Chapter 17 Nutrition
Nutrition is the sum of the processes involved in taking in, utilizing and assimilating nutrients. Nutrients such as proteins, carbohydrates, fats, vitamins and minerals are necessary for development, growth, normal functioning and maintenance of life. As the body cannot produce them, they need to be obtained from a variety of food sources. Nutritional status is affected by the amount and quality of food eaten; the digestion, absorption and utilization of food nutrients; and biochemical individuality. In westernized countries, eating enough food is not normally a problem. Many people, however, do not eat the correct balance of nutrients. Malnourishment causes impairment of health. In the United Kingdom it occurs for reasons different to those in developing countries, where food is scarce. Food quality may be affected by nutrient-deficient soil in which crops are grown for human or livestock consumption, or by the use of pesticides. The addition of chemical preservatives, colourings and flavourings to ready-prepared food, and antibiotics to meat, will also adversely influence nutrient absorption and utilization.
Digestion and absorption may be affected by general health or combinations of foods eaten. On the other hand, impaired absorption of certain nutrients may be iatrogenic, as when someone is taking specific drugs. Over-indulgence in some foods can affect absorption of essential nutrients; for example, coffee and tea interfere with absorption of zinc and iron from food. Similarly, alcohol, cigarettes or recreational drug abuse, or environmental factors including lead pollution, may lead to malnourishment through inadequate absorption and utilization of nutrients from food. Each person has unique nutritional requirements which alter according to age, gender, general health, activity level, genetic influences and stressors, including pregnancy. Some people need professional help to direct them towards the most appropriate diet.
Midwifery advice about healthy eating during pregnancy can have long-term benefits for the whole family. Inadequate preconceptional and antenatal nutrition may have adverse fetal effects, increasing the risk of perinatal mortality and morbidity, low birthweight or preterm infants, birth defects such as neural tube defects (Carmichael et al 2007, Tamura & Picciano 2006), or maternal complications (Bodnar et al 2006). Impaired maternal nutrition can also adversely affect fetal disease programming, increasing the tendency to hypertension and cardiovascular disease in adult life (Plagemann et al 2008, Woods 2007).
Infertility can be exacerbated by nutritional deficiencies (Chavarro et al 2007, 2008), and dietary advice is a major component of preconceptional care, especially for medical conditons (Tieu et al 2008). Ovulation is dependent on adipose tissue (fat) distribution equal to at least 17% of a woman’s total body weight; anorexics are thus less likely to conceive and more likely to miscarry from vitamin and mineral imbalances. Similarly, male infertility due to poor sperm production may be associated with nutritional deficiency exacerbated by contemporary western diets (Eskenazi et al 2005, West et al 2005). A nutritional diet is high in beneficial nutrients such as those that suppress the effects of toxicity caused by environmental pollution, and low in substances such as nicotine, tea, coffee, alcohol and drugs (Vujkovic et al 2007). The contraceptive pill interferes with the absorption of vitamin B6 and zinc and should ideally be discontinued for at least 3 months preconception. Premenstrual syndrome, triggered by magnesium, zinc, vitamin B6 and other vital nutrient deficiency, may impact on conception. Women who are deficient in essential fatty acids, zinc, manganese and vitamin E or who indulge in potentially toxic substances are also more susceptible to recurrent miscarriage (Bailey & Berry 2005, Ronnenberg et al 2007). Controversy continues regarding the amount of caffeine which may provoke miscarriage (George et al 2006). Alcohol has long been recognized as a possible contributor to fetal teratogenicity and morbidity; women are advised to avoid alcohol completely in the first trimester and to limit later consumption to no more than two alcohol units once or twice a week (NICE 2008a). Artificial preservatives can be harmful.
Expectant mothers should be advised to eat as much fresh food as possible, with a minimum of five portions of fruit, vegetables and salad daily. Organically grown food reduces the impact of fertilizer sprays used on crops but it is usually more expensive and the health benefits of organic foods have been questioned recently in the media. Some food-acquired infections may affect fetal wellbeing and women should reduce or eliminate their consumption of foods likely to harbour these pathogens (NICE 2008b). Examples include Listeria monocytogenes, found in non-pasteurized milk, soft cheeses such as Brie and Camembert, blue-veined cheeses, meat and vegetable pâtés, and uncooked or undercooked ready-prepared meals, whilst Salmonella infection can arise from eating raw or partially cooked meat or eggs or egg products, such as mayonnaise.
Most mothers gain between 11 and 15.75 kg (25–35 lb) in weight during pregnancy, but this depends upon maternal diet, activity, food availability, and gestational factors such as sickness or multiple pregnancy. In women of average weight at conception, a balanced diet usually results in full-term babies of adequate birthweight. Preconceptional, gestational and lactational nutrition affect the birthweight, wellbeing and long-term prognosis of infants, with impact on risk of maternal obesity in later life (Uauy et al 2008). Obesity has become a significant issue in the western world, with serious consequences for UK maternity services (Heslehurst et al 2007). The Confidential Enquiry into Maternal and Child Health 2003–2005 found that almost 30% of women who had a stillbirth or neonatal death were clinically obese, while 35% had a body mass index of 30 or above (Lewis 2007). Maternal obesity is associated with an increased risk of gestational diabetes, hypertension, pre-eclampsia, operative delivery and anaesthestic risks, postpartum haemorrhage, infection, thromboembolic disorders and fetal abnormalities (Dixit & Girling 2008), as well as a high risk of long-term weight problems and childhood obesity (Durand et al 2007). Obesity poses a very real risk to the progress and outcome of pregnancy, birth and the puerperium. Steps should be taken to reduce this risk through education, social support, appropriate obstetric care and management.
Women who restrict their energy intake in pregnancy also cause concern. Dieting to lose weight is not recommended antenatally, even for obese women, unless under medical supervision. In societies where lack of food forcibly restricts energy intake, maternal metabolic adaptations enable energy production for fetal growth. However, care must be taken when advising immigrant women in Britain, such as those from the Indian subcontinent. Pregnant Muslim women are required to comply with total fasting during Ramadan; midwives should be aware of current teachings regarding Ramadan, and should ask Muslim women if they are fasting.
Anorexia nervosa and bulimia nervosa are associated with poor pregnancy outcome, including sub-fertility, risk of miscarriage, obstetric complications, intrauterine growth retardation and postnatal depression. Midwives should be alert to signs of possible eating disorders, particularly in women with a very low body mass index, those who appear to have poor body image and those who report prolonged hyperemesis gravidarum.
Proteins are digested by being broken down into amino acids and transported to the liver, where amino acid transferase enzymes convert them into a more usable form. Essential amino acids include leucine, lysine, methionine, cystine, phenylalanine and tryptophan; non-essential amino acids include alanine, glutamic acid, glycine and tyrosine. This process requires vitamin B6; consequently, a high protein intake will require an increase in vitamin B6 intake. Pregnant women have higher blood levels of tryptophan, an amino acid converted to serotonin, a calming and antidepressive agent. Certain protein foods are potential infection sources for pregnant women, in particular contaminated meat; advice regarding thorough cooking may prevent gastrointestinal disorders. Raw meat may be contaminated with Listeria monocytogenes or Toxoplasma gondii, so pregnant women should avoid raw or undercooked meat. Listeria monocytogenes may also be present in unpasteurized milk, including in soft cheeses.
Fats are composed of triglycerides, which are broken down during digestion. Most fatty acids are synthesized by the body, with the exception of linoleic acid, linolenic acid and arachidonic acid, which must be obtained from food. Fatty acids are either monounsaturated or polyunsaturated. Unsaturated fatty acids are preferable to saturated ones, and polyunsaturated are the most favourable as they are more readily converted into energy; however, a balance of each type is required for adequate nutrition.
Fatty acids depend on adequate intake of zinc, magnesium, selenium, and vitamins B3, C and E. Fat requirements are slightly increased during pregnancy, for extra energy and to avoid protein calories being misused. Omega-3 fatty acids are essential for the developing fetus, particularly visual and cognitive functioning. They may prevent preterm labour, intrauterine growth retardation, pre-eclampsia and postnatal depression (Cetin & Koletzko 2008, Innis & Friesen 2008).
Carbohydrates are classified as sugars (mono- and disaccharides) or starches and fibre (polysaccharides). They are the most easily digested nutrients, which can be stored and released as energy when required, preventing excessive oxidation of fats for energy. All carbohydrates are partly broken down in the mouth but mainly in the small intestine, to the simplest compound, glucose; excess glucose is converted into glycogen and stored by the liver. Carbohydrate intake should equate to approximately half of all food consumed. This may indicate a need to increase starches and fibre and decrease fats and proteins.
Deficiency of vitamin A may cause anaemias, blindness, skin disorders, tooth decay, allergies and gastrointestinal disorders. Absorption can be impeded by vitamin D deficiency, alcohol, coffee, mineral oil, nitrate fertilizers and strong glaring sunlight. However, women should be discouraged from taking vitamin A supplements (more than 700 μg) or eating excessive amounts of vitamin A-containing foods, such as liver or liver products, during the first trimester, as birth defects have been reported (NICE 2008b).
Thiamin absorption is impaired by stress, food additives, alcohol, coffee, excessive sugar consumption, overcooking vegetables and some antibiotics. Thiamin requirements increase during pregnancy and lactation. Long-term deficiency can lead to irritability, insomnia, weight loss, oedema, poor reflexes and impairment of the cardiovascular, nervous and gastrointestinal systems.
Absorption of niacin is antagonized by alcohol, stress, coffee, high carbohydrate intake, antibiotics and antitubercular drugs. Various skin and gastrointestinal disturbances may result from inadequate intake, as well as headache, memory loss, insomnia and poor appetite. If a mother is deficient in vitamin B6, her niacin needs will also increase.
Absorption may be adversely affected by aspirin, the contraceptive pill, codeine, alcohol and nitrous oxide. Deficiency can result in pernicious anaemia, poor growth, memory loss, nervous disorders and ataxia. Although requirements do not increase significantly during pregnancy, certain women are at risk of deficiency, including vegetarians, epileptics and those with tapeworms. The risk of neural tube defects and that of neurological symptoms, including failure to thrive, irritability and poor milestone development, is increased in the infants of women with vitamin B12 deficiency (Dror & Allen 2008, Ray et al 2007).
The incidence of neural tube defects increases in women deficient in folic acid. The National Institute for Health and Clinical Excellence (NICE) recommends that all women intending to become pregnant should take 400 μg of a folic acid supplement daily before pregnancy and during the first trimester (NICE 2008a). In the mother, folic acid deficiency can lead to some anaemias, depression, nervousness, cell and tissue disruptions, and premature greying or loss of hair and may contribute to placental abruption (Nilsen et al 2008). Impaired absorption and utilization may occur if the woman is stressed, drinks alcohol, has recently discontinued the contraceptive pill, or is taking drugs such as aspirin, sulphonamides or anticonvulsants.
Inadequate levels of vitamin C lead to infections, bruising, oedema, haemorrhage, anaemia, poor digestion, tooth and gum disease and scurvy. Some drugs, including aspirin, anticoagulants, antibiotics, diuretics, cortisone, the contraceptive pill and antidepressants, interfere with absorption, as can pollution, industrial toxins, and overcooking or poor storage of food sources. There is some suggestion that daily vitamin C supplementation may reduce the incidence of urinary tract infections in susceptible pregnant women (Ochoa-Brust et al 2007).
The main source of vitamin D is the sunshine. Drugs such as laxatives and antacids inhibit absorption, therefore women with constipation or heartburn should take care not to overuse them. The mother and fetus both require additional vitamin D to prevent skeletal malformations, rickets, osteoporosis, poor muscle tone, and reduced kidney and parathyroid gland function. Women predisposed to pre-eclampsia should be encouraged to increase their vitamin D intake since vitamin D deficiency may contribute to the disease (Hyppönen et al 2007). Pregnant women who restrict their consumption of milk, a source of vitamin D, protein, calcium and riboflavin, may be at greater risk of having babies of low birthweight (Mannion et al 2006) or who suffer hypocalcaemic convulsions (Camadoo et al 2007). The NICE guidelines advocate vitamin D supplementation for pregnant women with limited exposure to sunlight, such as long-stay antenatal inpatients or those who habitually cover the skin when outdoors. This recommendation also applies to mothers with a body mass index of 30 or above, those who are breastfeeding and those who eat a diet low in foods containing vitamin D (NICE 2008a, 2008b).
Vitamin E is destroyed by food processing, rancid fats and oils, and inorganic iron. Absorption is adversely affected by mineral oil, the contraceptive pill, chlorine and thyroid hormone. Requirements for vitamin E increase during pregnancy: indeed, what was originally called vitamin E is now known to be a group of compounds called tocopherols. In humans, deficiency may result in spontaneous abortion, preterm labour, stillbirth, anaemia, and muscular or cardiovascular diseases.
High-protein or high-phosphorus diets will antagonize calcium absorption, as will either excessive or inadequate physical activity, or stress. Drugs affecting calcium absorption or utilization include antacids, laxatives, diuretics and anticonvulsants. Deficiencies may lead to bone disorders, such as osteoporosis or osteoarthritis, dental problems, palpitations, hypertension, insomnia or muscle cramps. Routine calcium supplementation may be helpful in women at risk of pre-eclampsia or those who have an identified low level of calcium.
Zinc requirements rise by approximately 30% during pregnancy to provide for the development of the fetal central nervous system, and 40% in lactating women. Absorption is enhanced by adequate intakes of calcium, copper, vitamins A, B6, B12 and C, and certain amino acids. Absorption and utilization are impaired by tea, coffee, alcohol, processed grains, iron tablets, the contraceptive pill, and by excess levels of phytates, found in bran, and calcium. Jewish women may be deficient in zinc, owing to the presence of phytates in unleavened bread. Zinc neutralizes the toxic effects of cadmium, a contributory factor in hypertension; conversely, high levels of cadmium, found in cigarettes, some processed and canned foods, instant coffee and gelatine, inhibit the action of zinc.
Excessive sweating can cause a loss of up to 3 mg of zinc per day. Zinc is lost in the urine at times of stress and during increased diuresis, such as following high alcohol consumption.
Zinc deficiency can lead to retarded growth and mental development, delayed sexual maturity or sterility (semen contains large quantities of zinc). It may exacerbate gestational sickness and worsen the appearance of striae gravidarum. Women who are zinc deficient may have white spots on their fingernails, experience a metallic taste in the mouth and have a poor appetite. Maternal intake of less than 6 mg daily may lead to babies of low birthweight or prematurity and impaired immune systems (Mahomed et al 2007). Zinc antagonizes lead and cadmium, both of which may be found in higher than normal quantities in the bones of stillborn infants; by inference, therefore, adequate zinc levels may decrease the risk of stillbirth caused solely by nutritional deficiencies.
An inadequate iron level will lead to anaemia, fatigue, headache, palpitations and heartburn. Supplementation will be required to treat iron-deficiency anaemia. Dietary iron consumption will normally achieve sufficient serum levels, although a high zinc intake, tea, coffee, intestinal parasites, antacids and tetracycline will interfere with absorption. Women who consume adequate amounts of foods containing vitamins C, E, B6, B12, folic acid, calcium, copper and other trace elements will normally be able to utilize efficiently the iron from dietary intake. Whilst there is no indication for routine iron supplementation in pregnancy (NICE 2008b), those who require additional iron should be advised to take tablets with orange juice (or other vitamin C-containing drink), which facilitates absorption of the iron, while overconsumption of tea hinders its absorption.
Many women find that nausea is exacerbated by hypoglycaemia, especially if they are also tired. Advice can be given by the midwife to eat small frequent meals of complex carbohydrate foods, such as bread, cereal or potatoes, but not those that are high in sugar or salt. Bananas are a good source of carbohydrate, and may also help to prevent potassium deficiency. Sickness in pregnancy is worse for women lacking in vitamin B6, magnesium and zinc. Women should be advised to eat foods rich in these substances or to take a good-quality supplement. Reducing the amount of dairy produce may also help, as may increasing the intake of citrus fruits or juices (Tiran 2004, 2006).
The midwife can advise women to increase their intake of high-fibre foods, but more importantly they must increase their fluid intake to at least 2 litres of water daily. Tea consumption should be decreased. Tannin reduces peristalsis and inhibits the absorption of iron, which might result in prescription of iron tablets; these, in turn, exacerbate constipation.
Women should eat plenty of fresh fruits, vegetables, unrefined carbohydrates, seeds, grains and pulses, such as beans (Derbyshire et al 2006). Bran should be avoided, unless there is a substantial increase in fluid intake, as it absorbs fluid from the intestines and makes the stool hard, increasing the severity of the constipation. Wheat and wheat products, such as bread and cereals, may increase bloating or abdominal discomfort, particularly if the problem was present before pregnancy, as it may be due to a mild wheat intolerance. Long-term use of laxatives should be discouraged as they will not treat the cause of the problem and can often create other side-effects. Vitamin C supplements may be necessary in some mothers. If iron tablets are prescribed for anaemia and found to exacerbate the problem, other sources of iron-containing foods should be advised. It may be necessary to suggest alternatives to medication, such as herbal liquid preparations, available from healthfood stores.
The mother should be advised to eat small frequent meals and avoid drinking with meals, but maintain a high fluid intake between meals. She should avoid foods which aggravate the condition, such as spicy or greasy foods, as well as coffee, tea, alcohol and cigarettes. Milk and milk products do not always help to relieve the symptoms, and may exacerbate them, as may sugar, sweet foods, wheat and bread. Excessive antacid use should be avoided, especially those containing aluminium, as this may be absorbed and cause mild toxicity. Using large quantities of garlic in cooking can be very helpful. It is best to use whole, peeled but uncut, cloves of garlic which, when cooked, can be squashed and stirred into the food. In this way, adequate quantities of the active ingredients, allicin and other sulphur-containing substances, will be consumed but there will be no excessively strong flavour nor the aftertaste or halitosis, of which many people complain.
Anaemia may be prevented, or the effects reduced, by encouraging the mother to eat foods rich in iron. Her diet should include plenty of fresh green leafy vegetables, such as cabbage, spinach, watercress, parsley, spring onions, chives, sprouted grains and seeds. Seaweeds, nettle tops and dandelion leaves are also good sources of iron. Dried prunes, raisins, figs and unsulphured apricots are helpful, as are blackcurrants, blackberries, cherries and loganberries. Wholegrain bread, oatcakes and chapattis should be eaten rather than highly refined carbohydrates. Pilchards, salmon, kippers and organic liver also provide iron. Bran should be avoided as it inhibits the absorption of iron from foods. Tea and coffee, particularly when taken with meals, have similar effects. Vitamin C-containing fruits and vegetables that enhance the uptake of iron include kiwi fruits, oranges, rosehips, potatoes, cauliflower, broccoli, brussel sprouts and parsley. If iron supplements are prescribed, the mother should be advised to take them with a glass of orange juice and avoid drinking too much tea or coffee.
Reflective activity 17.2
Reflect on some of the women you have cared for during pregnancy and explore how you may have been able to help them to relieve their symptoms by a more efficient management of their diet.
Keep a record during a week of your clinical practice to identify the dietary practices of the women you see: how many of them actively seek advice regarding their nutrition?
Candida albicans yeast infection (see Chapter 57) is common in pregnancy and if left untreated can complicate delivery and may develop into a chronic condition. Women on antibiotics, especially those who have had recurrent infections or when antibiotics are required long term, are more susceptible to thrush. Zinc deficiency compromises the immune system, so infection is more likely, and any nutritional deficiencies should be corrected, initially with an increase in foods containing the relevant minerals and vitamins, or with supplements.
Refined carbohydrates and yeast-containing foods exacerbate the condition and facilitate multiplication of the candida, so should be eliminated from the diet, especially white flour, white or brown sugar or any foods containing these. Similarly, foods containing yeast should be avoided, for example, bread, cheese, alcohol, yeast extract, frozen or concentrated orange juice, grapes, grape juice, unpeeled fruits, raisins, sultanas and B vitamin supplements (unless labelled as yeast-free). Food that is not absolutely fresh should not be consumed, whereas foods containing natural antifungal agents, such as garlic, fresh herbs, spices and fresh green leafy vegetables, can be eaten frequently. For vaginal thrush, a whole peeled but uncut clove of garlic can be inserted into the vagina to act as a local antifungal agent; daily consumption of garlic in food is also recommended.
Conclusion
Adequate nutrition during pregnancy and lactation is vital for good maternal and fetal health. The midwife is in an invaluable position to educate women, thereby influencing family nutrition and health from the beginning. This chapter has discussed the needs of normal women and no mention has been made of the special nutritional requirements of some mothers, for example, diabetics. Midwives should have a basic knowledge of the main dietary needs of mothers, and be able to advise women accordingly. However, it is also important that midwives are able to identify women more at risk of poor nutrition, so that they can be referred to a specialist nutritional therapist or dietician for appropriate information. It has not been possible here to provide more than a general introduction to the subject of nutrition, but further suggestions are on the website.
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