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The Importance of the Calcium-to-Magnesium Ratio

We need calcium. No one is going to dispute that fact. Calcium is the most abundant mineral in our bodies, 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:

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.

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)

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, Domesticated


Ca/100g Ca/Mg
Mushrooms, white 9.0 3.0 0.33
Tomatillo 20.0 7.0 0.35
Sorrel 102.1 44.0 0.43
Artichoke 42 21.0 0.50
Sweet potato leaves 61.0 37.0 0.61
Swiss Chard


51.0 0.63
Eggplant 14 9.0 0.64
Squash, Crookneck 27 20.0 0.74
Jalapeno pepper 15 12.0 0.80
Squash, Summer 17.0 15.0 0.88
Squash, zucchini 18.0 16.0 0.89
Tomato 11.0 10.0 0.91
Purslane 68.0 65.0 0.96
Bell pepper 10 10.0 1.00
Pumpkin leaves 38 39.0 1.03
Squash, Acorn 32.0 33.0 1.03


13.0 16.0 1.23
Spinach 79.0 99.0 1.25
Kohlrabi 19 24 1.26
Squash, butternut 29 41 1.41
Okra 57 81.0 1.42
Radicchio leaves 13.0 19.0 1.46
Cauliflower 15 22.0 1.47
New Zealand Spinach 39.0 58.0 1.49
Beet greens 70.0 117.0 1.67
Asparagus 14.0 24.0 1.71
Pumpkin 12 21.0 1.75
Palm hearts 10.0 18.0 1.80
Brussel sprouts 23 42.0 1.83
Squash, Spaghetti 11.0 21.0 1.91
Broccoli 21.0 47.0 2.24
Romaine lettuce 14.0 33.0 2.36
Iceburg lettuce 7 18.0 2.57
Butterhead (Bibb) lettuce 13.0 35.0 2.69
Lettuce, red leaf 12 33 2.75
Parsley 50.0 138.0 2.76
Loose leaf (Green Leaf) lettuce 13.0 36.0 2.77
Cabbage, red 16 45.0 2.81
Fennel bulb 17 49.0 2.88
Mustard greens 32.0 103.0 3.22
Chicory greens 30 100.0 3.33
Cabbage, green 12 40.0 3.33
Arugula 47 160.0


Endive (Escaroie) 15.0 52.0 3.47
Celery 11.0 40 3.64
Grape leaves 95 363.0 3.82


34.0 135.0 3.97
Rapini (Broccoli Raab) 22.0 108.0 4.91
Dandelion greens 36 187.0 5.19
Watercress 21 120.0 5.71
Napa (Chinese) cabbage 13 77.0 5.92
Turnip greens 31.0 190.0 6.13
Bok Choi (Chinese cabbage) 11 68.8 6.26

Collard greens

20 140.0 7.00
Nopales (cactus leaves) 22.0 164.0 7.46
Lamb’s quarters 34.0 309.0 9.09
Mean 28.9 67.6 2.56

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




Plantain 37 3 0.08
Banana 27.0 5 0.19
Star fruit 10 3 0.30
Passion fruit 29 12 0.41
Avocado 29 12 0.41
Lychees 10 5 0.5
Cherimoya 17 10 0.59
Honeydew melon 10 6 0.60
Cactus figs 85 56 0.66
Peach 9 6 0.67
Nectarine 9 6.3 0.67
Breadfruit 25 17 0.68
Watermelon 10 7 0.70
Cantaloupe 12.0 9 0.75
Guave 22 18 0.82
Pomegranate 12 10 0.83
Plum 7 6 0.86
Salmon berries 15 13.1 0.87
Persimmons 9 8 0.89
Payaya 21.0 20 0.95
Casaba melon 11.0 11.0 1.00
Blueberries 6 6 1
Pineapple 12.0 13 1.08
Mango 10 11 1.1
Raspberries 22.0 25 1.14
Oheloberries 6 7 1.17
Sweet cherry 11 13.0 1.18
Apple 5 6 1.2
Strawberries 13.0 16 1.23
Loganberries 21 26 1.24
Pear 7 9 1.29
Cranberries 6 8 1.33
Quince 8 11 1.38
Chayote 12 17 1.41
Grapes (Red or Green) 7 10 1.43
Blackberries 20.0 29 1.45
Boysenberries 16 27 1.69
Kiwi fruit 17.0 34 2.00
Mulberries 18 39 2.17
Chokecherries 27 60 2.22
Grapefruit 9.0 22.0 2.44
Gooseberries 10 25 2.50
Tangerine 12.0 37.0 3.08
Kumquats 20 62 3.10
Orange 10 40


Lemon 12 61 5.08
Lime 6 33.0 5.50
Elderberries 5 38 7.6
Mean 10.6 14.0 1.5

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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Trevor Connor, M.S.

Dr. Loren Cordain’s final graduate student, Trevor Connor, M.S., brings more than a decade of nutrition and physiology expertise to spearhead the new Paleo Diet team.

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Calcium/Magnesium Ratio

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