In this excerpt from the January/February 2012 edition of Journal of Family Health Care, Dr Lisa Waddell looks at the importance of supplementation for those that don't get all the vitamins and minerals they need through their diet. To read the article in full,subscribe here.
Vitamins and minerals, collectively known as micronutrients, are essential nutrients the body needs in small amounts to function properly. Most people get all the micronutrients they need from consuming a varied diet, but there are certain stages in life when dietary intakes tend to be less than healthy and /or it may not be possible to get everything that is needed from food alone. This article highlights when micronutrient supplementation should be considered during the maternal and early years period, which nutrients should be targeted, and from the vast array of micronutrient supplements available, which products are suitable to meet these requirements.
Role of vitamins and minerals
Vitamins can be classified as to whether they are fat-soluble (vitamins A, D, E, K) or water-soluble (B complex vitamins - B1, B2, B3, B6, B12, pantothenic acid, biotin, folate), vitamin C]. Minerals include the essential elements calcium, magnesium, iron and zinc. Trace elements such as selenium, chromium and iodine are also essential for body function but, in the main, deficiencies are rare. Concerns have recently been raised over the risk of iodine deficiency in the UK1.
Sources of vitamins and minerals
For the first six months of life, in the majority of cases where attention has been paid to adequate vitamin D supplementation during pregnancy and breastfeeding, breast milk or infant formula provides the full complement of micronutrients to support an infant's growth and development. After this period, an infant can no longer obtain sufficient nutrition from milk alone and weaning should commence. Although most foods contain a variety of vitamins and minerals, no single food contains the whole spectrum and therefore a diet consisting of a wide range of foods from all four key food groups is recommended, as described by the updated Eatwell plate:
● bread, rice, potatoes, pasta and other starchy foods
● fruit and vegetables
● milk and dairy foods
● meat, fish, eggs, beans and other non-dairy sources of protein
Recommended intakes of vitamins and minerals
Dietary Reference Values (DRVs) were published in the UK3 to set standards for healthy people for the:
i) amount of a nutrient that would meet the needs of the majority of the population (97.5%, known as the Reference Nutrient Intake or RNI)
ii) amount below which would be insufficient for the majority (Lower Reference Nutrient Intake or LRNI)
iii) average requirement for a nutrient for the population, known as the estimated average requirement (EAR); predominantly used in relation to energy.
The RNIs tend to be used for recommending intakes of vitamins and minerals for population groups.
For an individual, using the RNI will ensure that their requirements are highly likely to be met, if not exceeded. Care must therefore be taken when recommending a vitamin and mineral supplement for an individual, to ensure that they do not consume significantly more than the RNIs. Clinical signs and symptoms, such as whether they have low iron stores, are anaemic or have rickets also needs consideration, as a short therapeutic course, as prescribed by a medic, may be necessary. Water-soluble vitamins cannot be stored, and can be destroyed through cooking or exposure to light, so should be consumed from raw/lightly-cooked foods on a daily basis. There is a greater risk of toxicity with fat soluble vitamins and minerals that are stored in tissues, and an Expert Group on Vitamins and Minerals has determined safe upper limits for the majority of micronutrients. There are no labelling reference values for children; hence the EU Recommended Daily Allowances (RDAs) for adults are used by companies for comparing the micronutrient composition of their products. The RDA for each nutrient represents the amount that is recommended to be consumed on a daily basis. As a result, care must be taken in using these adult labelling references, as these could far exceed young children's RNIs for micronutrients.
Current intakes of vitamins and minerals
A report by the Scientific Advisory Committee on Nutrition (SACN) details a summary of findings from four National Diet and Nutrition Surveys (NDNS) conducted between 1992 and 20016. Whilst an annual rolling programme of the National Diet and Nutrition Survey commenced in 2008/2009, the combined results of years one and two7 suggest similar findings to those previously reported, and comparisons with previous surveys for the one-and-a-half to three years age group have not yet been done (planned for year three). As a result, the more detailed findings in the SACN report6 are described. Fruits and vegetables are a good source of a number of vitamins and minerals (Table 2), yet children were found to consume an insufficient amount, with only 39 per cent of one-and-a-half to four-and-a-half year-olds eating leafy green vegetables, 50 per cent eating apples, pears and bananas and only 25 per cent eating citrus fruits. Compared with the recommended 400g of fruits and vegetables daily (five portions) for people over five years8, 86 per cent of adults (19-64 years) consumed less than recommended, with a mean of 2.8 portions daily.
Average vitamin intakes were above the RNIs in all age groups except for vitamin A and riboflavin (B2), with 10 per cent of one-and-a-half to four-and-a-half year-olds demonstrating low plasma retinol levels, and marginal riboflavin status was found in 80 per cent of 15 to 18-year-old girls. High consumers of breakfast cereals had better thiamine, riboflavin, pyridoxine, folate and vitamin B12 status. Evidence of low vitamin D status was found in most population age groups but could not be correlated to vitamin D intakes, as the majority of vitamin D is derived from the action of sunlight on the skin, and not from foods. Suboptimal vitamin D concentrations have been found in 20 to 34 per cent of two-year-old Asian children9, attributed to the inhibitory effects of dark pigmented skin. Twenty eight per cent of young women (19 to 24-year-olds) were found to have vitamin D concentrations below 25nmol/l, which is of particular concern, being of childbearing age6. Compared with vitamins, mineral intakes tended to be lower in relation to RNIs6. Iron intakes were generally suboptimal and low iron stores (low serum ferritin concentrations), were found in 20 per cent of children under five years and 27 per cent of girls aged 15 to 18 years, with eight per cent and nine per cent respectively being anaemic (low haemoglobin concentrations). In children with the lowest iron status, eating red meat, fruit, fruit juice and salads improved iron status, while drinking tea had the opposite effect.
Overdependence on milk, which displaces iron rich foods, has been identified as a risk factor for poor iron status in four to 18-year-olds, but not if meat and/or fruit is consumed10. In adults, cereal and cereal products were the main food source of iron, providing over 40 per cent of the average intake. Intakes of calcium, magnesium, zinc and iodine were also suboptimal in a substantial number of women of childbearing age, with large proportions of intakes falling below the LRNI in females aged 11 to 18. Cereals and cereal products were the main sources of magnesium and also contributed around 25 per cent to zinc and 30 per cent to calcium. The main contributor to zinc was meat (33 per cent total zinc consumed) and milk, and milk products unsurprisingly dominated for calcium, especially in the younger age groups (65 per cent in one-and-a-half to four-and-a-half year-olds, decreasing to around 40 per cent of total calcium intake in adults). Milk was also the major source of iodine, providing over 40 per cent of the total intake for women.
At risk groups
The Department of Health (DH) has identified certain groups that are at greater risk from micronutrient deficiencies or excesses, and as a result, makes specific recommendations for women of childbearing age, pregnant women, breastfeeding women, infants and young children.
Folic acid recommendations
The DH's expert advisory group on folic acid and neural tube defects (NTDs)11 recommended that:
1. To prevent first occurrence of NTDs such as spina bifida, all women who are planning a pregnancy should:
i) Supplement their diet with 400μg folic acid until the 12th week of pregnancy
ii) Choose foods fortified with folic acid, such as some breakfast cereals (check label)
iii) Consume more folate-rich foods, which should not be overcooked
2. To prevent recurrence of NTDs in the offspring of women or men with a history of a previous child with a NTD, women who wish to become pregnant, or who are at risk of becoming pregnant should take a daily supplement of 5mg (5000μg) folic acid and continue until the 12th week of pregnancy. A report by the DH Committee on Medical Aspects of Food and Nutrition Policy (COMA)12 highlighted that campaigns to encourage women who might become pregnant to take folic acid have raised awareness, but because many pregnancies are unplanned, many women continue to be at risk. They suggested that in addition to routine supplementation with folic acid, fortification of flour used in food production with folic acid (240μg/100g) would reduce the risk of NTD by 41 per cent, without resulting in unacceptably high intakes in any population group. This recommendation is supported by the SACN13, but despite white flour already being fortified with thiamine, niacin, calcium and iron, fortification with folic acid has not yet occurred, in part due to concerns over the masking of vitamin B12 deficiency. A joint guideline by the Centre for Maternal and Child Enquiries (CMACE) and the Royal College of Obstetricians and Gynaecologists (RCOG) on the management of women with obesity in pregnancy also recommends that all obese women (BMI>30) should take 5mg folic acid peri-conceptually (at least one month prior to conception and during the first trimester of pregnancy), due to the increased risk of NTD in obese women.
This dose is also recommended for those with diabetes (NICE). Vitamin A caution High intakes of retinol are known to be teratogenic in the periconceptual period. Isotretinoin, an analogue of retinol, used for the treatment of acne commonly in adolescents, has been associated with miscarriage and congenital malformations, which is more likely in this age group, given that many pregnancies will be unplanned. There has been concern over the dramatic increase in the vitamin A content of animal liver over the last few decades, thought to be as a result of retinol being added to animal foodstuffs as a growth promoter. The Department of Health17, reinforced by NICE18 has subsequently advised all women of childbearing age to avoid excessive intakes of retinol, by avoiding liver and liver products such as pâté, and supplements containing retinol or fish liver oils. Vitamin A in the form of beta-carotene from fruits and vegetables is not thought to carry the same risks. Having more than an average of 1.5mg vitamin A daily (2 x RNI) over many years is also believed to increase the risk of osteoporosis19. If liver or liver pâté is eaten once a week, there is a risk that this upper level could be exceeded, and therefore these products should be limited in the adult population and avoided during pregnancy18,20. If vitamin D intakes are also suboptimal, as the NDNS data6 would suggest, the risk of osteoporosis is even greater.
This is considered to be the most common cause of preventable mental impairment worldwide and a significant number of adolescents and young women of childbearing age were deemed to be iodine deficient, with iodine intakes below the LRNI1. This is of greatest concern during the pre-conception and pregnancy stages, as developing foetuses are the most susceptible to iodine deficiency, resulting in adverse effects on neurodevelopment. Iodine deficiency was combated in the UK in the 1930s, due to the addition of iodine to cattle feed to improve milk production, which resulted in an increase in the iodine content of cow's milk. Cancer Research UK (CRUK) states that regularly going outside for a matter of minutes around the middle of the day in the UK summer sun, without sunscreen several times a week should be sufficient, and short enough to avoid the skin reddening or burning, although this time period should be extended for people with dark pigmented skin. The more skin exposed, the greater the chance of producing sufficient vitamin D before burning. SACN reiterate DH recommendations that all pregnant women should consider taking a daily supplement of 10μg vitamin D to ensure their own requirement is met and to build adequate fetal stores for early infancy. SACN highlight the need for a clear public health strategy and guidance on vitamin D supplementation for health professionals and at risk groups of the population, which has been addressed by the NICE revised antenatal guidelines and public health guidance, by the DH Healthy Start campaign and more recently reinforced by UNICEF UK28 and the CMO. There is a risk of vitamin D toxicity however, with symptoms of hypercalcaemia, soft tissue calcification and demineralisation of bones, and the FSA recommend an upper limit for chronic supplementation of 25μg vitamin D per day for adults.
The increased demand for calcium, predominantly during the last trimester, is likely to be met through the actions of raised biologically active vitamin D levels during pregnancy, which increase net calcium absorption and therefore there is no additional increment for calcium3. Subgroups at risk however, include:
● Women who consume little milk and dairy products
● Teenage mothers whose own calcium requirements are high, whose intakes can be suboptimal6 and where peak bone mass has not yet been achieved
● Ethnic minority groups with dark pigmented skin whose vitamin D status is likely to be sub-optimal. It is important these groups are offered alternative ways of increasing calcium intakes from foods and/or taking supplements containing calcium and vitamin
A need for folate
To prevent megaloblastic anaemia, the RNI for folate is increased by 100μg, which can be achieved by consuming a varied diet rich in green, leafy vegetable and folic acid fortified foods such as breakfast cereals. Women who had not been supplementing their diet with folic acid pre-conceptually and become pregnant should immediately start supplementation with 400μg folic acid and continue until the 12th week of pregnancy to minimise the risk of NTDs11.
The recommended intake of vitamin C increases by 10mg in pregnancy and is important in increasing the absorption of non-haem sources of iron. Women should be encouraged to include a source of vitamin C at each meal, from fruit and vegetables in particular, although fruit juice can also be used to increase intake. Supplementation is not thought to be essential during pregnancy, but as a safeguard due to its important role, it forms part of the DH Healthy Start vitamins for pregnant and breastfeeding women.
Iron and anaemia
The increased demand for iron in pregnancy to support fetal growth and development, the placenta, and expansion of maternal red cell mass to cover iron lost in blood during delivery is met through mobilisation of maternal iron stores, increased dietary absorption (from 10-20% up to 50% during pregnancy) and cessation of menstrual losses. Despite routine iron supplementation in pregnancy being common, both SACN30 and NICE18 recommend that iron supplementation should not be offered routinely to all pregnant women, as it is not necessary and may have unpleasant side effects such as constipation, but should be considered for women identified with haemoglobin concentrations <110g/l in the first trimester and 105g/l at 28 weeks. The FSA4 recommend that a supplemental guidance level of 17mg/d elemental iron should be tolerated by the vast majority. SACN30 recommend a balanced healthy diet as a means of achieving an adequate iron intake during pregnancy, although the NDNS data6 highlighted poor intakes of iron in women of childbearing age, with a significant number having low iron stores and anaemia.
Vitamin A and iodine
The risks of excessive retinol intakes during pregnancy and deficiencies in iodine have been covered in the previous section on women of childbearing age.
Whilst lactation imposes a heavy nutritional burden on the mother in relation to energy and micronutrient requirements, the maternal diet has a relatively small impact on milk composition, and women can produce most micronutrients, even when their own supplies are limited. Milk quantity and quality are maintained at the expense of maternal stores. Women most at risk of depletion are those who have a poor nutritional intake during pregnancy followed by a similarly inadequate intake during lactation.
Vitamin D deficiency
Breast milk is known to contain low levels of vitamin D, the concentrations of which depend on maternal vitamin D status, which in turn is affected by skin pigmentation, season and latitude. Breastfed infants can only maintain normal vitamin D status in the early postnatal period if their mothers' vitamin D status is normal and/or the infants are exposed to adequate amounts of sunlight31. As in pregnancy, the DH25,26, SACN23 NICE15 and CMO29 recommend that a supplement containing 10μg vitamin D is taken whilst breastfeeding. Despite supplementation whilst breastfeeding UNICEF UK28 emphasise that a baby born deficient in vitamin D will not restore their levels from breast milk alone.
It is estimated that calcium loss during lactation is approximately 210mg/day32. Lactating women should therefore ingest at least 1250mg calcium daily to meet their needs3, and in young women and adolescents who have not yet achieved maximum bone density, it may be as high as 1500mg daily33. It is expected that the additional calcium requirements can be met through diet, via key sources such as dairy foods and calcium fortified products. The FSA4 suggest that supplemental calcium up to 1500mg daily should be tolerated by the majority, but higher doses could cause adverse gastrointestinal symptoms.
Iron and zinc
Breast milk is a poor source of iron, and zinc concentrations decline dramatically between early and mature milk. Both the iron and zinc content are unaffected by maternal status, diet or supplementation31. The iron requirements of infants cannot be met by breast milk alone and the infant relies on its iron stores at birth for the first six months of life.
Infants and young children
It is recommended that exclusive breastfeeding takes place for around six months, during which time the infant should not need any additional nutrition or supplementation34. The only infants considered to be an exception would be those at high risk of vitamin D deficiency, due to poor maternal vitamin D stores, which would be most likely in families with dark pigmented skin and where the mother did not take a vitamin D supplement during pregnancy. In such high risk infants, vitamin D supplementation should be commenced from one month of age. Formula fed babies do not have the same risk, as formula is fortified with vitamin D.
The risk of vitamin D deficiency increases in breastfed babies from six months of age, associated with a rapid rate of bone growth and reducing vitamin D stores with minimal exposure to sunlight. The DH25,26,35, reinforced by NICE15 and CMO29, have recommended that the following groups take a vitamin supplement containing approximately 7μg vitamin D, to meet the RNI:
● all breastfed babies from six months of age (>1 month of age in those at high risk)
● formula fed babies who take less than 500ml formula daily
● all children from one to five years of age.
Children under five years of age have relatively high requirements for vitamin A and the NDNS data revealed that a significant proportion of this age group fail to meet the LRNI6. In light of the fact that vitamin A is essential for normal growth and development and a healthy immune system, the DH recommend supplementation with vitamin A35, supported by a recent Cochrane Review, but due to the risk of toxicity from excessive intakes, care should be taken to not far exceed the RNI and ensure that no more than one micronutrient supplement containing vitamin A is taken at any one time.
Vitamin C back up
Although there has been no evidence of poor vitamin C intakes in children, intakes were less in lower income groups6, and vitamin C is important in increasing the absorption of non-haem sources of iron, for which intakes have been found to be sub-optimal. Infants and children should be encouraged to work towards five children's portions of fruit and vegetables (fist size), although fruit juice can be used for one portion. Supplementation is not thought to be essential, but as a safeguard, as with the maternal DH vitamin supplement, it has been included as part of the DH Healthy Start Children's vitamin drops.
Iron and zinc stores
By six months of age, iron stores have diminished but the demand for iron to meet the needs of growth and development is high. A dietary source of iron is therefore imperative and iron deficiency anaemia has been shown to be common in infants and young children. Iron deficiency in the early years has been associated with impaired brain development and function, resulting in poorer motor, cognitive and social-emotional development later in life. Weaning should therefore not be delayed beyond six months and iron-rich foods should be introduced as early as possible.
Many weaning foods are fortified with iron, as is infant formula, with follow on formula containing more iron. The DH however, state that a first stage milk is suitable for the first year of life, and that there is no clear benefit for the use of follow on formula. Organic foods have to comply with the organic standards laid down in European Union Law which states that vitamins, minerals and trace elements can only be used in organic products where the law requires them to be used. As a result, organic infant formula does contain iron, but weaning foods do not. Iron supplementation should not be necessary if a varied weaning diet is successfully introduced from six months of age. Sub-optimal zinc intakes were found in a significant number of children of all ages, and deficiencies appear to be common in behavioural disorders such as Attention Deficit Hyperactive Disorder (ADHD).
Types of micronutrient supplements available
Data from the NDNS indicated that 20 per cent of children aged one-and-a-half to four-and-a-half years were taking non-prescribed supplements; mainly vitamins A, C, D and multivitamins6. Results from the Growth for Knowledge (GfK) Consumer Survey39 on vitamin and mineral supplementation, found 31 per cent of the population were taking a micronutrient supplement and 52 per cent of households claimed to be giving their children vitamin and mineral supplements. The NDNS data demonstrated that the inclusion of dietary supplements increased the mean intake of most vitamins and minerals, but had little effect on the proportion with intakes below the LRNI, indicating that supplements are generally taken by those who have an adequate micronutrient intake from food6. It is therefore the families most at risk of nutritional deficiencies who should be targeted and encouraged to take suitable vitamin supplements, in accordance with the DH recommendations. The complexity and vast number of micronutrient supplements available can make it difficult for the health professional to offer advice confidently, and they may wish to seek support from a dietitian.
The composition of these can be compared with RNIs, and it should be noted that the composition of some exceed the RNIs. Young children are at greater risk if the supplement is aiming to achieve 100 per cent of the adult EU labelling RDAs, as these figures are much higher than the RNIs for that age group. Higher intakes are of greatest concern for micronutrients that carry a risk of toxicity, such as the fat soluble vitamins A and D, and most minerals. In addition to micronutrients, other nutritional elements may also be added to supplements such as omega 3 fatty acids, particularly docosahexanoic acid (DHA) which is thought to be important for the neuro- and visual development of the fetus and baby, and eicosapentanoic acid (EPA) for optimum brain functioning in children. These are not necessary if the diet includes oily fish on a weekly basis and products containing DHA and EPA are generally more expensive and often do not contain such a comprehensive range of vitamins, minerals and trace elements. It is therefore useful when discussing healthy eating and the Eatwell Plate model, to highlight the importance of including oily fish weekly. Some microalgae oils, suitable for vegetarians and vegans, are rich in DHA, and research suggests that they may be as effective as fish oil41.
Folic acid is available on prescription, but can be purchased at low cost if a specific folic acid supplement is chosen rather than a more complete micronutrient preparation. If the latter is preferred, it is essential that one designed for pregnancy is chosen, as the majority of standard multivitamin products available (not tabled) contain significant amounts of vitamin A.
Children who refuse to eat meat and other animal sources of protein are more likely to be at risk of iron deficiency and may benefit from a supplement targeting this mineral. Iron deficiency has been linked with sub-optimal vitamin D levels in Asian children43. Minadex (Seven Seas), marketed as a tonic, is predominantly an iron supplement and the full dose (2-3 x 5ml daily) is almost a therapeutic dose, providing intakes of iron that are up to 6 x RNI for iron. The full dose usually results in black stools and may not be well tolerated, but this is the dose that would be required to provide a reasonable quantity of vitamin D (4.8μg), and in younger children (six months to three years), the full dose of 2 x 5ml daily only provides 3.2μg vitamin D. The prescribable iron supplement SytronR would be a better alternative if there were concerns around iron deficiency, and could be used at a dose of 1ml daily as a prophylactic iron supplement, providing 5.5mg iron; approximately the RNI.
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