Calcium-Rich Foods: A Complete Guide to Dietary Sources, Daily Requirements, and Supplements

Got milk? Millions of people remember this ad campaign, originally kicked off in 1993 and still ongoing through today, albeit with gaps. The goal of the campaign was to promote sales of dairy products — primarily milk — for their health benefits. The most widely promoted of those benefits was the high levels of calcium present in milk.

Calcium is a critical nutrient used throughout the body, most notably in the bones. In fact, the bones act as the reservoir of calcium, and the body will add or remove calcium from your skeleton in order to maintain calcium homeostasis elsewhere in your body.

There's no question that calcium is critical, but what is it used for, how much does the body need, and how can you make sure you're getting enough?

How Your Body Uses Calcium

By far, the most important use of calcium in the body is in bones and teeth. Calcium is the building block used to create and maintain healthy bones and teeth, including the development of bones as you grow and age, the maintenance of those bones through life, and the ability to heal them if something happens.

Another important use of calcium is as fuel for muscles. Calcium is a critical nutrient used when the brain tells muscles to contract. When a muscle is engaged, nerves stimulate the body into releasing calcium, which contracts the muscle fibers; by pulling the calcium back out of the muscles, they relax. This is the basis of how muscles work in a simple sense. With inadequate calcium, muscle regulation decreases.

Knowing this, you might assume that calcium is a critical part of the heart and cardiovascular system. This is true, but it goes beyond its use in flexing the heart muscle. Calcium is also used in the process of blood clotting, and there's a potential link between calcium and blood pressure, with higher calcium consumption correlating to lower blood pressure.

Calcium is also used as a cofactor for many different enzymes and enzymatic processes throughout the body. While much more study is needed to enumerate every use and reaction, research suggests that adequate calcium consumption may be related to a lower risk of high blood pressure in women during pregnancy, improved cholesterol values across the board, and even a lower risk of colorectal adenomas — a non-cancerous tumor.

How Much Calcium Your Body Needs

It's clear that adequate calcium is necessary to maintain proper bodily function. The average adult body contains 1,200 (for women) and 1,400 (for men) grams of calcium. The body is constantly using calcium, and cannot synthesize it from nothing, so dietary intake must keep up. How much is enough?

The amount of calcium needed starts at 200 mg per day at birth and rapidly increases throughout life. It's also a nutrient where requirements increase with age, especially in older adults. The older a person is, the harder it becomes for the body to maintain the calcium in bones, so higher intake is needed. The exception is the spike during adolescence, when final growth spurts draw on more calcium to establish adult bone mass.

These are the recommended daily intakes for calcium, as determined by the Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine.

The Risks of Low Calcium

What happens when the body doesn't get enough calcium?

The biggest and most common impact is on bone strength. Over time, low levels of calcium intake force the body to pull more and more calcium from the bones. This leads to osteoporosis, a common condition seen in older adults. Bones grow brittle and weak and are more likely to break, especially on impact or when falling. The stereotype of "falling and breaking a hip" is largely reflective of osteoporosis.

In children, inadequate calcium intake can stunt growth and cause rickets.

With calcium associated with blood pressure, cardiovascular health, and cholesterol, it's also possible that all of these can be affected negatively by low levels of dietary calcium, though there have been relatively few studies examining these links directly. The established importance of calcium for bone and muscle health is itself reason enough to prioritise adequate intake.

For example, an observational study of over 77,700 adults found that higher calcium intakes were associated with a lower risk of colorectal cancers. However, clinical trials examining the use of calcium supplements to reduce the risk of cancers have had mixed results.

In general, there are three groups most at risk of calcium deficiency.

• People reaching old age. The older a person is, the more the body may struggle to use the calcium available and the more may be needed to counteract it.
• Postmenopausal women. Menopause causes a decrease in estrogen production, which in turn leads to reduced calcium absorption. It's estimated that as much as a third of postmenopausal women have osteoporosis.
• People who avoid dairy products. By far the best dietary source of calcium is dairy, so people who are lactose intolerant, allergic to milk, or who avoid dairy for dietary reasons such as veganism are all at greater risk of not consuming enough calcium in their diet.

Fortunately, it's not terribly difficult to get calcium through the diet.

Dietary Sources of Calcium

By far, the best dietary sources of calcium are dairy products. Fortified foods, dark green vegetables, and some other vegetables are also good options.

Here are some of the best sources:

While dairy products are the best, a decent amount of calcium can also come from many other sources. A well-balanced diet is likely to have small amounts of calcium in just about everything consumed, so reaching the recommended daily amount may not require dramatic dietary changes.

Before moving on to actionable advice, there's one important factor we haven't yet discussed: the nutrient that makes calcium work.

Calcium's Enabler: Vitamin D

Unfortunately, it's not as simple as consuming enough calcium to maintain adequate levels. In order for the body to absorb and use calcium, adequate amounts of its enabler — vitamin D — are also required.

Vitamin D, also known as calciferol, is a fat-soluble vitamin. It's found in some foods naturally, it's fortified into other foods, and it's commonly available as a dietary supplement. It's also synthesized naturally by the body when the skin is exposed to UV radiation from the sun, producing an inert version of vitamin D that is then processed into usable form.

Therefore, in order to ensure that dietary calcium is properly absorbed, adequate vitamin D intake is essential. While sunlight exposure is the most effective way to get enough vitamin D, dietary consumption contributes meaningfully.

The recommended daily intake of vitamin D is:

These numbers were developed based on an assumption that individuals get little to no sun exposure and don't synthesize meaningful amounts of vitamin D endogenously. It's difficult to give specific sun exposure recommendations due to geographic differences in cloud cover, ozone cover, daylight hours and more. Moreover, UV rays are carcinogenic, making it difficult to recommend as a primary strategy, and adequate sunblock also blocks the triggering of vitamin D synthesis.

Dietary sources of vitamin D are limited to fortified foods like milk and cereal, fatty fish such as trout and salmon, eggs, cheese, and mushrooms.

How to Make Sure You're Getting Enough Calcium

What steps can be taken to ensure adequate calcium for strong bones and healthy bodily function?

Eat more dairy products. As the chart above shows, yogurt, mozzarella, milk, and cottage cheese are all very good sources of calcium and are often packed with other healthy nutrients as well. Dairy products are also frequently fortified with additional vitamin D to ensure calcium is better absorbed.

Fish. In particular, fatty fish such as salmon, tuna, and trout are all good options. They are also packed with other healthy nutrients, including omega-3 fatty acids. Fish with soft, edible bones, like sardines, also provide more vitamin D from those bones.

Fortified options. Many foods are fortified to include more vitamins and minerals like vitamin D and calcium. However, some of these foods are also full of excess sodium and preservatives. Carefully considering the foods chosen and aiming for a more whole-food, natural diet when possible is the better approach.

If you're vegan or unable to eat dairy products, focus on calcium-rich non-dairy foods. These foods include tofu made with calcium sulfate, soybeans and soy milk, and dark leafy greens like kale.

In general, a healthy diet shouldn't have a problem reaching adequate calcium intake, but without adequate vitamin D, that calcium may not be put to proper use — so getting enough of both is essential. For people who get limited sun exposure, live at northern latitudes, or regularly use sunscreen, dietary and supplemental sources of vitamin D become especially important for maintaining calcium absorption year-round.

Are Calcium Supplements a Viable Option?

Yes and no. If the diet is lacking in calcium, a supplement to help reach the recommended daily intake is a reasonable option. However, supplementing with calcium to exceed the recommended daily intake does not appear to offer any benefits, and may be associated with an increased risk of heart disease.

Rather than relying on supplements, striving to maintain a healthy diet and lifestyle and using small-scale supplements to make up for minor gaps in nutrition is the evidence-based approach. Taking a large dose of any nutrient is likely to have side effects — calcium is no different. People taking calcium supplements often report stomach problems and constipation, and some find an increased risk of developing kidney stones.

It's also worth noting that dietary calcium does not carry the same cardiovascular concerns associated with supplemental calcium. Multiple large studies have linked high-dose calcium supplementation to increased cardiovascular risk, while dietary calcium from foods like dairy, leafy greens, and fortified products has not been associated with those risks. This makes food-first approaches all the more important.

Sources

1. UpToDate – Calcium and Vitamin D for Bone Health: The Basics: https://www.uptodate.com/contents/calcium-and-vitamin-d-for-bone-health-the-basics?search=Calcium%20in%20Foods&source=search_result&selectedTitle=2%7E150&usage_type=default&display_rank=2
2. National Institutes of Health Office of Dietary Supplements Calcium Fact Sheet for Health Professionals: https://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/
3. Mayo Clinic – Calcium and calcium supplements: Achieving the right balance: https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/calcium-supplements/art-20047097
4. National Institutes of Health Office of Dietary Supplements Vitamin D Fact Sheet for Health Professionals: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
5. Independent associations of dairy and calcium intakes with colorectal cancers in the Adventist Health Study-2 cohort: https://pubmed.ncbi.nlm.nih.gov/28735581/
6. Calcium plus vitamin D supplementation and health outcomes five years after active intervention ended: the Women's Health Initiative: https://pubmed.ncbi.nlm.nih.gov/24131320/