Nutrition and Health, 2000, Vol. 13, pp. 199-211

0260-1060/00 $10

c 2000 A B Academic Publishers. Printed in Great Britain

NEW NUTRIENT INTAKE RECOMMENDATIONS A" NEEDED FOR CHILDBEARING

MARGARET WYNN AND ARTHUR WYNN

9 View Road, Highgate, London N6 4DJ, UK

ABSTRACT

British recommendations (DRVs and RNIS) include hardly any increments for pregnancy. British recommendations for protein are likely to cause unsatisfactory birth weight, What is the normal nutrient intake in pregnancy of healthy women? What evidence is there of special requirements for folate, iron, magnesium or iodine? New recommendations for nutrient intakes in pregnancy should be the responsibility of the Food Standards Agency and a survey of the diets of pregnant women is needed.

NO NATION CAN BE HEALTHIER THAN THE WOMEN WHO BEAR ITS CHILDREN.

The Acheson report refers to the effects a mother's nutrition has on her child's health for a lifetime and concludes that "the need for policies to improve the health of future mothers and their children is obvious".' The nutrition of women of childbearing age before and during pregnancy is an essential part of the start in life of the next generation .2 The cost of babies being born too small are difficult to exaggerate, particularly the cost of disabilities of the brain and central nervous system.' The absence of acceptable British nutritional recommendations for childbearing is a gap in public health policies.

THE INCOMPATIBILITY OF NATIONAL RECOMMENDATIONS FOR WOMEN'S DIET DURING PREGNANCY

The daily nutrient requirements of pregnant women recommended in three countries is shown in Table 1 4,5,6. The difference is seen to be substantial. One important result of these differences is that they undermine confidence in the validity of all three sets of recommendations and in the methods used in their conception. UTK recommendations are seen to be substantially lower than those for France or the USA for every one of the 16 nutrients listed. There are, indeed, no governmental recommendations for pregnant women in the UK which can be used with confidence.

The Reference Nutrient Intakes (RNIS) used in Table I for the UK were defined and quantified in 1991 by the Committee on Medical Aspects of Food Policy (COMA) of the Department of Health. The report says that the amount specified by the RNI of each nutrient is sufficient to meet the needs of practically all healthy persons. It is "just possible, but very improbable" that an individual consuming the RNIs will be consuming an insufficient amount of that nutrient. The French Apports Nutritionels Conseiles (ANCS) and the

American Recommended Dietary Allowances (RDAS) are similarly defined, with reservations in both cases that they exclude any requirements caused by illness, special working conditions, athleticism and other exceptional ways of life. There is nothing in the definition of the three lists which might explain the differences seen in Table 1. All three are said to be nutritional requirements for health and, whatever they are called, are recommendations from their definition.

TABLE I

Daily nutrient requirements of pregnant women as recommended in UK, France and USA

Source: see references 4, 5,6.

TABLE 2

Increase in daily intake of essential nutrients for pregnancy as recommended in UK, France, USA, and recorded for US women

Source: see references 4,5.6,16.

NUTRITIONAL INCREMENTS FOR PREGNANCY

The Introduction to the COMA report has a paragraph entitled "Pregnancy" which explains that no increments for pregnancy are given, as shown in Table 2, because in practice there is no increase in food eaten in pregnancy. No survey data or references are given showing that this is so. There have, in fact, been many studies over many years showing an increase in appetite and food consumption in pregnancy, for example in Chapter 5 of The Physiology of Human Pregnancy by Hytten and Leitch .7 The actual increased nutrient intake recorded for a representative sample of American women is discussed below and shown in Table 5.

The COMA report says that the increased demands of pregnancy should be met from maternal stores of the nutrient or from "increased efficiency of utilisation" and concludes that a woman's stores should be adequate for pregnancy. There are not, of course, different recommendations for women who intend and women who do not intend to become pregnant. The recommended nutrient intakes for women in the reproductive years who are not yet pregnant are, in effect, recommendations for a prepregnancy diet. How then do our three countries compare in what they recommend to women of childbearing age?

TABLE 3

Daily nutrient requirements of women of reproductive age as recommended in UK, France and USA

Source: see references 4, 5, 6.

NATIONAL RECOMMENDATIONS TO WOMEN OF REPRODUCTIVE YEARS

The three countries may be Compared in Table 3, Again the most substantial difference is between the RNIs and the recommendations for French and American women. A desirable prepregnancy diet was the subject of an I international conference convened by the New York Academy of Sciences ' in 1992 entitled Maternal Nutrition and Pregnancy Outcome.8 The proceedings include forty-seven papers from several countries and more than one thousand references. Two of the editors, who were also organisers of the conference, summarised:

"A major area of consensus of this conference was that prepregnancy nutritional status significantly affects pregnancy outcome. In conclusion, prevention of a significant proportion of birth defects, low birth weight infants, and sudden infant death syndrome has been shown to be possible by enhancement of the micronutrient status of women of childbearing potential and those already pregnant. Improved pre-pregnancy medical care, with strong emphasis on the nutritional needs of the embryo, fetus, neonate and mother is clearly warranted. Such a public health policy would prevent a significant proportion of adverse pregnancy outcomes."

The emphasis in this conference was not only on adequate energy and protein consumption but on food nutrient density which meant encouraging the eating of more fruit and vegetables.

THE FIVE A DAY MESSAGE

At this conference a recommendation in Diet and Health, a report of the US National Research Council, was quoted with much approval9:

"Every day eat five or more servings of a combination of vegetables and fruits, especially green and yellow vegetables and citrus fruits."

The conference also stressed the value of whole grain cereals as a source of important vitamins and minerals.

In January 1999 Tessa Jowell MP, Minister for Public Health, opened a conference of the National Food Alliance entitled Tackling Inequalities in Health and Diet-related Disease and explained that the Department of Health had funded a project to study "attitudes towards fruit and vegetables" and found that the five a day message is fairly well understood. Sustain; the alliance for better food and farming, to which the National Food Alliance now belongs, is promoting five a day.

The consumption of more fruit and vegetables by women is a big change which will increase the range of micronutrients which are vital in childbearing, especially in the early stages before and after conception when cell replication makes special demands. Looking ahead an increase in the same micronutrients will reduce the prevalence of cardiovascular disease and several types of cancer.9,10

However, the five a day message and the RNIs are incompatible and, indeed, opposed. The RNIs are a much lower level of micronutrients than would be consumed on a five a day diet. The nutrient density of food conforming to the RNIs for women with average energy intake is shown in Table 4 and is compared to the intake of women receiving benefits and also with the median intake of all women from the Dietary and Nutritional Survey of British Adults." The food nutrient density of the RNIS, defined as

1. extremely unlikely" to be insufficient, is seen to be much below that in fact achieved by poor women living on benefits, with the exception of their intakes of magnesium and iron. The Minister for Public Health is advocating five a day fruit and vegetables to increase the micronutrients in the nation's diet while the advisers to the Department are at the same time advocating nutrient intakes as sufficient which are much below what a five a day diet would provide.

TABLE 4

Food Nutrient Density: British Reference Nutrient Intakes (RNIs) for protein and micronutrients per 1,000 kcal for women compared to actual mean intakes and intakes of women in receipt of benefits

Source: see references 4,11.

PROTEIN REQUIREMENTS FOR PREGNANCY

It is seen in Tables 1, 2 and 3 that the RNI for protein in pregnancy is much below the recommendations in France or the USA. The COMA report assumes that protein is used with an efficiency of 55 per cent but gives no evidence. Very thorough classical nitrogen balance studies in pregnancy were undertaken at the Department of Nutritional Sciences of the University of California in the 1970s. One paper concluded l2:

"Protein during pregnancy should be based on NNU (net nitrogen

utilisation) of 30 per cent bringing the total protein recommendation to 85g /day."

In 1990 the US Institute of Medicine published a 468 page textbook entitled Nutrition during Pregnancy 13 which lists 17 studies of nutrient intake by pregnant women and compares their protein intake with the RDA of 60 g/day shown in Table 1. None of the 17 studies showed protein intakes as low as 60 g/day and the average was 78 g/day. This is 27 g/day higher than the RNI in the UK of only 51 g/day. Can it be shown that babies of mothers who eat a diet with 51 g/day of protein have babies as big or as healthy as the mothers who have an intake of 78 g/day? Evidence based medicine requires that recommendations which do not correspond to normal human behaviour should be based on adequate evidence and should be validated." The study of protein intake in pregnancy has a long history and protein intakes as low as 50 g/day have been shown to be associated with birthweights below the optimum and with increased maternal morbidity. 15 The COMA report has no discussion of the needs of pregnancy and makes no use of birthweight as an indicator. In the report the protein requirements of pregnancy have five and a half lines in 210 pages and the bibliography of 27 references has no reference to protein requirements in pregnancy.

THE LOGICAL BASIS OF SOUND NUTRITIONAL RECOMMENDATIONS

The diet of healthy people is the logical basis for nutritional recommendations intended to promote health. There is, however, an extensive literature which says that the diet of the median person could be improved. The five a day fruit and vegetables aim is such an attempt to improve the diet of most people. The population of other countries may have a better health record and it may be suggested that this indicates a better diet. It is at this point, however, that adequate evidence or validation are essential to show that an increase or a decrease n the intake of a particular nutrient, or nutrients, would improve the health of apparently healthy people who are not unwell and do not have a way of life at work or at leisure that affects their nutritional requirements. In the absence of adequate evidence there are no grounds for recommending any departure from the normal diet of people who are apparently healthy and do not have an unusual way of life.

THE DAILY INTAKE OF ESSENTIAL NUTRIENTS OF WOMEN PREGNANT AND NOT PREGNANT

No representative sample of the diet of British pregnant women has been found. The daily intake of nutrients by American women when pregnant and not pregnant from surveys of the US Department of Agriculture is shown in Table 5, and appeared to be the best of the 20 studies that have been found mostly describing less representative rather special populations. 16 It is also seen in Table 5 that the diet of a sample of London women who had babies in the optimum birthweight bracket did not differ much from the diet of American women who were pregnant and was about 20 per cent higher than the diet of women not pregnant." It is also seen in the table that when not pregnant the normal diet of American and British women Is very much the same.

However, for three nutrients in pregnancy, folate, iron and magnesium, the American RDA shown in Table I is higher than the actual intake by American pregnant women shown in Table 5. The French ANC shown in Table I for the three nutrients are higher still. Is there adequate evidence that these proposed departures from a "normal" diet are merited?

TABLE 5

Mean daily intake of essential nutrients by American women 1 9 to 39 not pregnant and pregnant compared to population of London women whose babies weighed 3,500g to 4,500g

Source: see references 16, 17.

SPECIAL REQUIREMENTS FOR PARTICULAR NUTRIENTS DURING CHILDBEARING

Folate requirements

Trials during the 1980s suggested that increased folate intake would prevent about 70 per cent of cases of neural tube defects. However, as reported in this journal in 1998, studies for ten years showed that such an increase in folate intake would also be likely to reduce the risk in later life of heart disease, stroke, cancer and nervous system disorders including Alzheimer's disease." The fortification of all grain products with folate was made mandatory in the USA in 1998 on the recommendation of the Food and Drug Administration.

Iron requirements

A maternal deficiency of iron during pregnancy can be very damaging to the unborn child increasing the risk of perinatal mortality, preterm birth and low birthweight. There are many risk factors for iron deficiency including vegetarianism, chronic use of aspirin, low intake of some nutrients that promote absorption of iron notably vitamin C or high consumption of tea and coffee.13 A commentary on the American RDAs suggests that an increment of 15 mg/day of iron in a normal pregnancy is needed throughout the pregnancy but that this increment cannot be met by the iron content of habitual US diets or from iron stores of some women.' The US Institute of Medicine recommends iron supplementation of 30 mg/ day for all women beginning about week 12 of gestational The French ANCs also include an increment of iron for pregnant women and the report suggest that this may involve supplementation.

The British Adult Survey showed a median intake by women aged 25 to 34 of only 9.6 mg/day of iron which is very much below the recommendations of all three countries in Tables I and 3.11 Indeed, 89 per cent of women aged 19 to 50 had an iron intake below the British RNI of 14.8 mg/day. The 1999 report of the British Medical Association entitled Growing up in Britain: Ensuring a healthy future for our children describes iron deficiency as "The most common nutritional disorder in childhood in the UK" (19 p 52) and describes its consequences:

"Iron deficiency is associated with many biochemical changes and clinical symptoms, with decreased performance, increased susceptibility to infections, and impaired neurological function." (p 51).

It is important that the child at birth and the mother for breast feeding have adequate iron stores.

However, iron supplements have acquired a bad reputation by being excessive in amount. Iron, like zinc, iodine, selenium and some other micronutrients are essential to life but harmful and toxic in excess. A supplement of iron of 20 mg/day is regarded as safe and adequate for all women before and during pregnancy and is the iron content of the tablets recommended in Britain by the Royal College of Obstetricians and Gynaecologists.20

Magnesium requirements

Low magnesium intake during pregnancy has been reported from a number of countries to be associated with low birthweight and maternal morbidity including preeclampsia since 1966 21,22. The apparent success of magnesium supplementation in France, Hungary, Germany and elsewhere prompted a double-blind controlled trial in Switzerland .23 This trial showed that the

supplemented mothers had 2.8 per cent of low birthweight or preterm babies which was significantly lower than the 8.2 per cent recorded for mothers who had not been supplemented. Moreover, the supplemented women had fewer admissions to hospital and significantly fewer days in hospital than the unsupplemented women. This Swiss trial was conducted in a generally healthy population.

Magnesium is the most abundant intracellular mineral except for potassium, and is essential for all cellular replication and biosynthetic reactions requiring energy and adequate magnesium concentrations are therefore important throughout pregnancy. There are two international journals on magnesium.21,24 The evidence of the importance of magnesium during pregnancy led the USA and France to recommend magnesium supplements for pregnancy. The French ANC report suggests that the increment has to be substantially larger than recommended by the American RDAs to achieve a desirable magnesium balance throughout pregnancy.' However, the British report on dietary reference values says 4:

"Physiological adaptation in pregnancy and release from maternal stores ensure an adequate supply" (p 147).

No supporting evidence is given.

Iodine requirements

The World Health Organisation has thrown doubt on the adequacy of iodine intake in all countries. A conference entitled Iodine Deficiency in Europe; a Continuing Concern was held in 1992.11 Following world wide deliberations the WHO recommended an intake of 150 mcg/day of iodine for women and an increment of 50 mcg/day for pregnancy.21 The British RNI for iodine is 140 mcg/day with no increment for pregnancy.

The WHO places emphasis on the importance of iodine for childbearing.27 Iodine deficiency can cause stillbirths, miscarriage, congenital anomalies, low birthweight, mental retardation and learning disability, deafness, spastic diplegia and motor skill impairment (25 p26). It is difficult to relate these impairments to ]Iodine deficiency in a particular child. Effects on the health of mothers has, therefore, been used to indicate iodine deficiency which causes damage to the maternal thyroid gland.28 Thyroid hormones are needed for all cell replication and an increased supply is essential in pregnancy. A deficiency of iodine, a constituent of thyroid hormones, results in damaging stress to the mother's thyroid gland during pregnancy which can result in chronic hypothyroidism.2' The American Health Interview surveys show that about 6 per cent of women aged 45 to 64 have such thyroid disorders compared with only I per cent of men. It has been shown that this much higher prevalence among women is attributable to iodine deficiency during pregnancy.

Comparable British data have not been found but interested general practitioners have reported a similar 4 to 10 times higher prevalence of thyroid disorders among women than among men.30

The WHO recommendations follow the principle that a supplement is desirable for everyone as iodine deficiency is difficult to diagnose and remedy. The WHO, therefore, recommends universal fortification of common salt or other foodstuff with iodine. 31 The UK return to the WHO enquiry stated that there is no problem of iodine deficiency in the UK which has, therefore, not followed the WHO recommendations for the iodine increment in pregnancy or for the fortification of salt or food." The Adult Survey shows, however, that many British women have iodine intakes below WHO recommendations and below the RNI .32

Essential fatty acid requirements

There are no RNIS, ANCs or RDAs for the essential fatty acids, but the US National Research Council in 1989 referred to the rapid development of knowledge and said that "the possibility of establishing RDAs for the N-6 and N-3 fatty acids should be considered".' The French ANC report includes a whole chapter on essential fatty acids and recommends 11 g /day of N-6 and 3 g/day of N-3 for pregnancy.5 The emphasis is on the risk of a shortage of N-3 which is less often a constituent of commonly eaten foods but is important in the development of the embryonic and fetal brain and eyes. The study of the diet of 513 London women during the first trimester of pregnancy found that the 165 mothers who had babies in the optimum birthweight range of 3,500g to 4,500g had an average intake of 11.3 g/day of N-6 but only 1.3 g/day of N-3 fatty acids.33 These mothers were not a representative sample but their N-6 intake was similar to the French recommendation and the N-3 was lower. The importance of the fatty acids is now well established and surveys leading to satisfactory recommendations are needed .34

Conclusions

The Dietary Reference Values (DRVS) and the Reference Nutrient Intakes (RNIS) 1991 relating to pregnancy and the preconception period should be revised with the aim of recommending intakes which would maximise the chances of adequate weight and health of the baby.

The Food Standards Agency is to be established and the Government White paper says:35

"The Agency will provide independent and authoritative advice to the public on a balanced diet, and on the nutritional value of foods, to help people make informed decisions about what they eat." (p111)

It should be a responsibility of the new Agency to ensure that nutrient intake recommendations relating to childbearing are adequate.

A survey of the actual diets of pregnant women in the UK is needed. It cannot be considered satisfactory for the UK to rely on the results of foreign particularly American surveys. The World Health Organisation has published an anthropometric report based on data from 20 countries showing the importance of nutrition before and during pregnancy for the prevention of low birthweight caused by both intrauterine growth retardation and preterm birth with all the increased risks of disability and long term effects on health." The dietary and nutritional surveys now cover infants aged 6 to 12 months, children aged 18 months to four and a half years, British School children, British Adults and elderly people. There has, however, been no survey of the period before birth when nutrition of the mother has so great an importance for the health of the new individual. Such a survey would be of particular value if it also recorded both maternal height and weight and birth outcome.

REFERENCES

1. Acheson D. Independent inquiry into inequalities in health. London: Stationery Office 1998.

2. Wynn M., Wynn A. No nation can rise above the level of its women; new thoughts on maternal nutrition. Caroline Walker lecture 1993. J Nutr Environ Med 1995; 5: 163-185.

3. Wynn M., Wynn A. The problem of low birthweight, the cost and possibilities of prevention. Nutr Health 1997, 11:159-184.

4. Department of Health. Dietary reference values for food energy and nutrients for the United Kingdom. Report on health and social subjects no 41. London: HMSO 1991.

5. Dupin H., Abraham J., Giachetti 1. Apports nutritionels conseilles pour la population francaise. Tec & Doc Lavoisier 1992.

6. United States Research Council. Recommended dietary allowances 10th edition. Washington DC: National Academy Press, 1989.

7. Hytten F.E., Leitch 1. The physiology of human pregnancy. Oxford: Blackwell, 1971.

8. Keen C.L., Bendich A, Willhite C.C. Maternal nutrition and pregnancy outcome. Ann New York- Acad Sci 1993 vol 679.

9. US National Research Council. Diet and health: implications for reducing chronic disease risk. Washington DC: Nat Acad Press, 1998.

10. World Cancer Research Fund and American Institute for Cancer Research. Food, nutrition and the prevention of cancer: a global perspective. Washington DC: 1997, 669 pages.

11. Gregory J., Foster K., Tyler H., Wiseman M. The dietary and nutrition survey of British adults. OPCS Social Survey Division. London: HMSO 1990.

12. Calloway D.H. Nitrogen balance during pregnancy. In: Winick M, ed. Nutrition and fetal development. New York: John Wiley 1974.

13. Institute of Medicine. Nutrition during pregnancy. Part I Weight gain. Part 11 Nutrient supplements. Washington DC: National Academy Press.

14. Wynn A., Wynn., M. The logical basis of recommendations. J. Nutr Med 1992; 3: 325-9.

15. Wynn M., Wynn A. The case for preconception care of men and women. Bicester: A B Academic Publishers, 1991.

16. Welsh S., Guthrie J.F. Changing American diets. In: Bendich A, Butterworth C.E. Micronutrients in health and disease prevention. New York: Marcel Dekker, 1991, 381-408.

17. Doyle W., Crawford M.A., Wynn A.H.A., Wynn S.W. The association between maternal diet and birth dimensions. J. Nair Med 1990, 1: 9-17.

18. Wynn M, Wynn A. Fortification of grain products with folate, should Britain follow the American example? Nutr Health 1998, 12: 147-161.

19. British Medical Association. Growing up in Britain: ensuring a healthy future for our children. London: BMA, 1999.

20. WellBeing. Preparing for pregnancy, Pregnancy and birth. London: Royal College of Obstetricians and Gynaecologists, 1999.

21. Doyle W., Crawford M.A., Wynn A., Wynn S.W, Maternal magnesium intake and pregnancy outcome. Magnesium Research 1989; 2: 205-10.

22. Wynn A., Wynn M. Magnesium and other nutrient deficiencies as possible causes of hypertension and low birthweight. Nutr Health 1988, 6, 69-88.

23. Spatling L., Spatling G. Magnesium supplementation in pregnancy: a double blind study. Br J Obstet Gynaecol 1988; 95:120-5.

24. Spatling L., Spatling G. Magnesium supplementation in pregnancy. Magnesium Bulletin 1986; 8: 252.

25. Delange F., Dunn J.T., Glinoer D., eds. Iodine deficiency in Europe; a continuing concern. New York: Plenum Press, 1993.

26. World Health Organisation. Trace Elements in human nutrition Card health. Geneva. WHO, 1996.

27. World Health Organisation. Global prevalence of iodine deficiency. Geneva: WHO, 1993.

28. Wynn M., Wynn A. Human reproduction and iodine deficiency: is it a problem in the UK'? J.Nutr Environ Med 1998; 8: 53-64.

29. Struve C., Ohlen S. Einflussfruhere Schwangerschaften auf Strumen und Knothaufigkeit bei schildrusengesunden Frauen. Dtsch Med Wschr 1990; 115: 1050-3.

30. Durrant-Peatfield B.J. Aspects of common missed diagnosis: thyroid dysfunction and management. J Nutr Environ Med 1996; 6: 371-8.

31. World Health Organisation. Iodine and health. Geneva: WHO, 1994.

32. Ministry of Agriculture, Fisheries and Food. The dietary and nutritional survey of British Adults:Further analysis. London: HMSO, 1994.

33. Wynn A.H.A., Crawford M.A., Doyle W., Wynn S.W. Nutrition of women in anticipation of pregnancy. Nutr Health 1991; 7: 69-88.

34. Crawford M.A. The role of essential fatty acids in neural developments implications for perinatal nutrition. Ani J Clin Nutr, 1994; 57: 7035-105.

35. Department of Health. Saving lives; our healthier nation. Cm 4386. London: Stationery Office, 1999.

36. World Health Organisation. Maternal anthropometry and pregnancy outcome. WHO Bulletin, vol 73. Geneve: WHO, 1995.

(Received 30 July 1999)