Vegans and Osteoporosis – Strontium, K2, and Vitamin D3

Horror stories abound of the vegans who go weak at the knees for the animals, literally, but it is not inevitable that all vegans develop osteoporosis, cavities, and other issues connected to musculoskeletal health.

Unfortunately, the hundreds of thousands of cases of osteoporosis in omnivores don’t really make for attention-grabbing headlines like “12 year old vegan has spine of an 80 year old.”

If anything, most vegans are more health conscious than your average omnivores and may actually look after their bone health more diligently… starting with reading articles like this! And the one I published recently about vitamin B12 and bone health.

The health of our bones relies on a whole bunch of things including exercise, diet, genetics, environmental factors, and our exposure to certain illnesses and diseases, and even to stress. We can’t change the genes we inherited but we can influence how they are expressed (this is called your phenotype), and researchers are plugging away at finding out more about how our diet and lifestyle, and certain drugs, can alter which genes are turned on and off and to what degree.


I find the field of epigenetics fascinating, and nutriepigenetics even more so, but that’s not the focus of this article. Instead, I’m just going to talk about three key nutrients in bone health that are sometimes overlooked because of the intense focus on calcium which, by the way, doesn’t simply look like a glass of cow’s milk, despite the dairy industry’s immense influence.

The nutrients I’ll cover are:

• Strontium
• Vitamin D
• Vitamin K2

These are all needed for the appropriate deposition of calcium in the bones and teeth, as well as for a bunch of other metabolic processes. When they’re missing from the diet it can actually be dangerous to increase calcium intake, which is the mistake many people make when diagnosed with osteopenia or osteoporosis. Calcium does not always make it into the bones if conditions are not right and this can lead to calcification of the arteries and an increased risk of heart attack and even stroke as calcium-containing plaques break free from arterial walls.

We’ve talked quite a bit about calcium on the blog before, however, so let’s move on to look at strontium, a mineral many don’t recognise.

Strontium – What is it and why do we need it?

This mineral is considered essential but most people are not considered to be at risk of strontium deficiency. Deficiencies in strontium have, however, been associated with certain types of osteoporosis and arthritis that are resistant to supplementation with calcium or the use of bisphosphonate medications.

Strontium is an element that is part of the same chemical family as calcium and magnesium and biologically strontium behaves in a similar way to calcium and tends to be present in foods naturally rich in calcium. Strontium accumulates in bone and teeth just like calcium, as well as in the aorta, just like calcium. Around 99% of the strontium in our bodies is found in the bone, with the total body content of strontium in an average man amounting to 323mg.

Typical intake of strontium from the diet is somewhere between 2 and 14mg daily, which is usually sufficient to cope with any turnover of the mineral in the bones. However, where osteoclast function (i.e. the bone-destroying cells) are working in overdrive, and osteoblast function (i.e. bone-building cells) are not provided with the right stimulus or material, bone weakness may develop.

Before we look at vegan food sources of strontium, let’s briefly look at some of the factors that affect mineral metabolism in bone.

Factors Affecting Strontium Status

Causes of mineral depletion from the bones can include an overly acid-forming diet, excessive use of antacids, kidney dysfunction affecting mineral reabsorption, and gastrointestinal problems affecting absorption of nutrients from food. These can all lead to low levels of circulating calcium and low levels of calcium in the cells of the body which prompt the release of calcium from the bones to stabilise serum calcium.

Hormonal fluctuations, such as from stress, or during the menstrual cycle, also affect calcium storage in bones. In particular it is thought that some people who suffer from premenstrual syndrome (PMS) actually have a form of calcium metabolism dysfunction that leads to prolonged hyperparathyroid hormone circulation. A lack of dietary calcium during the luteal phase of the menstrual cycle may then prompt the release of parathyroid hormone (PTH) which pulls calcium from the bones. PTH also pulls strontium from the bones.

There do not appear to be any long-term studies indicating a correlation between having PMS and hyperparathyroidism when younger and having an increased risk of osteoporosis when older but, theoretically, where hyperparathyroidism persists or occurs regularly, this could be the case, especially because PTH also controls vitamin D and phosphorus metabolism.

PMS may also be connected to magnesium and zinc insufficiencies.

Strontium Absorption

Unfortunately, strontium is poorly retained in our bodies, with net retention pretty close to zero. This mineral is excretion in urine and bile, which means that factors affecting kidney function and biliary health may also affect strontium metabolism. Wherever strontium and calcium are competing for passage across membranes in the body calcium typically wins out, which makes sense as the body needs a lot more calcium than it does strontium.

In addition, older people tend to absorb strontium less well than younger people, while those who are pregnant of breastfeeding have an increased efficiency in absorbing both calcium and strontium. People who have had gastric surgery such as a bypass may have reduced absorption of both these minerals because the greatest site of absorption appears to be the duodenum; the ileum is the most effective absorption site however.

Calcium and strontium are better absorbed in the presence of vitamin D, lysine and arginine and also lactose, but magnesium suppresses the absorption of both strontium and calcium, although it is needed to facilitate the transport of these minerals into the bones.

Absorption of Strontium in Vegans

A couple of specific issues which could affect a large number of vegans is that both alginates (e.g. from seaweed) and fibre such as cellulose (from plant foods), both depress calcium and strontium absorption. As such, cooking plant sources of calcium (such as kale, collards, and broccoli) to help break down cellulose, or choosing more legume and nut sources of calcium in a vegan diet, could improve calcium and strontium status more so than simply eating raw kale salads. Also, increasing calcium intake actually lowers strontium retention, and supplementation with both calcium and phosphorus really reduces strontium retention. Strontium appears best absorbed in fasting conditions, i.e. when not taken with food.

In general, strontium absorption in adults is in the range of 5 to 25%, but can be higher than 90% in young animals and as low as 0% in older animals. Absorbed strontium is poorly retained but the little that does make it to the bones and teeth is incorporated into tissues via ionic exchange, surface absorption, by binding to proteins and through the protracted process of being bound within bone crystals.

Strontium’s Benefits for Bones

Strontium is thought to be able to substitute for calcium in some enzyme systems but there are contradictory results from studies looking at the influence of strontium on the development of dental caries in animals and their offspring. Strontium ranelate is a medication used for the treatment of postmenopausal osteoporosis and is the first such agent that appears to affect both bone formation and resorption, increasing the first and decreasing the latter to build and maintain stronger bones.

Strontium ranelate increases the number of osteoblasts, as well as their activity, while reducing the activity and differentiation of osteoclasts. It also increases the number of bone nodules and the expression of alkaline phosphatase bALP, both of which improve bone-building activity. Strontium downgrades a whole load of osteoclast-related activities too, and has been seen to reduce the risk of vertebral and hip fractures by increasing bone mass in these areas. In animal studies (which I do cite on the site but do not support) strontium ranelate has even helped reduce the loss of bone density associated with immobilisation in rats whose hind limbs the researchers deliberately immobilised.

In one double-blind, placebo-controlled phase II trial [Meunier et al. 2002], either strontium ranelate (0.5, 1 or 2g/day) or placebo was given to 353 White women (mean age 66 years) and their lumbar bone mineral density (BMD) was measured annually. At the 2-yr conclusion of the study the increase in BMD for those taking 0.5g was 5.9%, an 8.3% increase was seen with 1g strontium per day, and a 13.6% increase for 2g/day. In addition during the second year of treatment, the 2 g/day dose was associated with a 44% reduction in the number of patients experiencing a new vertebral deformity.

41% Decrease in Fractures with Strontium

In another study by Meunier, et al. 2004, involving some 1442 individuals, 2g of strontium ranelate per day over a 3-year period resulted in a 41% reduction in the relative risk of experiencing a new vertebral fracture. The risk of clinical vertebral fractures was reduced by 38% and over the first 12 months, the reduction in relative risk was 49%. The patients receiving strontium had a 14.4% increase in lumbar BMD compared to those receiving placebo, and, importantly, strontium ranelate was well tolerated without any specific adverse events. Patients who continued to receive strontium ranelate over the next year also continued to show improvements in lumbar BMD while those patients switched to placebo actually had a reverse in BMD.

Strontium Supplements and Food Sources for Vegans

Strontium makes up 34% by weight of strontium ranelate, meaning that there is 680mg of elemental strontium in each 2g dose of strontium ranelate. This medication is typically provided as granules to be mixed in water, usually taken before bedtime to avoid consumption with food. Gut absorption is estimated to be around 25% meaning that on average those taking 2g of strontium ranelate are absorbing 170mg of strontium, much of which will not be retained.

Comparable levels can, with some care, be achieved through diet alone, with the best vegan sources of strontium including root vegetables, brazil nuts, and unrefined wholegrains, where most of the strontium is found in the peel of the vegetables and the bran part of wholegrains. Seafood and other animal products also contain strontium, as do beans and peas. California-grown lettuce also tends to be high in strontium as this plant takes up a lot of strontium from the soil in this region.

Good plant sources of strontium include:

• Root vegetables
• Carrots
• Celery
• Spinach
• Potatoes
• Wheat
• Barley
• California-grown lettuce
• Brazil nuts (a really great source of strontium!)

Flour, grains and breads average 2,150 mg per gram of stable strontium.

As always, diets high in refined, processed foods tend to offer very little in the way of strontium, and other nutrients, and such diets are associated with decreased bone strength.

There is also some evidence that strontium supplementation, or increased dietary intake perhaps, can help reverse the age-related decline in production of glycosaminoglycans (GAG). These substances include chondroitin sulphate and glucosamine sulphate which are essential for the health of the joints. So, not only is strontium helpful in osteoporosis, it could also be useful in osteoarthritis.

When I next get the chance, I’ll be discussing vitamin K2 in relation to bone health.

References

Meunier PJ, Slosman DO, Delmas PD, Sebert JL, Brandi ML, Albanese C, Lorenc R, Pors-Nielsen S, De Vernejoul MC, Roces A, Reginster JY. Strontium ranelate: dose-dependent effects in established postmenopausal vertebral osteoporosis–a 2-year randomized placebo controlled trial. J Clin Endocrinol Metab. 2002 May; 87(5):2060-6.
Meunier PJ, Roux C, Seeman E, Ortolani S, Badurski JE, Spector TD, Cannata J, Balogh A, Lemmel EM, Pors-Nielsen S, Rizzoli R, Genant HK, Reginster JY. The effects of strontium ranelate on the risk of vertebral fracture in women with postmenopausal osteoporosis. N Engl J Med. 2004 Jan 29; 350(5):459-68.

Tagged as: bones, calcium, nutrition

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