Updated 01 June 2015

Diet tips for pregnant moms – Part III

DietDoc explains why it is important that pregnant mothers get enough iron, zinc, folic acid and vitamin D – for their own health and the health of their babies.


In our third article about guidelines for pregnant mothers, we will explore some of the important nutrients women require during pregnancy, such as iron, folic acid, zinc, and vitamin D – for their own health and the health of their babies.


Most women are probably aware of the fact that they have a higher requirement for iron during their childbearing years to make up for the menstrual blood they lose every month, and for the increased demands of pregnancy and breastfeeding.

The best food sources of readily available and easily absorbable iron (so-called haem iron), are red meat (beef, mutton, pork), organ meats (liver, kidneys), poultry (chicken, turkey), egg yolk, and fish. Although many plants contain relatively high levels of iron, other compounds in the plant tissues such as phytic acid or oxalates tend to bind the iron and change it into insoluble complexes which the human body has difficulty absorbing.

Read: Iron deficiency anaemia

Spinach is a classic example: it has a relatively high iron content (2.7 mg per 100g of raw spinach), but the iron is bound to oxalates, which make it insoluble and lower its bioavailability.

Because many women enter pregnancy with an iron deficiency (due to heavy menstrual blood loss, avoidance of meat and other animal sources of iron), most doctors and clinics automatically prescribe an iron supplement for expectant mothers. Unfortunately many of the iron supplements used during pregnancy can cause unpleasant side-effects such as nausea, vomiting, flatulence, constipation or diarrhoea.

Prof Tappenden reports that the current approach to iron supplementation during pregnancy is firstly to encourage pregnant mothers to eat an iron-rich diet, which is based on foods derived from animals and iron-fortified cereals (in South Africa all maize meal and wheaten flour is fortified with iron and most women in the USA obtain up to 50% of their dietary iron from iron-enriched breakfast cereals).

Secondly, low-dose iron supplementation of about 30 mg 1-2 times a week is advised to reduce the side-effects that can put pregnant mothers off taking their iron supplements. Research showed that this intermittent iron supplementation can achieve the same improvements in body iron stores during pregnancy as a daily high dose of iron that may cause negative side-effects.

If you are pregnant and your doctor has prescribed an iron supplement for you that tends to make you feel nauseous or causes constipation or diarrhoea, discuss this with the doctor to see if you can use a lower dose iron supplement instead, but do not stop taking your iron without first consulting your doctor or dietician. Your dietician can help you with a diet that provides adequate supplies of readily available iron for you and your baby.

Folic acid

The current recommendation in the USA is that pregnant women should obtain 600 micrograms per day of folic acid. The best dietary sources are:

  • Legumes – dry cooked or canned beans, peas and lentils and all soy products, wet or dry (e.g. tofu, soy milk, or soy meat replacement products)
  • Green leafy vegetables
  • Liver
  • Citrus fruits (oranges, lemons, grapefruit, limes, naartjies)
  • Other fruit
  • Whole unprocessed grains such as crushed wheat, unsifted maize meal, sorghum, millet and other whole grains
  • In South Africa folic acid is added to wheat flour and sifted maize meal and this fortification has reduced the incidence of neural tube defect cases in newborn babies by 31%. 

Interestingly folic acid supplements are more bioavailable to the body than folic acid found in foods. This is often not the case with other vitamins and mineral supplements, but synthetic folic acid is absorbed twice as well as naturally occurring folic acid in food.

Read: No folly in folic acid

Supplementing your diet with folic acid at the recommended rate is, therefore, a good idea and Prof Tappenden emphasised that in the month before conception, all women in their childbearing years, as well as pregnant mothers after conception should have 400 micrograms of folic acid per day in addition to folate obtained from the above listed foods. As conception cannot be accurately predicted, this recommendation applies for most of the childbearing period if a woman is not practising birth control to prevent conception.


In addition to iron, zinc is probably one of the most important minerals for healthy foetal development. Many women tend to have a suboptimal zinc intake because of a variety of factors including:                  

  • Having undergone bariatric surgery which may hamper zinc absorption
  • A vegan diet which does not contain zinc that can be absorbed by the body
  • Using other diets that consist mainly of cereals or plants-based foods where zinc is bound to compounds called phytates in the plant material and is not easily absorbed
  • Zinc is also added to the vitamin and mineral mix used in South Africa to fortify wheat flour and maize meal, the two basic staple foods used in this country.  

In situations where a pregnant woman may develop a zinc deficiency, it is a good idea to use a zinc supplement to ensure an intake of 11 mg of zinc per day.

Vitamin D

It always seems strange to list vitamin D as a vital nutrient – not because of its great importance in the human body (with new roles being discovered every day), but because humans are basically able to manufacture vitamin D in their own bodies, provided their skins are exposed to sunlight for about 30 minutes daily.

During pregnancy vitamin D helps with the development of the bones and teeth, and boosts the immunity of both the mother and the child. But how many pregnant women spend 30 minutes a day sitting in the sun? In the USA for example, many foods such as milk and dairy products are fortified with vitamin D, but this is not the case in “sunny” South Africa.

Our modern lifestyles and fear of developing skin cancer have turned humans from sun-worshipping, outdoor fanatics to pale couch potatoes huddled in front of our TVs or over cell phones, laptops, tablets, Kindles and game consoles. Wearing clothing which covers the entire body for religious reasons, living in parts of the country that have little sunshine during the winter months or having darker skins, all interfere with the natural process of making vitamin D under the skin when it is exposed to sunlight.

Read: The miracle of vitamin D

Prof Tappenden recommends an intake of vitamin D in the form of a supplement such as cholecalciferol at a dose of 600 IU/day. This may at present be difficult to achieve in our country because there are currently no stocks of this vitamin available in the country because the Medicines Control Council (MCC) is investigating the purity of the supplements sold to the public. So, while we wait for the MCC to sort out this problem, all pregnant women should spend half an hour a day exposing their skin to the sun to make their own Vitamin D.

Because there are so many factors that play important roles in the nutrition of women before, during and after childbirth, it is really a good idea to consult a registered dietician for an assessment of your health, diet and weight before you conceive and during pregnancy to guide you through any dietary problems that may arise. Visit the website of the Association for Dietetics in SA (ADSA) and click on ‘Find a Dietician’ to find a dietician in your area.

Pregnancy should be a natural, happy time when you are glowing with health and helping your baby grow strong and clever. Remember that a dietician will help to allay your diet fears, sort out your weight issues and advise you about diets, supplements and foods at any time during your journey to motherhood.

Read more:

Diet tips for pregnant moms – Part I

Diet tips for pregnant moms – Part II

Am I eating to optimise my pregnancy?


- Tappenden KA (2015). Eating for Two. Best Practices for Maternal Nutrition. Paper presented at the Nutritional Solutions CNE Event, 16 April 2015, Johannesburg.

Image: Pregnant mom with supplements from Shutterstock

Dr Ingrid van Heerden is a registered dietician and holds a doctoral degree in Nutrition and Biochemistry. She believes that "we are what we eat" and offers free nutrition and weight loss advice via her DietDoc service on Read more of her articles.


Read Health24’s Comments Policy

Comment on this story
Comments have been closed for this article.

Live healthier

Exercise benefits for seniors »

Working out in the concrete jungle Even a little exercise may help prevent dementia Here’s an unexpected way to boost your memory: running

Seniors who exercise recover more quickly from injury or illness

When sedentary older adults got into an exercise routine, it curbed their risk of suffering a disabling injury or illness and helped them recover if anything did happen to them.