Calcium in diet
Calcium, the most abundant mineral in the body, can be found in certain foods, added to other food products, included in certain medications like antacids, and available as a dietary supplement.
Calcium is essential for the structure of bones and teeth, as it contributes significantly to their composition. Additionally, calcium plays a vital role in maintaining various tissues' rigidity, strength, and flexibility, enabling normal bodily movement. It also mediates critical bodily functions such as blood vessel contraction and dilation, muscle function, blood clotting, nerve transmission, and hormonal secretion.
Calcium from food sources and dietary supplements is absorbed through active transport and passive diffusion across the intestinal mucosa. Active transport is primarily responsible for absorption when calcium intake is lower, while passive diffusion becomes more significant as calcium intake increases.
It is worth noting that the presence of vitamin D is essential for absorbing calcium through active transport in the gut and maintaining adequate calcium levels in the bloodstream.
How much calcium do I need?
Getting adequate calcium is vital for maintaining strong bones throughout your life. This is especially important during the first 20 years, as it is the time when your body develops and strengthens its bones. As you age, it is equally important to continue consuming enough calcium to slow down the natural bone loss that occurs.
According to the Australian Dietary Guidelines, incorporating 2 to 3 servings of dairy foods into your daily diet is recommended to ensure you meet the recommended dietary intake (RDI) of calcium.
A healthy and balanced diet can support your bone health and overall well-being.
Recommended dietary allowances for calcium
| Age | Male | Female |
| 0–6 months | 200 mg | 200 mg |
| 7–12 months | 260 mg | 260 mg |
| 1–3 years | 700 mg | 700 mg |
| 4–8 years | 1,000 mg | 1,000 mg |
| 9–13 years | 1,300 mg | 1,300 mg |
| 14–18 years | 1,300 mg | 1,300 mg |
| 19–50 years | 1,000 mg | 1,000 mg |
| 51–70 years | 1,000 mg | 1,200 mg |
| >70+ years | 1,200 mg | 1,200 mg |
Calcium - Food Sources
The human body obtains the necessary calcium through two methods. Firstly, it acquires calcium by consuming foods or taking supplements rich in calcium. Secondly, it utilises the calcium already present in the body.
In case of insufficient intake of calcium-rich foods, the body will extract calcium from the bones. Ideally, the calcium borrowed from the bones should be replenished later on. However, this is only sometimes the case, and simply increasing calcium consumption may not consistently achieve this.
Here are various foods rich in calcium to include in your diet:
Seeds
Seeds possess remarkable nutritional value, with several varieties being excellent sources of calcium. Notably, poppy, sesame, celery, and chia seeds are among those that offer this essential mineral.
To illustrate, a mere tablespoon (9 grams) of poppy seeds provides 127 mg of calcium, equivalent to 10% of the recommended Daily Value (DV).
Moreover, seeds are also abundant in protein and beneficial fats. For instance, chia seeds are particularly rich in plant-based omega-3 fatty acids.
In addition to calcium, sesame seeds contribute 7% of the DV in just one tablespoon (9 grams), providing other vital minerals like copper, iron, and manganese.
Yoghurt
Yoghurt is a highly beneficial food that offers a rich source of calcium. Additionally, various types of yoghurt contain probiotics, which are beneficial bacteria that can enhance immune function, promote heart health, and improve nutrient absorption.
A single cup of plain yoghurt, weighing 245 grams, provides 23% of the daily value (DV) for calcium and a substantial amount of phosphorus, potassium, and vitamins B2 and B12. If you opt for low-fat yoghurt, you can obtain a higher calcium content, with 34% of the DV in one cup.
However, it's worth noting that Greek yoghurt, while an excellent protein source, contains less calcium than regular yoghurt.
Cheese
Dairy products may offer further health advantages. Research suggests that increasing dairy intake may be associated with an elevated risk of heart disease. In addition to calcium, cheese is also a good source of protein.
Most cheeses are rich in calcium, and Parmesan cheese stands out as the highest source, providing 242 mg or 19% of the Daily Value (DV) per ounce (28 grams).
On the other hand, softer cheeses generally contain less calcium. A benefit of dairy products is that the body more easily absorbs the calcium they contain than from plant sources.
Furthermore, aged and hard cheeses have naturally low levels of lactose, making them more digestible for individuals with lactose intolerance.
Nevertheless, it is essential to note that full-fat cheese might be high in saturated fat and calories. Additionally, certain cheeses may contain high levels of sodium, which may need to be limited by some individuals.
Sardines and canned salmon
Canned salmon and sardines are rich in calcium due to their consumable bones. A 3.75-ounce (92-gram) can of sardines contains 27% of the Daily Value (DV) of calcium, while 3 ounces (85 grams) of canned salmon with bones provides 19% of the DV. These oily fish are also excellent omega-3 fatty acids and high-quality protein sources.
Although seafood can contain mercury, sardines and salmon have lower levels of this toxin. Moreover, both sardines and salmon are high in selenium, a mineral that can reverse and prevent mercury toxicity.
Beans and lentils
Beans and lentils contain fibre, protein, and essential micronutrients like iron, zinc, folate, magnesium, and potassium. Certain varieties of beans, such as winged beans, contain significant amounts of calcium. A single cooked cup (172 grams) of winged beans provides 244 mg of calcium, equivalent to 19% of the DV.
Interestingly, beans are associated with numerous health benefits commonly linked to plant-based diets. Beans can help in reducing the risk of developing type 2 diabetes and lower levels of LDL (bad) cholesterol.
Leafy green vegetables
Leafy green vegetables are known for their exceptional health benefits, and several are rich in calcium. Examples of these vegetables include collard greens, spinach, and kale.
For instance, a cooked collard greens serving about 1 cup or 190 grams contains 268 mg of calcium. This amount accounts for approximately 21% of the recommended daily calcium intake.
It's important to note that certain varieties of leafy greens, like spinach, contain oxalates. Oxalates are natural compounds that bind to calcium and hinder its absorption in the body.
Therefore, even though spinach is a good source of calcium, its absorption is less efficient than other calcium-rich greens with lower oxalate levels, such as kale and collard greens.
Tofu
Tofu is a rich source of protein, encompassing all the amino acids required by the body. Additionally, it offers a diverse range of vitamins, minerals, fats, and carbohydrates. Tofu that has been prepared with calcium is exceptionally high in calcium content. Just half a cup or 126 grams of calcium-fortified tofu contains over 66% of the recommended daily value for calcium.
Fortified foods
Fortified foods like cereals can be helpful to make sure you meet your daily requirement of calcium. Some cereals can provide up to 1,000 mg of calcium per serving, 100% of the recommended daily value. It's worth mentioning that this calculation doesn't include the calcium content from milk, which is often added to cereals.
However, it's important to remember that the body cannot absorb all the calcium at once, so it's best to distribute your calcium intake throughout the day.
In addition to cereals, flour and cornmeal can be fortified with calcium. This is why certain breads, tortillas, and crackers contain significant amounts of calcium.
Almonds
Among all nuts, almonds have one of the highest calcium contents. Just 1 ounce (28 grams) of almonds, equivalent to approximately 23 nuts, supplies 6% of the DV. Almonds are also rich in fibre (3.5 grams per ounce), healthy fats, protein, magnesium, manganese, and vitamin E. Additionally, consuming nuts may help reduce blood pressure, body fat, and other risk factors associated with metabolic diseases.
Edamame beans
Another excellent source of calcium is edamame beans, which are young soybeans still enclosed in their pods. A serving of cooked edamame, approximately 1 cup or 155 grams, provides 8% of the recommended daily value for calcium. Additionally, edamame is a good source of protein and supplies your entire daily folate requirement in just one serving.
Calcium supplements
Calcium is found in various dietary supplements, such as multivitamin/mineral products and supplements that specifically contain calcium and vitamin D. The amount of calcium in these supplements can vary significantly.
Commonly used forms of calcium in supplements are calcium citrate and calcium carbonate. In individuals with low levels of stomach acid, the solubility rate of calcium carbonate is lower, which may result in reduced absorption of calcium from calcium carbonate supplements unless taken with a meal.
On the other hand, calcium citrate does not rely as heavily on stomach acid for absorption and can be taken without food.
The percentage of calcium absorbed from supplements, similar to that from food sources, is influenced by the type of calcium used and the total amount of elemental calcium consumed at once.
Individuals taking calcium supplements may experience gastrointestinal side effects, such as gas, bloating, constipation, or a combination of these symptoms.
Ways to include calcium in your diet
It is advisable to cook your foods using minimal water and for the shortest duration possible to ensure sufficient calcium intake in your diet. This cooking method, such as steaming or sautéing, helps retain more calcium in the foods you consume, compared to boiling them.
Being mindful of the other foods you consume alongside calcium-rich foods is essential. Certain fibres, like wheat bran, and foods containing oxalic acids, such as spinach and rhubarb, have the potential to bind with calcium and hinder its absorption by the body.
Consequently, leafy greens alone cannot be considered a reliable source of calcium since the body needs to utilise a significant portion of the calcium they contain. Individuals following a vegan diet should ensure the inclusion of soy products and fortified items in their meals to meet their calcium requirements.
Bioavailability of calcium
Calcium is a mineral of significant size that is not easily broken down in the digestive system. The quantity of calcium indicated on the Nutrition Facts label of a food item represents the amount of calcium present in the food. Still, it does not necessarily reflect the amount the body will absorb.
The amount of calcium absorbed and utilised by the body is referred to as "calcium bioavailability." Certain foods have a higher calcium bioavailability compared to others.
For instance, dairy products have a bioavailability of approximately 30% absorption.
Therefore, if a food label on milk states that it contains 300 mg of calcium per cup, only around 100 mg will be absorbed and utilised by the body.
One drawback of some plant-based foods is that they naturally contain "anti-nutrients." These anti-nutrients, such as oxalates and phytates, bind to calcium and reduce its bioavailability. Despite having the highest calcium content among leafy greens at 260 mg per 1 cup cooked, Spinach is also rich in oxalates, which significantly lowers its bioavailability.
As a result, only about 5% or approximately 13 mg of calcium can be effectively utilised by the body. Suppose you are examining food labels to meet a specific daily calcium requirement. In that case, it is essential to continue aiming for the Recommended Dietary Allowances (RDAs) established for your age group and gender.
The RDAs take into account the bioavailability of calcium in food. Additionally, it is worth noting that the amount of calcium the body absorbs may vary.
