Health professionals need to spread the message about vitamin D, calcium and healthy eating during pregnancy and breast-feeding, says paediatric dietitian Jacqui Lowdon
Jacqui Lowdon MSc BSc PCGE(FE) Chief Paediatric Dietitian Manchester and The Royal Manchester Children's Hospital Manchester
Maximising bone health begins with maternal heath and nutrition, which influences skeletal mass and bone density in the fetus. Maternal health and nutrition, as well as the baby's intake of Vitamin D and calcium during breastfeeding and weaning, may have a long-lasting effect on the baby's future health.Vitamin D and calcium (alongside physical activity) play key roles in bone health for both mother and baby. However, for many people in the UK achieving optimum nutritional status is difficult. This may be through lack of education, lack of access to appropriate foods or being part of a high-risk sub-group. It is essential that pregnant and breast-feeding women are provided with information on the benefits of a healthy diet and advice on how to eat healthily. Simple, practical campaigns, such as the Dairy Council's 3 a day campaign and better publicity by the Government, as well as easy access to vitamin D supplements, will help to achieve this. Journal of Family Health Care 2008; 18(4): 137-141
_ The fetus depends on the mother's vitamin D and calcium to develop healthy bones
_ Pregnant and breast-feeding women should take a vitamin D supplement such as the Healthy Start supplement
_ Adequate calcium and vitamin D intake is particularly important for teenage mothers
_ Human breast milk contains little vitamin D and mothers are recommended to take a supplement while breast feeding to ensure the baby does not become vitamin D-deficient
_ The Department of Health recommends a vitamin supplement at the correct dose for babies and children from six months to five years - e.g. the Healthy Start children's vitamins
_ Mothers' and children's diets should include three portions a day of foods containing calcium
Our lifetime of bone health starts right at the beginning, with the fetus. To develop bones fit for the demands ahead, the fetus depends on the mother for essential vitamin D and calcium. After birth the baby's bone health will be affected by the amount of vitamin D and calcium in the mother's breast milk, the availability of a vitamin D supplement and the quality of the weaning diet. All these factors are important not only in infancy but because they influence future bone health in childhood and adulthood, including protection against osteoporosis. It is important for health professionals and public health specialists to be aware of these issues, and to ensure mothers receive the information they need to help them choose a healthy diet.
Pregnancy: meeting the vitamin D and calcium needs of mother and fetus
Bone health and development in the fetus and beyond is influenced by the mother. Maternal body stature, nutrition, smoking and physical activity during pregnancy have all been shown to predict the bone mass of infants at birth1. The risk of fractures from osteoporosis later in life increases with adverse environmental stimuli during intrauterine life2. According to epidemiological studies, birth weight predicts peak bone mass and bone mass in later life3.
There is also direct evidence that vitamin D deficiency in mothers during late pregnancy is associated with a deficit in the accrual of bone mineral in their children, as has been shown at nine years of age4. This is of particular concern as vitamin D deficiency is well known to occur in otherwise healthy, pregnant women5. During pregnancy, vitamin D is also essential to sustain increased calcium absorption and utilisation. Along with an adequate vitamin D status, adequate calcium intake influences peak bone mass. The fetus accumulates about 30 g of calcium in utero from its mother and 80% of this transfer occurs in the last trimester of pregnancy6. Supplying the fetus with sufficient calcium depends on many factors, including maternal calcium intake and vitamin D status7. Until recently, the consensus has been that the concentration of maternal free 1,25 dihydroxyvitamin D3 is raised during pregnancy, which increases the net absorption of calcium and adequately meets the mother's increased requirement for calcium in pregnancy. To date, no increment has therefore been made to the current RNIs for calcium for adult women (Table 1). The average UK calcium intake of 800-1,000 mg/day will meet these recommendations8. However, new evidence is questioning the adequacy of increased calcium absorption during pregnancy, and the current recommendation is that pregnant women should take a vitamin D supplement (Table 2). It is important to recognise that there are some sub-groups who are at risk of calcium inadequacy. More details are given in Table 3 but in summary, health professionals should keep a particular
watch for calcium deficiency in:
_ Women who consume little or no milk or dairy products
_ Teenage mothers
_ Asian women who, in addition to having a low vitamin D status, may consume a high fibre diet, which additionally compromises calcium absorption.
Several studies have examined the effect of pregnancy during adolescence on bone turnover, the risk of osteoporosis and fetal bone development, suggesting that adequate calcium intake is important for pregnant teenagers9. This issue is particularly worrying since it is reported that adolescent girls are not meeting the current recommended dietary intakes for calcium10. Also, the decline in calcium intake begins around the time of puberty, which is the time when calcium absorption and bone deposition rates peak in girls11.
During lactation it is recommended that the mother's calcium intakes are increased to accommodate the needs of the infant as well as those of the mother, and the UK Government recommends 1,250 mg per day. At birth, infants will have a store of vitamin D and some exposure to sunlight will act as a further source. Human milk contains little vitamin D12-14 (approximately 20 IU/litre) and so lactating mothers with low vitamin D levels will provide their babies with even less than mothers who are sufficient in vitamin D. This will have an impact on the baby's vitamin D status, as well as on bone health in childhood4,15.
The poor vitamin D content of human milk increases the infant's risk of vitamin D deficiency when breast milk is the sole source of nutrition without vitamin D supplementation13,14,16,17. A recent study from the USA investigating the vitamin D status of breast- and bottle-fed infants and toddlers (8-24 months) found low vitamin D status in 12% of infants (25-hydroxyvitamin D <50nmol/l) and 40% with vitamin D status below optimal levels (25-hydroxyvitamin D <75nmol/l). Breast-fed infants without vitamin D supplementation were 10 times more likely to be vitamin Ddeficient compared to fully bottle-fed infants18.
The early years
According to epidemiological studies, weight in infancy2,19 has been shown to predict peak bone mass and bone mass in later life. As well as poor intrauterine growth, poor childhood growth has also been associated with approximately double the risk of hip fracture six decades later21. Vitamin D is necessary for skeletal growth during infancy and childhood. A retrospective cohort study demonstrated an association between premature infants supplemented with vitamin D during the first year of life and an increase in whole bone mass at 12 years of age22. This was not associated with overweight or obesity. There is growing evidence that even a mild vitamin D insufficiency can have a detrimental effect on bone mineral mass in children23,24 and adolescent girls25, and that poor vitamin D status has an impact on markers for bone turnover in children26.
Vitamin D and the mother's health
Vitamin D is critical for the formation and maturation of bone matrix. It promotes the uptake of calcium and phosphorous and regulates bone mineral losses. Deficiency of vitamin D in adults can result in osteomalacia and osteoporosis. Suboptimal vitamin D status (25-hydroxyvitamin D <70 nmol/l) has been shown to exacerbate bone mineral losses and has been associated with lower bone density - both these factors increase the risk of osteoporosis and fractures. Deficiency of vitamin D during pregnancy could therefore also cause injury to the skeleton of the mother. Since teeth are also composed mainly of calcium and phosphorus, deficiency of the vitamin will also affect the quality of the enamel.
There is also increasing evidence that a poor vitamin D status may add to the risk of developing chronic diseases, such as hypertension, diabetes mellitus, cardiovascular disease, some forms of cancer, and some inflammatory and autoimmune diseases27.
Vitamin D supplements for children and mothers
The Department of Health has highlighted the need for vitamin D supplementation for pregnant and breast-feeding mothers28 as well as infants and children up to the age of five years, in order to stop the escalating prevalence of rickets in the UK29. Children's vitamin drops are recommended:
_ From six months (or earlier if maternal status is poor) for breast-fed infants
_ Once the intake of formula milk intake is below 500 ml/day for formula-fed infants.
The Healthy Start vitamins recently launched in the UK are available free of charge to those qualifying for the Healthy Start scheme. They are as follows:
_ Vitamin drops for infants and children - vitamins A (232 μg), C (20 mg), D3 (7.5 μg)
_ Supplements for women who are pregnant or breast-feeding - vitamins C (70 mg), D3 (10 μg) and folic acid (400 μg).
In 2001 the World Health Organization issued guidelines that babies should be exclusively breast-fed for the first six months of life. In 2003, the Department of Health issued similar guidelines, echoed by the British Dietetic Association, the Royal College of Midwives and the Community Practitioners' and Health Visitors' Association. Earlier this year, the European Society of Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) published a position statement on this30. The main points are highlighted in Table 4. With the current emphasis on exclusive breastfeeding for the first six months of life, it is even more imperative that pregnant and breast-feeding women are recommended to take vitamin D supplements and are made aware of the few dietary options available, to them as well as being provided with advice on achieving an adequate calcium intake.
Dietary sources of Vitamin D
Vitamin supplements are essential in pregnancy and children aged six months to five years as dietary sources are few. However, it is important to try to include such foods within the diet and to introduce them as soon as possible during weaning.
_ Oily fish is a rich source
_ Meat, eggs and offal contain very small quantities
_ In the UK, dairy foods are a poor source of vitamin D as they are not fortified.
Some foods are fortified with vitamin D:
_ All infant formula and follow-on formulae
_ Some fortified breakfasts cereals (e.g. All Bran, All Bran Crunch, Bran Flakes, Ricicles, Special K, Shreddies)
_ Two different brands of children's fromage frais.
More information on dietary sources of vitamin D appears in an earlier article in the "Young Bones" series (Lowdon J. Low vitamin D status: on the increase? Journal of Family Health Care 2008; 18: 55-57)
3-a-day campaign - a practical approach
In the UK, the majority of our calcium intake comes from milk and dairy products (45%). A significant contribution is derived from cerealbased products (27%). This is because white and brown flours and breakfast cereals are fortified with calcium. Table 5 provides good examples of foods containing calcium. The Dairy Council, along with the US and Irish Dairy Councils, has launched the 3-a-day campaign. This provides health professionals with a simple, practical public health message on obtaining sufficient calcium. The message is simple - have three daily servings of milk, cheese or yoghurt. Each serving will meet one-third of the UK recommended calcium intake (RNI). As different ages will have different calcium requirements, serving sizes will increase with age (Table 6). Pregnant and breastfeeding mothers, and parents and carers, will be able to simply count up the number of portions eaten per day to know if they have achieved the required amount.
More information on 3-a-day can be found in the first article in this series (More J. Children's bone health and meeting calcium needs. Journal of Family Health Care 2008; 18: 22-24).
* It is worth noting that many different spreads are available in addition to margarine. Whereas food regulations stipulate that products labelled "margarine" must be fortified with vitamin D, fortification of spreads is optional so it would be necessary to read the labels to check whether they contain vitamin D. Butter contains almost no vitamin D.
Maximising bone health starts right at the beginning, with maternal health and nutrition. This is crucial for the future bone health of childhood and adolescence. It is also crucial for the longterm bone health of the mother and child and for the possibility of reducing the risk of long-term chronic diseases.
Vitamin D and calcium both play key dietary roles in bone health. It was previously thought that we obtained sufficient vitamin D from the sun. We now know that for many people this is insufficient and there are few dietary sources of vitamin D. Calcium is much more easily obtained from the diet, and so deficiency should be less of a problem. However, not all of the population consumes adequate amounts of calcium. With the emphasis on exclusive breast-feeding for the first six months of life and because of the low levels of vitamin D in breast milk, it is imperative that pregnant and breast-feeding women are made aware of these possible deficiencies, their impact and what actions they can take. In March 2008 NICE published antenatal guidelines31 highlighting diet in pregnancy, vitamin D and the Healthy Start vitamins. Early in pregnancy, women should be provided with information on the benefits of a healthy diet and practical advice on how to eat healthily throughout pregnancy. Simple, practical campaigns, such as the Dairy Council's 3-a-day message will help in achieving this.
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8. Department of Health (DH). Dietary Reference Values for Food, Energy and Nutrients in the UK. Committee on Medical Aspects of Food Policy (COMA). Report on Health and Social Subjects No. 41. London: HMSO, 1991
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30. Agostini C, Decsi T, Fewtrell M et al; ESPGHAN Committee on Nutrition. Complementary feeding: A commentary by the ESPGHAN Committee on Nutrition. Journal of Pediatric Gastroenterology and Nutrition 2008; 46(1): 99-110
31. National Institute for Clinical Excellence (NICE). Antenatal Care: Routine Care for the Healthy Pregnant Woman. CG 62. London: NICE, 2008. www.nice.org.uk (accessed 30 June 2008)
British Dietetic Association (BDA) www.bda.uk.comProfessional association which has "Food Fact" information sheets, written by registered dietitians, available to download for use by professionals. Topics include Vitamin D, Healthy Eating in Pregnancy, Weaning Your Child. Resources produced by the Paediatric Group of the BDA also available.
The Dairy Council www.nationaldairycouncil.org Non profit-making organisation providing information, recipes and educational materials and campaigns on milk, cheese and other dairy foods. Co-ordinates the 3-a-day compaign. Has information for the general public, schools and professionals.
Produces free publications for health professionals to order and fact sheets to download. Professionals can also subscribe to a newsletter to be kept abreast of latest research and publications.
Food Standards Agencywww.food.gov.ukIndependent Government body protecting the public's health and consumer interests. The Food Standards Agency (FSA) website has information on milk and dairy products, vitamins and minerals, in the nutrition section. www.eatwell.go.uk/agesandstages/childrenAlso from the FSA, this website includes practical advice for the general public on food and nutrition for toddlers and children.
Infant and Toddler Forum www.infanttoddlerforum.com Expert group producing nutritional information for health professionals. Supported by an educational grant from Nutricia Ltd but content independent. Fact sheets on infant and toddler nutrition.
Healthy Start schemewww.healthystart.nhs.ukLive Well websitewww.nhs.uk/livewellNHS website, containing information and tips for healthy living for all ages.
The Vegetarian Societywww.vegsoc.org Charity promoting vegetarian diet. Website contains recipes and menus (with nutritional analysis) for vegetarians to help increase calcium content in the diet.
Caroline Walker Trustwww.cwt.org.uk Charity promoting public health nutrition and working to improve nutrition for vulnerable groups.
Agostini C, Decsi T, Fewtrell M et al; ESPGHAN Committee on Nutrition. Complementary feeding: A commentary by the ESPGHAN Committee on Nutrition. Journal of Pediatric Gastroenterology and Nutrition 2008; 46(1): 99-110 Scientific Advisory Committee on Nutrition (SACN). Update on Vitamin D. Position Statement by the Scientific Advisory Committee on Nutrition. London: The Stationery Office, 2007 National Institute of Clinical Excellence (NICE). Public Health Guidance 11. Maternal and Child Nutrition. London: NICE, March 2008. www.nice.org.uk/PHO11
National Institute for Clinical Excellence (NICE). Antenatal Care: Routine Care for the Healthy Pregnant Woman. CG 62. London: NICE, 2008. www.nice.org.uk (accessed 30 June 2008)