Vitamin D is a key nutrient in the maintenance of bone health in children and adults. It helps regulate the amount of calcium and phosphate in the body, which are needed to keep bones, teeth and muscles healthy.
Vitamin D insufficiency/deficiency may contribute to a number of health issues such as hypertension, diabetes type I and II, some autoimmune conditions, and some cancers.i Because vitamin D is essential for promoting calcium absorption in the body, in a relatively small number of cases its deficiency can also lead to rickets in children, a condition that affects bone development, causing the bones to become soft and weak and potentially leading to bone deformities. In adults, rickets is known as osteomalacia or soft bones and it can lead to osteoporosis if left unchecked long term.ii
Breastmilk doesn’t naturally contain high levels of vitamin D as, in the past, babies would absorb most of their vitamin D from exposure to sunlight. However, changes in the way we live our lives, with less exposure to sunlight and only a few of the foods we eat containing vitamin D (such as egg yolk, beef liver, oily fish like mackerel, tuna and salmon, as well as fortified foods like some breakfast cereals, fat spreads, and non-dairy milk alternatives), might mean that mothers may not have enough vitamin D in their own bodies to pass to their babies via breastmilk. Current recommendations that babies are not exposed to strong direct sunlight have also led to a decrease in their absorption of vitamin D. When this is combined with a mother having low levels, it further reduces the amount that passes through breastmilk.iii
Guidelines for Vitamin D intake
In July 2016 Public Health England issued new guidelines on Vitamin D intake,iv based on recommendations from the Government’s Scientific Advisory Committee on Nutrition (SACN). The guidelines state that although roughly one in five people has low vitamin D levels, this is not the same as a vitamin D deficiency, and most people are being asked to consider taking supplements. Specifically, PHE suggests that adults and children over the age of one consider taking a daily supplement containing 10 microgramsv (400 IU) of vitamin D, particularly during autumn and winter when the sun is not strong enough.
Although some people choose not to take a supplement during the summer months when they are exposed to adequate sunshine, people who have a higher risk of vitamin D deficiency, as well as pregnant and breastfeeding women, are being advised to take a supplement all year round. According to SACN’s review, at-risk groups include people whose skin gets little or no exposure to the sun, such as people who are not often outdoors or who cover their skin when they are outside. People with dark skin, from African, African-Caribbean and South Asian backgrounds, may also not get enough vitamin D from sunlight in the summer and may also want to consider taking a supplement all year round.
Can I get enough Vitamin D from sunlight?
Our bodies are designed to make very large amounts of vitamin D through exposure to the sun (10,000-20,000 IU in 24 hours, after 15-20 minutes of summer-sun exposure in a bathing suit or 45-60 minutes of exposure for people with darker skin tones). However, the desire to avoid overexposure and sunburn has eclipsed the ability of both children and adults to absorb adequate amounts of sunlight to keep normal levels of vitamin D.vi
The NHS website says, “Most people can make enough vitamin D from being out in the sun daily for short periods with their forearms, hands or lower legs uncovered and without sunscreen from late March or early April to the end of September, especially from 11am to 3pm.
A short period of time in the sun means just a few minutes – about 10 to 15 minutes is enough for most lighter-skinned people – and is less than the time it takes you to start going red or burn. Exposing yourself for longer is unlikely to provide any additional benefits.
People with dark skin, such as those of African, African-Caribbean or south Asian origin, will need to spend longer in the sun to produce the same amount of vitamin D as someone with lighter skin”.vii
However, SACN didn’t make any specific recommendations about how much sunlight people would need to get enough vitamin D, because there are a number of factors that can affect how much vitamin D is produced in the skin. For example, those living in northern climates don’t have as much chance to absorb vitamin D. Therefore, the recommendations assume “minimal sunshine exposure”.
The NHS website goes on to say that it’s important not to burn in the sun and that young babies should not be exposed to strong direct sunlight. Sitting indoors by a sunny window doesn’t aid vitamin D production, as the ultraviolet B (UVB) rays can’t get through glass. Neither are sunbeds a recommended way of making vitamin D.
Does my baby need Vitamin D supplements?
The Department of Health currently recommends that all babies from birth to one year of age (including breastfed babies and formula-fed babies who have less than 500ml a day of infant formula, already fortified with vitamin D) and all children aged one to four years are given a supplement, whether or not you are taking a supplement yourself.
Babies up to the age of one year need 8.5 to 10 micrograms (340-400 IU) of vitamin D a day. Children from the age of one year need 10 micrograms (400 IU) of vitamin D a day.
The Academy of Breastfeeding Medicine (ABM), a global organisation of medical doctors dedicated to the promotion of breastfeeding, recommends that “The breastfeeding infant should receive vitamin D supplementation for a year, beginning shortly after birth in doses of 10–20 mcg/day (400–800 IU/day). This supplement should be cholecalciferol, vitamin D3, because of superior absorption unless a vegetable source such as ergocaliferol vitamin D2, is desired4…”viii
Knowing that human milk is designed specifically for your baby, and is the most complete food both nutritionally and immunologically, it may seem confusing to be told a breastfed baby needs vitamin D supplements. If you choose to supplement your baby and are uncomfortable with supplementation of vitamins other than D (since your milk alone provides optimal amounts of those other nutrients), ask your doctor to recommend a vitamin D-only preparation for your baby.
Can I take Vitamin D instead of giving to my baby?
The ABM states that “Vitamin D also may be delivered adequately through human milk.” ix Some mothers find it preferable to take the supplement themselves rather than trying to give it directly to the baby,x also because supplementing the baby does not address any potential deficiency in the mother, which may compromise her long-term health.
According to La Leche League International, breastfeeding mothers who have adequate amounts of vitamin D in their bodies can successfully provide enough vitamin D for their nursing children through breastmilk. However, as lifestyle changes have led to some women not having enough vitamin D, LLLI recommends that pregnant and nursing mothers obtain adequate vitamin D, or supplement as necessary.
Research shows that high dose maternal vitamin D supplementation (4000-6400 IU/day or a single monthly dosage of 150,000 IU) can enrich breastmilk adequately for infants.xi One study suggested that maternal supplementation alone may improve vitamin D intake of the nursing infant in an environment where infant supplementation rate is low.xii As the currently recommended safe upper limit for vitamin D intake is 4000 IU/day, it is very important to check with your doctor and have your own vitamin D status assessed by a blood test before you begin supplementing at levels higher than the current RDI of 400 IU/ day.
Debates continue over what an optimal level of vitamin D is for an adult, and research has indicated that pregnant and lactating women might need more vitamin D than adults who are not bearing children.xiii If you are not sure whether you need a supplement, you can have a simple blood test before making a choice to supplement. Vitamin D insufficiency is represented by a blood level of less than 32 ng/mL. Those with blood levels below 20 ng/mL are considered deficient in vitamin D.xiv
You may also opt to have your baby’s vitamin D level assessed with a blood test measuring 25-hydroxy vitamin D (25 OH-D). Your baby’s doctor can help you determine whether vitamin D supplements are, indeed, warranted.
Study supports maternal Vitamin D Supplementation
A 2015 study by Professor Bruce Hollis, PhD, of the Medical University of South Carolina, found that “maternal vitamin D supplementation with 6400 IU/day safely supplies breast milk with adequate vitamin D to satisfy her nursing infant’s requirement and offers an alternate strategy to direct infant supplementation”.xv
When asked by La Leche League GB if mothers should continue to take supplements once their babies were over six months old, Professor Hollis replied “The mother should continue to take the vitamin D as long as she is lactating.” He added this was because of the lack of Vitamin D in most foods.xvi
If a baby is born with a deficiency in Vitamin D, due to the mother’s own low levels, this may not be reversed by the mother taking supplements.xvii
Too much or too little?
While there is no risk of your body making too much vitamin D from sun exposure (although the usual precautions should be taken to cover or protect skin before it turns red or starts to burn), you could get too much vitamin D through supplements. The NHS says that taking too many vitamin D supplements over a long period of time can cause too much calcium to build up in the body (hypercalcaemia). This can weaken the bones and damage the kidneys and the heart.
If you choose to take vitamin D supplements, 10 micrograms (400 IU) a day is likely to be enough for most people, including pregnant and breastfeeding women, the elderly, and children aged 11 to 17 years. Children aged one to ten years should not have more than 50 micrograms (2,000 IU) a day. Infants under 12 months should not have more than 25 micrograms (1,000 IU) a day. Some people have medical conditions that mean they may not be able to safely take as much. If in doubt, you should consult a health professional to get up-to-date information on recommended doses. A medical professional will also be able to help you assess whether taking more than 100 micrograms (4,000 IU) of Vitamin D a day to provide enough for your baby through breastmilk may be harmful in your specific circumstances.
Breastfeeding continues to be of significance
Breastmilk remains the optimal choice for infant nutrition, and its unique structure and functions cannot by replicated by infant formula. Your milk continually adapts throughout the day and over time to suit your baby’s needs. Human milk remains the best source of nutrition during the first year, with the appropriate introduction of complementary foods from around the age of six months, which can include foods rich in vitamin D.
Your milk becomes a supplement to solids during your baby’s second year, but keeps significant nutritional value, as well as emotional benefits. There is evidence that the longer a baby is breastfed, the greater the protection from ill health and the more positive impact on their long-term health (UNICEF 2012).xviii
Low levels of Vitamin D may cause problems, not breastfeeding
Some research published in the American Journal of Public Health in 2016 implied that a lack of vitamin D in breastmilk may contribute to the development of rickets.xix While reports occasionally give the impression that breastfeeding is causing problems, the real issue is that in today’s world women may not have enough Vitamin D themselves to pass to their babies through breastmilk.
The answer is to address any possible deficiencies in that area so that babies will receive the Vitamin D they need, whether this is via Vitamin D supplements and/or regular, small amounts of exposure to sunlight, as well as through their diet once they’re old enough to have complementary foods.
Alterations to our normal routine may mean that at present people may be spending more time indoors and not getting enough vitamin D. The Department of Health says people might want to consider taking 10 micrograms (400 IU) of vitamin D a day to keep their bones and muscles healthy.
Compiled by Anna Burbidge for La Leche League GB, January 2021
Oberhelman SS, Meekins ME, Fischer PR, et al. Maternal vitamin D supplementation to improve the vitamin D status of breast-fed infants: a randomized controlled trial. Mayo Clin Proc. 2013; 88(12): 1378-1387.
Wagner, C.L., Taylor, S.N., and Hollis, B.W. New Insights Into Vitamin D During Pregnancy, Lactation, & Early Infancy. Amarillo, TX: Hale Publishing, 2010