Most of the calcium in our bodies, around 99%, is in our bones and teeth. The skeleton stores calcium and releases it into the blood stream for many functions. For example muscle contraction, nerve cell transmission and cell multiplication. Some calcium is regularly lost in the urine and must be replaced from the diet. Calcium blood levels must be maintained at a strict range as changes can be life threatening. The body scavenges calcium from the bones when levels are low to regulate this. Therefore measuring calcium in the blood is not a good way to tell what your overall stores are.
Chronic low calcium intake will lead to disrupted bone health and can eventually cause osteoporosis. Osteoporosis is a debilitating disease where the density and quality of the bone is reduced and leads to porous fragile bones that can fracture(break) easily.
You can calculate your fracture risk by using a score such as a FRAX score.
Bone mass is built up during childhood and adolescence and peaks in our twenties. By age forty we are no longer able to replace bone as fast as we lose it and this process increases for women after menopause. Therefore exercise and good nutrition with plenty of calcium is important during childhood and adolescence to build a large bone mass but equally important later in life to slow bone loss.
For most of human history people got their calcium from plants. Dairy foods didn’t become a part of the human diet until around 10,000 years ago. For many populations in the world the ability to drink milk into adulthood is lost. The enzyme (lactase) that digests milk sugar disapears after being weaned off milk as children. There is evidence that a mutation in Northen Europeans developed some ten centuries ago resulting in the continued production of this hormone. This allowed milk consumption throughout adulthood for some populations. Lack of this enzyme in the Western world is often termed ‘lactose intolerance’ however this isn’t an abnormality but part of normal human development.
Many other cultures in the world still get ample calcium in their diets without dairy. RDA (Recommended daily calcium allowance) for calcium: (what you should be aiming for daily)
|Age||Calcium pre day|
The amount of calcium actually absorbed from the intestine varies for different foods and is called bioavailability. Some leafy greens such as silver beat, spinach and rhubarb have compounds called oxalates that bind to calcium making it harder to absorb. However many others are low in oxalates such as kale, collards, broccoli and turnips making their bioavailability up to 50%. Calcium absorption from soy foods and fortified soy foods is similar to dairy at around 25-30%. Nuts are lower at around 20%. The RDA for calcium is based on the assumption that people absorb around 30% from their diets.
|Food||Calcium per 100g||Calcium per typical serve|
|Dairy milk blue||120mg||300mls (1 cup)|
|Soy milk cali plus||160mg||400mg (1 cup)|
|Tofu||210mg||315mg (3/4 cup)|
|Oat milk - bone essential||120mg||300mg (1 cup)|
|Chickpea||140mg||221mg (1 cup)|
|Almond||266mg||186mg (1/2 cup)|
|Sesame seeds||266mg||164mg (1/2 cup)|
|Figs||200mg||160mg (1/2 cup)|
|Soy yoghurt||105mg||160mg (1 pottle)|
|Tempeh||110mg||136mg (3/4 cup)|
|Kale||280mg||120mg (1 cup)|
|Hazel nut||190mg||117mg (1/2 cup)|
|Brazil nuts||180mg||117mg (1/2 cup)|
|Parsley||330mg||105mg (1/2 cup)|
|Current||95mg||83mg (1/2 cup)|
|Harcot beans||157mg||82mg (1 cup)|
|Black beans||137mg||82mg (1 cup)|
|Peanuts roasted||88mg||66mg (1/2 cup)|
|Rocket||200mg||56mg (1 cup)|
|Tahini||330mg||53mg (1 Tbsp)|
|Dried apricot||67mg||50mg (1/2 cup)|
|Sundried tomatos||110mg||40mg (1/2 cup)|
|Macadamia nut||70mg||43mg (1/2 cup)|
*Information sourced from NZ food composition database per 100g - www.foodcomposition.co.nz
Tips for getting enough calcium
Choose a calcium fortified milk alternative and shake well before pouring.
Look for tofu set in calcium (it will have calcium sulphate listed as an ingredient). Most tofu is either set in calcium sulphate or magnesium chloride (nigari)
Make your own trail mix with nuts, figs and other dried fruit to snack on during the day.
Substitute tahini or nut butters for normal butter.
Get into greens- kale chips, rocket salad, broccoli soup…
Exercise is good for your bones, especially weight bearing!