What’ is calcium?
Calcium is alkaline earth-metal, soft, malleable, ductile and it’s the fifth most abundant element on earth (1,6% of the crust) You can’t find it in it’s native state in nature, being it normally part of rocks or other minerals.
Besides being the 5th most abundant element on earth, it’s also the most abundant metal in your body, specially as calcium carbonates. From the approximately 1200 grams of calcium found in an adult body, 1110 grams can be found in bones. The remaining 90 grams are used for other diverse functions such as: cellular membrane activities, muscle contractions, nervous impulses, control of the acidity of the blood, cellular division, hormonal control and blood coagulation.
Through erosion and other natural transformations, calcium will be deposited in the soil and that’s how it ends up in our diet.
Plants absorb from the soil all the minerals it needs, being calcium one of them. This mineral gets first in animal diet through the ingestion of plants from the soil and afterwards, by the consumption of those same animals, into us and other predators. This means that plants are filled with minerals, being calcium one of them. Enough calcium to help the construction of the bones of colossal herbivors such as elephants and buffalos. And we, humans? History is made of humans that grew healthy and strong way before animals had been domesticated. These humans didn’t hunt pregnant cows to suck on their tits to drink milk. These men fed on plants, from fertile soils. There’s thousands of healthy skeletons found belonging to the period before animal husbandry.
The balance of calcium in our organism is maintained by three systems – digestive system, urinary system and skeletal system. These three systems are extremely precise and efficient in the regulation of calcium in our bodies. If our diet is low in calcium, the gastrointestinal tract cellules will act vigorously to absorve a higer percentage of calcium from the food you digest. The same happens with your kidneys, that will work to keep calcium in your body. On the other hand, if we consume too much calcium, those same organs will act in complete reverse, trying to get rid of the excess. If we didn’t have this capacity, the calcium excess would have to be deposited in our soft body tissues – such as heart, kidneys, muscles, skin, etc. – we would probably get sick and die. Clearly the human body has many defense mechanisms to secure the essential minerals perfect balance.
The World Health Organization recommends between 700mg and 1300 mg of daily calcium depending on your age., gender or part of the globe you live in.
Besides not being very exaggerated values, it would be impossible to reach for most of the world population, if it wasn’t the exaggerated consumption of milk and milk products. It’s for this reason that omnivorous humans normally consume a daily dosage of 1000mg, while herbivores consume around 600mg.
However, the WHO itself does not state that these values are scientifically proven and neither that the calcium consumption alone fully prevent osteoporosis.
“In countries with a high fracture incidence, a minimum of 400–500 mg of calcium intake is required to prevent osteoporosis. When consumption of dairy products is limited, other sources of calcium include fish with edible bones, tortillas processed with lime, green vegetables high in calcium (e.g. broccoli, kale), legumes and by-products of legumes (e.g. tofu). The interaction between calcium intake and physical activity, sun exposure, and intake of other dietary components (e.g. vitamin D, vitamin K, sodium, protein) and protective phytonutrients (e.g. soy compounds), needs to be considered before recommending increased calcium intake in countries with low fracture incidence in order to be in line with recommendations for industrialized countries.”(1)
This means that not only it is not necessary to consume calcium in excess, that it can even be useless, if you don’t consider physical activity and the consumption of other nutrients.
Besides, there’s some studies that show that there is really low need for calcium to keep a good and healthy bones. A study from 2003 in inuit children – eskimo tribe -, didn’t show any deficiency related to calcium despite the fact their diet is high in protein and animal fat, and without providing more than 120mg of daily calcium comsumption (10).
And as stated by the Department of Biochemical Medicine, of the Univeristy of Dundee in 1978 (11):
“Many official bodies give advice on desirable intakes of calcium but no clear evidence of a calcium deficiency disease in otherwise normal people has ever been given. In Western countries the usual calcium intake is of the order of 800-1000 mg/day; in many developing countries figures of 300-500 mg/day are found. There is no evidence that people with such a low intake have any problems with bones or teeth. It seems likely that normal people can adapt to have a normal calcium balance on calcium intakes as low as 150-200 mg/day and that this adaptation is sufficient even in pregnancy and lactation. Inappropriate concern about calcium intake may divert attention and resources from more important nutritional problems.”
Animal Protein and Osteoporosis
As mentioned above, those following a plant base diet, tend to have lower dietary calcium values than those following an omnivorous diet. Normally the vegan community states “Well you’re bones are f*cked up because you eat meat and drink milk!”. This is based in two pieces of evidence:
- Ecological studies have crossed data between milk and dairy products consumption and bone fracures. It has been observed that countries with higher dairy products consumption tend to show a higher number of fractures, nominately of the hip bone. African and Asian countries consume way less milk and they’re populations seem to have less bone fracture. (2) (3)
- Metabolic studies have shown that after consuming animal protein, people urinate more quantities of calcium. Therefore the theory saying that calcium consumption is not that important to prevent ostheoporosis and that people in a plant based diet are “protected” due to the lack of animal protein in their diet. (4) (5)
I consider it “pieces” of evidence because some of the info could be a bit deceiving. In regards to epidemiological studies (ecological is a type of epidemiological study), the first study about bone fractures in the Asian population – The Osteoporosis Study of Hong Kong – shows that besides the hip fractures being very few in Hong Kong compared to Sweden, the same would not happen with lumbar spine fractures. (6)
It is said:
“The observed ethnic differences in fracture incidences may be due to the fact that hip fracture risk was affected by fall risk, whereas the risk of vertebral fracture mostly depends on bone strength. Despite the low hip fracture rate in our population, Hong Kong women had a higher prevalence of osteoporosis (…) han US Caucasian women (35.8% vs. 20%, respectively) and a similar prevalence of about 6% in Hong Kong and US Caucasian men.”
In other words, at least in this study and as shown in the graphic below the connection between calcium consumption and bone fracture was not verified.
In an epidemiological review made in 2009, The American Journal of Clinical Nutrition concludes (7):
“A small positive effect of protein supplementation on lumbar spine BMD in randomized placebo-controlled trials supports the positive association between protein intake and bone health found in cross-sectional surveys. However, these results were not supported by cohort study findings for hip fracture risk. Any effects found were small and had 95% CIs (Confidence Interval) that were close to zero. Therefore, there is a small benefit of protein on bone health, but the benefit may not necessarily translate into reduced fracture risk in the long term.”
In regards to metabolic studies, there’s a theory that states that higher protein intake leads to higher osteoporosis due to the fact of loosing calcium through urine. The idea is that protein, specially aminoacids that contain sulphur, will lead to higher acidity in the blood, can lead to a higher renal charge. In a way to neutralize this acid, calcium is used as a buffer and therefore urinated.
There are however somes studes that go against this. A literary revision of the European Journal for Clinical Nutrition in 2012 concludes (8):
“However, increased calcium excretion due to HP (High Protein) diet does not seem to be linked to impaired calcium balance. In contrast, some data indicate that HP intakes induce an increase of intestinal calcium absorption. Moreover, no clinical data support the hypothesis of a detrimental effect of HP diet on bone health, except in a context of inadequate calcium supply.”
So what makes the bones go weaker? Well, genetics seems to be one of the main reasons in regards to osteoporosis, specially in women. Besides, it could also be related to estrogen levels.
There’s however some adaptations that we can make to our diet that have shown good scientific evidence. I think it’s fair to say that physical activity, a good physical composition and an adequate calcium consumption, vitamin D, vitamin K, phosphore, potassium and magnesium seem to prevent the disease. However, smoking, elevated consumption of sodium and caffeine, low consumption of protein, excess of vitamin A (retinol and not beta-carotene) and a possible deficiency in B12 vitamin, seem to lead to the weakening of the skeleton.
Considering that calcium concentrations in animals is entirely dependant of the calcium in the soil, it’s easy to understand that if a plant does not have enough calcium to keep your bones healthy it won’t keep a cows bones healthy either. Therefore if a cow has low calcium levels, she will have a supplemented diet. Same happens with milk that a lot of times is enriched with calcium, vitamin D, magnesium, vitamin B12, etc. The good news for you is that vegetable milk are also enriched with these nutrients. Another good news is that the calcium absorption of that calcium despite the fact that it isn’t as good as the one from the cows milk, it’s still considered good. This, because in very broad terms, the higher the concentration of oxalate in a particular food, the less it will be it’s absorption. That’s why it is as important to consider your calcium sources as the values in it. (9)
Some of the best calcium sources seems to be -kale, cabbage and turnip greens, bok choy and broccoli. Basically green leafed vegetables with the exception of spinach. Other good sources are enriched milks with calcium and vitamins, such as soy, almond, rice milk, etc, sesame seeds, tahini, blackstrap molasses, raisins, dried figs and apricots and other dried fruits. Some types of tofu and bread are also very rich in calcium.
So where are we?
It seems that there’s a bit of a discordance about the recommended daily dosage and what’s really needed to keep your bones healthy. As we can see, there’s a different number of factors that drive the preservation of the bone, being the absorption of calcium itself depending on other factors. What seems to maintain the bone health is really the complete scene. Still, there isn’t any reason for a person that follows a plant based diet to believe is protected against osteoporosis for that simple reason. It is safer to consider that in any diet it is important to eat calcium rich foods and to try to reach the daily recommended dosage. Correct or not, a consumption of 1000 or 1300 mg of calcium seems to be safe for most people. It is not recommended however to go over 1400m daily.
In my opinion, there is no reason to be afraid of fortified milk. If you still don’t want to drink it, you know what to do. The beans and pasta soup your grandmother does and a lot of green stuff! 😀
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Many thanks to Margarida Guerreiro for medical data revision and to Vasco Cartó for helping with the translations!
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