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The Importance of the Calcium-to-Magnesium Ratio

By Trevor Connor, M.S., CEO
November 21, 2020
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We need calcium. No one is going to dispute that fact. Calcium is the most abundant mineral in our body, critical to bone health and muscle function. (1,2) Without adequate calcium we could not survive. So, it is no wonder that for several decades, the need for calcium (either through diet or supplementation) has been promoted for good health—from milk moustache advertisements touting strong bones to osteoporotic women being told to supplement by their GPs.

The result of this increased awareness is that daily calcium intake nearly doubled in women from 1977 to 2011. Much of that increase was due to supplementation. (3)

So, what impact did this awareness have on health? The increased calcium consumption, particularly from milk, has been associated with a higher risk of heart disease, cancer, insulin resistance, inflammation, and all-cause mortality. (4–11) And while many are increasing their calcium intake to strengthen their bones, evidence that higher calcium consumption prevents bone degeneration or factures is limited and sometimes contradictory. (7,12)

Does this evidence suggest that calcium is actually bad for us? Of course not. Calcium is essential for life. But as with all things in nutrition, it’s not a simple matter of “more is better.” This is best summarized by a 2018 concept paper in the highly respected journal Nutrients:

[This] goes beyond the classical approach of evaluating each micro or macro nutrient by itself; which may be a relic of the past when deficiency type studies dominated… Micronutrient ratios may confer more comprehensive information than the concentration of a single nutrient… This suggests that the underlying issue is a disruption in the ratios of micronutrients in the Western diet. (13)

Which brings us to the calcium-to-magnesium ratio. What may be more important than the absolute quantity of calcium in the diet, or magnesium for that matter, is a healthy ratio of the two.

Are ratios more important than absolute quantities?

The same 2018 paper showed, using NHANES data, that men over the age of 50 consumed 1,589 mg/d of calcium compared to the recommendation of 1,000 mg/d, while women over 50 consumed 1,177 mg/d compared to the 1,200 mg/d recommended.

In short, looking purely at their calcium intake, the subjects were getting enough. Yet, in the general population, osteoporosis has been on the rise. So, there is more to this issue than the absolute quantity of calcium.

Which brings us to the calcium-to-magnesium ratio. What may be more important than the absolute quantity of calcium in the diet, or magnesium for that matter, is a healthy ratio of the two. In the same period from 1977 to 2011, the ratio in women increased from approximately 2.6-to-1 up to 3.7-to-1. This is illustrated in Figure 1 below:

Figure 1. The change in the calcium-to-magnesium ratio from 1977 to 2012 in women (A) and men (B) from diet alone and from diet and supplementation. The data is from the USDA Agricultural Research Food Surveys. (3)
Figure 1. The change in the calcium-to-magnesium ratio from 1977 to 2012 in women (A) and men (B) from diet alone and from diet and supplementation. The data is from the USDA Agricultural Research Food Surveys. (3)

Extensive research on the subject has shown that a ratio of approximately 2-to-1 is considered healthy, while ratios above 2.6-to-1 and below 2-to-1 can lead to heart disease and other conditions. (3,14) Several recent studies showed decreased mortality rates when magnesium intake was increased by 200 mg/d or more in subjects with a 3-to-1 or higher ratio. (15–17)

The importance of a healthy ratio may explain the contradictory results seen in research studies that only looked at calcium concentrations. High, low, and recommended calcium consumption has been inconsistently shown to contribute to heart disease. The results may have more to do with the ratio of calcium-to-magnesium, as explained in the 2016 review by Rosanoff et al.:

Dietary intake studies of either magnesium or calcium alone may be unwittingly confounded by the unmeasured calcium or magnesium… it appears that too much or too little of either calcium or magnesium might not be beneficial and there may be an optimal range of human calcium and magnesium intake. (3)

In the United States, the average calcium-to-magnesium ratio is above 3-to-1 and frequently higher in women. In Japan, the ratio is below 1.7-to-1. Both levels are considered unhealthy. (3)​

The danger of increasing calcium in isolation

In an effort to stop rising osteoporosis rates in North America, as previously mentioned, calcium RDAs were increased in women to 1,200 mg/d. Other recommendations have even taken it higher, to 1,300 mg/d. Calcium is the only RDA where the recommendation is higher for women.

There are several problems with this strategy. First, there are risks associated with increasing calcium intake in isolation. Two recent studies in BMJ demonstrated this risk. The first, a 2010 meta-analysis of 26 studies, clearly showed that calcium supplementation increases the risk of both heart attacks and sudden death. (8)

The second, a 2013 cohort study of over 61,000 women, found that high calcium intake increased the death rates from all-cause mortality in women. (6) However, conversely, a 2011 randomized controlled trial found that calcium supplementation in women over 70 did not find an increased risk of vascular disease. (18)

The second problem with increasing calcium in isolation is that it is nearly impossible to achieve these RDAs for calcium on a natural diet without either consuming dairy or supplementing. (5)

Dr. Cordain has written extensively about milk and how it contributes to a host of health issues including heart disease, acne, cancer, and insulin resistance. (4) In short, dairy has a calcium-to-magnesium ratio of around 12-to-1, which is the highest of any food we eat. So, drinking milk regularly may help you meet the RDAs for calcium, but it is only going to push this critical ratio into more unhealthy ranges. So, drinking milk regularly may help you meet the RDAs for calcium, but it is only going to push this critical ratio into more unhealthy ranges.

In fact, a 1993 study by Dr. Artaud-Wild et. al, found that milk and its components (including calcium) had the highest relationship with cardiovascular death rates of any food examined. (19)

You may be following your doctor’s advice by consuming more milk and supplementing with calcium, but without proportionally increasing your magnesium consumption, the results could be devastating. And this is a concern because it appears that over 50 percent of Westerners get inadequate magnesium. (3)

Why the Mg/Ca ratio is important

Calcium and magnesium appear to have a synergistic relationship in the body. (20) Each can affect both the absorption and excretion of the other. For example, multiple studies have shown that magnesium deficiency can alter cellular calcium levels. (21–24)

In fact, consuming enough magnesium may be as important, if not more so, than maintaining adequate calcium levels or the actual quantity of calcium you consume. Multiple studies have shown that even when people do not get enough calcium in their diet, the negative calcium balance in the body can be reversed by consuming more magnesium. (3,25) A 2002 study showed that “rats fed a magnesium-adequate diet have the ability to maintain calcium homeostasis during calcium depletion by increasing bone resorption”. (26)

Adequate magnesium has been associated with many health benefits including preventing arrhythmias (27,28), improved blood lipid profiles (29,30), reduced stroke risk (31), insulin sensitivity (21), lowered inflammation (21,26), and reduced migraines. (32)

This also means that magnesium deficiency can lead to a host of diseases. (28) However, an increasing body of research is showing that these health benefits associated with magnesium may have more to do with magnesium’s interaction with calcium in the body than the magnesium levels alone. (4)

In one study on rats, a diet very low in magnesium increased multiple markers of inflammation, oxidative stress, and increased plasma triglycerides—all of which are associated with heart disease. However, when rats were fed a diet that was very low in both magnesium and in calcium, the inflammation did not appear despite lacking both essential nutrients. This led the researchers to conclude that “calcium is implicated in the inflammatory response”. (26) Another rat study showed that excess calcium increased the lethality of endotoxic shock (an inflammatory response). (9)

An important study from 1993 led by Dr. Jerry Nadler traced a mechanism for how magnesium deficiency can contribute to hypertension, heart disease, and insulin resistance. The deficiency appeared to impact aldosterone levels and inflammatory prostaglandins. While this study was published before the bulk of the calcium-to-magnesium research had been conducted, the authors recognized that “magnesium deficiency may lead to these changes by increasing intracellular free calcium levels” (21).

While the direct conclusion of these studies pointed to the health consequences of magnesium deficiency and of excess calcium, they also demonstrated a larger and potentially more significant trend—the relationship between magnesium and calcium.

Magnesium appears to be able to mediate many of the negative effects of calcium. It also appears that excess calcium consumption can lower magnesium absorption and increase its excretion leading to magnesium deficiency. (12,33,34) Unfortunately, many people supplement with calcium and drink milk to help their bones, not knowing that the high calcium levels are exacerbating magnesium deficiency, which is critical to bone health.

Strong bones require more than just calcium. Vitamin D is essential for the body to be able to use available calcium for bone development. This is why vitamin D deficiency contributes to rickets, a bone disease. (35) Magnesium is essential to several enzymes involved in the synthesis and metabolism of vitamin D. Magnesium deficiency leads to lower levels of vitamin D in the body and inhibits its functions, including those involved in bone growth. (3,36) Magnesium has been shown to be important in the treatment of osteoporosis. (37) Even independent of bone health, a 2013 study found that magnesium impacts the association between vitamin D and mortality. (38)

Getting the optimal ratio

Americans do not get sufficient magnesium. Furthermore, the typical Western diet has a calcium-to-magnesium ratio above 3-to-1. (3) The solution for most of us is to increase magnesium consumption.

That raises the question: How much more do we need? Unfortunately, that’s difficult to answer. Our bodies maintain a very tight magnesium concentration in our blood. If we do not eat enough, our bodies will sacrifice bone and intracellular stores in order to maintain plasma levels. As a result, people can be magnesium deficient while still having normal serum levels—a condition called “chronic latent magnesium deficit” or CLMD. (3)

Unfortunately, simply supplementing with magnesium is often not a solution. It’s important to get a ratio of calcium-to-magnesium around 2-to-1. Straying too high or too low from that ratio is unhealthy. But since most people don’t know how much calcium or magnesium they are getting in their diet and there isn’t a good blood test to determine our magnesium levels, it’s hard to know how much to supplement. Furthermore, according to Rosanoff et. al., adults who supplemented with magnesium overcompensated with calcium and made their calcium-to-magnesium ratio worse. (3)

Ultimately the best solution is through a natural diet. (26) Analyses of hunter-gatherer diets have shown that daily intake approximated the optimal ratio of 2-to-1. (14)

Since, for most North Americans, the issue is bringing down the ratio below 3-to-1, eating fruits, vegetables, and nuts (such as almonds), which are high in magnesium, can help you get adequate magnesium in your diet while also ensuring you obtain the calcium you need for an optimal ratio and good bone health.

Dr. Loren Cordain, founder of the Paleo Diet® created the following two tables of fruits and vegetables showing their calcium-to-magnesium ratios as a guide:

TABLE 1: calcium and magnesium content and calcium-to-magnesium ratio of common vegetables sorted by ratio

Vegetables, DomesticatedMg/100gCa/100gCa/Mg
Mushrooms, white9.03.00.33
Sweet potato leaves61.037.00.61
Swiss Chard81.051.00.63
Squash, Crookneck2720.00.74
Jalapeno pepper1512.00.80
Squash, Summer17.015.00.88
Squash, zucchini18.016.00.89
Bell pepper1010.01.00
Pumpkin leaves3839.01.03
Squash, Acorn32.033.01.03
Squash, butternut29411.41
Radicchio leaves13.019.01.46
New Zealand Spinach39.058.01.49
Beet greens70.0117.01.67
Palm hearts10.018.01.80
Brussel sprouts2342.01.83
Squash, Spaghetti11.021.01.91
Romaine lettuce14.033.02.36
Iceburg lettuce718.02.57
Butterhead (Bibb) lettuce13.035.02.69
Lettuce, red leaf12332.75
Loose leaf (Green Leaf) lettuce13.036.02.77
Cabbage, red1645.02.81
Fennel bulb1749.02.88
Mustard greens32.0103.03.22
Chicory greens30100.03.33
Cabbage, green1240.03.33
Endive (Escaroie)
Grape leaves95363.03.82
Rapini (Broccoli Raab)22.0108.04.91
Dandelion greens36187.05.19
Napa (Chinese) cabbage1377.05.92
Turnip greens31.0190.06.13
Bok Choi (Chinese cabbage)1168.86.26
Collard greens20140.07.00
Nopales (cactus leaves)22.0164.07.46
Lamb's quarters34.0309.09.09

TABLE 2: calcium and magnesium content and calcium-to-magnesium ratio of common fruits sorted by ratio

Star fruit1030.30
Passion fruit29120.41
Honey dew melon1060.60
Cactus figs85560.66
Salmon berries1513.10.87
Casaba melon11.011.01.00
Sweet cherry1113.01.18
Grapes (Red or Green)7101.43
Kiwi fruit17.0342.00

Remember that it's not the ratio of any one particular food, but the overall ratio of your daily diet that’s important. That said, making sure you eat foods with a low ratio to balance foods with a high ratio will help keep you in a healthy range.

And the best way to do that is to simply follow the guidelines in our Paleo 101 section, as well as visiting our great collection of recipes.


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