Macro and microelements: optimal intake and body concentration in reproduction, pregnancy and postpartum

VIDEO 5

Nutritional status during pregnancy can have a significant impact on maternal and neonatal health outcomes. Requirements for macronutrients such as energy and protein increase during pregnancy to maintain maternal homeostasis while supporting fetal growth. Certain micronutrients are also vital for improving pregnancy outcomes, including folic acid to prevent neural tube defects and iodine to prevent hypothyroidism.

The double burden of malnutrition is a growing concern affecting women globally. The prevalence of obesity continues to rise, significantly increasing the risk of metabolic diseases and cardiovascular conditions. Additionally, obesity during pregnancy is associated with a higher risk of adverse perinatal outcomes. The issue is complex, as its primary determinants are systemic and span multiple sectors, including economic, political, food environments and cultural factors. One of the key contributors to obesity is the current food environment, which promotes overconsumption of energy. This environment is characterized by the widespread availability and accessibility of ultraprocessed foods, large portion sizes and aggressive marketing strategies. Ultraprocessed foods are usually hyperpalatable, convenient and provide energy, but often they are high in fat and saturated fat, have added sugars and are very low in fiber and micronutrients. These foods contribute to low-grade chronic inflammation, which is a key factor in the development of obesity and related diseases.

Given global dietary trends, it is unsurprising that micronutrient deficiencies remain widespread. One-third of the global population is affected by iron deficiency. Recent data from several countries indicate that 69% of women of reproductive age suffer from deficiencies in iron, zinc and/or folate. Iodine deficiency also remains prevalent, affecting approximately half of the population. Anemia continues to be a significant public health issue, with the global prevalence of anemia among women estimated at 31% in 2021. The causes of anemia are multifactorial, including genetic disorders, nutrient deficiency, chronic disease, inflammation, heavy menstrual bleeding, HIV, parasitic infection and perinatal complications. Data from 2019 showed that 36% of pregnant women globally are anemic, with postpartum anemia affecting 50% of women in developed countries and up to 80% of women in developing countries. Notably, from 2000 to 2019, the rate of decline in anemia prevalence was not significant. Anemia screening is vital, particularly during pregnancy. A hemoglobin (Hb) level below 11 g/dL generally indicates anemia. According to the Centers of Disease Control (CDC), specific thresholds for different trimesters should apply to detect anemia: below 11 g/dL in the first and third trimesters, and below 10.5 g/dL in the second trimester. Postpartum anemia is defined as Hb levels lower than 10 g/dL after delivery. The World Health Organization (WHO) defines postpartum anemia as an Hb level below 11 g/dL at 1 week postpartum and below 12 g/dL at 8 weeks postpartum. Approximately 50% of anemia cases are attributed to iron deficiency. Ferritin levels should be measured in women with conditions such as hemoglobinopathy, previous parenteral iron therapy, prior anemia, multiple pregnancy, short interpregnancy interval, adolescent pregnancy, history of bleeding or high bleeding risk, and those on a vegetarian diet.

Another common micronutrient deficiency is vitamin D, which is particularly prevalent among women and during pregnancy. Some countries report up to 90–100% of pregnant women experiencing vitamin D deficiency. Vitamin D status is typically assessed through the measurement of 25-hydroxyvitamin D (25-OH-D), the circulating form of the vitamin. Although there is debate regarding the precise cut-off to define deficiency, it is generally accepted that vitamin D deficiency is indicated by a 25-OH-D level below 20 ng/mL, with an adequate status defined as higher than 30 ng/mL.

Inadequate intake of various other vitamins and minerals is also common, including calcium, iron, vitamin A, vitamin C, zinc, riboflavin and folate. Low intake of omega-3 fatty acids and excessive consumption of saturated fats are also widespread. In most countries, the intake of omega-3 fatty acids from seafood is low, while saturated fat intake exceeds the recommended 10% of total energy intake.

According to the above, a healthy diet before, during and after pregnancy is critical for maternal and fetal health. A balanced dietary pattern, based on locally available, fresh and minimally processed foods, should be promoted. Such a diet includes a high intake of vegetables, fruit, whole grains, legumes and fish, along with moderate amounts of seeds, nuts, eggs and dairy products. This type of diet provides the necessary energy and protein for pregnancy and lactation, including vegetable protein, healthy carbohydrates (including fiber), healthy fats, and a rich array of vitamins, minerals, antioxidants and polyphenols. These dietary components have anti-inflammatory, antioxidant and prebiotic properties, all of which support maternal and infant health. In addition, diet should provide adequate energy and macronutrients to meet higher demands of pregnancy and lactation. Energy needs during pregnancy are determined by the synthesis of new tissues, increased maternal fat deposition, and the maintenance and growth of the new tissues. During breastfeeding, energy needs are influenced by milk energy output, the efficiency of milk production, and energy mobilization from maternal stores. Recent updates to dietary reference intakes from the National Academy of Sciences (US) include new equations for estimating total energy expenditure during pregnancy. For women with normal weight, the energy cost of pregnancy in the second and third trimesters is 200 kcal/day. In contrast, for women with obesity, there is no increase in energy expenditure; in fact, it is estimated to decrease by 50 kcal/day. The energy cost of breastfeeding is approximately 404 kcal/day, assuming a milk output of 808 g/day and a monthly weight loss of 640 g. For the second half of lactation, the energy cost is estimated at 380 kcal/day.

Pregnant and breastfeeding women have higher protein requirements than non-pregnant women. According to the WHO, protein deposition during pregnancy increases by 11 g/day in the second trimester and 31 g/day in the third trimester. During the first 6 months of lactation, protein deposition is estimated to be 21–23 g/day, with an additional 14 g/day required during the second half of breastfeeding. Pregnancy also increases the need for carbohydrates. The recommended intake is 175 g/day during pregnancy and 210 g/day during breastfeeding, according to the Institute of Medicine. A recent review has suggested that an additional 220 g/day may be needed to support fetal brain and placenta development. It is important to note that, while most women meet the required quantity of carbohydrates during pregnancy and lactation, the quality of the carbohydrates consumed often needs improvement. Healthy carbohydrates – those with a low glycemic index or high-fiber content – should be prioritized. These include whole grains, legumes, fruit, vegetables and dairy products. Similarly, healthy fats, particularly omega-3 fatty acids and monounsaturated fats, should be promoted. Oily fish, such as salmon, sardines and trout, and seafood, are key sources of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), essential omega-3 fatty acids crucial for brain and visual development. The recommended intake is 300–350 g of oily fish per week. If this intake is not achievable, supplements should be considered. Plant-based sources of omega-3, providing alpha-linolenic acid (ALA), can also be consumed, though ALA must be converted into DHA and EPA in the body, and this conversion is often inefficient. The recommended intake of fats for women, including those who are pregnant or breastfeeding, is 20–35% of total energy intake. Omega-6 fatty acids should represent 5–10% of total energy intake, while omega–3 fatty acids should comprise 0.6–1.2% (approximately 1.4 g/day). The optimal ratio of omega-3 to omega-6 fatty acids is approximately 1 : 5. A minimum of 250 mg of DHA and EPA is recommended for women of reproductive age, with an additional 100–200 mg of DHA needed during pregnancy.

Adequate micronutrient intake during the whole lifecycle is key. Iron requirements increase in pregnancy, with a recommended intake of 27 mg/day. Iron deficiency can lead to hypoxia, decreased hemoglobin levels, impaired hematopoiesis and increased oxidative stress. It is also associated with placental adaptations that can result in altered maternal vascular perfusion, increasing the risk of fetal growth restriction, preterm birth and miscarriage. During lactation, the requirements decrease (9 mg/day). Vitamin B12, folate and other B-complex vitamins are essential for proper metabolism, nerve and muscle function, and for the production of red blood cells. These nutrients participate as methyl donors in the one carbon metabolism, being essential for regulating homocysteine concentrations and participating in multiple epigenetic reactions. Maternal status can be assessed through various biochemical markers, including total serum B12 and active B12, as well as indirect indicators like methylmalonic acid and homocysteine levels. Vitamin D plays a key role in bone health, immune function, calcium balance, insulin sensitivity, and fetal growth. Its primary source is sun exposure, though dietary intake is also important. The recommended intake of vitamin D varies, with recent evidence suggesting that 600–1000 IU/day is appropriate during pregnancy, with higher doses (1500–2000 IU/day) recommended for breastfeeding women. Recent meta-analyses of studies have been consistent in showing that maternal vitamin D deficiency increases the risk of pre-eclampsia, gestational diabetes, preterm birth and having a low-birth-weight or a small-for-gestational-age newborn. Vitamin A plays a role in maternal night vision and fetal ocular health, in fetal reproductive system development, synthesis of steroid hormones and embryo development, and it enhances the immune response and the body’s antioxidant capacity. Deficiency is associated with congenital malformations, fetal growth restriction and anemia. High doses of vitamin A (>10 000 IU/day) may be teratogenic and should be avoided. Calcium intake is also critical for maternal and fetal health, with a recommended intake of 1000 mg/day for all women, including during pregnancy and lactation. During pregnancy, calcium absorption increases significantly, while breastfeeding may lead to temporary maternal bone demineralization to prioritize increasing the concentration of calcium in breast milk. Calcium deficiency is associated with low bone mineral density, disorders of bone metabolism and an increased risk of preterm birth and pre-eclampsia. Zinc requirements also increase during pregnancy and lactation (11 mg/day and 12 mg/day, respectively). Zinc deficiency is common and is associated with fetal growth restriction, pre-eclampsia, GDM, miscarriage and preterm birth, and with impaired glucose metabolism in the offspring. Iodine is an important nutrient to support maternal thyroid hormones and metabolism and thyroid and has a role in embryogenesis, fetal growth and developing the infant's brain, nervous system and mental abilities. Iodine deficiency is frequent in countries without salt fortification and it is associated with maternal thyroid hormone imbalances that may increase the risk of adverse perinatal outcomes (miscarriage, hypertensive disorders of pregnancy), and impaired neuropsychological development in infants.

CONCLUSION

Women are increasingly affected by the dual burden of malnutrition, with both high rates of obesity and metabolic disorders, as well as prevalent micronutrient deficiencies and anemia. Inadequate nutrition, including low omega-3 fatty acids and micronutrient intake, raises the risk of adverse perinatal outcome and impaired infant health. Ensuring optimal nutrition before, during and after pregnancy is essential for the health of both women and infants. A thorough nutrition assessment is crucial for the early detection of deficiencies and the timely initiation of targeted interventions, including appropriate supplementation. This approach can help mitigate risks and improve long-term maternal and child health outcomes.

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