Nutrient Deficiencies After Birth: The Complete Guide to What Gets Depleted (And What to Do About It)

This article is part of the Nella Vosk Postpartum Nutrition & Recovery: Complete Guide for New Mothers — your complete resource for nourishing your body through every stage of postpartum recovery.

This article answers one specific question within that guide: which nutrients are most commonly depleted by pregnancy, birth, and breastfeeding, and what does each deficiency actually mean for how you feel and function? It is intended as the reference guide you can return to, share with your GP, and use to make sense of your blood results.

1. Iron and Ferritin

What it does: Iron is the core component of haemoglobin, the protein in red blood cells that carries oxygen from your lungs to every cell in your body. It is also stored in ferritin, the protein that holds iron in reserve. Both are essential for energy production, immune function, cognitive performance, and mood regulation.

Why it depletes: Pregnancy increases iron requirements significantly — the NHMRC recommends 27mg daily during pregnancy compared to 18mg outside it — to support foetal red blood cell development and placental growth. Birth blood loss then compounds whatever depletion occurred during pregnancy. Research suggests that up to 40 percent of Australian women enter pregnancy already iron-deficient. After a vaginal birth, and particularly after a caesarean, significant iron stores are lost with blood.

What depletion feels like: Iron deficiency produces a fatigue with a distinct physical character: breathlessness on minor exertion, heart palpitations, cold hands and feet, pallor (visible in the inner lower eyelid, which should be pink), and a heavy, leaden quality to the body that does not respond to rest. Cognitive fog and low mood are also common, because the brain’s function depends on adequate oxygen delivery.

The testing distinction: Standard postpartum blood panels check haemoglobin — the protein that carries iron in red blood cells. But haemoglobin only falls when iron deficiency is advanced. Ferritin — the stored form of iron — falls much earlier. A mother can have normal haemoglobin and significantly low ferritin, and still feel exhausted. Ask your GP specifically for a ferritin test, not just a full blood count. Many practitioners now consider ferritin below 30μg/L symptomatic; optimal for energy and wellbeing is often cited as above 50μg/L.

Australian food sources: Haem iron (most bioavailable): red meat, lamb, liver once weekly, sardines, kangaroo. Non-haem iron (plant-based, less bioavailable but meaningfully improved by vitamin C at the same meal): lentils, chickpeas, tofu, pumpkin seeds, spinach, fortified cereals. Avoid tea, coffee, and calcium-rich foods within one hour of iron-rich meals — all inhibit absorption.

2. Omega-3 Fatty Acids (Particularly DHA)

What it does: DHA (docosahexaenoic acid) is a long-chain omega-3 fatty acid that is a primary structural component of the brain and retina. It plays a central role in neurological function, mood regulation, reduction of inflammation, and the quality of breast milk — breast milk DHA content directly influences infant brain development.

Why it depletes: DHA is transferred preferentially to the foetus throughout pregnancy, with the transfer rate accelerating significantly in the third trimester as foetal brain development peaks. By the end of pregnancy, maternal DHA stores are substantially reduced. Breastfeeding continues the transfer: the DHA content of breast milk reflects maternal DHA status, and maintaining that content draws from the mother’s own supply. Many Australian women are already low in omega-3 before pregnancy due to insufficient oily fish intake in the general population.

What depletion feels like: Low DHA is associated with increased postpartum depression risk, poor concentration and cognitive function, low mood, dry skin, and fatigue. The mood effects of omega-3 depletion are well-supported in the research literature — multiple systematic reviews have found associations between low omega-3 status and postpartum mood disorders.

Testing: Omega-3 status can be assessed via an omega-3 index blood test (measuring the percentage of EPA and DHA in red blood cell membranes), but this is not routinely offered in Australian general practice. If your diet includes minimal oily fish (less than two serves per week), supplementation with a quality fish oil or algae-based omega-3 is a reasonable default rather than waiting for a test.

Australian food sources: Oily fish two to three serves per week: salmon, sardines, mackerel, trout, and canned tuna (lower DHA than oily fish but still worthwhile). Plant-based omega-3 from walnuts, linseed, and chia seeds provides ALA, which the body converts to DHA inefficiently — algae-based omega-3 supplements provide direct DHA for those who avoid fish.

3. Vitamin D

What it does: Vitamin D functions more like a hormone than a vitamin. It is required for calcium absorption and bone mineralisation, immune regulation, mitochondrial energy production, mood regulation, and thyroid function. Vitamin D receptors are found in virtually every tissue in the body, which reflects how broadly its deficiency is felt.

Why it depletes: Despite Australia’s reputation for sun exposure, vitamin D deficiency is endemic across the Australian population — particularly in southern states during the autumn and winter months, in women who cover up for skin cancer prevention, and in those whose lifestyle does not involve regular outdoor activity. Pregnancy increases vitamin D requirements and the foetus draws on maternal stores throughout. Postpartum life — characterised by indoor time, night feeds, and limited outdoor movement — offers little opportunity for solar vitamin D synthesis to replenish stores.

What depletion feels like: Vitamin D deficiency produces a generalised fatigue with a distinct musculoskeletal quality: muscle weakness, bone aches (particularly in the back, hips, and legs), low mood, and a tendency to worsen through winter months. It is easily dismissed as ordinary postpartum exhaustion, which is partly why it is so consistently missed.

Testing: Vitamin D status is assessed via a 25-OH vitamin D blood test. Ask your GP to include this in your postpartum panel. Deficiency is generally defined as below 50nmol/L in Australia; optimal is often cited as 75–150nmol/L. Vitamin D is fat-soluble, meaning that high-dose supplementation without monitoring can cause toxicity — supplementation above standard doses should be guided by blood results and GP advice.

Australian food sources: Food sources of vitamin D are limited: oily fish (salmon, sardines), eggs, and fortified foods provide small amounts. Solar synthesis — 10 to 15 minutes of direct sun exposure on arms and legs outside peak UV hours, most days of the week — is the most effective natural source when achievable. For many postpartum mothers, supplementation is the practical solution, particularly through winter.

4. Iodine

What it does: Iodine is essential for the production of thyroid hormones T3 and T4, which regulate metabolism, energy production, brain function, mood, and the development of the infant brain and nervous system during pregnancy and the early months of breastfeeding. Adequate iodine in breast milk is critical for infant neurological development.

Why it depletes: Australia has a history of mild iodine deficiency in its general population, partly because Australian soils are naturally iodine-depleted and this affects food grown in them. Mandatory iodine fortification of bread was introduced in 2009 and has improved population status, but many women remain borderline, particularly in Tasmania and parts of Victoria and New South Wales. Pregnancy increases iodine requirements significantly (220μg/day versus 150μg/day outside pregnancy), and breastfeeding increases them further to 270μg/day. The demands of growing and then feeding a baby draw on maternal iodine stores consistently throughout.

What depletion feels like: Iodine deficiency affects thyroid function, producing symptoms that overlap significantly with postpartum thyroiditis: fatigue, weight changes, cold intolerance, cognitive fog, and low mood. Subclinical iodine deficiency — insufficient for optimal thyroid function but not severe enough to produce overt goitre — can affect maternal energy and mood without being identified on standard blood panels, because TSH (thyroid stimulating hormone) may remain within the normal range until deficiency is significant.

Testing: Iodine status is most accurately assessed via a spot urinary iodine test, which is not routinely offered in Australian general practice. Thyroid function tests (TSH, T3, T4) can flag thyroid dysfunction but do not directly measure iodine stores. Given the known population-level iodine insufficiency in Australia, routine supplementation during pregnancy and breastfeeding is recommended by RANZCOG and NHMRC guidelines — most postnatal supplements include iodine for this reason.

Australian food sources: Seafood (particularly seaweed, fish, and shellfish), dairy products, and eggs are the richest Australian dietary sources. Iodised salt contributes if used, but most processed food in Australia is manufactured with non-iodised salt. Given the difficulty of meeting breastfeeding iodine requirements through food alone, a postnatal supplement providing 150–220μg of iodine daily is recommended for breastfeeding women.

5. Zinc

What it does: Zinc is involved in over 300 enzymatic reactions in the body, including immune function, wound healing, cell division, protein synthesis, and the production of thyroid hormones. It is also required for taste and smell acuity, reproductive hormone function, and the structural integrity of skin, hair, and nails.

Why it depletes: Zinc requirements increase during pregnancy (11mg/day) and breastfeeding (12mg/day in the first four months, 11mg/day thereafter). Foetal zinc demands are high throughout the second and third trimesters. Breastfeeding continues the transfer — breast milk zinc content, while lower in mature milk than colostrum, still draws on maternal stores. Many Australian women have borderline zinc status before pregnancy due to low red meat intake and the inhibitory effect of phytates (found in whole grains and legumes) on zinc absorption from plant foods.

What depletion feels like: Low zinc presents with reduced immune function (recurring minor illnesses, slow wound healing), loss of taste or smell acuity, skin changes (particularly around the eyes, nose, and mouth), and mood disturbance. Hair thinning beyond normal postpartum shedding can reflect zinc insufficiency as well as iron and thyroid issues. Because zinc is involved in so many systems, its deficiency is often diffuse and non-specific.

Testing: Serum zinc is not perfectly sensitive — the body maintains serum zinc at the expense of tissue stores for some time before blood levels fall. A normal serum zinc does not guarantee adequate zinc status. Ask your GP to include zinc in your postpartum blood panel, particularly if you have persistent immune, skin, or wound-healing concerns.

Australian food sources: Oysters are by far the richest dietary zinc source. Red meat, lamb, and chicken are practical everyday sources. Plant-based sources — pumpkin seeds, cashews, legumes, wholegrains — contain zinc but at lower bioavailability due to phytate content. Soaking and sprouting legumes and grains reduces phytate levels and improves zinc absorption.

6. Vitamin B12

What it does: Vitamin B12 is essential for the formation of red blood cells, the maintenance of the myelin sheath around nerve fibres, DNA synthesis, and the production of neurotransmitters including serotonin and dopamine. It works in close partnership with folate in one-carbon metabolism, and deficiency in either can mask deficiency in the other on standard blood tests.

Why it depletes: B12 is found almost exclusively in animal products. Women who eat minimal meat, fish, eggs, or dairy are at significant risk of B12 deficiency, particularly during and after pregnancy. B12 is also impaired in women taking long-term medications including metformin (commonly prescribed for PCOS) and proton pump inhibitors (for reflux). Breastfeeding continues to draw on maternal B12 stores, and infants of B12-deficient mothers receive inadequate B12 in breast milk, which can affect infant neurological development.

What depletion feels like: B12 deficiency produces a fatigue with neurological character: tingling or numbness in the hands and feet, cognitive slowing, difficulty concentrating, memory lapses, low mood, and in more advanced deficiency, a megaloblastic anaemia that produces similar symptoms to iron deficiency anaemia. The distinction matters because treating B12 deficiency with iron (or vice versa) does not address the underlying problem.

Testing: Serum B12 is routinely available on request. Note that standard laboratory reference ranges for B12 in Australia are often set at levels (below 148 pmol/L) where neurological symptoms may already be present. Many practitioners consider anything below 300 pmol/L to warrant attention, particularly in symptomatic women. Methylmalonic acid (MMA) and homocysteine are more sensitive markers of functional B12 deficiency but are not routinely offered.

Australian food sources: Red meat, liver, fish, eggs, dairy, and shellfish are the primary sources. Nutritional yeast and some fortified plant milks provide B12 for those eating plant-based. For women with minimal animal product intake, B12 supplementation is strongly recommended throughout pregnancy and breastfeeding rather than relying on dietary sources alone.

7. Magnesium

What it does: Magnesium is required for over 300 enzymatic processes, including energy production (ATP synthesis), protein synthesis, muscle and nerve function, blood glucose regulation, blood pressure regulation, and the production of the calming neurotransmitter GABA. It also plays a significant role in cortisol regulation — the stress hormone that is chronically elevated in the postpartum period.

Why it depletes: Magnesium requirements increase during pregnancy and breastfeeding. Chronic stress — the inevitable companion of new parenthood — depletes magnesium further, because cortisol and magnesium have an inverse relationship: elevated cortisol increases urinary magnesium excretion, and low magnesium makes the cortisol stress response harder to regulate. Sleep deprivation compounds the problem. Many Australians have borderline magnesium status as a baseline, because the mineral content of food has declined with modern agricultural practices and soil depletion.

What depletion feels like: Low magnesium presents with muscle cramps and twitching (particularly at night), poor sleep quality even when the opportunity to sleep exists, anxiety and irritability, headaches, constipation, and fatigue. The sleep-anxiety-cortisol triad of postpartum life creates a particularly efficient magnesium drain: stress depletes magnesium, low magnesium worsens stress response and sleep quality, poor sleep raises cortisol further, and the cycle continues.

Testing: Serum magnesium is a poor indicator of total body magnesium status, because the body maintains serum levels at the expense of intracellular and bone stores. A normal serum magnesium does not rule out magnesium insufficiency. Given its safety profile and wide clinical use, magnesium supplementation (particularly in the form of magnesium glycinate, which is gentle on digestion and well-absorbed) is a reasonable approach for most postpartum women experiencing sleep difficulty, anxiety, or muscle cramps without requiring a blood test to confirm.

Australian food sources: Dark leafy greens (spinach, silverbeet), pumpkin seeds, almonds, cashews, dark chocolate (70 percent cocoa or above), legumes, wholegrains, and avocado. Cooking and processing reduce the magnesium content of foods, so whole, minimally processed sources are preferable.

8. Choline

What it does: Choline is a nutrient that most people have never heard of, and yet it is one of the most critically important for both maternal and infant health. It is essential for cell membrane integrity, neurotransmitter synthesis (specifically acetylcholine, which is involved in memory and muscle function), DNA methylation, liver function, and — critically — infant brain and spinal cord development. Choline is the least-known and most consistently under-consumed nutrient in the postpartum period.

Why it depletes: Choline requirements during pregnancy are 440mg per day, rising to 550mg per day during breastfeeding — some of the highest requirements of any nutrient across the life cycle. The foetus draws on maternal choline for brain development throughout pregnancy, particularly in the third trimester. Breast milk is rich in choline, and maintaining that concentration draws heavily from maternal stores. Australian dietary surveys suggest that the majority of women do not meet choline requirements even outside pregnancy, making postpartum depletion almost certain in those who are not actively supplementing or eating choline-rich foods.

What depletion feels like: The cognitive symptoms of choline deficiency are particularly relevant postpartum: difficulty concentrating, poor memory, brain fog, and fatigue. Choline is the precursor to acetylcholine, the neurotransmitter most directly involved in attention and memory. Liver function can also be affected by sustained choline deficiency, contributing to fatigue and hormonal clearance difficulties.

Testing: Plasma choline can be tested but is not routinely available in Australian general practice. Given the near-universal inadequacy of dietary choline intake in Australian women and the high requirements during breastfeeding, dietary prioritisation and supplementation are the practical approach rather than waiting for a test.

Australian food sources: Egg yolks are by far the richest and most practical source of choline available in Australian supermarkets — one whole egg provides approximately 150mg. Liver provides the highest concentration of any food but is recommended only once weekly due to its vitamin A content. Salmon, beef, chicken, soybeans, and cruciferous vegetables (broccoli, brussels sprouts, cauliflower) also contribute. Eating two to three whole eggs daily is one of the simplest ways to meaningfully improve choline intake in the postpartum period.

This article covers the nutrients. For the full context of how depletion develops and what recovery involves as a whole-body process, the Postpartum Nutrition & Recovery: Complete Guide for New Mothers is your starting point.

Also in this cluster: the signs of postpartum depletion and what to do about them, for understanding how these deficiencies present in the real postpartum experience, and the best foods for lactation for the specific nutritional picture of supporting milk supply alongside recovery.