Prenatal Nutrition Guidelines for Health Professionals - Iron Contributes to a Healthy Pregnancy
© Her Majesty the Queen in Right of Canada, represented by the Minister of Health Canada
ISBN: 978-1-100-12207-6 (PDF Version)
Cat. No.: H164-109/1-2009E-PDF (PDF Version)
Iron is an essential nutrient at every stage of life. It is a critical component of proteins such as enzymes and hemoglobin. Almost two-thirds of iron in the body is in the hemoglobin present in circulating red blood cells. Hemoglobin moves oxygen to the tissues for metabolism (IOM, 2001). During pregnancy, women need more iron to support the increased maternal red blood cell mass. This supplies the growing fetus and placenta, and supports normal brain development in the fetus. In the third trimester of pregnancy, the fetus builds iron stores for the first six months of life (Fernández-Ballart, 2000).
Key Messages on Iron for Pregnant Women
- Eating according to Canada's Food Guide and taking a daily multivitamin that has 16 to 20 mg of iron will help you have a healthy pregnancy.
- Some women may need more iron than others. Talk to your health care provider to find out how much iron is right for you.
Recommended iron intake during pregnancy (IOM, 2001)
Hemoglobin mass changes very little during the first trimester of pregnancy. However, it expands greatly during the second and third trimesters. This means, as pregnancy progresses, women need more iron.
The Recommended Dietary Allowance (RDA)Footnote 1 for iron during pregnancy is 27 mg per day. This is the average amount of iron most healthy pregnant women need each day to meet their iron needs. The RDA is set at a level that lets women begin storing iron early in their pregnancy. That way, they build up the iron they'll need to take them through their third trimester. This level takes into account:
- normal iron losses,
- iron used by the fetus and related tissues,
- iron needed as a woman's hemoglobin mass expands, and
- that approximately 25% of iron from a mixed dietFootnote 2 is absorbed during the second and third trimesters of pregnancy.
Taking an iron supplement during pregnancy
Most pregnant women in North America have trouble getting the iron they need through diet alone (Fernández-Ballart and Murphy, 2001; Hercberg et al, 2000; IOM, 2001; Turner et al, 2003; Cooper et al, 2006). Health Canada used a statistical modelling process to determine the level of iron from supplements that would be needed to complement usual dietary iron intakes of Canadian women. The combined intake (usual dietary intake + supplement) was evaluated using the iron requirement values given and assessment methods developed by the Institute of Medicine (IOM, 2000). Health Canada also conducted a safety assessment to ensure that the combined intake did not exceed the Tolerable Upper Intake Level (UL)Footnote 3 for pregnancy, which is 45 mg of iron each day.
Information on this modelling process is available for review (Cockell et al, 2009).
How much supplemental iron do pregnant women need?
A daily supplement containing 16 to 20 mg of iron is recommended during pregnancy. Based on the results of the modelling process, it was concluded that a supplement of 16 mg per day throughout pregnancy would be effective and safe for pregnant women who are in good health. When added to the iron they get from a mixed dietFootnote 4, these women would have all the iron they need for pregnancy (Cockell et al, 2009). Additionally, supplementing well nourished pregnant women with 20 mg of iron per day has been shown to be effective in reducing the prevalence of iron deficiency and iron deficiency anemia at the time of delivery (Makrides et al, 2003).
Selecting an iron-containing supplement
Health Canada recommends a supplement that has 16 to 20 mg of iron in each daily dose. Health Canada also recommends that pregnant women take a daily multivitaminFootnote 5 containing 400 mcg (0.4 mg) of folic acid (Health Canada, 2009). Women can find both nutrients in a multivitamin.
Iron deficiency and iron deficiency anemia
During pregnancy women may not get enough iron because they:
- need more iron than they did before they were pregnant,
- do not eat enough foods containing iron, or
- do not absorb enough iron from the foods they eat due to low iron bioavailability of the diet.
Not getting enough iron during pregnancy can cause: fatigue, reduced work capacity, cardiovascular stress, lower resistance to infection and iron deficiency. Iron deficiency can lead to:
- maternal anemia,
- premature delivery,
- low birth weight, and
- an increased risk of perinatal infant mortality (Hercberg et al, 2000; IOM, 2001).
Iron deficiency anemia is the most common nutritional deficiency during pregnancy (WHO, 1992). It happens most often during the third trimester of pregnancy (IOM, 2001). The stages of iron deficiency and iron deficiency anemia are well documented and clinical diagnostic cut-off values have been established (IOM, 2006).
The recommendations in this document were not established for women who have pre-existing iron deficiency or iron deficiency anemia. These women should be assessed to determine how much additional iron they need from supplements.
Choosing dietary sources of iron
Dietary iron has two forms: heme iron and non-heme iron. Heme is found only in meat, poultry and fish. It is better absorbed than the non-heme form. It is also less affected by dietary factors that hinder iron absorption. This makes it an important dietary source of iron. Heme iron can provide up to one third of the total dietary iron that the body absorbs (Bjorn-Rasmussen et al, 1974).
Most of the iron we eat is in the non-heme form (IOM, 2006). About 60% of the iron found in meat, poultry and fish is in the non-heme form (Beard et al, 1996). Eggs and plant-based foods, such as legumes, vegetables, fruit, grains, nuts, and iron fortified grain products contain only the non-heme form.
Tables 1 and 2 list foods that contain heme and non-heme iron.
|Food||Iron in milligramsTable 1 footnote a per Food Guide Serving
(75 g, cooked)
Table 1 footnotes
|Fish (such as salmon, trout, halibut, haddock, perch)Table 1 footnote b||0.5-1 mg|
|Other sources of heme iron|
|Wild duck||7.5 mg|
|Heart , kidney||4-9 mg|
|Oysters, mussels||5-7 mg|
|Blood pudding||5 mg|
Note: Although liver is an excellent source of iron, it is not included on this list because of its high vitamin A content. A single Food Guide Serving (75 g, cooked) from most types of liver exceeds the Tolerable Upper Intake Level (UL) for vitamin A for women of childbearing age.
|Food||Food Guide Serving||Iron in milligramsTable 1 footnote a|
Table 2 footnotes
|Pumpkin seed kernels||60 mL||8.5 mg|
|Tofu, medium or firm||150 g||2-7 mg|
|Legumes (such as beans, lentils, chickpeas)||175 mL||2-6.5 mg|
|Instant hot cereal (enriched with iron)||175 mL||3-6 mg|
|Cold cereals (enriched with iron)||30 g||4 mg|
|Some vegetables (such as pumpkin, artichoke hearts, peas, potatoes, spinach)||125 mL||1-2 mg|
|Nuts, peanuts and sunflower seeds||60 mL||0.5-2 mg|
|Pasta (enriched with iron)||125 mL||1-1.5 mg|
|Prune juice||125 mL||1.5 mg|
|Peanut butter and nut butters, such as almond butter||30 mL||0.5-1.5 mg|
|Bread (enriched with iron)||1 slice||1 mg|
Absorbing iron from dietary sources (IOM, 2001)
The amount of iron available to the body through food can vary greatly. How much iron gets absorbed depends on what other foods are eaten at the same time. These other foods can enhance or inhibit non-heme iron absorption. For example, in non-pregnant adults, the body absorbs only 18% of the iron it gets from food. This result is based on typical North American diets that contain both heme and non-heme iron, and vitamin C. This level lowers to 10% for vegetarian diets (containing only non-heme iron). Very strict vegetarian diets may have even lower results at approximately 5% overall absorption rate.
Enhancers and inhibitors
Foods contain both enhancers and inhibitors. Paying special attention to the foods that make up meals can help women reduce the effect of inhibitors and improve dietary iron absorption.
There are three main inhibitors of non-heme iron absorption in the diet: polyphenols from tea and coffee, phytate in legumes and some vegetables, unrefined rice and grains, and calcium at levels greater than 300 mg (Hallberg and Huthen, 2000).
Ascorbic acid, or vitamin C, strongly enhances iron absorption. It releases non-heme iron bound to inhibitors (Fernández-Ballart, 2000). The effect is strongest when vitamin C containing foods are eaten with foods containing high levels of inhibitors. For instance, a glass of orange juice can help minimize the effect of phytate in breakfast cereal and calcium in milk.
Meat, fish and poultry can also improve non-heme absorption (IOM, 2006). Even modest amounts of these foods can improve the absorption of non-heme iron in a meal.
Implications for practice
Selecting a multivitamin containing iron
To ensure proper use of multivitamin supplements:
- Use the 'Key messages on iron for pregnant women' to write or talk about iron supplementation during pregnancy.
- Encourage women to look for a multivitaminFootnote 7 that provides 16-20 mg of iron per daily dose. The supplement should also include vitamin B12 and 400 mcg (0.4 mg) of folic acid per daily dose (Health Canada, 2009).
- Ensure that women look for a Drug Identification Number (DIN) or Natural Product Number (NPN) on the product label showing that the product is government-approved for safety, efficacy, and quality.
- Emphasize the importance of reading product labels. Some supplements may include cautionary notes about their use during pregnancy and breastfeeding.
- Caution women not to take more than one daily dose of their multivitamin. This will help women not to go over the UL for vitamin A, which is 3,000 mcg retinol activity equivalent (RAE)Footnote 8 or 10,000 IU.
- Remind women to keep all supplements stored out of reach of young children.
Optimizing dietary iron intake and iron absorption
Following a healthy eating pattern and choosing foods that are rich in nutrients helps women meet their requirement for iron, vitamin C and other nutrients. To promote adequate dietary iron intake:
- Encourage women to follow Canada's Food Guide. It describes a healthy eating pattern that is rich in dietary iron. Following Canada's Food Guide will also help women meet their needs for other nutrients and will help them achieve overall health.
- Promote the use of tools such as My Food Guide Servings Tracker. This can help women keep track of the amount and type of food they eat each day and compare their intake to Canada's Food Guide.
- Emphasize that meat, poultry and fish are important dietary sources of iron. They also help the body absorb non-heme iron.
- Suggest the use of nutrition labellingFootnote 9 to help women choose foods fortified with iron. They can make informed choices by looking for the term 'iron' in the ingredient list when choosing grain products such as cereals, bread and pastaFootnote 10. Women can also use the Nutrition Facts table on food labels to compare and choose products that contain more iron per serving.
- To optimize non-heme iron absorption, encourage women to include at least one source of vitamin C with their meals. This is particularly important at meals that do not include meat. Vitamin C is found in a variety of foods: broccoli, cantaloupe, citrus fruits and their juices, kiwis, mangos, potatoes, strawberries, sweet peppers, tomatoes, and tomato sauce.
- Encourage women to drink tea or coffee 1 or 2 hours between meals rather than with meals. These drinks can interfere with iron absorption.
- Advise women not to take a calcium supplement or calcium-containing antacids with meals. Too much calcium can reduce the amount of iron absorbed by the body. If the supplement is taken 1 to 2 hours after a meal, the high dose of calcium will not interfere with the absorption of iron in the meal (Gleerup et al, 1993).
- Refer women to a Registered Dietitian if they have a significantly restricted food intake. This can happen when women exclude an entire food group or have severe nausea or vomiting. These women can benefit from comprehensive nutritional assessment and counselling.
- Refer nutritionally at-risk women to services or programs that can help. The Canada Prenatal Nutrition ProgramFootnote 11 Website provides contact information for programs and services for vulnerable pregnant women.
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Bjorn-Rasmussen E, Hallberg L, Isaksson B, Arvidsson B. 1974. Food iron absorption in man. Application of the two-pool extrinsic tag method to measure heme and non-heme iron absorption from the whole diet. J Clin Invest 53(1):247-56.
Cockell KA et al. 2009. Application of the Dietary Reference Intakes in Developing a Recommendation for Pregnancy Iron Supplements in Canada. Submitted January, 2009.
Cooper MJ, Cockell KA, L'Abbé MR. 2006. The iron status of Canadian adolescents and adults: Current knowledge and practical implications. Can J Diet Pract 67(3):130-8.
Fernández-Ballart J. 2000. Iron metabolism during pregnancy. Clin Drug Invest 19(Suppl. 1):9-19.
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Health Canada. 2009. Prenatal Nutrition Guidelines for Health Professionals - Folate contributes to a healthy pregnancy (Ottawa: Health Canada).
Hercberg S, Galan P, Preziosi P, Aissa M. 2000. Consequences of iron deficiency in pregnant women. Current issues. Clin Drug Invest 19suppl(1):1-7.
Institute of Medicine. 2000. Dietary Reference Intakes: Applications in Dietary Assessment. (Washington DC: National Academies Press).
Institute of Medicine. 2001. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (Washington DC: National Academy Press).
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Makrides M, Crowther CA, Gibson RA, Gibson RS, Skeaff CM. 2003. Efficacy and tolerability of low-dose iron supplements during pregnancy: a randomized controlled trial. Am J Clin Nutr 78(1)145-53.
Turner RE, Langkamp-Henken B, Littell RC, Lukowski MJ, Suarez MF. 2003. Comparing nutrient intake from food to the estimated average requirements shows middle- to upper-income pregnant women lack iron and possibly magnesium. J Am Diet Assoc 103(4):461-6.
Health Canada sincerely thanks the members of the Expert Advisory Group on National Nutrition Pregnancy Guidelines who generously gave their time and expertise over the course of preparing these guidelines:
Aline Allain-Doiron, RD, Public Health Nutritionist-Dietitian, Regional Health Authority B, Zone 7
Andrée Gruslin, MD, FRCS, Director of the Post-graduate Residency Training Program in Obstetrics and Gynaecology, University of Ottawa
Sheila M. Innis, RD, PhD, Director of Nutrition Research Program, Child and Family Research Institute, University of British Columbia
Kristine G. Koski, RD, PhD, Director School of Dietetics and Human Nutrition, McGill University
Michel Lucas, PhD, MPH, RD, Epidemiologist/Nutritionist, Axe Santé des populations et environnement, Centre Hospitalier de l'Université Laval (CHUL-CHUQ)
Ann Montgomery, RM, associate midwife and preceptor, Midwifery Collective of Ottawa
Deborah L. O'Connor, RD, PhD, Director of Clinical Dietetics, The Hospital for Sick Children, and Associate Professor, Department of Nutritional Sciences, University of Toronto
Kay Yee, RD, Public Health Nutritionist, Regina Qu'Appelle Health Region
We gratefully acknowledge Dr. George H. Beaton, Professor Emeritus, University of Toronto, who provided expert advice on the methodology for the modeling of supplement level and dietary iron adequacy.
Health Canada would also like to thank the many stakeholders who took part in the online consultation process and provided feedback on draft content of the guidelines.
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