As I sat down to write this week’s newsletter on ‘calcium’ what should pop into my inbox but an article written by a colleague of mine on just that topic. Naturopath Lisa Costa-Bir from www.thefoodcoach.com.au has written a fantastic article on the problems with calcium sources from dairy and plant based alternatives. As I couldn’t have written it better myself, she has allowed me to forward it to you all. Keen to hear your thoughts, happy reading!
Calcium is a highly important nutrient that is best known for its role in bone health. According to Osteoporosis Australia one million Australians are affected by osteoporosis. Lack of calcium is often touted as a causative factor, however, is it really lack of calcium that is the problem or something else?
Dairy products such as milk, yogurt and cheese are often the first sources of food we think of when asked to name foods that are high in calcium, however, there are also plenty of plant-based foods that contain substantial quantities of calcium.
More dairy, worse bone health?
Studies of countries that consume very little calcium from dairy products (such as Japan), show they do not seem to have as much of a problem with osteoporosis when compared to Western countries such as Australia, where dairy intake is extremely high. Why is it then, that the countries that consume the most dairy have the highest rates of osteoporosis? Shouldn’t it be the opposite?
Research suggests that the type of diet we consume has a lot to do with it. The typical diet rich in processed food and low in fruit and vegetables consumed by Westerners increases the risk for osteoporosis due to excess acid supplied from the diet. Over time it is hypothesised that an acid-producing diet causes calcium to be excreted from the bones and these acid-induced calcium losses promote reduced bone mass and osteoporosis. (1). Comparatively a less acidic diet where there is plenty of fruit and vegetables is thought to help balance any excess acidity by providing plenty of potassium rich bicarbonate-rich foods which act as buffers reducing acid load. The extent to which how detrimental a prolonged acidic diet can be is highlighted by a small study involving healthy male volunteers consuming an acid-forming diet(2). The men’s urinary calcium excretion was found to be increased by 74% than when compared with an alkaline diet.
So apart from its alkaline action, why else is plant-based calcium useful?
Unlike dairy products which typically only contain calcium, plant sources of calcium (such as leafy greens) come with plentiful amounts of other micronutrients and cofactors such magnesium, potassium, vitamin C and vitamin K1 all of which are required for bone formation. Additionally, plant sources of calcium also contain other plant chemicals which prevent oxidation and reduce inflammation; both of which have been found to exacerbate bone loss.
Critics may question the absorbability of calcium from plant sources however many plant sources are exceptional. For example, take the leafy green vegetable kale. Research shows us it has been found to be superior to milk in terms of calcium absorption (3). Broccoli and Asian greens such as Bok Choy and Pak Choy are also examples of highly absorbable forms of plant-based calcium. Spinach, though high in calcium, does not enjoy the same absorbability of calcium as the kale example above, due to the presence of oxalic acid which decreases absorption of calcium, reducing bioavailability; cooking does reduce oxalic acid so this is one way to get around this issue (4).
So far we have seen that the source from where we get our calcium is highly important, but what about the quantity, do we really need as much as the government recommends?
From the research reviewed it appears that if we eat a healthy diet that is primarily plant based with an abundance of fresh fruit and vegetables (with much more then the recommended 2 fruits and 5 vegetables) then we probably don’t need to consume as much calcium as is recommended due to the diet not being as acidic, leading to less calcium excretion and less loss of bone density.
A study undertaken on Buddhist nuns, who for years had consumed a vegan diet with much smaller quantities of calcium than recommended here in Australia, revealed that though the nuns had much lower intakes of dietary calcium and protein than meat eating nuns with the same body composition, their vegan diet did not have an adverse effect with regards to bone mineral density(5). Similarly, the Bantu women of Africa who consume no dairy and very little calcium (under 400mg per day) but traditionally have an alkaline diet rich in vegetables also have a very low incidence of osteoporosis.
So there you have it. We know calcium is a highly important mineral, however the source from where we get it and the overall quality of our diet are both factors that need to be considered. Plant sources of calcium offer a highly nutritious form of calcium(6) that are equally useful for the omnivore, vegan or for those that cannot tolerate dairy foods such as those with lactose or casein allergy. We do not need to become vegans or even vegetarians to benefit from more of a plant based diet, however the evidence is clear, by reducing the quantity of meat and processed foods we consume and increasing our quantity of organic, bio-dynamic (due to more mineral rich soil) fruit and vegetables, particularly the leafy green variety, we make a priceless investment with regards to our bone health.
Lisa’s top 7 plant sources of calcium:
- 2 cups cooked broccoli=120mg calcium
- 1 cup cooked bok choy=158mg calcium
- 1 cup cooked kale=179mg calcium
- 2 tbsp tahini=128mg calcium
- 100g parsley=138mg calcium
- 1 cup nori=56mg calcium
- 5 dried figs=100mg calcium
1 & 2. Wynn E, Krieg MA, Lanham-New SA, Burckhardt P. Postgraduate Symposium: Positive influence of nutritional alkalinity on bone health.Proc Nutr Soc. 2010 Feb;69(1):166-73
3. Heaney RP, Weaver CM. Calcium absorption from kale Am J Clin Nutr. 1990 Apr;51(4):656-7.
4. Chai W, Liebman M. Effect of different cooking methods on vegetable oxalate content.J Agric Food Chem. 2005 Apr 20;53(8):3027-30.
5. Ho-Pham LT, Nguyen PL, Le TT, Doan TA, Tran NT, Le TA, Nguyen TV. Veganism, bone mineral density, and body composition: a study in Buddhist nuns.Osteoporos Int. 2009 Dec;20(12):2087-93
6.Park HM, Heo J, Park Y. Calcium from plant sources is beneficial to lowering the risk of osteoporosis in postmenopausal Korean women Nutr Res. 2011 Jan;31(1):27-32