Calcium is a key nutrient of concern when on a low-FODMAP diet, or when dairy-free because foods containing lactose are excluded, and lactose is in dairy foods, and dairy foods are a key source of calcium for many people.
However, there are many ways to get enough calcium each day, and I’m going to talk about that in this article.
What does calcium do?
Calcium is the most abundant mineral in the human body and 99% of the body’s calcium is in our bones and teeth. Calcium is needed in infancy, childhood and teenage years as our bones mineralise, and grow in length and width. Throughout our life our bones are being remodelled, with calcium being taken out and put back in throughout the process.
Calcium also serves an important role in muscle (including the heart) and nerve function because it activates proteins required for regulating muscle contractions. It is also needed for maintaining blood pressure and in blood clotting.
How much calcium do we need every day?
Children 1-3 years require 500mg
Children 4-8 years require 700mg
Children 9-13 years require 1000mg
Teenagers 13-18 years require 1300mg
Adequate calcium is crucial for children and teenagers because at this stage of life bones are being formed, lengthened, and peak bone mass is being attained. The teenage years are a particularly vulnerable time, because not only do daily requirements increase, but milk consumption typically decreases. Over half our bone mass is formed between 13 and 18 years and once peak bone mass is formed, it’s set for life.
Adults require 1000mg per day
Women over 50 years require 1300mg or 3.5 serves of dairy – this is because estrogen promotes calcium absorption and retention, so when estrogen production decreases sharply with menopause, calcium needs increase.
Men over 70 require 1300mg
Older adults also require more calcium because absorption (the amount our body actually uses from what we eat) decreases with age.
Interestingly, pregnant and lactating women don’t require additional calcium to provide for the fetus or milk production. In pregnancy, the body increases absorption to around 50% rather than the usual 25%, and in lactation calcium is sourced from the mother’s blood calcium and losses are replaced after weening.
A serve of dairy usually provides 200-300mg of calcium, this is equivalent to 1 cup of milk (240mg) or 200g yogurt (350mg)
If you can’t consume milk or yogurt, what are other food sources of calcium?
If you can’t drink milk, there are lots of options for getting enough calcium. Many nut and oat milks, and orange juice are fortified with calcium, but the content varies so check the nutrition labelling. In a fortified food you want at least 100mg calcium per 100mL.
Other examples of sources are:
40g hard cheese: 222mg
100g tofu: 510mg
20g dried figs: 46mg (any serve greater than this is medium to high-FODMAP)
100g kale: 130mg (note: although spinach contains calcium it is not a good source because it also contains calcium binders that prevent absorption)
42g chickpeas: 18mg (any serve greater than this is medium to high-FODMAP)
50g chia seeds: 315mg
12g almonds: 60mg (any serve greater than this is medium to high-FODMAP)
80g broccoli: 56mg
What else do we need to know?
How much calcium our body actually absorbs varies, as does the bioavailability of calcium in different foods. However, given that people tend to get their calcium from a few different sources, bioavailability isn’t really taken into account in the guidelines. Calcium from green vegetables tends to be more bioavailable than that from dairy.
Calcium requires vitamin D to be absorbed – this is why vitamin D is also essential for healthy bones and supplements often contain both.
Calcium can interfere with the absorption of other minerals such as iron and magnesium. For this reason it is best to get your calcium from food sources and not supplements, but if you choose to take supplements or your doctor recommends them, take care not to take more than the recommended dose, and don’t take at the same time as other mineral supplements. For example if you also take an iron supplement, take the iron in the morning and calcium at night, and always take with food.
Excess calcium can also cause kidney stone formation – another reason to be cautious with supplements.
Likewise, fibre can impair calcium absorption; this isn’t usually a problem with fibre from food but if you take a fibre supplement, take it at a different time to calcium-rich foods or supplements.