The best known role for calcium is that it is essential for bone health with 99% of calcium being stored in your bones/teeth. However, it is also required in the blood and is involved in cardiac function, releasing hormones such as insulin and in regulating the operation of your muscles, blood vessels and nerves. Unfortunately, most of the Australian population is consuming on average around 20% less than the recommended daily intakes, though worsening to nearly 50% less than the recommended intake in post-menopausal women and older men.
If you do not consume sufficient calcium, your body will take calcium from your bones to maintain adequate levels in the blood, this increases your chance of brittle bones – leading to fractures and osteoporosis. This is especially relevant for women who are particularly susceptible to low calcium levels post-menopause. Please note that there’s a lot of misinformation out there about dairy ‘acidifying the blood and leaching calcium out of your bones’. Be wary of any practitioners touting this nonsense as it illustrates a complete lack of understanding of basic chemistry and physiology and also please note that in the absence of an allergy, dairy does not cause inflammation either.
Life Nutrition emphasises the importance of getting your vitamins and minerals from wholefoods where possible. For most of us, around 60% of our calcium comes from dairy products and so restricting these in the absence of a confirmed allergy or intolerance is problematic and highly increases your risk of deficiency.
Bioavailability (or how much calcium actually ends up being absorbed in your body) differs between foods and is reduced in those foods rich in oxalic acid (eg spinach, beans) or phytic acid (seeds, nuts, grains).
Calcium rich foods include:
- Dairy – milk, cheese or yoghurt or fortified alternatives such as almond, soy, coconut, rice or oat milk – read our article here for more info. Fortification of milk-alternatives should be minimally 275-300mg of calcium/250ml serve and please note to regularly shake these milks during consumption as the calcium salts tend to settle on the bottom and are disproportionally discarded in the dregs.
- Leafy or cruciferous greens – broccoli, kale, spinach etc
- Canned fish with bones (eg salmon or sardines) – note though that canned fish without bones are not a significant source of calcium
- Beans and lentils
- Other fortified products (less ideal than naturally occurring calcium in foods, but preferable to taking isolated calcium tablets)
Each day, you should be consuming the following amounts of calcium based on your gender/age:
Supplementation may be required if you cannot consume sufficient calcium for your age/gender via your diet, if you are vegan, if your diet is especially high in sodium and/or protein (as this increases the excretion of Ca) or if you have conditions such as Crohns disease where absorption may be negatively impacted. Ideally, to maximise absorption – your supplements should be taken twice a day as – generally 2x500mg will be adequate for most.
Note that you should never take above your recommended intake as higher calcium supplement use has been associated with increased risk for prostate cancer, kidney stones and may have negative impacts on heart health. Supplementation can also interfere with other medications – if in doubt, please talk further about this with your pharmacist or doctor.
You need to be very careful with supplementation, especially if there is suspected deficiency in iron, magnesium or zinc as these minerals compete with calcium for digestion/absorption. Try to take your supplements at a time when you are not consuming foods rich in these other minerals, though noting that if you take calcium supplements on an empty stomach this can also cause irritation/digestive upset – so it’s advisable to take your supplements with some food. If you tend to have digestive issues or irritable bowel syndrome, ensure that any supplements/fortified foods contain calcium citrate as this is the supplemental form least likely to cause side effects such as pain, gas or bloating.
- Note that sometimes supplements may list the calcium in ‘mmol’ units – if so, 1mmol of Calcium = 40mg so you’d be looking for a supplement of around 12.5mmol to be equivalent to a 500mg calcium dose. As your pharmacist for help if required!