Calcium: What your Child Needs and Where to Find It

First things first: what is calcium?

Calcium is a chemical element. You might recall from chemistry class that it’s ‘Ca’ on the periodic table. It is found naturally in and on the earth. In fact, it’s the fifth most abundant element in the earth's crust and the third most abundant metal on our planet after iron and aluminum. The most common calcium compound is calcium carbonate, found in rocks.

And what about inside the human body? Well, calcium is the most abundant mineral there! 

Why is it important to our bodies?

Calcium is a mineral that your body needs to build and maintain strong bones, among other important functions. 

Almost all calcium (more than 99%) in the body is stored in bones and teeth, giving them structure and hardness. 

The remaining bodily calcium (less than 1%) is involved in a variety of vital functions. These include blood coagulation (blood clotting), muscle contraction, the transmission of nerve impulses, cellular secretory activity, cellular death/regulation, cell differentiation, enzyme activation, our immune response, and even egg fertilization. That’s a lot for one mineral!

But we should understand that calcium is not synthesized (i.e., made) by the human body, so our calcium needs must be supplied by outside sources—mainly food.

How much calcium does my child need? How much do I need?

Like all minerals and nutrients, the amount of calcium you—and your child—need each day depends on age and sex. Average daily recommended amounts, courtesy of the U.S. Department of Agriculture, are listed below in milligrams (mg):

So, as you can see, calcium intake is vital for—and relative to—each life stage. That said, this ^ data shows its special importance to women, especially breastfeeding and pregnant women and older women. 

How does my body—and my baby’s body—absorb it?

Calcium from foods and dietary supplements is absorbed in the intestine, through a barrier called the intestinal mucosa (basically, the inner lining of the intestinal tract). Calcium is both actively transported across this barrier, especially when calcium intake is on the lower side, and can also passively pass through it when Ca intake is on the higher side. 

And how is it transported? Enter Vitamin D. This vital nutrient is required for calcium to be absorbed in the gut through active transport—and vitamin D is essential to maintaining adequate calcium levels in blood. Talk about teamwork!

Most calcium (90%+) is absorbed in the small intestine, whereas ~3–6% of calcium is absorbed in the colon (which is a part of the large intestine). (For a quick refresher, when we eat, our food gets processed by the small intestine first, before moving to the large intestine.)

Interestingly, there’s an inverse relationship between calcium intake and absorption. Let’s say you get 200mg/day of calcium from food. About half of that will be absorbed. Now, let’s say you get 2,000mg/day of calcium. Only 15% of that will be absorbed. And the older you are, the less you absorb. Our infants and young children absorb about 60% of the calcium in their diets—which makes sense since their little bones need it!—but us adults, we only absorb about 25% of the calcium in our diets. And that goes further down later in life.

This is why our Recommended Daily Intakes are high for calcium—to offset the losses. 

So when we’re thinking about how much calcium our families should get, we should consider its ‘bioavailability‘—the proportion of a nutrient present in a food that is actually absorbed and utilized in metabolic processes. 

Calcium bioavailability can be influenced by many factors—vitamin D availability, for instance, but also age, pregnancy, disease, and even the food the calcium is coming from (what other nutrients are in it), which we’ll get into in a minute.

After calcium is absorbed, where does it go?

About 98% of the calcium is stored in our bones (and our teeth). Our bones basically act as a reservoir for calcium, enabling our bodies to maintain ‘calcium homeostasis’—i.e., the right amount for optimal functioning. In our bones, the vast majority of calcium hangs out as ‘calcium hydroxyapatite,‘ which is a mixture of calcium and phosphate. 

Our bones are dynamic: they undergo continuous remodeling as calcium is constantly deposited and stored there. This process is vital since bone remodeling enables bone growth as our babies get older; bone repair when bones get damaged (oops!); calcium maintenance; and other benefits. 

This is why calcium is so important for women in particular. 

At birth, the body contains about 26 to 30g of calcium. This amount rises quickly after birth, reaching about 1,200g in women and 1,400g in men by adulthood. These levels remain constant in men, but they begin to drop in women at the start of menopause. 

For older women, calcium deficiency can reduce bone strength and lead to osteoporosis, which is characterized by fragile bones and an increased risk of falling. 

What about my children? 

Sixty percent of peak bone mass is acquired during puberty, which is why a constant intake of calcium during—and leading up to—this intense growth period is essential in strengthening bones and reducing the risk of osteoporosis later in life.

In children, severe calcium deficiency, usually accompanied by severe vitamin D deficiency, can cause ‘rickets‘—a childhood disease characterized by soft and distorted bones, usually resulting in bow legs. 

Another effect of chronic calcium deficiency is ‘osteomalacia‘—which is a defective bone softening that can occur in children and adults. 

For the prevention and treatment of rickets and osteomalacia, the requirements for calcium and vitamin D are inversely related: the lower the vitamin D level, the more calcium is needed to offset these diseases. This again emphasizes the unique and symbiotic relationship between D and Ca.

Do I need to worry about these ^ diseases for my children?

Most likely not. Nowadays, rickets is rare in developed countries like the U.S. Around a century ago, that was not the case, particularly among the working poor in cities. Today, it is mostly developing low- and middle-income countries and territories that suffer severe calcium deficiencies (especially in rural and very urban areas). To this point, Greece, the Netherlands, and Denmark have some of the highest rates of calcium intake, whereas China and India have some of the lowest.

For those of us in the U.S. and other developed places, we should still monitor how much calcium our children are getting (and how much we’re getting) because a substantial proportion of people in the U.S. consume less than recommended amounts of calcium. 

An analysis of 2007–2010 data from the National Health and Nutrition Examination Survey found that 49% of children aged 4–18 years and 39% of all individuals aged 4 and older consume less than the Estimated Average Requirement for calcium from foods and supplements.

More on this point: average daily intakes of calcium from foods and beverages are 1,083mg for men aged 20 and older, and 842mg for women. 

For children aged 2–19, average daily intakes of calcium from foods and beverages range from 965 to 1,015 mg. 

Perhaps for these reasons, around 22% of men, 32% of women, and 4 to 8% of children take a dietary supplement containing calcium. 

In total, then, average daily calcium intakes from both foods and supplements are 1,156 mg for men, 1,009 mg for women, and 968 to 1,020 mg for children—all lower than the USDA’s daily recommended amounts.

According to 2009–2012 data from the National Health and Nutrition Examination Survey, rates of calcium inadequacy are higher among non-Hispanic Blacks and non-Hispanic Asians (47–48%) than among Hispanics (30%) and non-Hispanic Whites (24%) in the U.S. 

Poverty also plays a role. National Health and Nutrition Examination Survey data from 2007 to 2014 shows that the risk of inadequate calcium intake is 11.6% higher (among adults aged 50 and older) in households earning less than $20,000 per year than households making more than this.

Knowing this, what can we do to make sure our families get enough calcium?

Fortunately, calcium is found in many foods. You can get the recommended amount by eating a variety of foods, including the following:

• Milk, yogurt, and cheese provide major sources of calcium—which is why, in the U.S., approximately 72% of our ingested calcium comes from dairy products and foods with added dairy ingredients. Dairy products are unique in that they offer high calcium availability and content—and at the same time, stimulate bone development and maximize peak bone mass. 
• Canned sardines and salmon with bones offer another important source of calcium.
• Vegetables—specifically kale, broccoli, and Bok choy—also contain calcium.
• Certain beverages, including many fruit juices and animal milk substitutes such as soy and almond beverages, additionally provide calcium. 
• Some brands of tofu and ready-to-eat cereals are another go-to source. 
• Most grains (such as breads, pastas, and unfortified cereals) do not have high amounts of calcium. However, because people eat them often, their small amounts add up in helpful ways. (And on top of that, some grains are fortified.)

When it comes to calcium absorption, not all food is equal. And keep in mind that even with calcium-rich foods, other variables can hinder their absorption: caffeine, phosphorus, and low amounts of vitamin D, among them.

The absorption rate from dairy products is about 30%—which might seem low but know that milk and dairy products—cheese, butter, cream, yogurt, and kefir (a fermented milk drink)—are essential to meeting our calcium needs.

For instance, 100g of milk or yogurt offers between 100mg and 180mg of Ca. Compare this to cereal: 100g usually provides 30mg of calcium.

Certain compounds in plants can decrease calcium absorption by forming indigestible salts with calcium. As a result, absorption of calcium is only about 5% for spinach, whereas it is much higher with milk—close to 30%. Other foods similar to spinach in this regard include collard greens, sweet potatoes, rhubarb, and beans. In contrast, broccoli, kale, and cabbage have absorption rates similar to that of milk, although the amount of calcium per serving is much lower. (Kale, broccoli, and watercress contain between 100 and 150mg of calcium per 100g, but the kicker is that not everyone eats 100g of these vegetables every day! 100g of kale = 1.5+ cups of raw, chopped kale.)

Now, back to the point on spinach and other vegetables with lower calcium absorption rates. We aren’t saying: don’t eat spinach. Spinach is great for you! What is important, though, is to eat many different types of foods, including different vegetables. With nutritional diversity, concerns about certain plant compounds hindering Ca absorption don’t matter as much. 

Interestingly, natural mineral waters are another potential source of calcium. Water makes up about 60% of the human body and is involved in many functions, including being the carrier of nutrients and the main vehicle to eliminate waste and toxins. So, mineral water that is naturally high in calcium (>150mg/L) is a double plus! 

Since the 1990s, studies have been carried out to assess the bioavailability of Ca contained in calcium-rich mineral water. While the number of these studies is limited, and generally small groups of participants were recruited, the results nonetheless lead to a single and exciting conclusion: the bioavailability of calcium from calcium-rich mineral waters is equivalent to, or possibly higher than, that of calcium contained in milk and dairy products. Wow! This means that certain mineral waters could be very helpful for all of us, but especially those of us who are lactose intolerant.

We at Amara care about questions like ‘how much calcium should my child get?’ and ‘where do I source calcium-rich foods for my family?’ because we’re in the business of food that is nutrient-dense. Check out our baby blends like Kale, Potato, Veggie Mash. It’s 100% organic kale, potatoes, onions, and bananas—that’s it. All you have to do as the parent or provider is add breastmilk, water, or formula to the powdered blend—and it’s ready for your little one! And yes, with its ingredients and the addition of breastmilk or formula, your baby will get a healthy dose of calcium!

How does your family meet its calcium needs? Any recipes or tips to share?

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Article researched by:
Amara's Chief Nutritionist: Sonia A. Schiess, PhD in Nutrition, specialized in the introduction of solids and liquids to infants. Sonia's passion started when she was studying nutrition and dietetics in university, completing a post degree in Human Nutrition. Later on, she completed her PhD as a nutritionist, with a focus on introducing food in the first year of a baby's life. Her wide experience gives her a unique perspective, drawing from her time in clinics, hospitals, independent consulting and university research. She's authored several papers including "Introduction of complementary feeding"; "Introduction of potentially allergenic foods in the infant's diet during the first year of life" and "Intake of energy providing liquids during the first year of life" in five European countries. The combination of Sonia's science and our chef's magic ensures every Amara product is not only optimized for your baby's health but is delicious as well.

References:

https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional

https://ods.od.nih.gov/factsheets/Calcium-Consumer/

Hendrie GA et al., Improving children’s dairy food and calcium intake: can intervention work? A systematic review of the literature. Public Health Nutrition 2012

Shkembi B & Huppertz T, 2011. Calcium Absorption from Food Products: Food Matrix Effects. Nutrients 2021

Vannucci L et al., Calcium Intake in Bone Health: A Focus on Calcium-Rich Mineral Waters. Nutrients 2018