Robert Karp, MD
SUNY-Downstate Medical Center
Brooklyn, NY
Pretest (detailed explanations at the bottom):
Q1. T or F. The daily requirement of folate sufficient to prevent Neural Tube Defects (NTDs) is uniform across racial and ethic groups.
Q2. Best answer. A woman asks which micronutrient supplement would be best to meet periconceptual nutrient needs?
A. One providing 400 micrograms of folate.
B. One providing 400 micrograms of folate and 6 micrograms of B12.
C. One providing 400 micrograms of folate and 6 micrograms of B12 and 2 mg of Pyridoxine (B6).
D. One providing 400 micrograms of folate and 6 micrograms of B12 and 2 mg of Pyridoxine (B6) and 10mg of iron.
Q3. Best answer. Which of the following food provides the most folate in a serving?
A. Spinach
B Almonds
C Brown rice
D Whole wheat Bread
Q4. Best answer. Which of the following provides folate at the lowest cost per 100 calories?
A. Spinach
B. Almonds
C. Brown rice
D. Whole wheat Bread
Q5. Best answer. Pyridoxine (B6) and folate affect infant birth weight by:
A. Facilitating degradation of homocysteine.
B. Promoting single carbon transport for production of DNA.
C. Preventing seizure activities in adults taking isoniazid
D. Preventing megalobastic anemia.
Q6. True or False. Neural tube defects are found commonly among spontaneously aborted fetuses.
Q7. True or False. With respect to the long-range health of the mother, a diet rich in folate and other micronutrients has distinct advantages over specific micronutrient supplementation.
Objectives:
The Residents will:
1. Gain an understanding of folate metabolism
2 Recognize the impact of genetic variability on folate mediated DNA synthesis and the pathogenesis of NTDs.
3 Gain an appreciation for folate and other nutrient needs in the prevention of prematurity and IUGR.
4 Recognize the importance of folate and other nutrients in CHD prevention.
5 Develop an advocacy model to ensure availability and intake of folate and other B vitamins.
Facilitator Preparation:
The facilitator should review the sections in Pediatric Nutrition Notes on folate, pyridoxine (Vitamin B6), and B12. The biochemical pathways affected by these nutrients in the synthesis of DNA and degradation of homocysteine are presented in a Figure in case study.
Chapters in Modern nutrition in health and disease, 9th edition edited by Maurice Shils and colleagues (Williams Wilkins Lippincott, Baltimore, 1999) provide the commonly accepted body of knowledge on these topics -- Folate by V Herbert, Vitamin B12 by DG Weir and JM Scott, and Vitamin B6 by JE Leklem. TO School and WG Johnson provide a state of the art review Folic Acid: influence on the outcome of pregnancy. (Am J Clin Nutrition. 2000;71(suppl):1295-1305S.)
Please review these and the other two references provided to gain an appreciation of the importance as well as the complexity of folate nutrition through the life cycle. The paper by Motulsky provides the history of folate-NTD investigations as well as a rationale for the effect of hyper-homocysteinemia on both coronary artery disease and pregnancy outcome. Robert Brent has been an eloquent spokesman for prenatal nutrient supplementation. His short commentary provides a compelling argument for folate supplementation of every woman who might become pregnant. Gopalan makes a similarly compelling argument for a healthy diet promoting the general well being of women. The case study examines the importance of both arguments.
See "References" listed at end of module for a comprehensive review of this subject.
INTRODUCTION
Folate is necessary through the life cycle. This topic is presented in the section on pre-adolescence [Hyperlink to pre-adolescence???] because the nutritional need for folate in pregnancy has a profound affect on the occurrence of neural tube defects [Hyperlink to Handicapped child], low birth weight [Hyperlink to early infancy], and the Metabolic Syndrome early in adult life. Metabolic Syndrome is the combination of truncal obesity associated with insulin resistant diabetes mellitus, hypertension, and coronary heart disease. [Hyperlink to cholesterol and adult DM and Hypertension modules]
Folic acid, also referred to as folate, is an essential micronutrient for both fetus and mother because a relative decrease in circulating folate increases the risk for neural tube defects (NTDs), intra-uterine growth retardation (IUGR) and prematurity, and other birth defects. The incidence of NTDs varies greatly with respect to the racial/ethnic background of the mother suggesting that there are genetic factors affecting the likelihood of NTDs occurring. The interaction of heredity and folate on gestation and fetal growth has not been studied.
Later in life, as children mature, folate and pyridoxine intake affect the incidence of coronary heart disease (CHD). This effect is mediated by ineffective degradation of homocysteine with folate/B6 deficiency. It has been hypothesized that the mechanisms leading to prematurity and IUGR are similar to those for CHD. Of note, folate must never be given without Vitamin B12.
Reasons for limited intake of naturally occurring folate -- dark green vegetables and beans B include:
1) cost of folate and other B vitamin rich foods,
2) loss of social support within contemporary food culture,
3) lack of cooking skills, and
4) a need to satisfy children's food preferences. For immigrant populations, additional concerns are
5) an inability to obtain familiar seasonings and 6) a socialization process that encourages change from healthful indigenous foods (e.g., beans) to less healthful convenience foods.
Successful programs for nutrition awareness and knowledge address cost, culture and behavior by:
1) creating consortiums of community based organizations,
2) forming focus groups,
3) developing programs unique to targeted communities,
4) preparing material that promotes use of new foods, and
5) holding cooking classes, and
6) evaluating the effectiveness of their intervention.
With respect to food costs and availability, supplemental programs (WIC and Food Stamps) are particularly effective in maintaining a high quality diets. They provide nutritious food, and they allow money saved to raise the quality of foods purchases. Foods highest in folate content are organ meats, beans and legumes, dark green leafy vegetables such as spinach and broccoli. Note that the best folate nutrition come from foods that are expensive for energy content. These are often restricted in the diets of poor families.
CASE STUDY
Tamia B is the 2nd born child of a G4 P1,1,2,2 mother B pregnant four times with 2 spontaneous abortions, one premature infant (TB), and one full term, low birth weight infant. Mrs. B is an immigrant from the Dominican Republic. She speaks Spanish. Her English language abilities are low. Tamia and her brother are the living children. Tamia was born at 36 weeks gestation. Her weight was 2,100 grams. Prior to delivery, Ms. B complained that Tamia did not move about a great deal.
Mrs. B didn't actually arrive for prenatal care until she was 28 weeks pregnant. Though she was a legal immigrant with a "green card", she thought that applying for Medicaid would be considered as becoming a "public charge" (welfare), and she would lose the right to apply for citizenship. She found a flyer at a health fair in her church which informed her that applying for Medicaid, Child health Plus, WIC and Food Stamps is not considered a public charge. She then came in for care. An elevated measure of alpha feto protein suggested a leak of neural fluid. The presence of a meningeomylocoele and spina bifida were confirmed by ultra sound. The child was born with a neural tube defect B an NTD [Hyperlink to handicapped child]
At term, the neurosurgery team placed a V-P shunt. The defect in the spinal cord was patched, and postnatal care was arranged. A retrospective diet h istory was taken. Mrs. B had lived on a native Caribbean diet with rice, beans and meat at least once a day plus fruits and vegetables and bread through out the day. In the US, she had switched over to a diet that had replaced the beans with fried foods. There was little salad greens eaten before or after immigration.
Q1. Why are folate and B12 needed at conception?
A1. Early fetal life is with doubt the most metabolically active period in the life cycle. Folate is required for production of single carbon units, cell division, and the metabolism of amino acids. It is necessary for trans methylation and trans sulfurization reactions. Folic acid, with vitamin, is essential for the synthesis of thymidylate and DNA. Figure 1. (from Victor Herbert) shows the essential element of the pathway for providing single carbon units.
FIGURE 1: The need for Methyl Tetra Hydro Folate + B12
Methyl THF + B12
Homocysteine -----------------------> Methionine ----------- >
C>S-Adenosyl-methionine -------> Methyl groups for DNA synthesis
CAPTION: A Vitamin B12-containing enzyme removes a methyl group from methyl folate and delivers it to homocysteine, thereby converting homocysteine to methionine (methyl homocysteine) and regenerating THF [tetro hydro folic acid], from which the 5,10 THF in thymadilate synthesis is made. (V Herbert in Shils 9th edition, p440)
In the absence of Vitamin B12, folate in the body will be "trapped" as methyl folate which explains why folate must be provided with adequate B12. The relative absence of B12 and folate decreases the availability of single carbon (methyl) groups, and restricts production of thymidylate and DNA.
The failure to maintain adequate folate and B12 levels results in decreased availability of methyl groups after the block and raised homocysteine levels before the block. This provides a link between prevention of NTDs and early coronary heart disease. The current theory is that the vascular toxicity associated with rising homocysteine levels contributes to early coronary vessel disease as well as placental dysfunction leading to prematurity and IUGR.
A second pathway permitting removal of homocysteine is available. This requires pyridoxine as pyridoxal 5'-phosphate or PLP
Table 1. Citations from the literature
- Homocysteine concentrations are significantly higher among women who give birth the offspring with NTD. (S & J)
- The rate of NTDs in spontaneous abortions is ten fold that of the rate of NTDs at birth.
- Prematurity and IUGR are three times more likely when intake of folate is < 240micro grams per day
- The odds ration for prematurity and IUGR increases by 1.5-1.6% per mmol/L decrease in serum folate level when measured at 28 weeks of gestation
- In one study of women who had an IUGR or premature infant and who had homocysteinemia because of the defect in MTFTR, next infant birth weight went up 1,800 grams and pregnancy duration increased 7.3 weeks.
- Studies of folate enrichment for "white" and "Bantu" women in South Africa showed no change in IUGR for white but a four fold reduction for Bantu women. (Ref 69 in S&J)
- Low red cell folate (<1.9ng/ml) predicts delivery before 39 weeks gestation. (Ref 62 in S&J)
- Serum folate levels are 1.1 ng/ml lower in women delivering <39 weeks (Ref 63 in S&J)
- Serum homocysteine and folate levels have a negative correlation for 35 pregnant women in good health. Higher maternal homocysteine levels correlate with prematurity and IUGR. High folate levels correlate with birth weight and gestation. (Ref 60 in S&J)
Q2. In what ways might a mother become folate deficient?
A2. The six factors listed below could be applied to all micronutrient deficiencies
Table 2. Factors Affecting Folate Availability
1. Inadequate intake
- poor diet by choice (culture), cost (poverty, or disease-related restriction
- alcoholism (substitution of alcohol calories for food)
2. Malabsorption
- Non-specific (gluten enteropathy, drug induced, structural)
- Specific for folate (lack of bile salts)
3. Inadequate use (metabolic block)
- drugs - methotrexate and other anti-metabolites
- enzyme deficiencies - methyltetrahydrofolate transmethylase (MTFTR)
- other vitamin deficiencies - B12
4. Increased requirement with disease
- Extra tissue demand in pregnancy, by the fetus, infancy, and adolescence
- with malignancies
5. Increased excretion
- Vitamin B12 deficiency
- Liver and kidney disease
6. Increased destruction
- Nutrient-nutrient toxicities with "mega doses" of antioxidant nutrients B Vitamins C and E, Retinoids and selenium
Q3. Are there genetic factors affecting folate requirements in pregnancy?
A3. A common allele variant AC677T alters methyl tetrahydrofolate transmethylase (MTFTR) leaving it less effective in transmethylation and trans sulphuration reactions. In combination with inadequate intake (most common) or other factors listed above, women will have significantly reduced levels of metabolically active THFA available for single carbon transport, cell division, and amino acid metabolism.
At conception, the fertilized egg and then the dividing zygote live in the extra cellular fluid of the mother. The needs are great. If intakes are low and the genetics make availability even lower, there is a greater chance for an NTD to occur. The gene frequency for allele variant C677T differs from one ethnic group to another and there are large differences in dietary intake within each group. Thus, adequate folate intake must be assured for everyone.
Q4. Why not just give folic acid, alone?
A4. Folate is given with Vitamins B12 and B6 for the following reasons. First, folate is never given without Vitamin B12. This nutrient, also known as "Cobalamin", is needed for activation and utilization of folate. Second, folate alone, without Vitamin B12, could mask the hematologic and promote the neurologic effects of Cobalamin deficiency. This disorder is known as subacute combined spinal degeneration. It is called `vegan=s back= because the strictest vegetarians could exclude all sources of B12 while consuming large quantities of folate. Third, pyridoxine, Vitamin B6, is also needed to keep homocysteine levels low. As shown in the figure, failed transmethylation (inadequate N5-methyl THF) prevents the passing of a methyl group from homocysteine to make methionine.
Q5. How much folate and other micronutrients are needed?
A5. Ideally, women will be well nourished at conception. To meet basic needs at conception, a woman should have the level of intake of folate and B vitamins necessary to keep the population well nourished B the Recommended Daily Allowance or "RDA" level. Once pregnancy is confirmed, or known NTD child in family, higher levels are suggested. [Hyperlink to RDA]
TABLE 3. Periconceptual needs of a woman are best met with RDA levels of intake.
- 400 micrograms of folate,
- 6 micrograms of Cyanocobalamin (B12), and
- 2 mg of Pyridoxine (B6)
- 10 mg of iron each day is necessary for maternal iron stores
Q6. What should we advise this mother on how to prepare herself for the next pregnancy?
A6. The simple answer is to insure that she takes an adequate quantity of the three micronutrients folate, B12, and B6. Having one infant with an NTD increases risk for having another. Use of the three micronutrients at the level of the Daily Recommended Intake (DRI) B 800 micrograms of folate daily -- is likely to prevent recurrence unless the mother is very obese. Issues of accessibility to health care, good nutrition and nutrient supplements must be considered, also. With respect to NTDs, 3% of the next born children will have a clinically significant NTD unless preventive measures are taken. As many as 10% will have one of the lesser forms of NTD such as failure of closure of a vertebral body or a sacral dimple.
Q7. What would you advise Mrs. B?
A7. You have a special need for a vitamin called Afolic acid@ or "folate" to help prevent the same thing from happening again to your next child. There is a vitamin called "folate". It is found naturally in organ meats, dark leafy green vegetables, broccoli, beans, and wheat germ. And it is added to bread and flour that you buy in the store.
Another source of folate is a vitamin tablet. I'm going to recommend a high dose vitamin such as the one you used during your last pregnancy.
Are you able to get enough food, or do you worry about this at the end of the month? There are food programs like WIC and Food Stamps that will help you. And please don't worry, your eligibility for a green card or citizenship is not hurt by applying for or receiving food support.
For the residents
The Table below shows the comparative advantages the three approaches to folate supplementation.
Table 4.
Advantages of foods that are naturally high in folate:
- Infant birth weight and mortality as well as adult mortality and morbidity are greatly affected by the over-all quality of the diet.
- Folate sufficiency is only one element of the complex providing a sound nutritional foundation for a healthy life.
- Foods containing folic acid, especially dark green vegetables, whole-wheat products and beans, promote good health because
- High potassium and low sodium content maintain low blood pressure
- Caloric density is low promoting weight control and
- These foods have substantial fiber, which is filling, absorbs cholesterol, and maintains normal bowel function
- There are phytochemicals in foods that provide a large variety of health benefits
Advantages of foods that are fortified with folate:
- Bread products are fortified. They are commonly used, and they are the least expensive source of folate. Spinach -- the best source of folate, nuts and even beans are far more expensive.
- They also increase fiber content of the diet, especially whole-wheat products.
Advantages of micronutrient supplements:
- Immediate effects are more likely when providing micronutrient supplements containing folate, B12, and B6
- Studies in urban poor Camden NJ and Minneapolis, MN showed effectiveness of promoting supplement use, Diet change promotion was not.
Thus, with respect to the long-range health of the mother, a diet rich in folate and other micronutrients has distinct advantages over specific micronutrient supplementation. With respect to providing folate and other micronutrients to the fetus, however, specific micronutrient supplementation is effective. Promoting dietary change is not.
Q8. What kinds of programs could be effective?
A8. Model programs provide both a process for reaching women to delive a message with material to support that message. The model must, however, have as its foundation an appreciation for how women in each particular culture address their own nutrition needs. We need to meet nutrient needs on a food-based, rather than drug-based, solutions. Food resources available within the country should be put to maximal use instead of resorting to commercial pharmaceutical shortcuts." (Gopalan, 2002)
Successful programs address cost, culture and behavior by:
- creating consortiums of community based organizations,
- forming focus groups,
- developing programs unique to targeted communities,
- preparing material that promotes use of new foods (flyers, cook books, and videos),
- holding cooking classes, and
- evaluating the effectiveness of their intervention.
- Finally, supplemental programs (WIC and Food Stamps) are particularly effective in maintaining a high quality diets. Nutritious food is provided, and money saved is used to purchase the remainder of daily nutrition needs with higher quality foods.
The need, therefore, is to develop model programs capable of increasing awareness and knowledge of the need to increase periconceptual B vitamin intake unique for non-English speaking immigrant women. They are at highest risk. That risk is complicated by lack of access to both health care and resources that enable increased B vitamin nutrition with food or nutrient supplements.
Post-test
Q1. T or F. The daily requirement of folate sufficient to prevent Neural Tube
Defects (NTDs) is not uniform across racial and ethic groups.
Answer = True
Q2. Best answer. A woman asks which micronutrient supplement would be best to meet periconceptual nutrient needs?
A. One providing 400 micrograms of folate.
B. One providing 400 micrograms of folate and 6 micrograms of B12.
C. One providing 400 micrograms of folate and 6 micrograms of B12 and 2 mg of Pyridoxine (B6).
D. One providing 400 micrograms of folate and 6 micrograms of B12 and2mg of Pyridoxine (B6) and 10mg of iron.
Answer = D.
Q3. Best answer Which of the following food provides the most folate in a serving?
A Spinach
B Almonds
C Brown rice
D Whole wheat Bread
Answer = A
Q4. Which of the following provides folate at the lowest cost per 100 calories?
A Spinach
B Almonds
C Brown rice
D Whole wheat Bread
Answer = D
Q5. Best answer
A Pyridoxine and folate affect infant birth weight by facilitating degradation of homocysteine.
B Promoting single carbon transport for production of DNA.
C Preventing seizure activities in adults taking isoniazid
D Preventing megaloblastic anemia.
Answer = A
Q6. True or False. Neural tube defects are found commonly among spontaneously aborted fetuses.
Answer = True
Q7. True or False. Folate enrichment is effective in preventing NTDs regardless of the nutritional status of the mother.
Answer = False
Q8. Best answer
A Food cultures of immigrants are often deficient in folate.
B Children=s preferences can be easily over-ridden by parent insistence of food choices
C Acculturation of immigrants often leads to replacement of folate rich foods with foods of lower nutrient density
D Food cost issues can be easily overcome with information about the importance of periconceptual folate.
Answer = C
Q9. True or False
With respect to the long-range health of the mother, a diet rich in folate and other micronutrients has distinct advantages over specific micronutrient supplementation.
Answer = True
References:
Barnhart JM, Mossavar-Rahmani Y, Nelson M, Raiford Y, Wylie-Rosett J. An innovative, culturally sensitive dietary intervention to increase fruit and vegetable intake among African-American women: A pilot study. Topics in Clinical Nutrition 1998;13:63-71.
Botto LD, Mulinare J, Erickson JD. Occurrence of omphalocele in relation to maternal multivitamin use: A population based study. Pediatrics 2002;109:904-08.
Brent RL, Okay GP, Mattison DR. The unnecessary epidemic of folic acid-preventable spina bifida and anancephaly. Pediatrics 2000;106:677-83.
Motulsky AG. Nutrition ecogenetics: homocysteine related arteriosclerotic vascular disease, neural tube defect, and folic acid. Am J Human Genetics. 1996;58:17-20.
Scholl TO, Johnson WG. Folic acid: Influence on the outcome of pregnancy. Am J Clin Nutrition. 2000;71(suppl):1295S-1303S.
Gopalan C. Multiple micronutrient supplementation in pregnancy. Nutrition Reviews. 2002;60,#5,p2:S2-S6.
Graham IM, Daly Le, Refsum H, et al. Plasma homocysteine as a risk factor for vascular disease. The European Concerted Action project. JAMA 1997;277:1775-81.
Herbert V. Folic Acid.(in) Shils,ME, JA Olson, M Shike, and AC Ross. (eds) Modern nutrition in Health and Disease, 9th edition. Williams and Wilkins, Baltimore, MD. 1999. 443-46.
Karp RJ. (1993) Problem of changing food habits - 1: How habits are formed (in) Karp RJ (ed).
Malnourished Children in the United States: Caught in the Cycle of Poverty Springer Publishing Company of New York. 177-193.
Karp, RJ Malnutrition among children in the United States. The impact of poverty. (in) Shils ME, JA Olson, Shike, and AC Ross. (eds) Modern nutrition in Health and Disease, 9th edition. Williams and Wilkins, Baltimore, MD. 1999. Pp 989-1002.
Kumanyika SK, Morssink C, Agurs T. Models for dietary and weight change in African-American women: identifying cultural components. Ethnicity and Disease. 1992;2:166-175.
Mahan LK, Escott Stump S (1996) . Krause=s Food Nutrition and Diet Therapy, 9th edition. WB Saunders=s Company, Philadelphia.
Motulsky AG. Nutrition ecogenetics: homocysteine related arteriosclerotic vascular disease, neural tube defect, and folic acid. Am J Human Genetics. 1996;58:17-20.
Scholl TO, Johnson WG. Folic acid: Influence on the outcome of pregnancy. Am J Clin Nutrition. 2000;71(suppl):1295S-1303S.
Nelson M, Bowser R, Jackson MY, et al. (1993) Problem of changing food habits -2 : Reaching families through their own cultures. (in) Karp RJ (ed) Malnourished Children in the United States: Caught in the Cycle of Poverty Springer Publishing Company of New York. 194-211.
Ritchie J.(1968) Learning Better Nutrition. Food and Agriculture Organization of the United Nations, Rome, Italy.
Scholl TO, Johnson WG. Folic acid: Influence on the outcome of pregnancy. Am J Clin Nutrition. 2000;71(suppl):1295S-1303S.
Shankar S, Klassen A. Influences on fruit and vegetable procurement and consumption among urban African-American public housing residents, and potential strategies for intervention. Family Economics and Nutrition Review. 2001;13:34-46.
Annotated Pre-test Answers
A1. Answer is False. The incidence in the populations of the British Isles far exceeds that of others even after migration to this country. The expression of NTDs, however, is a classic [hereditry X envoronment] phenomenon. For this reason, the requirement of folate for women from all ethnic backgrounds is increased.
A2. Answer is D. Maternal need for folate cannot be separated from that for B12. Pyridoxine (B6) has a beneficial affect on homocysteine metabolism, and one must always attend to the increased need for iron in pregnancy
A3. Answer is A. Spinach!!! Folate, not iron, is what Popeye was getting to give strength. A serving of spinach will provide almost half the daily requirement for folate. The problem, however, is that the cost for energy is very high for a serving of spinach, and as such, the mother most in need often can or will not purchase spinach.
A4. Answer is D. Recently, the flour used for commercial baking has had its folate content increased. Thus, bread may be the more effective vehicle for folate in the diet.
A5. The answer is A. Pyridoxine (B6) and folate affect infant birth weight by degrading homocysteine. Folate will enhance production of nucleic acid and prevent megalobastic anemia, but not B6. On the other hand, B6 is necessary to prevent seizure activity while on INH.
A6. This is True. The number of actual cases of neural tube defect is a relatively small percentage of potential cases given the number of spontaneous abortions and undiagnosed partial effects.
A7. This is True. Multivitamin provision is necessary for the periconceptual period, but over the long term, the multiple benefits of good food, including folate-fortified flour, are substantial.
