The metabolism of calcium and magnesium is closely related and interdependent. The two work together, but they can also antagonize each other. Studies have found that calcium can compete with magnesium for intestinal absorption and transport, especially if calcium intake is much higher than magnesium intake. For example, if the gut has more magnesium than calcium, the magnesium will be preferentially absorbed, but if there is a much higher amount of calcium, magnesium absorption will be diminished. This is important, because high dose calcium supplementation is common, and many people don’t eat enough good food sources of magnesium. When magnesium is too low, insufficient parathyroid hormone is produced and blood calcium levels are also reduced so it is really important to get enough magnesium.
If you can’t get your calcium from food, and must supplement, current evidence indicates to ensure the best absorption it’s best to take more frequent, lower doses of calcium and avoid doses over 250 mg at one time. If you do supplement with both calcium and magnesium, because calcium and magnesium compete for absorption, it’s best to not take them together. The even better approach, is to not take a calcium supplement at all and get your calcium from food. If a significant amount of your calcium is from plant foods, like kale, almonds, and legumes then you get both your calcium and magnesium. With my clients I often find they are over-supplementing with calcium and not eating enough foods high in magnesium. Often, they don’t eat beans, they avoid nuts and whole grains.
Some research suggests that the calcium to magnesium ratio is more important than calcium intake alone. I can’t help but wonder, could all the years of recommending women take 1200 mg of calcium as a supplement, combined with the probability that many were not eating enough whole grains, nuts, leafy greens, seeds, and legumes to provide them with adequate magnesium contributed somewhat to the high prevalence of osteoporosis we see today in western countries.
According to the Nutritional Magnesium Association, the 2:1 calcium-to-magnesium ratio was initially recommended by a French researcher in an effort to help avoid overconsumption of calcium. In some studies ratios above this level have been associated with greater inflammation. There is some current debate as to what the best ratio of calcium to magnesium is for supplements, and research in this area is ongoing. Rather than focus on a ratio, I suggest focusing on good food sources of calcium and magnesium and minimizing the need for supplements. Supplements are not a magic bullet for osteoporosis, or any condition. The purpose of supplements should be to address deficiency states or make up for what you are unable to adequately consume from food. Your goal should be to avoid such deficiencies and nutrient shortfalls by eating foods rich in these nutrients.
posted on 5/10/2023