tapesthat were designed to provide results representative ofthe U.S. population. Following completion of the initialmodelings, the agency performed supplemental analysesto check the reasonableness of the estimates obtainedwith the 1987–1988 Nationwide Food Consumption Sur-vey. Consideration was given to the sources and natureof error in food and nutrient intake estimates. The agencyconcluded, after consideration of all the potential sourcesof error, that it was likely that its projections underesti-mated, rather than overestimated, potential folate intakeswith fortification. Overall, the agency examined a total of11 fortification options and estimated intakes of folatewith fortification of cereal-grain products, juices, anddairy products.2,3

The modeling procedures undertaken by the FDAbefore proposing its fortification options illustrated anumber of complex issues and general principles thatneed to be considered in evaluating fortification of thegeneral food supply as a means to address a public healthproblem. Fortification with folic acid was thus illustra-tive of the complex issues that need to be considered andthe FDA’s deliberations with respect to folate will be

applicable to potential future evaluations of other nutri-ents that might be of concern (e.g., vitamin B12).

These concerns include the following: (a) FDA’smodeling results found a significant heterogeneity infolate intakes within the eight age-gender groups exam-ined. Differences of fourfold or more were observedbetween the lowest and highest percentiles examined insome age-gender groups. The existence of such hetero-geneity emphasizes the need to estimate intake distribu-tions rather than simply mean intakes; (b) the agency’sresults also showed the substantial impact of reportedsupplement use at the high end of the distribution curvesand thus emphasized the need to consider nutrient intakefrom all sources; (c) the results illustrated that fortifica-tion of the U.S. food supply tends to increase intakes ofhigh consumers in both target and non-target groups to agreater extent than it does among low consumers in thetarget population; (d) the agency was also able to con-clude from the modeling that sources of error must beconsidered in interpreting results, including errors thatmay result from self-reports of food intake or fromestimation of the nutrient content of foods, and that otherfactors should also be considered, such as changing foodsupplement use patterns over time.9–11

Level of Fortification: 140 �g/100 g EnrichedCereal-grain ProductThe agency’s final rule included fortification of a widerange of cereal-grain products at a level of 140 �g/100 gand also provided for addition of folic acid to breakfastcereals, infant formula, medical foods, foods for specialdietary use, and meal replacement products.2,3,5 Theenriched cereal-grain fortification level of 140 �g folate/100 g appeared to provide the best possible accommo-dation between competing concerns regarding effective-ness for the target population and safety for the muchlarger non-target population. It was originally estimatedthat the U.S. folate fortification program would add80–100 �g folic acid per day to usual intakes of lowconsumer women in the target population who do not usedietary supplements and 70–110 �g folic acid per day tousual intakes of low consumers in non-target populationgroups. For adults �19 years of age who use dietarysupplements, intakes with the 140 �g/100 g cereal-grainfortification were estimated to be 800–880 �g folate/day.

Cofortification with Vitamin B12

BackgroundThe last extensive examination of fortification of food inthe U.S. occurred in the early 1970s.12 The source of dataused in evaluating the adequacy of nutrient intakes forthe 1974 NAS report was the USDA’s Nationwide Sur-vey of Food Intake of Individuals. Actual data collec-


tions for this survey occurred in 1965.12 Based on thelimited data available, a conclusion was reached thataverage diets of all gender-age groups except women 65years and over approached or were above the recommen-dation for vitamin B12. Therefore, this vitamin was notincluded in mid-1970s recommendations for fortifica-tion. Possibly as a consequence, the extensive vehiclesuitability and stability testing that was performed formany other vitamins was not performed for vitamin B12.Thus, there is little information available regarding rec-ommended levels, appropriate vehicles, and the stabilityof this nutrient added to foods. Limited work withfortification of enriched ready-to-eat breakfast cerealswith vitamin B12 revealed an average production loss of17% for the vitamin and 4 and 17% average lossesfollowing storage for 6 and 12 months, respectively, atroom temperature.13

FDA Proposal of October 14, 1993The issue of co-fortification with vitamin B12 arose earlyin FDA’s discussions regarding folic acid fortification.Because there was considerable interest in raising theproposed folate fortification level of 140 �g/100 g ofcereal-grain product to levels of 350 �g/100 g or 700�g/100 g, proponents of higher levels of fortificationsuggested that considerably higher folate fortificationcould be safely implemented if simultaneous fortificationwith vitamin B12 (cobalamin) at a level of 1 mg was alsorequired. These suggestions were based on assumptionsthat the greatest potential for adverse effects with highfolate intake is its masking of the anemia of vitamin B12

deficiency, with continued progression of neurologicdamage and that provision of oral vitamin B12 wouldnegate this concern.

In August, 1993, the PHS’s Centers for DiseaseControl and Prevention held a meeting on surveillancefor adverse effects of increased intakes of folate.2 Sev-eral experts commented on the suggestion that highdoses of vitamin B12 be added to foods and supplementsfortified with folic acid to reduce the potential for ad-verse effects in persons with vitamin B12 deficiency. Oneexpert noted that recommendations to fortify with vita-min B12 would require a demonstration that vitamin B12

added with folic acid remained biologically active andsafe.

In its 1993 proposed rules for folic acid fortification,the FDA did not propose to include the addition ofvitamin B12 to foods fortified with folic acid. The agencyrequested comments, specifically data, on the appropri-ateness, potential effectiveness, and safety of use ofsimultaneous fortification with high levels of vitamin B12

for the purpose of possibly minimizing the adverseeffects of increased folic acid intakes.2

FDA Final Rule of March 5, 1996The agency received many comments in response to itsproposals regarding both a folate/neural tube birth defecthealth claim and folate fortification. However, theagency did not receive any data addressing the issue ofco-fortification with vitamin B12. While several com-ments recommended revising the proposal to require theaddition of vitamin B12 in a one-to-one ratio with folicacid, they provided no data regarding the potential ef-fectiveness of such a plan. Thus, the agency had no basison which to determine whether co-fortification proposalswere appropriate. In addition, proposals to fortify withvitamin B12 failed to recognize the potential for otheradverse effects of increased folate intakes in populationgroups such as pregnant women, children, those onanti-epileptic medications or those on anti-folate medi-cations.

Because data were not available that addressed forthe general population the issue of simultaneous fortifi-cation of foods with both folate and vitamin B12, theagency could not establish what level of vitamin B12

might be sufficient to protect most persons with vitaminB12–related problems from potential adverse effects ofincreased intakes of folate. In addition, questions regard-ing the appropriateness, potential effectiveness, andsafety of such an approach remained unanswered. Vita-min B12 deficiency, including pernicious anemia, is aserious condition that, if untreated, can lead to irrevers-ible neurological damage.

The FDA was not persuaded that the co-fortificationapproach suggested by the comments it received ad-dressed all of the safety concerns relating to persons withvitamin B12 deficiencies. FDA rejected the recommen-dation because the available data did not establish thatrequiring the addition of vitamin B12 whenever folic acidis added will eliminate the safety concerns relating topersons with vitamin B12 deficiencies that arise becauseof deficiencies in intrinsic factor (pernicious anemia) orother vitamin B12–related deficiencies. The FDA isaware that doses of about 1 mg/day of vitamin B12 (about500 times the RDI for this vitamin) without intrinsicfactor (i.e., without the protein factor necessary for theabsorption of vitamin B12 and the factor whose lackcauses pernicious anemia) have provided adequate treat-ment for some persons with pernicious anemia.6,7 How-ever, Hathcock and Troendle14 have noted that regard-less of the widespread availability of oral vitamin B12

preparations, patients with pernicious anemia or others atrisk of vitamin B12 deficiency should be diagnosed,treated and monitored by a physician.

Institute of Medicine Report, 1998Shortly after initiation of the cereal-grain fortificationprogram, the Food and Nutrition Board of the NationalAcademy of Sciences’ Institute of Medicine (IOM), in


the course of its continuing work on establishing refer-ence values for nutrient intakes, identified a tolerableupper intake level (UL) for folate.15 The IOM exten-sively reviewed potential hazards associated with highfolate intake and gave consideration to the metabolicinterrelationships between folate and vitamin B12. Theseinterrelationships include: (a) shared participation of thetwo vitamins in a specific enzymatic reaction; (b) iden-tical hematological complications resulting from defi-ciency of either vitamin; (c) amelioration by folate ad-ministration of the hematological complications causedby either folate or vitamin B12 deficiency; and, (d) invitamin B12 deficiency, the occurrence of neurologicalcomplications that do not respond to folate administra-tion. The IOM set the UL for adults at 1 mg/day (1000�g/day) of folate from supplements or fortified foods.The IOM’s conclusions considered the devastating andirreversible nature of neurological consequences, datasuggesting that pernicious anemia may develop at ayounger age in some racial or ethnic groups and uncer-tainty about the occurrence of vitamin B12 deficiency inyounger age groups. ULs for children 1 to 3, 4 to 8, 9 to13, and 14 to 18 years were set at 300, 400, 600, and 800�g/day of folate, respectively, from foods or supple-ments.15

Assessing the Effects of Fortification

Folic acid fortification of enriched cereal-grain productsbecame mandatory in the U.S. on January 1, 1998.Interest continues to be focused on assessing the effectsof this fortification on risk of neural tube birth defects,for which the fortification was initially intended, and onfolate intake relative to homocysteine (Hcy) concentra-tions and risk of vascular disease.16–18 Elevated Hcy hasbeen identified as a risk factor for cardiovascular andcerebrovascular disease but a causal relationship be-tween the two has not been demonstrated.

Indirect EstimatesPrior to the availability of data that directly assessedchanges in folate status following fortification, a numberof different types of studies were used to provide indirectmeasurements of the program’s potential effects. Severalstudies measured indicators of folate status (e.g., serumfolate, red blood cell (RBC) folate, homocysteine [Hcy])in volunteers given graded amounts of folic acid infortified food (e.g., a breakfast cereal) for a specifiedperiod of time (Malinow et al.).19 Such studies provideinteresting data regarding potential effects of short-termexposure to a single fortified food but do not address theeffects of consuming a wide range of fortified foods fora long period of time. Short-term studies are thus likelyto underestimate the potential effects of the broad-basedfortification program.

Another approach involves estimating intakes thatmight result from a fortified food supply by combiningfood consumption data with calculated amounts of folicacid that would be present in foods following fortifica-tion (Lewis et al.).20 This approach relies heavily on foodconsumption survey data that typically underestimate theamounts of food consumed. In addition, because food-by-food analyses are not conducted, broad assumptionsmust be made regarding the folate content of foods afterfortification. This approach also likely underestimatesfolate intakes.

A third approach involves an examination of theeffect of the fortification regulations on folic acid contentof commonly ingested foods. For example, folate contentof foods eaten by participants of the CSFII survey(1994–1996) was determined upon completion of theCSFII survey and, retrospectively, using a database (SR12 ‘98) which reflected the new folate regulations. Therecent report of Cho et al.21 indicated that folate levels ofbaked products, cereal grains and pasta doubled or tri-pled after the new regulation took effect and that break-fast cereals were one of the most highly fortified foodsources of folate.

Direct Assessments: Changes in Indices ofFolate StatusJacques et al.22 provided the first data that directlyassessed effects of fortification on folate status. Theseauthors measured substantial improvements in folatestatus in middle-aged and older adults participating in the5th (1991–1994) and 6th (1995–1998) examinations ofthe Framingham Offspring study cohort. Blood sampleswere obtained from a control group before fortification(January 1995–September 1996) and a study group afterfortification (September 1997–March 1998). For non-users of B-vitamin supplements, mean plasma folateincreased from 4.6 �g/L before fortification to 10.0 �g/Lfollowing fortification. The prevalence of high Hcy con-centrations (i.e., �13 �mol/L) decreased from 18.7 to9.8%. The authors concluded that the fortification ofenriched cereal-grain products was associated with asubstantial improvement in folate status in the middle-aged and older adults who participated in the study.22

Lawrence et al.23,24 reviewed data for serum folatein 98,000 blood samples submitted to Kaiser Permanen-te’s Southern California Endocrinology Laboratory be-tween 1994 and 1998 and found that the median pre-fortification serum folate value in 1994 of 12.6 �g/L hadincreased to 18.7 �g/L by 1998. Serum folate valuescontinued to increase in 1999 and levels in many of the1999 samples exceeded the maximal value of 20.0 �g/Lof folate per liter using the clinical laboratory’smethod.23

The U.S. Centers for Disease Control and Preven-tion reported that the mean red blood cell (RBC) folate


level in women aged 15–44 years participating in the1988–1994 National Health and Nutrition ExaminationSurvey (NHANES) that was conducted prior to folic acidfortification was 181 �g/L and increased 74% to 315�g/L in those participating in the 1999 NHANES.25

Comparison of median serum folate and RBC folatelevels obtained several years prior to and about one yearfollowing full implementation of fortification showedtwo- to three-fold increases. Increases of similar magni-tude occurred across all groups of women 15–44 years ofage (i.e., in pregnant versus non-pregnant women, sup-plement users versus non-supplement users). Thus, thesechanges were considered to be due to the national forti-fication program.25

Canada began its mandatory fortification of all flourand some corn and rice products with folic acid inNovember 1998. Ray et al.26 evaluated folate and vita-min B12 status in Ontario, Canada following this fortifi-cation. These authors performed a retrospective cross-sectional study using a community database of allOntario samples analyzed by a laboratory that was amajor provider of diagnostic laboratory services in Can-ada. A total of 711 samples were evaluated. Ray et al.26

reported that concentrations of serum folate and RBCfolate were much higher than expected: the geometricmean serum folate level for all subjects was 34.5 nmol/Land the geometric mean RBC folate level was 956.8nmol/L. These data are in agreement with those ofJacques et al.22 and Lawrence et al.23,24 who had reportedsignificant increases in serum folate levels in the generalU.S. population.

Caudill et al.27 also investigated folate status inhealthy non-pregnant women (18 to 45 years) followingfolic acid fortification. The study was cross-sectional indesign and a fasting blood sample was obtained fromsocio-economically advantaged (n � 85) and disadvan-taged (n � 50) women residing in Southern Californiawho had not consumed supplemental folic acid withinthe past 12 months. Serum folate, red cell folate, andplasma homocysteine were measured and methylene tet-rahydrofolate reductase genotype was determined. Se-rum folate and red cell folate concentrations for “advan-taged” and “disadvantaged” women greatly exceeded thelevels deemed acceptable for these parameters. 95% ofadvantaged and 78% of disadvantaged women achievedred cell folate concentrations �906 nmol/L, which areassociated with very low risk of neural tube defects.Significant reductions in Hcy were also observed. Thedata of Caudill et al.,27 while obtained from a smallsample of women, showed that economically disadvan-taged women were receiving significant benefits from thefortification.

Caudill et al. 27 were among the first to note that thehigh concentrations of RBC and serum folate observed in

their participants suggested that the fortification programwas delivering more than the approximately 100 micro-gram folic acid/day originally estimated. Total dietaryfolate was assessed in the study of Caudill et al.27 andwas found to be approximately 100 to 200 micrograms/day higher than nationwide pre-fortification intakes. Themedian red cell folate concentration for all women in thestudy (1246 nmol/L) implied that fortification was deliv-ering an additional 200 to 400 micrograms/day of folate.

Reduction in Prevalence of Neural TubeDefectsHonein et al.28 reported the results of a study designed toevaluate the impact of folate fortification on the birthprevalence of neural tube defects. These authors carriedout a national survey of birth certificate data for livebirths to women in 45 states and the District of Columbiabetween January 1990 and December 1999. Honein etal.28 reported that the birth prevalence of neural tubedefects decreased from 37.8 per 100,000 live birthsbefore fortification to 30.5 per 100,000 live births con-ceived after mandatory fortification. This represented a19% decline in birth prevalence of NTDs. While suffer-ing from some limitations (e.g., poor sensitivity fordetecting birth defects at birth and no information aboutbirth defects that are prenatally diagnosed and electivelyterminated), birth certificates are the only data sourceavailable at the national level to monitor trends in birthdefect prevalences.

Another method of assessing the effects of fortifica-tion is to determine temporal trends in the prevalence ofneural tube defects. Williams et al.29 determined theprevalences of spina bifida and anencephaly during thetransition to mandatory folic acid fortification. Theseauthors used 24 population-based surveillance systems toidentify 5630 cases of spina bifida and anencephaly from1995 through 1999. The cases were divided into threetemporal categories, depending upon whether neural tubedevelopment occurred before folic acid fortification: (1)pre-fortification period (January 1995–December 1996);(2) optional fortification period (January 1997–Septem-ber 1998); and (3) mandatory fortification period (Octo-ber 1998–December 1999). Prevalences for each defectwere calculated for each time period and the data werealso stratified by programs that did or did not ascertainprenatally diagnosed cases. Prevalence ratios were cal-culated by dividing the prevalence from the mandatoryfortification period by the prevalence from the pre-forti-fication period. Combined data from 24 population basedsurveillance programs indicated that the prevalence ofspina bifida decreased 31% from the pre- to the manda-tory fortification period and that the decline was tempo-rally associated with folic acid fortification. Prevalenceratios for spina bifida from all programs were 5.15 per


10,000 for the pre-fortification interval and 3.54 per10,000 for the mandatory fortification interval. Declinesfor spina bifida were 40% and 28% for programs withand without prenatal ascertainment, respectively. Theprevalence of anencephaly declined 16% among the 24participating programs and it was not clear whether thisdecline was temporally associated with the fortification.

Health Canada implemented a fortification plan thatrequired that specific grain products be fortified withfolic acid at a level of 0.15 mg/100 g by November 1,1998. It was anticipated that this program would reducethe annual incidence of NTDs by about 22%.30 Theresults of a population-based study from Nova Scotiathat included all NTDs (in live births, stillbirths andterminated pregnancies) were recently published.30

Persad et al.30 extracted the total number of births andstillbirths with NTDs and the number of terminatedpregnancies affected with NTDs from perinatal and fetalanomaly databases. Persad et al.30 reported that theincidence of open NTDs decreased by 54% after theCanadian fortification program was implemented. Themean annual rate was 2.58 per 1000 births from 1991–1997 and 1.17 per 1000 births during 1998–2000. TheCanadian data indicate that the significant decline wasobserved for both spina bifida and anencephaly. Persad etal.30 note that the inclusion of all affected pregnancies(live births, stillbirths, and terminated pregnancies) isparticularly important because a failure to include allaffected pregnancies may underestimate the benefit offolic acid fortification.

Gucciardi et al.31 used data from the CanadianCongenital Anomalies Surveillance System and hospitaldata on terminated pregnancies to calculate the totalincidence of neural tube defects in Ontario from 1986 to1999. They reported that the total neural tube defectincidence rate decreased from 16.2 per 10,000 in 1995 to8.6 per 10,000 by 1999, a decline of 53%, and suggestedthat the decline may have been due to increased folic acidintake among women at the time of conception.

Folate Intakes Exceed PredictionsCaudill et al.27 had noted that the RBC folate valuesfound in their study suggested that the fortification pro-gram was providing 200 to 400 �g folic acid/day. Persadet al.30 commented that the greater than anticipatedreduction in prevalence of open NTDs in their studycould have been due to the women receiving more folicacid from fortified foods than was originally estimated orthat the calculated response was underestimated. Analternative explanation might be that a higher back-ground prevalence of open NTDs in Nova Scotia mayreflect a population that is more sensitive to the effects ofincreased folic acid (e.g., the population had a higher rateof folate-responsive NTDs). While it is not possible at

this time to determine what proportion of a populations’NTDs are folate-responsive, several recent reports attestto the fact that the fortification program in the U.S. isproviding significantly more folate than was initiallyestimated.

Rader et al.32 surveyed 83 enriched cereal-grainproducts that are required to be fortified with folic acidand an additional 79 products that contained enrichedcereal-grain ingredients or that are currently fortified. Allproducts were collected between February 1998 andApril 1999 and analyzed for total folate content by amicrobiologic assay using tri-enzyme digestion. Formany enriched cereal-grain products, amounts of folatefound on analysis were significantly higher than amountsrequired by Federal regulations. In part because of this,label declarations of folate content were also in error.Significant discrepancies were found in products withlonger shelf lives (e.g., among macaroni products) aswell as among enriched bread, rolls and buns. The highvalues found in some enriched cereal-grain products mayrepresent manufacturers’ overages as well as the pres-ence of higher-than-expected levels of endogenous fo-lates. Frequent consumption of such foods would beexpected to lead to more rapid than expected, or higherthan expected changes in indices of folate status. Anotherfactor that should be considered is the fortification of awide range of products that were not included in theoriginal regulations (e.g., breakfast bars, toaster pastries,powdered breakfast drinks) and an increased number ofnon-standardized products that provide 100% of thedaily value for folate per serving.

Choumenkovitch et al.33 estimated the effect offortification on intake of folic acid and total folate and onprevalence of individuals with inadequate intake andwith high intakes. Data on food and nutrient intake from1480 individuals who took part in 5th and 6th examina-tions of the Framingham Offspring Cohort Study wasused to estimate “pre”- and “post”-fortification intakes.Fortification became mandatory during the 6th examina-tion study cohort and made possible a comparison ofthose non-exposed and exposed to the fortification. Pub-lished data on total folate content of enriched cereal-grain products was used to estimate intakes post-fortifi-cation. Choumenkovitch et al.33 reported that amongnon-supplement users, folic acid intake increased by amean of 190 �g/day (95% CI, 176–204; P�0.001) andtotal folate intake increased by a mean of 323 (95% CI:296–350) �g dietary folate equivalents (DFE)/day (P �0.001) in the fortification-exposed participants. Theprevalence of exposed individuals with total folate intakebelow the estimated average requirement (320 �g DFE/day) decreased from 48.6% before fortification to 7%following fortification. The prevalence of individualswith folic acid intakes above the upper tolerable intake


levels of 1000 �g folic acid/day) increased only amongsupplement users and increased from 1.3 to 11.3% (P �0.001). By these estimations, Choumenkovitch et al.33

reported that folic acid fortification resulted in a meanincrease in folic acid intake that was approximately twiceas large as previously projected.

In the most recent study to date, Quinlivan andGregory34 used a “reverse prediction” methodology toestimate the effect of folic acid fortification on theamount of folate consumed by individuals in the U.S.These authors performed a linear regression analysis ofpublished data to determine the relationship between achronic folic acid dose and the resulting increase insteady state concentrations of folate in plasma or serum.They found that increases in circulating folate concen-trations were linearly related to folic acid intake over therange of 100 to 1000 �g/day (r � 0.984, P�0.0001).Using the regression equation and reverse prediction,they quantified the increase in folic acid intake thatwould be required to achieve the increase in plasma orserum folate observed in the published studies. Thepredicted increases in folic acid intake from fortifiedfood ranged from 215 to 240 �g/day.

Future Considerations

Careful post-fortification monitoring over time and theability to make adjustments if necessary are fundamentalto the long-term success of nationwide food fortificationprograms. All of the recent data cited above show thatthere have been significant improvements in folate statusin the U.S. population over a very short time period. Therapidity with which these changes were recognized andthe results published emphasize the importance of well-designed and executed surveillance systems such as theU.S. NHANES.

The primary motivation behind the folic acid forti-fication was to reduce a woman’s risk of having apregnancy affected by an NTD. Reports of a 19% de-crease in birth prevalence of NTDs (determined frombirth certificates)28 and a 31% decrease in prevalence(derived from data from 24 population-based birth de-fects surveillance programs)29 indicate the progress thathas occurred toward this goal. The recent report ofPersad et al.30 of a more than 50% reduction in bothspina bifida and anencephaly in Nova Scotia followingimplementation of a fortification program very similar tothat of the U.S. emphasizes the importance of completecase ascertainment in deriving data to accurately assessthe effects of the fortification programs in the U.S. andCanada.

There is much we do not know about the long-termeffects of the fortification program. Recent reports indi-cate that the fortification program is providing abouttwice as much folic acid as was originally estimated.33,34

Quinlivan and Gregory34 note that while small oral dosesof folic acid are efficiently metabolized to 5-methyltet-rahydrofolate, intakes above about 200 �g appear tooverload this metabolic capacity and can lead to theappearance of unmetabolized folic acid in plasma, aphenomenon observed by Kelly et al.35 Since the currentestimated net folic acid intakes are about 200 �g/day,39,34 the consequences of the chronic presence ofunmetabolized folic acid in plasma is unknown and itseffects on normal homeostatic mechanisms (e.g., thoseregulating cellular retention and metabolic function offolate) remain to be determined.

Similarly, FDA’s conclusion that fortification withfolic acid was unlikely to affect those on antifolate drugtherapies was based on the limited data available at thetime and on estimations that the fortification programwould provide an additional 100 �g folic acid per day.6,7

This earlier conclusion may need to be reassessed in lightof the higher estimated current intakes and newer data oneffects of folic acid on antifolate drugs.34 This concernregarding effects of increased folic acid intakes in thoseon antifolate anticonvulsants and antifolate therapeuticssuch as methotrexate has been expressed by the IOM inits 1998 report.15

In addition, we have no data regarding the effects oflong-term exposure of young children to multiples oftheir recommended daily intake of folic acid. This is ofsome importance because the daily recommended intakefor children is 200 to 300 �g and the Institute ofMedicine has established a tolerable upper limit of folicacid intake of 300 �g/day for children aged 1 to 3 yearsand 400 �g/day for those aged 4 to 8 years.15 Estimatesof folic acid intake in several U.S. population groupssuggested that some people may already by consumingquantities of folic acid that approach or exceed theIOM’s upper limit for folic acid.20 The recent work ofChoumenkovitch et al.33 supports this.

There are as yet no data on effects of in vivo chronicexposure of adult and fetal cells to the synthetic form offolic acid; it has never been investigated at the popula-tion level, and the issue of potential adverse effects ofexcess folate in individuals with untreated vitamin B12

deficiency remains unresolved. Monitoring to determinewhether there is a change in the natural history ofvitamin B12 deficiency (e.g., an increase in the presenta-tion of vitamin B12 deficiency neuropathy in the absenceof anemia) may not be possible in the presence of ahighly fortified food supply.

It is still too early to determine whether other healthbenefits such as possible reduction in rates of vasculardisease or in rates of certain cancers may result from thefolic acid fortification program. Only careful monitoringover time will determine whether the program is func-


tioning as planned and does not have unintended conse-quences.

1. Department of Health and Human Services, PublicHealth Service (DHHS/PHS). Recommendations forthe use of folic acid to reduce the number of casesof spina bifida and other neural tube defects. MorbMortal Wkly Rep MMWR. 1992;41:1.

2. Food and Drug Administration, USA. Food stan-dards: food labeling: health claims and label state-ments—folate and neural tube defects; proposedrule, (21 CFR Part 101). Federal Register.1993;58:53254–53295.

3. Food and Drug Administration, USA. Food stan-dards: amendment of standards of identity for en-riched grain products to require addition of folicacid: proposed rule, (21 CFR Parts 136, 137 and139). Federal Register. 1993;58:53305–53312.

4. Office of the Federal Register, National Archives andRecords Administration, Code of Federal Regula-tions § 104.20. Nutritional Quality Guidelines forFoods, Subpart B—Fortification Policy. Washing-ton, DC: U.S. Government Printing Office; April 1,2002:177–180.

5. Food and Drug Administration, USA. Food additivespermitted for direct addition to food for humanconsumption: folic acid (folacin); proposed rule, (21CFR Part 172). Federal Register. 1993;58:53312–53317.

6. Food and Drug Administration, USA. Food stan-dards: food labeling: health claims and label state-ments—folate and neural tube defects; final rule, (21CFR Part 101). Federal Register. 1996;61:8752–8781.

7. Food and Drug Administration, USA. Food stan-dards: amendment of standards of identity for en-riched grain products to require addition of folicacid: final rule, (21 CFR Parts 136, 137 and 139).Federal Register. 1996;61:8781–8797.

8. Food and Drug Administration, USA. Food additivespermitted for direct addition to food for humanconsumption: folic acid (folacin); final rule, (21 CFRPart 172). Federal Register. 1996;61:8797–8807.

9. Crane NT, Wilson DB, Cook A, Lewis CJ, Yetley EA,Rader JI. Evaluating food fortification options: gen-eral principles revisited with folic acid. Am J PublicHealth. 1995;85:660–666.

10. Yetley EA, Rader JI. Folate fortification of cereal-grain products: FDA policies and actions. CerealFoods World. 1995;40:67–71.

11. Yetley EA, Rader JI. The challenge of regulatinghealth claims and food fortification. J Nutr. 1996;126:765S–772S.

12. National Academy of Sciences. Proposed Fortifica-tion Policy for Cereal-Grain Products. Washington,DC: National Academy of Sciences; 1974.

13. Steele CJ. Cereal fortification: technological prob-lems. Cereal Foods World. 1976;21:538–540.

14. Hathcock J, Troendle G. Oral cobalamin for treat-ment of pernicious anemia. J Am Med Assoc. 1991;265:96–97.

15. Food and Nutrition Board, Institute of Medicine,National Academy of Sciences. Dietary referenceintakes for thiamin, riboflavin, niacin, vitamin B6,folate, vitamin B12, pantothenic acid, biotin and

choline. Washington, DC: National Academy Press;1998;196–305.

16. Shane B. Folate fortification: enough already? Am JClin Nutr. 2003;77:8–9.

17. Rader JI, Yetley EA. Nationwide folate fortificationhas complex ramifications and requires carefulmonitoring over time. Arch Intern Med. 2002;162:608–609.

18. Rader JI. Folic acid fortification, folate status andplasma homocysteine. J Nutr. 2002;132:2466S–2470S.

19. Malinow MR, Duell PB, Hess DL, et al. Reduction ofplasma homocysteine levels by breakfast cerealfortified with folic acid in patients with coronaryheart disease. N Engl J Med. 1998;338:1009–1015.

20. Lewis CJ, Crane NT, Wilson DB, Yetley EA. Esti-mated folate intakes: data updated to reflect foodfortification, increased bioavailability, and dietarysupplement use. Am J Clin Nutr. 1999;70:198–207.

21. Cho S, Johnson G, Song WO. Folate content offoods: comparison between databases compiledbefore and after new FDA fortification requirements.J Food Comp and Anal. 2002;15:293–307.

22. Jacques PF, Selhub J, Bostom AG, Wilson PW,Rosenberg IH. The effect of folic acid fortification onplasma folate and total homocysterine concentra-tions. N Engl J Med. 1999;340:1449–1454.

23. Lawrence JM, Petitti DB, Watkins M, Umekubo MA.Trends in serum folate after food fortification. Lan-cet. 1999;354:915–916.

24. Lawrence JM, Chiu V, Petitti DB. Fortification offoods with folic acid [Letter]. N Engl J Med. 2000;343:970.

25. Department of Health and Human Services, PublicHealth Service, Centers for Disease Control andPrevention (DHHS/PHS). Folate status in women ofchildbearing age: United States, 1999. MMWR Mor-bid Mortal Wkly Rep. 2000;49:962–965.

26. Ray JG, Cole DEC, Boss SC. An Ontario-wide studyof vitamin B12, serum folate, and red cell folatelevels in relation to plasma homocysteine: is a pre-ventable public health issue on the rise? Clin Bio-chem. 2000;33:337–343.

27. Caudill MA, Thia Le MS, Moonie SA, et al. Folatestatus in women of childbearing age residing inSouthern California after folic acid fortification. J AmColl Nutr. 2001;20:129–134.

28. Honein MA, Paulozzi LJ, Matthews TJ, Erickson JD,Wong L-YC. Impact of folic acid fortification of theU.S. food supply on the occurrence of neural tubedefects. JAMA. 2001;285:2981–2986.

29. Williams LJ, Mai CT, Edmonds, LD, et al. Prevalenceof spina bifida and anencephaly during the transi-tion to mandatory folic acid fortification in theUnited States. Teratology. 2002;66:33–39.

30. Persad VL, Van den Hof MC, Dube JM, Zimmer P.Incidence of open neural tube defects in Nova Sco-tia after folic acid fortification. Can Med Assoc J.2002;167:241–245.

31. Gucciardi E, Pietrusiak M-A, Reynolds DL, Rouleau.Incidence of neural tube defects in Ontario, 1986–1999. Can Med Assoc J. 2002;167:237–240.

32. Rader JI, Weaver CM, Angyal G. Total folate in


enriched cereal-grain products in the United Statesfollowing fortification. Food Chem. 2000;70:275–289.

33. Choumenkovitch SF, Selhub J, Wilson PF, Rader JI,Rosenberg IH, Jacques PF. Folic acid intake fromfortification in the United States exceeds predic-tions. J Nutr. 2002;132:2792–2798.

34. Quinlivan EP, Gregory JF III. Effect of food fortifica-tion on folic acid intake in the United States. Am JClin Nutr. 2003;77:221–225.

35. Kelly P, McPartlin J, Goggins M, Weit DG, Scott JM.Unmetabolized folic acid in serum: acute studies insubjects consuming fortified food and supplements.Am J Clin Nutr. 1997;65:1790–1795.


modeling the level of fortification and post-fortification assessments: u.s. experience

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