Nutrition Research Notes

Eating poorly is not by itself a reason to give a supplement. Look at the growth curve first. If, on the Korea Disease Control and Prevention Agency's 2017 growth charts, height and weight keep rising between the 3rd and 97th percentiles, uneven meals are usually not a problem. A supplement is a way to fill a specific nutrient that is actually missing because a whole food group has dropped out for weeks; it does not replace meals.

They do not have to be in the same product. The functional claim the Korean MFDS recognises for vitamin D is that it is needed for calcium and phosphorus to be absorbed and used, but that claim rests mainly on adult data. In children, several studies found that giving more vitamin D did not increase calcium absorption. A 2011 BMJ meta-analysis of six randomised trials in 884 children also found that supplements did not raise bone density in children whose blood vitamin D was normal. So the first question is not whether to take them together, but whether your child is actually short of vitamin D.

There is no legal age threshold. The 2025 Korean Dietary Reference Intakes set an adequate intake for EPA plus DHA of 100 mg a day at 0-5 months, 150 mg at 6-11 months, 150 mg at 1-2 years and 200 mg from 3 to 18 years, so the standard itself starts before the first birthday. Before one year, though, breast milk and formula are the reference, and after that a child who eats fish such as mackerel about twice a week is already getting that amount from food. Whether to add a product depends less on age than on how much fish the child eats, and if you do add one, follow the intended age and daily amount printed on the back of the pack.

Yes. Vitamin D and zinc especially. They appear in multivitamins, calcium products, probiotics and fortified milk, so the total adds up fast. When the Korea Consumer Agency tested 18 children's probiotic products in 2023, the five containing vitamin D held 173-319% of the 5 µg adequate intake for ages 6-8, and the eleven containing zinc held 46-193% of the recommended intake for the same ages. Checking is simple: line up everything your child takes, add the same nutrient across products in mg and µg, and compare the total with the tolerable upper intake level for your child's age. If adding it up by hand is a chore, the AI supplement analysis in the Wooathing app uses the same reference table to add several products together and show whether the daily limit is crossed (available to customers who have purchased a Wooakle product). In the full release, an AI health agent will tailor the guidance to each child. It does not replace a doctor or pharmacist.

Start from the amounts printed in the "nutrition and function" panel on the back. For calcium, the 2025 Korean Dietary Reference Intakes recommend 550 mg a day at ages 3-5, 700 mg at 6-8 and 800 mg at 9-11, and a child who drinks two glasses of milk a day (about 470 mg of calcium) may not need a supplement at all. Then check four things: the form of the nutrient (for calcium, carbonate or citrate), how much is taken at once, which other nutrients come with it, and whether any of them overlap with a product your child already takes. Read the claims on the front last.

Most cases are no worse than an upset stomach. Of the 3,551 adverse-event reports filed for health functional foods in Korea in 2025, compiled by the Korea Food Safety Information Service, indigestion and abdominal pain were the most common symptoms. The cases that needed treatment involved several times the labeled amount taken for months, not label-dose use. That data covers mostly adult products; no separate figures for children are published. At home, start from the daily amount on the label and compare it with the tolerable upper intake level in the 2025 Korean Dietary Reference Intakes. For magnesium from supplements the upper level is 90mg a day at ages 3-5 and 130mg at ages 6-8.

Whether the supplement goes down with a meal matters more than morning versus evening. A 2010 study in the Journal of Bone and Mineral Research found that taking vitamin D with the largest meal of the day raised blood levels by an average of 57% after two to three months, and a 1989 study in the American Journal of Clinical Nutrition found calcium absorption 10-30% higher when taken with a meal. Omega-3 is also better right after a meal. If your child takes a separate iron supplement, keep it at least two hours apart from calcium. The idea that an evening dose helps sleep has not been shown in children. Most of this research was done in adults, so pick the meal your child never skips.

According to the 2025 Dietary Reference Intakes for Koreans (Ministry of Health and Welfare and the Korean Nutrition Society), the recommended calcium intake for children is 450 mg a day at ages 1-2, 550 mg at 3-5, 700 mg at 6-8 and 800 mg at 9-11, and at 12-14 it is 950 mg for boys and 850 mg for girls. A 200 mL cup of milk has 236 mg of calcium, so a 3-5-year-old needs a little over two cups' worth and a 9-11-year-old about three and a half. Milk alone does not have to cover it; adding cheese, yogurt and anchovy side dishes so the daily total comes close to these numbers is enough.