fOOD SAfeTY 99
vulnerable groups are babies, the elderly, immunocompromised individu-als, and pregnant women. The risk of vertical transmission ranges from 15%
in the first trimester to 65% in the third trimester.27 If the infection is con-tracted during the first trimester of pregnancy, then severe fetal damage is likely and may result in miscarriage or stillbirth. If it is contracted during the third trimester, then the risk of the fetus being infected is higher. Babies with congenital toxoplasmosis may develop encephalitis, cerebral calcification, convulsions, and chorioretinitis.
Immune status can be determined by serological screening, although rou-tine testing in the UK is not offered, as it is predicted that 80% of women would be negative.28 If infection during pregnancy is suspected, blood tests for antibodies will be able to detect whether the infection is recent, and amniocentesis or cordocentesis will determine whether the fetus is affected. Management may include antibiotic therapy. Termination of preg-nancy may be offered when there is evidence of fetal damage or infection.
Avoiding the infection is the simplest and best way to prevent con-genital toxoplasmosis; therefore, the following advice should be given to pregnant women.
• Only eat well- cooked meat which has been cooked thoroughly right through (i.e. no traces of blood or pinkness).
• Avoid cured meats such as Parma ham.
• wash hands and all cooking utensils thoroughly after preparing raw meat.
• wash fruit and vegetables thoroughly to remove all traces of soil.
• Take care with hygiene when handling dirty cat litter. wear rubber gloves when clearing out cat litter and wash hands and gloves afterwards. If possible, get someone else to do the job.
• Cover children’s outdoor sandboxes to prevent cats from using them as litter boxes.
• wear gloves when gardening, and avoid hand- to- mouth contact. wash hands afterwards.
• Avoid unpasteurized goats’ milk or goats’ milk products (although this route of transmission is rare).
• Avoid sheep that are lambing or have recently given birth.
There is no contraindication to breastfeeding by a woman who has, or is undergoing treatment for, toxoplasmosis.
Vitamin A
vitamin A is a fat- soluble vitamin that is essential for embryogenesis, growth, and epithelial differentiation. The retinol form of vitamin A is found chiefly in dairy products, such as milk, butter, cheese, and egg yolk, in some fatty fish, and in the liver of farm animals and fish. experiments in animals have shown that retinoids, but not carotenoids, can be teratogenic.29
A high dietary intake of vitamin A before the seventh week of pregnancy has produced an increased frequency of birth defects, including cleft lip, ventricular septal defect, multiple heart defects, transposition of the great vessels, hydrocephaly, and NTDs.
Retinol is given to animals as a growth promoter, and any excess is stored in the liver. Since 1990, women who are pregnant or planning a pregnancy have been advised to avoid eating liver and liver products, such as pâté or liver sausage, as they contain large amounts of retinol.
vitamin A deficiency is largely a problem of developing countries and is relatively uncommon in the developed world in the absence of disease. In the UK, the reference nutrient intake (RNI) is 600 micrograms/ day, with a 100 micrograms/ day increase during pregnancy.30 Most women in the UK have a vitamin A intake in excess of the RNI.
Cod liver oil supplements may contain large amounts of vitamin A and should not be taken during pregnancy, except on medical advice.
Caffeine
Caffeine is a methyl xanthine, a naturally occurring compound found in plants. It is present in tea, coffee, and chocolate and acts as a stimulant.
It is also added to some soft drinks and so- called ‘energy’ drinks, as well as over- the- counter antiemetics and analgesics.31 In pregnant women, it is metabolized more slowly, and studies have suggested an association between the ingestion of caffeine and an increased risk of spontaneous abortion.32 During breastfeeding an excessive intake can cause irritability and sleeplessness in both the mother and the baby.
The Committee on Toxicity of Chemicals in food, Consumer Products and the environment looked at the effects of caffeine on reproduction and concluded that caffeine intakes above 200mg/ day may be associated with low birthweight and, in some cases, miscarriage. Therefore, the food Standards Agency33 has issued advice to pregnant women to limit their intake of caffeine to less than the equivalent of two mugs of coffee a day.
It is not necessary for women to cut out caffeine in the diet completely, but it is important that they are aware of the risks, so they can ensure that they do not have more than the recommended amount. A total of 200mg of caffeine is roughly equivalent to:
• Two mugs of instant coffee (100mg each)
• 2 1/ 2 cups of instant coffee (75mg each)
• Two cups of brewed coffee (100mg each)
• four cups of tea (50mg each)
• Three cans of cola (up to 80mg each)
• four (50g) bars of chocolate (up to 50mg each).
References
26 food Standards Agency (2016). Listeria Guidance. Available at: M https://www.food.gov.uk/
news-updates/news/2016/15253/listeriosis-guidance-published in Scotland available at: M www.
foodstandards.gov.scot.
27 Tommy’s (2014). Toxoplasmosis and pregnancy. Available at: M www.tommys.org/ pregnancy- information/ pregnancy- complications/ toxoplasmosis- and- pregnancy?gclid=CN2hiNGgjs4CfQ 8z0wodalMIMA.
28 elsheikha HM (2008). Congenital toxoplasmosis: priorities for further health promotion action.
Public Health 122: 335– 53.
29 Azais- Braesco v, Pascal G (2000). vitamin A in pregnancy: requirements and safety limits. Am J Nutr 71: 13255– 335.
fOOD SAfeTY 101
30 Department of Health (1991). Report on Health and Social Subjects 41. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Dietary Reference Values for the United Kingdom.
London: HMSO.
31 Jordan S (2002). Pharmacology for Midwives: The Evidence Base for Safe Practice. Hampshire:
Palgrave, p. 18.
32 Cnattingius S, Signorello LB, Anneren G, et al. (2000). Caffeine intake and the risk of first- trimester spontaneous abortion. N Engl J Med 343: 1839– 45.
33 food Standards Agency (2008). Food Standards Agency publishes new caffeine advice for pregnant women. Available at: M www.food.gov.uk/ news/ pressreleases/ 2008/ nov/ caffeineadvice.