Calcium Foods: A Practical Guide

What does calcium do in your body?  

Adequate calcium is required for healthy development and maintenance of your bones and teeth, muscle contraction, blood clotting, and nerve transmission.  

Calcium is essential for children as they grow and develop.  Children who don’t get enough calcium may not grow to their full potential height or may develop other health issues.

In older people, too little calcium can increase your risk of developing osteoporosis, or frail and porous bones that easily fracture. 

Osteoporosis is especially common in older women, which is why it is recommended that women consume more calcium.  Fractures from falls are common in older people with low muscle mass and fragile bones and are often difficult to recover from.

Availability of calcium

The chart below shows that the calcium content of commonly available foods has decreased significantly since the widespread introduction of chemical fertilisers and modern farming practices in the 1940s (data from USDA Economic Research Service).  

This decrease in calcium is closely correlated with the rise in obesity.  Today, you need to make an effort to consume food that contains more calcium to meet the minimum intake levels, let alone optimal intake levels.

Calcium deficiency symptoms 

Lower intakes of calcium are associated with:

Calcium supplements 

As well as adequate calcium, it’s important to note that you also need sufficient Vitamin D to ensure that the calcium is used in your bones and teeth and not in your arteries.  

Excess calcium can also build up in your kidneys as your body tries to excrete excess calcium.  

Both calcium from food and vitamin D from adequate sun exposure is critical to ensure your calcium is doing the right job.

Studies suggest that a diet rich in calcium protects against heart disease, but supplemental calcium may increase the risk. 

  • A 2010 study in the BMJ study found that those who used calcium supplements had a 139% greater risk of a heart attack while an increased intake of calcium from food did not increase the risk. 
  • A meta-analysis of studies involving more than 12,000 people also found that calcium supplementation increased the risk of heart attack by 31%, stroke by 20% and death from all causes by 9%.
  • An analysis of 12,000 men found that intake of more than 1,000 mg of supplemental calcium per day from multivitamins or individual supplements was associated with a 20% increase in the risk of death from cardiovascular disease. 

The sudden dump of calcium from supplements may lead to calcification of arteries, whereas calcium obtained from food is absorbed more slowly and is less likely to build up in places where it doesn’t belong.  

Extra calcium intake from supplements, beyond what is required to build your bones and teeth, is excreted in the urine, increasing the risk of calcium kidney stones.  

Excess calcium circulating in the blood may attach to atherosclerotic plaques in your arteries or heart valves.   

Satiety response 

Our satiety analysis shows that foods with more calcium tend to be more satiating, particularly up until around 2.0 g per 2000 calories.  

The average intake for Optimisers was 1.0 g per 2000 calories with an 85th percentile of 1.6 g per 2000 calories.  This is higher than the Estimated Average Requirement of 0.84 g/day and the Daily Recommended Intake of 1.0 g per day but less than the upper limit of 2.5 g per day set for supplementation with calcium due to the increased risk of kidney stones.  

Absorption and bioavailability of calcium

Foods that contain phytates (e.g. spinach, rhubarb, chard, legumes, grains and cereals) can decrease the absorption of calcium in your diet.  

Around 20 – 25% of the calcium in legumes is absorbed.  Soaking legumes can be a useful strategy to remove phytates before eating to improve calcium absorption.  A little over 30% of the calcium in milk is absorbed, 40 – 60% of the calcium in cruciferous vegetables is absorbed.  However, only 5 – 9% of calcium is absorbed from rhubarb and spinach.  

Calcium absorption is improved by Vitamin D status and resistance training while it is made worse by exposure to lead, high alcohol consumption and low acid levels in the stomach.

This is unlikely to be a significant concern if you consume a broad range of nutrient-dense foods, particularly given you can get too much calcium in your diet.  However, if you drink a lot of green smoothies expecting to absorb all the calcium, you may be disappointed. Most people will struggle to consume excessive amounts of spinach.

A standard western diet consisting of predominantly refined grains, not only provides minimal calcium, but the phytates ensure that it is not adequately absorbed.  

Synergistic nutrients

Calcium works synergistically with vitamin A, C, E, D, K, arginine, boron, carnosine, chromium, copper, lysine, magnesium, methionine, phosphorus and selenium.   Hence, it is important to get your calcium from whole food sources that typically come packaged with these other nutrients rather than relying on supplements.  

Getting enough calcium means we need less vitamin D, but getting too much phosphorus will increase our requirement for calcium.  While you need to ensure you are getting enough of each of the individual nutrients, you also need to ensure you are not getting so much that you overwhelm your body’s ability to use the other nutrients properly.  

The optimal calcium:magnesium ratio

In addition to vitamin D and phosphorus, your body also needs adequate levels of magnesium to use calcium properly.  

  • Magnesium deficiency affects calcium metabolism and alters levels of certain hormones that regulate calcium in the body.
  • A high intake of calcium may interfere with magnesium levels by reducing intestinal absorption and increasing urinary losses.  Magnesium deficiency is also known to induce calcium deficiency.
  • Calcium and magnesium also compete with one another and interfere with the other’s functions if they are out of balance.  
  • Magnesium may prevent calcium from performing its function in helping you to contract your muscles when the ratio of magnesium to calcium is out of balance.

The ideal calcium:magnesium ratio is said to be between 1:1 to 2:1.  This means that you should not push excessive calcium intake without first ensuring that you are getting at least as much (and ideally twice as much) magnesium.  

Nutrient Optimiser can help you manage your calcium:magnesium ratio and ensure that you do not emphasise nutrients that will push this ratio further out of balance.  

Optimal calcium intake 

Based on this analysis, we have set a stretch target of 2.0 g/day for men and 1.6 g/day for women.  However, before prioritising higher levels of calcium, you should first make sure you are getting at least as much magnesium (ideally twice as much).

Once you have started to get the hang of nutrient density, you could ‘level up’ by working towards these stretch targets to truly optimise your nutrition.  

nutrient averageEAR RDIULstretch (men)stretch (women)
calcium (g)1.00.841.

Calcium-rich food sources  


  • parsley  
  • kale  
  • broccoli  
  • cabbage
  • lettuce
  • sauerkraut
  • garlic
  • asparagus  
  • cucumber


  • milk 
  • cheese 
  • yogurt  
  • eggs  


  • oyster
  • anchovy
  • crab
  • caviar


  • almonds
  • cream cheese
  • Brazil nuts
  • walnuts

Nutrient profile 

The nutrient fingerprint chart below shows that we can obtain plenty of calcium in a nutrient-dense diet.   

Nutritious foods to boost your calcium intake naturally

If you are experiencing any of the symptoms of low calcium or are concerned that your current calcium intake is low, then you may be interested in our lists of calcium-rich foods and meals. 

What you will get:

  • Our Nutritional Optimisation Kickstart Guide.
  • A list of the most popular 50 foods that contain more calcium.
  • A list of 100 popular foods that contain calcium, and 
  • An even longer list of 150 common foods that contain more calcium to allow you to expand your nutrient-dense repertoire further.