Calcium is well known to be an important component of our bones, but it’s also needed for numerous other biological processes, such as the contraction of muscles and blood vessels and the functioning of the nervous system. A lot of calcium is stored in our bones, so our body can regulate to keep it available. But if one’s intake is too low, their bones will make up the shortfall and can weaken over time, leading to osteoporosis. Excessive calcium intake can also have its dangers, such as increasing the risk of atherosclerosis and therefore certain cardiovascular diseases. So how much calcium should one consume to avoid deficiency without harming themselves?

How much calcium do people ingest?

Both American and European health organisations recommend a daily calcium intake of around 1000 mg, but very few people in the world meet this limit. A data review covering 74 countries found that average calcium intakes vary widely, ranging from 175-1233 mg per day.(1) In African and Asian countries, most people consume less than 500 mg of calcium per day, while intakes above 1000 mg are found in only 1-2 countries.

In the Palaeolithic era, it’s estimated that calcium intakes were as high as 1500-2000 mg per day, while in some primitive tribes such as the Pygmies and Bantu intake levels were very low.(2)(3) However, calcium intakes of similar primitive people may have not been calculated precisesly, so it”s not possible to draw conclusions based on this speculation alone. It’s also worth noting that, despite low calcium intake, incidences of osteoporosis and bone fractures are lower in Asia than in some European countries with much higher calcium intakes.(4)

Why is it difficult to accurately determine calcium requirements?

There’s clearly huge variation in people’s calcium intake. It’s difficult to determine the ideal amount for a number of reasons. Vitamin D, for example, is necessary for calcium to be absorbed, so more calcium gets used even when a lower amount is supplemented. On the other hand, if one has calcium deficiency, they are consuming big doses of calcium in vain.(5) In addition to vitamin D, vitamins K and A are important for calcium metabolism and bone health, so deficiencies also lead to poor bone health.(6,7)

Potassium and magnesium are also related to calcium. Although the theory is somewhat controversial, it’s thought that one reason for osteoporosis may be that the body compensates for the 'acidifying' effects of a Western-style diet rich in meat and refined carbohydrates by partly extracting calcium from the bones. A meta-analysis in 2022 found no significant association, but the diets with the highest acid production already significantly reduced bone density in participants.(8) The results may also show that protein intake itself is important for bone health, so this may have partly compensated for the negative effect.

With higher levels of vitamin D, a diet richer in potassium and magnesium and lower in refined grains may be sufficient to reduce calcium intake.

The foods source from which calcium is obtained should also be considered, as their absorption varies considerably. Spinach, for example, only absorbs 5% of calcium due to its high oxalate content, while milk absorbs 27.5%.(9) In contrast, vegetables with lower oxalate and phytic acid content (e.g. curly kale and celery) are good sources of calcium.(10) As with other micronutrients, calcium is affected by body weight, age and other factors.

What calcium intake seems optimal based on research?

Several epidemiological studies are available on the relationship between calcium intake and various chronic illnesses. The results are quite mixed, but they have a number of interesting findings. It’s worth noting that most of the studies have been done in countries where people consume a lot of dairy products, and where they don’t, calcium intake may have come mainly from vegetables. This is significant because those with lower calcium intakes may well have less healthy diets in other aspects as well, while those with higher intakes are likely to have more regular intakes of vitamin K1, magnesium and potassium.

These micronutrients are known to be protective against most chronic illnesses, and deficiencies are very common. (Calcium supplementation will not be discussed here as it will be analysed in detail in another post; calcium supplementation may be useful for those who are unable to achieve optimal intakes through diet, but even then the recommended way of supplementation can largerly differ.)

A 2015 meta-analysis based on a pooled analysis of 22 studies found no significant association between dietary calcium intake, cardiovascular disease, cancer or mortality from any cause.(11) Studies with a follow-up of less than 10 years demonstrated a protective effect of higher calcium intake, but longer studies showed an increased incidence of cardiovascular disease. Very high intakes, especially above 1400 mg, are not recommended in the long term, as several studies have already shown a 40-50% higher risk compared to 600-1000 mg per day. And one study shows that those with genetically higher calcium levels have a significantly higher cardiovascular risk.(21)

A British study in 2021 found that excessively low calcium intakes may also be associated with problems: doses higher than 770 mg per day were associated with fewer cardiovascular and all-cause deaths than lower doses.(13)

A meta-analysis in 2020 summarised the results of 16 randomised trials alongside 26 observational studies, showing that dietary calcium intakes ranging from 200 mg to 1500 mg per day had no significant effect on cardiovascular disease risk.(12)

Based on an earlier meta-analysis in 2016, the healthy range may be even wider: 4 randomised trials and 26 observational studies were analysed and found that from 200 mg up to the officially recommended maximum of 2000-2500 mg per day, calcium intake had no effect on CVD incidence.(14)

Further research to establish the optimal amount more precisely

A 2014 meta-analysis was perhaps the most helpful in determining the optimal range is. In this study, a U-shaped curve was observed in the association between calcium intake and cardiovascular mortality.(15) Here, the optimal intake was 800 mg of calcium per day, with both much lower and much higher intakes having negative effects.

A similar U-shaped curve was observed in a Chinese study from 2022. The study examined how calcium consumption in youth affected the risk of high blood pressure later in life. (16) The lowest risk (based on an average 2000 kcal diet) was observed at a daily calcium intake of ~700-800 mg, while lower and higher intakes increased the risk of developing high blood pressure several-fold.

An observational study in 2011 comparing calcium intake with the risk of bone fractures found similar results as well: ~800 mg calcium per day was the optimal amount, above which the risk increased slightly.(17)

A 2015 review also shows that there is no benefit from very high calcium intakes, and that calcium intake on its own is not nearly enough for bone health. This suggests that dietary calcium intake has no effect on the risk of bone fractures (18).

Studies that have determined the amount of calcium needed to balance the body’s intake have also found that between 700-800 mg per day is ideal. This 2007 study found ~741 mg per day,(19) while the EFSA summary based on several similar studies found ~715 mg per day, to which +40 mg was added for calcium loss from teeth, which also yields a nearly identical result.(20)

Summary

So to summarise the results of the research, calcium can be consumed in  a wide range, but for adults, roughly 700-800 mg per day seems optimal. It’s important, however, to bear in mind the other factors mentioned earlier: with adequate vitamin D3 and other micronutrient intakes, and using well-absorbed forms, up to 400-600 mg of calcium per day may be sufficient, but in some cases not even 1000-1200 mg would cause any problems. To be on the safe side, one should aim for 700-800 mg per day, as this amount has not only been shown to be effective, but has no known drawback.