Last update May 22, 2019
Very Low Risk
Vitamin D (vit. D) metabolite.
The two main forms of vit. D are vitamin D3 or cholecalciferol and vitamin D2 or ergocalciferol (SACN 2016).
Vit. D can be obtained from diet but the main source of vit. D, when there is suitable exposure to the sun, is the one formed in the dermis:
1. in the skin, via 7-dehydrocholesterol, due to the effect of ultraviolet rays (from the sun or artificial ones) vit. D3 or cholecalciferol is produced.
2. in the liver it is hydroxylated to calcifediol, also called calcidiol or 25-hydroxyvitamin D (25OHD).
3. in the kidneys it becomes hydroxyl forming calcitriol which is the natural active form and the most potent form of Vit. D in animals (SACN 2016).
Calcitriol and other vitamin D metabolites are used in the treatment and prevention of Vit. D deficiency and hypocalcemia due to hypo- or hyperparathyroid disorders. The need for Vit. D and calcium to treat hypoparathyroidism is very low during breastfeeding; it is necessary to reduce them to avoid causing hypercalcemia in mother and infant (Sweeney 2010, Caplan 1993 and 1990, Greer 1984).
An excess of vit D administration can cause toxic symptoms: hypercalcemia, hyperphosphatemia, ectopic calcifications, cardiovascular damage, fatigue, headaches, nausea and vomiting.
Vitamin D deficit causes rickets and osteomalacia.
Normal plasma levels of 25OHD are 25 to 250 nanomoles (nmol)/L (10 to 100 mcg/L) (SACN 2016). Many authors consider optimal values > 50 nmol (20 mcg)/L.
Obesity is associated with lower plasma levels in the mother and exclusively breastfed infants (Sen 2017).
A breastfeeding mother and infant’s daily Vit. D needs are 400 international units (IU) per day respectively (Sauberan 2019). Theoretically, the mother should be able to get them from her diet, the infant from being exclusively breastfed and both from exposure to sun, but this is not always the case, so it is recommended to administer 400 IU of Vit. D daily to mother and baby (SACN2016, Wagner 2008).
With limited exposure to the sun, maternal supplementation with 400 IU of Vit. D per day was not sufficient to maintain plasma levels> 20 mcg (50 nmol)/L of 25OHD neither in mothers nor infants; maternal supplementation with 1,200 IU per day did assure maternal levels of 25 OHD, but not those of infants (Czech 2014).
Therefore, some experts believe that the daily needs of Vit. D can be much higher in pregnant and breastfeeding mothers, from 2,000 to 6,400 IU per day (Hollis 2007 and 2004, Wagner 2006).
It is excreted in breast milk in tiny amounts (OPKO 2016, Fontus 2008).
Vit. D is a natural component of breast milk where it is found primarily as cholecalciferol, but also as ergocalciferol and its respective 25-hydroxylated metabolites.
The milk from the end of a feed has up to twice as much concentration of Vit. D than at the start (see Streym 2016).
The pasteurization of breast milk decreases the levels of all vitamin D metabolites by 10% to 20% (Gomes 2016).
Depending on exposure to sun, diet and supplementation, the average vitamin D content in breast milk is very variable. Without maternal supplementation it is usually <20 IU/L.
Mothers supplemented with 400 to 2,000 IU of Vit. D daily have a milk concentration of 50 to 80 IU/L (Sauberan 2019, við Streym 2016, Wagner 2006, Hollis 2004). With 4,000 IU per day, the milk levels were 130 IU/L, which is a dose of 20 IU/Kg for the baby (Hollis 2004), well below the recommended daily dose.
In Denmark the concentration of Vit. D in breast milk contributed <20% of the recommended daily dose for the infant (see Streym 2016).
Daily maternal supplementation of 6,400 IU of Vit. D achieved levels in milk between 374 and 874 IU/L, which supposed a dose of 56 to 131 UI/kg to the infant, enough to ensure the recommended daily dose (Wagner 2006).
Several guidelines for supplementation have been proposed with Vit. D3 to breastfeeding mothers during the first months and even from the last trimester of pregnancy as an alternative to direct supplementation from the infant to maintain normal Vit. D levels in infants:
- 2,000 to 6,400 IU per day (Hollis 2015, March 2015, Oberhelman 2013),
- 60,000 IU per day for 10 days in postpartum (Naik 2017),
- 100,000 to 150,000 IU per month (Wheeler 2016, Chandy 2016, Oberhelman 2013).
No clinical or biochemical abnormalities have been observed in infants whose mothers took between 400 and 6,400 IU of Vit. D per day (Hollis 2015, Czech 2014).
American Academy of Pediatrics: Vitamin D is usually compatible with breastfeeding. With high pharmacological doses, maternal and infant calcifications should be monitored (AAP 2001).
Note: divide the IU number by 40 to get the mcg.
- 40 IU = 1 mcg of Vit. D; 40,000 IU = 1 mg of Vit. D
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