Osteoporosis, Calcium & Vitamin D

Calcium and vitamin D play a central role in bone metabolism: in children and during adolescence it is part of building the skeleton, in adults and especially in the elderly it is required to avoid excessive bone loss.

Calcium is just one of many puzzle pieces when it comes to bone stability and, subsequently, osteoporosis. Genetics, hormone levels, exercise and nutrition play other important roles. Often the interaction of several nutrients is responsible for the build-up and maintenance of the bone tissue. If you are undersupplied with the building blocks of bone tissue in the longterm, it has serious consequences for bone strength.

Especially during childhood and adolescence, large amounts of calcium are required to build up a sufficiently high peak bone mass. Calcium is THE building material of the bone and as such is by far the most important mineral in the body in terms of quantity.

Vitamin D is needed so that calcium can be absorbed in the intestine in sufficient quantities. In the “elderly” a lack of vitamin D leads to osteoporosis due to increased bone loss.

In young adults, calcium and vitamin D are required to keep the balance between bone loss and bone formation. In older adults, especially in women after menopause, they are needed to avoid increased bone loss. Calcium deficiency in combination with the lack of vitamin D is the main cause of the so-called senile osteoporosis (patients over 65 years).

Usually, vitamin D can be produced in our skin. This requires sufficient exposure to the UV rays of sunlight. Additionally, the ability of the skin to produce vitamin D itself decreases significantly with increasing age: approx. 80% of over sixty-year-olds suffer from a significant lack of vitamin D.

In the summer months, it is relatively easy to achieve your vitamin D requirements through sunlight. It is recommended to spend up to 25 minutes a day outside, with bare arms or legs and the face uncovered, so that the body can produce the vital substance itself. During the winter months, most people do not manage to get enough exposure to sunlight and many people are deficient in vitamin D during those months.

A recent European study showed that blood vitamin D levels were the lowest in southern countries such as Greece, Italy and Spain. In northern countries (Norway, Finland, Sweden) the levels were significantly higher. One reason could be that Nordic countries, the US, and sometimes in Switzerland, foods are often enriched with vitamin D.

Did you know that certain foods can also provide part of the vital vitamin in the low-sun season? Herring, salmon or eel are good sources. If you are vegetarian, certain mushrooms such as porcini mushrooms, chanterelles or mushrooms are good alternatives.

Milk & Dairy Products

Milk and dairy products are still the main calcium sources in our daily nutrition. But it’s not for everyone: some are allergic, other’s don’t like it. Especially about milk, there are so many contradictory statements these days, some claiming that calcium from milk cannot be absorbed by our body at all. The majority of studies have shown that there is not a great difference in the extent of calcium absorption in the intestine from milk products, vegetables, fruits or calcium tablets.

And what about the high protein content of milk causing high acid levels in the blood? At this time, there is not much scientific proof that the high protein content of milk has a negative influence on calcium absorption. More the opposite, high protein intake seems to improve bone health.

While women tend to benefit from milk in terms of health, the situation is different for men with a type of cancer: according to research, very high amounts of milk are likely to increase the risk of prostate cancer and men should therefore not consume milk and calcium-rich cheese in excessive quantities.

Calcium-rich Veggies

Only few vegetables (broccoli, kale), herbs (chervil, cress, parsley) or fruits (dates, figs) or nuts contain large amounts of calcium, it is usually simply impossible to meet the daily calcium requirement (1200-1500mg ) with these foods alone. Just think about it, you better start eating the needed 600g (!) parsley at breakfast.

Other calcium-rich foods include spinach, fennel, chickpeas, hazelnuts, almonds, chia, poppy, lin and sesame seeds.

Keep in mind that calcium from plants or plant foods is not absorbed by the intestine as well as calcium from animal foods.

Mineral Water

Bottled mineral water is an often neglected calcium source. There are only few brands on the market with high magnesium levels, so check your water bottle’s label: it should contain at least 300-400mg calcium per litre. And be low in sodium (mineral water is considered to be low in sodium for levels up to 20 mg per litre). Tap water usually does not contain sufficient amounts of calcium.

But remember, you will always need to get enough Vitamin D to absorb  sufficient calcium in your intestine.


The safest and most convenient way to supplement your diet are chewable or effervescent tablets containing calcium and vitamin D in the right dosage. The recommended preventive dosages are 500 mg of calcium and approx. 500 international units of vitamin D.

Even if this dosage is doubled, for treatment of osteoporosis, it is a safe supplement. With the exception of kidney function disturbances or increased calcium blood levels. Rumours stating that calcium uptake causes arteriosclerosis are rubbish.

Another fake recommendation are so-called “calcium cures”. Taking calcium tablets once a year for a few weeks does not give the bone the calcium it needs for the year. It is necessary to take calcium through the entire year.

Enemies of Calcium Absorption

Even if you eat enough foods with calcium, you might not achieve the blood levels you are aiming for, simply because you are eating your calcium with the wrong companion food: phosphorus and phosphate reduce the absorption in the intestine. And not only that, phosphorus (when consumed in excess) can release calcium from the bones (which is then excreted through the kidneys and hence lost to the body). Oxalic acid and salt also the reduce the absorption of calcium. Phosphorus and phosphates are in many foods: processed food  (including processed cheese) and ready-made meals, fast food, chips, cola and lemonades, and yeast. Meat (especially pork) and sausage are particularly high in phosphates.

Foods with a very high oxalic acid content (> 50mg per 100g) are peppermint leaves, various black teas, spinach, star-fruits, rhubarb, yam, Swiss chard, sorrel or certain types of wheat bran. Cooking and steaming can significantly reduce the oxalic acid content in food.

To avoid phosphate or oxalic acid to reduce the absorption of calcium in the intestine, a 30-60 minutes gap between the consumption of the two groups is recommended. 

Childhood and Adolescence

By the way, if you are a parent of a teenage girl, ensure that they get sufficient calcium, too. Studies have shown that only approx. 58% teenage girls get adequate amounts of calcium (for example through two glasses (0.2l) of milk per day). But don’t forget, men can be affected by osteoporosis, too, so boys should also get sufficient calcium.

As a reminder:

Osteoporosis might only “start” in adults over 50 but the supply of sufficient calcium and vitamin in D in childhood, adolescence and young adult life is key to positively influence bone density into old age.

Calcium Requirement Per Day

  • Children up to 15 years: 600-1000 mg
  • Adolescents between 15 and 19 years: 1200 mg
  • Adults: 1000 mg
  • Pregnant and nursing mothers: 1200 mg
  • Osteoporosis patients: 1500 mg

Calcium Uptake Through Food

A sufficient intake of calcium can usually be achieved through food. For example, with the daily consumption of

  • two small cups of yoghurt (300 g) plus
  • two slices of hard cheese (50-60 g) plus
  • a glass of milk (200 ml)

approx. 1000 mg calcium are achieved. Drinking one litre of calcium-rich mineral water (see above) provides an additional 300 mg.

Another side note:

For good bones health, you should also ensure sufficient magnesium in your diet: a minimum of 300 mg magnesium per day is recommended, which corresponds to six to seven bananas or 2 bars of chocolate. Adolescents, athletes, pregnant women and nursing moms have an increased need for magnesium. Vitamin C and copper also play important roles in bone strength.


The exclusive focus on a calcium-rich diet without regular exercise is of little use to bone health. Calcium intake is important but you do not have to consume dairy products to ensure adequate calcium intake.

Research has not yet reached a consensus. The future will show whether there will be a change in nutritional guidelines and which form of calcium intake is optimal for humans.

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Posted on June 29, 2020 by Luitgard Holzleg

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