Calcium is only one of 18 nutrients needed for healthy bones.[1] Our bones need this mix of minerals for sufficient strength and malleability: a physical property opposite of stiffness, which allows bones to absorb mechanical force instead of fully opposing it, thus avoiding breaking.

Considering we need magnesium for more vital bodily processes than any other nutrient[2], it may come as a surprise to some that magnesium is a metal. Yet metals are known for being malleable, which helps explain why over 60% of our body’s magnesium is found in bone,[3] where it is known to reduce the rate of bone mineral degradation[4] and overall bone loss,[5] and why magnesium-deficient bones are more fragile despite higher levels of other bone minerals.[6]

This also sheds light on why magnesium deficiency and low magnesium intake result in brittle, fragile bones as well as osteoporosis.[7-10]

The relationship between magnesium deficiency and osteoporosis is even more clear when we see how magnesium is ingrained in the very nature of bone metabolism and formation[11]:

Our bone tissue is comprised of two complimentary parts:

1. A physical framework or “matrix”osteoid. called
2. A mixture of bone minerals stored within this framework.

To see how bone formation requires magnesium, let’s look at the four main cells involved in life’s ongoing cycle of breaking down and rebuilding bone tissue:

1. Osteoclasts: break down bone matrix (osteoid) & release the minerals.[12-15]
2. Osteoblasts: lay down new bone matrix (build and rebuild our bones).[15-18]
3. Osteocytes: which were once osteoblasts, [19] are embedded in the bone matrix. These cells sense any mechanical stress placed on our bones,[20-24] and respond by activating functional  osteoblasts to build more bone.
4. Lining cells: dormant osteoblasts on our bones’ outer border.

The video[v1] shows how osteoblasts secrete the collagen-based bone “matrix” onto our bones.[18,25] The matrix solidifies into a physical framework called osteoid, into which a mineral mixture of calcium, phosphate, magnesium and others, is deposited.

Now that we have a grasp on how our osteoblasts build and maintain strong bones, let’s see how this requires magnesium.

Our bones are in a constant dance of being broken down by osteoclasts, and being rebuit or grown by osteoblasts. Thus to prevent osteoporosis and keep healthy bones, we need enough osteoblast activity, so we don’t break down more bone than we make. Our osteoblasts can’t function without magnesium: They depend on it for three main factors:

1. Energy:

To make bone matrix, osteoblasts need energy in the form of ATP molecules (adenosine triphosphate)[26-29] which are made from the fat and carbs we eat. Not only is magnesium a physical part of every active ATP molecule[30-34] but the processes of our cells absorbing carbs and fat,[35-42] and then converting them into ATP, both require magnesium.[43-48]

Simply put, without magnesium osteoblasts have no energy. In fact, the calcium:magnesium ratio is so critical to energizing our cells, that if calcium inside our cells rises too high above magnesium, this slows down energy production![49] In other words, to much calcium in our bone cell prevents proper bone formation!

2. Bone matrix production:

Bone matrix is made of various proteins, over 90% of which are collagen[17,25]. The process of making these proteins is called protein synthesis. It has two phases: copying DNA, and then converting the copy into an actual protein. Both of these phases require magnesium.[50-53] Osteoblasts need magnesium to make bone matrix.

3. Osteoblast production:

Both magnesium and magnesium-dependent ATP are mitogenic to osteoblasts.[28,55,56] This means they help osteoblasts divide and replicate. This can largely be explained by their facilitation of the various enzymes needed for DNA replication before cell division. [57-59] In fact magnesium has been shown to directly raise the number of osteoblasts in bone.[60]

Besides replication, we also get osteoblasts from the process of cell differentiation, when our body’s stem cells transform into osteoblasts,[18] via the magnesium-dependent process of protein synthesis.

When we add the fact that magnesium deficiency is known to increase bone-destroying osteoclasts,[61] it’s no surprise that magnesium increases our overall bone formation[62]:

Simply put, our osteoblasts – the cells responsible for building, repairing and maintain healthy bones – all depend on magnesium for energy, building bone matrix, and replication!

Bones need bone matrix to absorb calcium, and magnesium helps make this bone matrix by fueling our osteoblasts. This helps explain why higher dietary and supplemental magnesium intake is linked with higher bone mineral density.[63,64]

Yet magnesium also controls calcium absorption by regulating three important “calciotropic” hormones:  calcitonin, parathyroid hormone and calcitriol.[65]  These hormones activate our osteoblasts and osteoclasts and thus regulate our calcium absorption/release [66-69]:

Calcitonin:

This hormone has been studied for over 50 years and still new information is being drawn about its effects on bone metabolism. What we do know is that calcitonin increases osteoblast population and function (and thus bone formation), and it decreases osteoclast function and bone destruction.[70-73] We also know that magnesium increases this hormone.[74-76]

Parathyroid Hormone:

Parathyroid hormone has both opposite effects to calcitonin,[68,77,78] as well as complimentary effects. It stimulates osteoclasts to break down bone matrix and release calcium into our blood stream. However it also exhibits bone-building effects when it is  secreted intermittently.[79,80

Magnesium regulates parathyroid hormone production in a way that is favorable to bone formation.[81] While a rise in magnesium can inhibit parathyroid hormone secretion,[82] research also shows that acute drops in magnesium increase parathyroid hormone and acute spikes decreases it.[83,65]

It seems that magnesium’s fluctuational effects on parathyroid fall in line with the hormone’s beneficial effects being tied to its intermittent secretion, especially when we consider magnesium deficiency’s association with osteoporosis.

Magnesium’s intelligent regulation of parathyroid hormone also seems to favor keeping safe levels of calcium in our blood, [84] which can prevent excess parathyroid production and bone loss. Furthermore, similarly to all other organs, the parathyroid glands still require magnesium to function which is why magnesium deficiency can lead to hypoparathyroidism.

Simply put, magnesium is critical to the function of this complex hormone that regulates bone formation and blood calcium levels.

Calcitriol:

Calcitriol is the active form of Vitamin D which is in fact a hormone that impacts bone formation and dietary calcium absorption, and which needs magnesium for its activation:

The vitamin D we get from food or sunlight (whose UVB rays convert our cholesterol into Vitamin D), is in the inactive form [85,86] known as D3 or cholecalciferol.[87]

1. Our liver then converts this inactive form into the storage form: calcidiol
2. Our kidneys then convert this storage form into the final active form: calcitriol.

We need magnesium for this vitamin D activation, because the enzymes that facilitate the above conversions belong to the cytochrome P450 family of enzymes[88-91] which is magnesium-dependent.[92]

Remember: when we have low calcium in our blood, parathyroid hormone takes calcium from our bones to replenish our blood. Calcitriol helps prevent this by increasing our gut’s dietary calcium absorption[93-95] while decreasing our kidneys’ excretion of calcium. This maintenance of blood calcium prevents high levels of parathyroid hormone which otherwise cause bone loss.[96] Thus magnesium’s activation of vitamin D can help prevent excess bone loss.

However this brings up an important issue: it may not be ideal to supplement with vitamin D when we are severely deficient in magnesium, because supplements have non-active vitamin D, whose conversion into the active form depletes our body’s magnesium further. In fact, a low vitamin D level may indicate magnesium deficiency.[97-99]

This is why experts say 3 different tests should be done for vitamin D status, to show how much active and inactive vitamin D we have, and if we have healthy levels of magnesium for the conversion. The tests are:

1. Calcidiol (storage vitamin D) also called   25(OH)D25 hydroxyvitamin D   or  
2. Calcitriol (active vitamin D) also called   1,25(OH)2 D3   or   1,25 hydroxyvitamin D
3. Magnesium red blood cell test

Now, because magnesium is needed for vitamin D activation and most people are magnesium-deficient to some degree, this helps explain why taking vitamin D supplements without magnesium supplementation to prevent and treat bone diseases is not recommended.[100,101]

Magnesium’s role in calcium regulation also explains why calcium supplementation while severely magnesium-deficient, may actually increase the onset of various health conditions:

We now know that magnesium is vital to the three main factors of bone health:

1. It provides malleability and prevents brittle bones.
2. It allows our osteoblasts to form bone.
3. It regulates our hormones in favor our bones’ calcium absorption & formation.

This explains why magnesium deficiency causes dysregulated and misplaced calcium, leading to eventual problems such as osteoporosis. But weak bones aren’t the only result. Calcification and damage of tissues like our heart, arteries, kidneys and brain[102] are also consequences of calcium misplacement caused by magnesium deficiency.

As we look at magnesium’s natural ability to keep excess calcium out of the cells of our soft organs, tissues and joints,[103] it explains why some experts say that calcium supplements on their own are actually not that effective in treating and preventing osteoporosis,[100,104] and why taking them is at times linked to increased risk of heart disease. [105-107]

Magnesium’s central role in calcium regulation means that its deficiency reaches beyond our bones, with negative effects being found in other major organs. This sheds light on why scientists are now finding links between osteoporosis and heart disease. [108-110]

Rather than these specific diseases occurring mostly due to genetic mutations, perhaps the human body is simply experiencing the consequences of calcium being taken out of its rightful place (bones) and being put in vulnerable places it doesn’t belong: soft tissues.