Vitamin D in Pregnancy & Breastfeeding: Why Almost Everyone Is Low
If there were a prize for the nutrient that flies under the radar while affecting almost everyone, vitamin D would be a strong contender.
Most people have heard of it. Most people vaguely associate it with sunshine. Many people assume they're probably getting enough. And yet vitamin D deficiency is remarkably common, particularly here in the UK where sunshine can feel more like a pleasant surprise than a reliable source of nutrition.
During pregnancy and breastfeeding, vitamin D becomes even more important. Your body is building a baby, supporting rapid growth and development, maintaining your own nutrient stores, and potentially producing breastmilk around the clock. That's a lot to ask of one nutrient. The challenge is that many women can be deficient without realising it because the symptoms are often subtle, easy to dismiss, or mistaken for the general exhaustion that comes with modern life, pregnancy, and early motherhood.
Let's talk about why vitamin D matters, why so many of us are running low, and what you can do about it.
Why Vitamin D Deficiency Is So Common
Unlike most nutrients, vitamin D is a bit unusual. While we can get small amounts from food, our bodies are actually designed to make most of it through exposure to sunlight. Historically, this worked pretty well. Humans spent far more time outdoors than we do now, and daily life naturally involved enough sun exposure to support healthy vitamin D levels.
Modern life looks rather different.
Many of us simply aren't getting enough sunlight to maintain optimal vitamin D levels, particularly in northern countries like the UK. Factors such as skin pigmentation, time spent indoors, clothing coverage, and the strength of the sun all influence how much vitamin D we produce. The result is that deficiency has become surprisingly common, even among people who eat well and take good care of their health.
Pregnant and breastfeeding women are particularly vulnerable because their needs increase during a time when many are already stretched physically and nutritionally.
Why Vitamin D Matters During Pregnancy
Vitamin D is often talked about in the context of bone health, and that's certainly part of the story. One of its most important jobs is helping the body absorb and utilise calcium. Without adequate vitamin D, even a calcium-rich diet becomes less effective because the body struggles to properly absorb and use that calcium where it's needed.
During pregnancy, this becomes especially important. Your baby's skeleton is developing rapidly, which means calcium demands increase significantly. Vitamin D helps support this process while also protecting your own stores. It's one of the reasons healthcare practitioners pay close attention to both nutrients during pregnancy.
But vitamin D's role extends far beyond bones.
Researchers have identified vitamin D receptors throughout the body, suggesting that it influences many different systems. It plays a role in immune function, cell growth, gene expression, and healthy fetal development. While scientists are still uncovering the full extent of its impact, it's clear that vitamin D is involved in far more than simply building strong bones.
Your baby also depends on your vitamin D status during pregnancy. Vitamin D crosses the placenta, meaning your baby draws from your stores to build their own reserves before birth. I often think of pregnancy as a time when you're effectively filling two nutrient bank accounts at once. Your body is trying to meet your needs while simultaneously supporting the growth and development of an entirely new human being. When nutrient stores are already running low, that balancing act becomes much more challenging.
The Surprising Truth About Breastmilk and Vitamin D
One of the most surprising things about vitamin D is that breastmilk is naturally quite low in it
At first glance, this can feel contradictory. Breastmilk is often described as the perfect food for babies, and rightly so. It contains antibodies, enzymes, living cells, hormones, and nutrients that adapt to a baby's needs in remarkable ways.
The reality is that vitamin D is one of the few exceptions. Breastmilk was never intended to be a baby's sole source of vitamin D, which is why supplementation is commonly recommended for breastfed babies today. This isn't because breastmilk is inadequate. It's simply because vitamin D can be difficult to obtain through breastmilk alone.
Should Breastfed Babies Take Vitamin D?
Current UK guidance recommends that breastfed babies receive a daily vitamin D supplement from birth. This recommendation exists because vitamin D plays a crucial role in healthy bone development and growth, and deficiency during infancy can increase the risk of conditions such as rickets.
For many parents, this advice can initially feel confusing. If breastmilk is designed for babies, why would we need to supplement anything? The answer is that vitamin D is one of the few nutrients that can be difficult for babies to obtain through breastmilk alone.
Formula-fed babies are slightly different because infant formula is fortified with vitamin D. In the UK, babies who are regularly drinking around 500ml or more of formula per day generally do not require additional vitamin D supplementation, although individual circumstances may vary.
Why Breastfeeding Mothers Need Vitamin D Too
One aspect of vitamin D that often gets overlooked is that the postpartum period remains a nutritionally demanding time.
There's a tendency to focus heavily on nutrition during pregnancy and then assume the job is done once the baby arrives. In reality, breastfeeding places significant demands on the body. You're still recovering from pregnancy and birth, you're adapting to disrupted sleep, and you're producing breastmilk, often while caring for a newborn around the clock.
Vitamin D requirements remain elevated during breastfeeding. Yet many women stop thinking about supplementation after birth, particularly if they stop taking their prenatal vitamin.
This can create a situation where a mother enters the postpartum period with low vitamin D stores and gradually depletes them further over time. It's one of the reasons postpartum nutrition deserves far more attention than it typically receives.
Signs You Might Be Low in Vitamin D
One of the frustrating things about vitamin D deficiency is that it can be surprisingly difficult to identify.
The symptoms are often vague and nonspecific. Fatigue, low mood, muscle aches, getting sick more frequently, feeling generally run down—none of these automatically point to vitamin D. In fact, they sound remarkably similar to how many parents describe life with a baby or young children.
It's easy to see how deficiency can go unnoticed.
A pregnant woman who feels tired may assume it's simply pregnancy. A new mum who feels exhausted may attribute it to night feeds and broken sleep. Someone experiencing low mood may blame stress, work, or the endless juggle of family life.
Of course, all of those things can absolutely contribute. Vitamin D isn't the answer to every symptom. But because deficiency is so common, it's worth considering whether it could be part of the picture.
The only way to know your vitamin D status for certain is through testing. If you're concerned about your levels, speak with your healthcare provider about whether testing may be appropriate.
Can You Get Enough From Food?
This is where things get a little tricky.
There are foods that contain vitamin D, but there aren't very many of them, and most contain relatively modest amounts compared with what our bodies can produce from adequate sun exposure.
Some of the richest dietary sources include oily fish such as salmon, sardines, mackerel, and herring, along with egg yolks and certain fortified foods. If you're vegetarian, vegan, or simply not eating these foods regularly, your intake may be even lower.
Even for people who do eat these foods, relying on diet alone can be challenging. You'd need to consume them consistently and in fairly significant quantities to meet your needs.
This is one of the reasons vitamin D is different from nutrients like vitamin C or folate, which can be obtained from a wide range of foods. For most people, food can certainly contribute, but it's rarely the whole solution.
Vitamin D3, K2 and Supplement Choices
If you decide to supplement, you’ll quickly discover that there are multiple forms of vitamin D available.
The NHS currently recommends that pregnant and breastfeeding women take a daily supplement containing 10 micrograms (400 IU) of vitamin D throughout pregnancy and breastfeeding. Because vitamin D deficiency is so common in the UK, this recommendation applies regardless of how healthy your diet is.
It’s also worth remembering that the NHS recommendation is a broad public health guideline, not a personalised nutrition plan. The amount needed to maintain healthy vitamin D levels can vary significantly from person to person, which is one reason some healthcare practitioners recommend testing vitamin D levels and tailoring supplementation accordingly.
Vitamin D3, also known as cholecalciferol, is generally considered the preferred form because it appears to be more effective at raising and maintaining vitamin D levels than vitamin D2. This is the form you’ll find in many high-quality prenatal and postnatal supplements.
You may also come across discussions about vitamin K2. These two nutrients are often talked about together because they both play important roles in calcium metabolism. Vitamin D helps the body absorb calcium, while vitamin K2 helps direct calcium towards bones and teeth rather than allowing it to accumulate in soft tissues.
For that reason, many practitioners prefer vitamin D and K2 to be taken together, particularly when supplementation is being used long term.
It's also worth checking your prenatal or postnatal supplement rather than assuming you're covered. Vitamin D amounts vary considerably between products, and many women are surprised to discover that their supplement contains less than they expected.
The Bottom Line
The thing about vitamin D is that it's one of those nutrients that rarely gets the same attention as folate, iron, or omega-3s, yet it quietly influences so many aspects of health. It supports calcium absorption, bone health, immune function, pregnancy, postpartum recovery, and your baby's developing body.
The challenge is that you can be doing almost everything "right" and still come up short. You can eat a nutrient-dense diet, spend time outdoors when the weather allows, and take a good-quality prenatal, yet still find yourself with lower-than-optimal levels. That's largely because vitamin D was never designed to come primarily from food. It was designed to come from sunlight, and modern life simply doesn't provide the same opportunities for sun exposure that human bodies evolved to expect.
If you're pregnant, breastfeeding, or planning a pregnancy, vitamin D is one of the most worthwhile nutrients to pay attention to. Simply because understanding your nutrient needs is one small way of supporting a body that is already doing something extraordinary.
And if you've recently discovered you're low? You're in very good company. In fact, you're probably in the majority.
The reality is that most women aren’t walking around with a spreadsheet tracking their vitamin D levels, calcium intake, or nutrient stores. They’re growing babies, feeding babies, recovering from birth, navigating sleepless nights, and trying to remember where they left their coffee.
That’s exactly why nutrition doesn’t need to be perfect to matter. Sometimes it’s simply about paying a little more attention to the things that support you behind the scenes.
At Milk it, that’s what we care about most. Supporting mums through pregnancy, breastfeeding, and postpartum with practical nourishment that fits into real life. Not another thing to add to your to-do list. Just thoughtful ingredients, comforting flavours, and a small reminder that your body deserves looking after too.
Our cookies are made with ingredients traditionally used to support breastfeeding, including oats, flaxseed, brewer’s yeast, and fenugreek, alongside the things that make a cookie worth eating in the first place: proper butter, chocolate, nuts, spices, and generous chunks of flavour.
Because feeding a baby is important. But so is feeding the person doing the feeding.
Written by Mel Brittner: doula and postpartum nutrition consultant
