Preventing rickets comes down to ensuring children get enough vitamin D and calcium during their growing years. The most critical window is infancy through adolescence, when bones are actively lengthening and mineralizing. All major pediatric guidelines recommend 400 IU of vitamin D daily for every infant from birth, regardless of whether they’re breastfed or formula-fed.
Why Vitamin D and Calcium Matter for Bones
Children’s long bones grow through a process where cartilage is gradually replaced by hard bone tissue. For that hardening step to work, the body needs adequate levels of both calcium and phosphorus at the growth plates. Vitamin D plays a central role because it controls how much calcium your child’s gut actually absorbs from food. Without enough vitamin D, calcium absorption drops, and the body compensates by pulling calcium from bones and lowering phosphorus levels in the blood.
When phosphorus drops too low, the cartilage cells at the ends of growing bones don’t die off on schedule the way they’re supposed to. They pile up instead, causing the growth plates to widen abnormally. This is what produces the classic signs of rickets: soft bones, bowed legs, knock-knees, and swollen wrists or ankles. The key point for prevention is that this entire chain reaction starts with not enough vitamin D, not enough calcium, or both.
Vitamin D Supplements for Infants
A 2016 global consensus statement and the American Academy of Pediatrics both recommend 400 IU of vitamin D per day for all infants during the first 12 months of life. This applies to breastfed, partially breastfed, and formula-fed babies alike. Breast milk contains very little vitamin D regardless of the mother’s diet, and formula only provides enough once a baby is drinking about a liter per day, which typically doesn’t happen until they weigh more than about 13 pounds.
Liquid vitamin D drops designed for infants are widely available and easy to give. A single drop per day is all most products require. Starting supplementation in the first few days of life is standard practice in most countries, and it should continue through the first year. After 12 months, children still need 600 IU daily, which they can get from a combination of food, sunlight, and supplements.
Vitamin D During Pregnancy and Breastfeeding
Babies are born with vitamin D stores they built up in the womb, so a mother’s levels during pregnancy directly affect her newborn’s starting point. The Institute of Medicine sets the adequate intake at 600 IU per day for pregnant and breastfeeding women. Most prenatal vitamins contain this amount. If a deficiency is identified during pregnancy, experts generally consider 1,000 to 2,000 IU per day safe, with an upper safety limit of 4,000 IU per day.
Even with good maternal intake, breast milk alone won’t supply enough vitamin D for the baby. That’s why infant supplementation is recommended on top of whatever the mother takes.
Food Sources of Vitamin D
Very few foods naturally contain significant vitamin D, which is why deficiency is so common. The richest natural sources are fatty fish and fish liver oil. A tablespoon of cod liver oil delivers about 1,360 IU. Three ounces of cooked rainbow trout provides 645 IU, and the same amount of sockeye salmon gives 570 IU. White mushrooms that have been exposed to UV light contain 366 IU per half cup.
Fortified foods fill some of the gap. A cup of fortified cow’s milk has about 120 IU, and fortified soy, almond, or oat milks range from 100 to 144 IU per cup. Fortified cereals add roughly 80 IU per serving. A scrambled egg contains just 44 IU. Common foods like chicken, beef, fruits, vegetables, grains, and nuts contain essentially zero vitamin D. For most children, food alone won’t be enough without either sunlight or a supplement.
Getting Vitamin D From Sunlight
Your skin manufactures vitamin D when exposed to UVB rays from the sun. The practical guideline is to expose about 20% of your body’s surface (roughly the arms and face) to sunlight for about half the time it would take to develop slight pinkness. That amount of exposure produces the equivalent of roughly 1,400 to 2,000 IU of vitamin D.
Several factors make sunlight unreliable as a sole source, though. Geography matters enormously. Above about 33 degrees latitude, vitamin D production from sunlight drops off sharply in winter. In Boston, at 42 degrees north, the skin produces essentially no vitamin D from November through February. Even in summer, vitamin D synthesis only happens between roughly 10 a.m. and 3 p.m., when the sun is high enough in the sky.
Time of year and cloud cover aside, the window for effective sun exposure also shifts with skin tone. In one study, white adults raised their blood vitamin D levels more than 30-fold after UVB exposure, while Black adults showed no significant increase from the same dose. The darker skin group needed about five times more UVB to achieve a meaningful rise. This is because melanin, the pigment that darkens skin, acts as a natural sunscreen, converting about one-tenth as much of the precursor molecule into vitamin D compared to lighter skin. For children with darker skin, supplementation is especially important.
Who Is at Highest Risk
Certain children are far more likely to develop rickets, and prevention efforts should be most aggressive for these groups:
- Exclusively breastfed infants who don’t receive vitamin D drops, since breast milk provides minimal vitamin D.
- Children with darker skin living in northern or southern latitudes, where UVB exposure is low for much of the year. The sunscreening effect of melanin makes their “vitamin D safe zone” smaller and shifted closer to the equator.
- Children who spend little time outdoors or who are consistently covered with clothing or sunscreen, reducing skin exposure to UVB.
- Children with limited dietary calcium, including those with dairy allergies, lactose intolerance, or restrictive diets.
- Immigrant children who have moved from equatorial regions to higher latitudes, creating a mismatch between their skin pigmentation and available sunlight.
Rickets has historically been called a disease of poverty and migration, and that pattern holds today. Children living in urban environments with little access to outdoor play and limited dietary variety are at particular risk.
Calcium Intake by Age
Vitamin D gets most of the attention, but calcium is the other half of the equation. Without enough calcium in the diet, even adequate vitamin D can’t fully protect bones. The recommended daily calcium intake increases as children grow: infants need 200 to 260 mg (easily met through breast milk or formula), children ages 1 to 3 need about 700 mg, children 4 to 8 need 1,000 mg, and adolescents 9 to 18 need 1,300 mg per day.
Dairy products are the most concentrated source. A cup of milk provides roughly 300 mg of calcium, so an adolescent would need the equivalent of about four cups of milk daily. For children who don’t consume dairy, fortified plant milks, calcium-set tofu, canned fish with bones, and fortified orange juice can help close the gap. In diets where dairy and fortified foods are scarce, a calcium supplement may be necessary.
Spotting Early Warning Signs
Prevention sometimes means catching the problem before it becomes severe. The earliest signs of rickets tend to be subtle: delayed closure of the soft spot on an infant’s skull, slow growth compared to peers, or unusual fussiness that could reflect bone tenderness. As the condition progresses, the wrists and ankles may appear wider than normal, the legs may start to bow or angle inward, and the ribcage can develop a visible ridge where the bone meets cartilage.
If your child has any of the risk factors above and you notice delayed motor milestones (late walking, reluctance to bear weight), those warrant a closer look. A blood test measuring vitamin D and calcium levels, along with a simple X-ray of the wrists, can confirm or rule out rickets quickly. Caught early, nutritional rickets is fully reversible with supplementation.