Sunshine in a Bottle: Why Vitamin D3 is Essential for Your Baby

By: Sabrina Granniss, IBCLC


5 min

Sometimes called “vitamin sunshine,” Vitamin D is a key nutrient for maintaining healthy bones and absorbing calcium and phosphorus. Vitamin D is a fat-soluble vitamin used by many of the body’s organs and tissues, helping to control infections and reduce inflammation in the body. As a result, it can help you and your baby recover from colds quicker and be protective in maintaining overall health. It is particularly important for infants' bone development and teeth health. Breast milk, while a complete food for your baby, may not provide sufficient vitamin D, making it necessary to supplement your baby with high-quality vitamin D3 & K2.


Vitamin D3 is absorbed by the skin or from foods we eat. However, it isn't ready to be used by the body just yet; it remains inactive until it goes through a more complex process. It is stored in fat cells and stays dormant until it is needed. 

Vitamin D has to be metabolized by the body into its hormonally active form called 25-dihydroxycholecalciferol. (8) It is first converted in the liver before entering the bloodstream. Then, it is taken up by the kidneys and converted to the hormonally active form of Vitamin D called calcitriol. This active form of Vitamin D helps the gut absorb calcium and prevents calcium loss from the kidneys.

Why do we need Vitamin D?

  • Healthy bones and skeletal development
  • Development of healthy teeth
  • Healthy cardiovascular system
  • Maintain bone density
  • Helps maintain the body’s proper phosphorus and magnesium levels
  • Reduces the risk of high blood pressure
  • Reduces the risk of insulin resistance and diabetes

Why infants need vitamin D

If a mother’s vitamin D levels are low, it can impact her baby’s vitamin D levels at birth. One study showed that 81% of women of childbearing age do not have sufficient levels of vitamin D. (9) This leaves infants at risk for vitamin D deficiency. 

Infants need Vitamin D for healthy bones and immune systems. In addition, because of its role in calcium absorption, it is necessary for helping your baby develop strong teeth and reduce the risk of tooth decay.

Is my breast milk enough? 

How much Vitamin D breast milk has depends on the mother's Vitamin D status. The amount of Vitamin D is higher in the fattier parts than in the more watery parts. (1)

Breastmilk is a complete food for your baby. It is recommended to exclusively breastfeed for the first six months of the baby's life and continue for the first year, beginning to add in foods after the first six months that are complementary to breastfeeding. After the first year, the American Academy of Pediatrics recommends that breastfeeding continue until age two or as long as mutually desired. (2) 

A study of 107 healthy Caucasian women in a nine-month follow-up study found that their exclusively breastfed infants received <20% of the daily recommended amount of Vitamin D during the first year of life. (5)

The best way to know that your baby is getting the right amount of Vitamin D is to give them a high-quality Vitamin D3 supplement. The American Academy of Pediatrics recommends that all infants be supplemented with Vitamin D3, whether they are exclusively breastfed or partially breastfed. In addition, babies should be supplemented with Vitamin D3 for the first year after birth. (10) Premature infants are not more deficient in Vitamin D than babies born at term, and the recommendation for supplementation is the same.

How much Vitamin D do we need? (7)

RDA - stands for Recommended Daily Allowance. 


  • 0-12 months - RDA is 400 IU/day unless the baby is exclusively breastfed and the mother is taking 6400 IU/day
  • 1-70 years - 600 IU/day
  • During pregnancy and lactation - 600 IU/day
  • Over 70 years - 800 IU/day

How to make sure mom & baby are getting enough Vitamin D

  1. Supplement both mom and baby with Vitamin D3 based on the recommended daily amount to maintain sufficient levels.
  2. Mom takes 6400 IU/day Vitamin D3 supplement and does not supplement her baby as long as the baby is still exclusively breastfed.

Why should Vitamin D3 & Vitamin K2 be taken together?

Although Vitamin D3 and vitamin K2 have their respective benefits, they can work together to transport calcium best when taken together. (6) Vitamin D3 is a vehicle moving calcium where it needs to be.

Vitamin D3 helps absorb calcium from your intestines into the blood. Vitamin K2 picks it up from there and gets it to your bones. 

Vitamin D2 doesn’t raise levels of the active form of Vitamin D in our bodies as well as vitamin D3. So, when choosing a vitamin D supplement, choose one that contains vitamin D3.

Legendairy Milk Baby Vitamin D3 & K2 Liquid Drops are a synergistic blend of plant-sourced Vitamin D3 and K2 MK-7 that work better together than alone. One drop delivers the recommended daily intake for your baby. The drops are unflavored, certified organic with no unwanted additives, and easy to use. Many Vitamin D3 drops for babies do not include Vitamin K2, which is essential for calcium absorption.

Foods that are high in Vitamin D

  • Fatty fish like salmon, tuna, mackerel, sardines, and trout
  • Meat, especially beef liver
  • Egg yolks
  • Shiitake, white, and portabella mushrooms that have had at least 6 hours of UV light exposure for two days (3)
  • Fortified foods, meaning foods that have had Vitamin D added, are found in dairy-free alternative milk
  • Cow’s milk doesn’t contain enough vitamin D and is fortified with 115-124 IU per 8 oz serving (4)

Ensuring your baby receives sufficient vitamin D is vital for healthy bone development, immune system function, and strong teeth. While breast milk is a complete food for your baby, it may not provide enough vitamin D, making it necessary to supplement with high-quality vitamin D3 & K2. After 6 months of age, offering your baby foods high in Vitamin D helps their overall status but is not considered enough. So, getting out in the sunshine, eating a diet of Vitamin D-rich foods, and taking a high-quality D3 + K2 vitamin supplement will ensure your baby is getting what they need.


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