Vitamin D for Babies and Children: Why, Until When, Signs of Deficiency

The paediatrician wrote "vitamin D" on the maternity discharge prescription, and your grandmother is surprised: "With the sun we have in Morocco?" It is a fair question. Yet the answer is clear: babies often lack vitamin D, even at our latitudes, and a supplement is the rule in most countries.

You still need to know why, until when, and how to avoid the opposite mistake: giving too much. Here is what to remember, without any dose, since it is for the doctor to set it for your child.

What is vitamin D for?

It allows the body to absorb the calcium and phosphorus from food, then fix them in the bones. Without it, a child's skeleton mineralises poorly during growth. The Canadian Paediatric Society reminds us that a prolonged lack can cause rickets, a disease that deforms growing bones.

It also plays a role in the strength of teeth and in muscle function. In adults, a lack of it causes osteomalacia, softening of the bones.

Why a supplement, even in Morocco's sunshine?

Because the two natural sources of vitamin D are insufficient in a young child.

Food first. Breast milk contains very little, explains the Canadian Paediatric Society, even when the mother eats well. The foods that provide it are rare: oily fish such as sardines or tuna, egg yolk. A baby does not eat enough of them to cover their needs.

Then the sun. The skin makes vitamin D under the sun's rays, but babies must precisely be protected from it. The British NHS insists: even a child who often plays outside needs their supplement. The Moroccan daily Le Matin lists other brakes, which apply here too: olive or dark skin, covering clothes, sunscreen, city pollution, living in an apartment. So you don't put your baby in the sun "for the vitamin D": the protection rules stay the same, as our article on babies at the beach and in the sun explains.

Moroccan figures confirm the problem. According to the Ministry of Health's 2019 national micronutrient deficiency survey, cited by Le Matin, about one child in three aged 6 months to 12 years lacked vitamin D. And according to the 2012-2020 national nutrition survey, about two thirds of women of childbearing age had a deficiency or insufficiency.

Breastfed baby, formula-fed baby: who needs it?

The breastfed baby is the first concerned. In Canada as in the United Kingdom, they receive a daily supplement from birth, whether their mother takes one or not. Breastfeeding remains the best choice: this supplement is not a flaw of breast milk, just an addition for a nutrient that nature mainly supplies through the sun. For the first days at the breast, see how to get breastfeeding off to a good start.

The formula-fed baby already gets some, because these milks are fortified. The NHS gives no supplement to a baby who drinks more than 500 ml a day. Below that, or with mixed feeding, the paediatrician decides.

In Morocco, the Ministry of Health runs a supplementation programme for pregnant women and newborns, which it declared maintained in February 2023. Ask at your health centre or your doctor what is planned for your baby.

Until what age should vitamin D be given?

The answer depends on the country, and this is one of the points where recommendations differ the most.

These gaps are explained by sunshine, the fortified foods available and the habits of each country. In Canada, for example, cow's milk sold in shops is fortified with vitamin D, which is not the case in every country. Keep one simple rule: at each follow-up visit, ask the paediatrician whether to continue.

What are the signs of a lack of vitamin D?

A mild deficiency is not visible. When it sets in, the signs mostly affect the bones. The doctors cited by Le Matin describe:

• a skull that stays soft, a fontanelle that is slow to close;
• wrists and ankles that thicken;
• bowed legs, with a marked gap between the knees when the feet touch;
• slowing growth and motor milestones that come late, such as walking;
• deformities of the chest.

A big drop in calcium can also cause cramps, even a spasm of the larynx that hinders breathing. It is rare, but it is an emergency.

Too much vitamin D: the danger of double doses

An excess of vitamin D is not harmless. The French national order of pharmacists reports several serious cases of hypercalcaemia (too much calcium in the blood) in infants, after food supplements fortified with vitamin D. Its advice is precise: prefer forms sold as medicines, give vitamin D only on prescription, check the quantity at every dose and never multiply products.

The risky situations are often ordinary:

• two parents who each give the day's dose, without telling each other;
• daily drops and an ampoule received elsewhere;
• a "multivitamin" supplement or cod liver oil added on top, which the NHS advises against;
• a bottle left within reach of an older brother.

In Morocco, the highly dosed ampoule forms were also the subject of a Ministry of Health circular in February 2023, which regulated their use. The experts interviewed then reminded readers that daily intake is often preferred in infants. Keep vitamin D with the other medicines in your baby's medicine cabinet, up high.