Vitamin D is not really a vitamin, it is a hormone produced by the body when skin is exposed to sunlight. A small amount of vitamin D comes from our food—sources include oily fish, cod liver oil, egg yolk, red meat, liver, and some artificially fortified foods—but the main source is from sunshine. This article looks at why we need vitamin D, why some people are deficient in vitamin D and how this might affect breast milk, and shares current recommendations for supplements for mother and baby.
Why do we need vitamin D?
Vitamin D is essential for healthy bones, teeth and muscles and is also said to protect against autoimmune disorders, cardiovascular disease, dementia and some cancers, it is important for mental health, supporting our immune systems and general well-being.12 Deficiency can lead to rickets, or osteomalacia (softening of the bones), and is linked to diabetes, seizures and tooth decay.3 4 5 Other symptoms of deficiency cited include frequent illness, feeling tired all the time, aches and pains in bones or muscles, impaired wound healing, depression and anxiety.6
Why are some people deficient in vitamin D?
Our bodies make vitamin D when our skin is exposed to sunlight but because of changing lifestyles in some countries—such as limiting our time outdoors in the sun, or using a lot of sun protection—many of us are at risk of vitamin D deficiency. In the absence of enough sunlight, it’s difficult to get enough vitamin D from diet alone because not many foods contain it. Those of us who are particularly at risk of low vitamin D levels include:
- People who have little exposure to the sun or who cover their skin all the time with clothing or sun screen. Babies and toddlers often fall into this category due to concerns about sunburn from direct sun exposure on their skin.
- People who live further north from the equator where day light hours are reduced for example in the UK between October and March7
- People with darker skin—more sun is needed to make the same vitamin D compared with that of a fair skinned person8
- People who have difficulty digesting fat in their diet (Nair and Maseeh, 2012)
- People who are overweight with a body mass index (BMI) above 30.9
Vitamin D and breast milk
If a woman has sufficient vitamin D levels before and during pregnancy, her baby will be born with good vitamin D stores. After birth, these stores, combined with regular sunlight on the baby’s skin and the small amount of vitamin D in breast milk would historically provide enough of this vitamin for the breastfed baby. In recent years however, there has been a growing realisation that many women (and men) are deficient in vitamin D which can reduce both the baby’s body stores (via pregnancy) and the levels available in breast milk.
Vitamin D levels in pregnancy
If a mother has low vitamin D levels throughout her pregnancy, her baby will also be born with low stores of this vitamin and could be at risk of deficiency. Correcting low levels during pregnancy will ensure babies are born with good stores. The UK’s National Health Service recommends supplementing vitamin D in pregnancy between September and March and suggest 10 micrograms (400 IU) daily or no more than 100 micrograms (4,000 IU) daily.10 This ten fold difference between 400 IU and 4,000 IU is explained by the Vitamin D Council as follows:
How much vitamin D you need when you’re pregnant is a complicated subject and one which doctors and scientists have yet to agree on. Not all organizations recommend the same amount of supplement each day.
Vitamin D levels during lactation
Breast milk has relatively low levels of vitamin D and if the mother is deficient herself, her breast milk will have even lower levels. Where babies are not getting vitamin D stores at birth, or any sun exposure on their skin for fear of sunburn, insufficient levels in breast milk can increase the risk of deficiency. Ideas to raise vitamin D levels in breast milk via supplements, sunshine exposure and diet are discussed below.
Raising vitamin D levels in breast milk
Research suggests that when a breastfeeding mother has high enough doses of a vitamin D dietary supplement, her breast milk will have significantly higher levels.1112 However health advice varies widely regarding the recommended levels of vitamin D to take as a supplement during lactation to achieve this. Balasubramanian (2011) says:
there is no consensus on the dosage of vitamin D that needs to be supplemented to pregnant women nor is there robust scientific evidence to support implementation of a vitamin D supplementation programme for pregnant and lactating mothers.
What des research say?
Research suggests that the amount of supplement required to maintain adequate levels of vitamin D in breast milk is much higher than the recommended intakes often suggested to maintain a mother’s own levels (Vitamin D Council, 2019).
Studies in 2012 and 2013 advocated for maternal supplements of 4000 and 5000 IU/day1314, while one study in 2015 and one in 2019 both cited maternal supplements of around 6,000 IU/day to sufficiently enrich breast milk.1516 These same levels are mirrored in the current recommendation from the Academy of Breastfeeding Medicine (Protocol #29) (6,400 IU daily) 17 and the Vitamin D Council (6000 IU/day)18
Some older papers caution that the safety of high-dose vitamin D supplementation in lactating women has not been proven1920, and some health organisations prefer to recommend babies be given vitamin D supplements directly.
In 2020 Tan et al reviewed 19 studies looking at the effect of vitamin D supplementation of mother and/or baby on the bone density and growth of healthy breastfed babies and found the quality of evidence around supplementation to be low or very low in all outcomes.21 They state:
There is currently insufficient evidence to recommend routine supplementation of vitamin D for breastfeeding mothers or their infants in populations at lower risk of vitamin D deficiency. In populations at high risk of vitamin D deficiency, vitamin D 400 IU per day given to the infant, or higher doses given to the breastfeeding mother, may prevent vitamin D deficiency, although effects on bone health are unclear.
How much sunlight is needed for an adult to make sufficient vitamin D?
Amounts of sunshine needed to ensure healthy levels of vitamin D vary due to many factors such as the amount of skin exposed, skin tone and climate. In certain latitudes there is very little sunshine for much of the year and skin tones with darker pigmentation need more exposure to reach sufficient levels. The UK based Breastfeeding Network (a breastfeeding charity) suggests:
Sunlight exposure needed is 2 hours per day (if only the face exposed), 20-30 minutes a day if the face, arms and neck are exposed without sunscreen. Sun protection factor in excess of 8 prevents absorption of the UVB sufficient to make vitamin D. Need increases for those with darker skins. In all cases it is important to avoid sunburn, particularly in babies.
Heaney compares higher supplement amounts to sun exposure:
…while 5,000–6,000 IU may initially seem high, it is important to remember how much the sun produces for us. A single 15 minute whole body exposure to sun at mid-day in summer produces well over 10,000 IU.
Optimising vitamin D
Although not specific to breastfeeding mothers, author and dentist Dr Steven Lin discusses tips to optimise levels of vitamin D production in his article Vitamin D Through Sun: 9 Tips to Optimize Your Levels.
Babies and sunlight
Too much direct sunlight could burn a baby’s sensitive skin so it is important to cover or protect a baby’s skin before it goes red or burns.22￼ UK’s NHS recommends keeping babies under six months out of direct sunlight.23
Foods that contain vitamin D include cod liver oil, oily fish, fortified dairy products, some mushrooms and eggs 24
Vitamin drops for baby?
As with maternal supplementation, the recommendations for supplementing babies with vitamin D vary between authors. Many health recommendations currently advocate giving oral vitamin D drops to breastfed babies to ensure they are receiving enough of this vitamin. However, others such as Robert Heaney MD25 favour giving sufficient supplements to the breastfeeding mother so that mother and baby both have enough vitamin D in preference to giving vitamin drops to the baby.
The Breastfeeding Network (BFN) states that low vitamin D levels in a baby can’t be reversed by breast milk alone even if the mother starts to replenish her own deficient vitamin D status and recommend giving vitamin D drops direct to baby.26 However this may depend on the dose of maternal supplementation since Dawodu et al found that maternal supplements of 6000 IU/day optimised vitamin D status for both mother and baby:
Maternal 6000 IU/day vitamin D3 supplementation alone safely optimizes maternal vitamin D status, improves milk vitamin D to maintain adequate infant serum 25(OH)D.
Recommendations for vitamin D and breastfeeding
Guidance from the United Kingdom
The Scientific Advisory Committee on Nutrition (SACN) produced a report in July 2016 upon which Public Health England (PHE) base their recommendations. They recommend 340 to 400 IU per day for all breastfed babies from birth to one year of age unless they have more than 500ml of fortified formula per day (formula is fortified with vitamin D) and 400 IU per day for a breastfeeding mother:
SACN is now recommending:
- a reference nutrient intake (RNI) of 10 micrograms [400 IU] of vitamin D per day, throughout the year, for everyone in the general population aged 4 years and older
- an RNI of 10 micrograms [400 IU] of vitamin D per day for pregnant and lactating women and population groups at increased risk of vitamin D deficiency
- a ‘safe intake’ of 8.5 to 10 micrograms [340-400 IU] per day for all infants from birth to 1 year of age
- a ‘safe intake’ of 10 micrograms [400 IU] per day for children aged 1 to 4 years.
Guidance from USA
The Academy of Breastfeeding Medicine recommends supplementing the breastfed baby or, if contraindicated, supplementing the mother 160 μg/day (6,400 IU/day)
The breastfeeding infant should receive vitamin D supplementation shortly after birth in doses of 10–20 μg/day (400–800 IU/day) (LOE IB). This supplement should be cholecalciferol, vitamin D3, because of superior absorption unless a vegetable source such as ergocaliferol vitamin D2, is desired (LOE IIA). Randomized trials demonstrate that safe vitamin D supplementation may be provided to a nursing mother to achieve healthy vitamin D status in her breastfeeding infant, when there is objection or contraindication to direct infant supplementation. A maternal dose of 160 μg/day (6,400 IU/day) is suggested.
The Vitamin D Council recommends supplementing the breastfeeding mother. They discuss their recommendations for pregnant and breastfeeding mothers and those of The Food and Nutrition Board and The Endocrine Society in their article Vitamin D During Pregnancy and Breastfeeding. The article discusses how to take sunshine exposure into account when deciding on supplementation for the nursing mother. The Vitamin D Council recommends that if a mother is taking 6,000 IU per day as a supplement, her breast milk will have sufficient levels and she won’t need to supplement her baby. If she is not taking a supplement, or not getting good sun exposure or taking less than 5000 IU per day she should give her baby a vitamin D supplement.
if you take a supplement of 6,000 IU of vitamin D each day you shouldn’t need to give your baby any vitamin D supplement. Your breast milk has enough vitamin D for your baby.
if you aren’t taking a supplement or getting a good amount of sun exposure, or if you’re taking less than 5,000 IU/day of vitamin D, you should give your baby a vitamin D supplement.
The American Academy of Pediatrics (AAP) recommends that all breastfed babies receive 400 IU of oral vitamin D drops until age one year, with 600 IU (15 mcg) per day for children over one year.27 and that nursing women should take at least 600 IU of vitamin D daily noting that many sources state 1500–2000 IU daily28
Vitamin D and the newborn’s gut
Vitamin D drops are widely recommended for babies (see above). How oral doses of vitamin drops in the early weeks of life could affect a newborn baby’s gut is not clear but Talsness et al discuss how vitamin D can affect the baby’s microbiome (balance of microorganisms living in the digestive system)29. A study by Hyppönen et al suggested babies supplemented with vitamin D during their first year of life had more allergies at age 31 years.30 while Katikaneni et al found babies who had vitamin D supplements had an increased risk of urinary tract infections 31.
In addition some brands of vitamin D drops may contain multiple ingredients. Wellbaby vit D drops contain olive oil and vitamin D3 (cholecalciferol)32 while Heathy Start vitamin D drops contain vitamin A, C and D, water, glycerol, polysorbate 80, banana flavour, alpha-tocopherol (a type of vitamin E), and medium chain triglycerides.33
Summary—more research needed
Many people are deficient in vitamin D due to a general lack of sunlight in modern lifestyles. If a breastfeeding mother’s vitamin D levels are low, the levels in her breast milk will also be low. Many health organisations recommend giving vitamin D supplements to both mothers and babies as a safety measure. Some studies have indicated that providing breastfeeding mothers with specific higher doses of vitamin D ensures breast milk has sufficient levels. However, some authors believe more research is needed to evaluate the long-term effects of giving high doses of supplement to the lactating mother. It is often recommended to give vitamin D drops by mouth direct to baby.
The need for vitamin D supplementation varies across the globe according to climate and lifestyle. The recommendations above may change as more research is revealed. Discuss the latest recommendations advised in your part of the world with your own health professionals to find the right advice for you and your baby.