Who Is Andrea Rosanoff?
Andrea Rosanoff, PhD is a nutritional researcher and Director of Research and Science Information Outreach at the Center for Magnesium Education & Research in Hawaii. She has published extensively on magnesium nutrition, dietary inadequacy, and the health implications of suboptimal magnesium intake — with particular focus on the population-level data that shows most Americans are not getting enough magnesium.
If Shealy and Waring address how magnesium gets into the body transdermally, Rosanoff addresses the foundational question underneath all of it: why does it matter that so many people are deficient in the first place?
Core Research: Magnesium Inadequacy in the US Population
Rosanoff's most significant contribution to the field is her rigorous analysis of national dietary survey data — particularly the USDA's National Health and Nutrition Examination Survey (NHANES) — showing that a large portion of the US population does not meet even the Estimated Average Requirement (EAR) for magnesium from diet alone.
Key Findings from Population Data:
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Approximately 48% of Americans consume less than the Estimated Average Requirement for magnesium from food — and this figure may be an underestimate because it doesn't account for absorption losses
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The decline in magnesium content of food over the past 50–70 years — due to soil depletion, food processing, and agricultural practices — has widened the gap between dietary intake and physiological need
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Groups at highest risk include older adults, people with type 2 diabetes, people with GI disorders, and people taking medications that deplete magnesium (diuretics, PPIs, antibiotics)
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Women are disproportionately affected due to hormonal factors affecting magnesium metabolism and the additional demands of pregnancy
📚 Rosanoff A, Weaver CM, Rude RK. Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutrition Reviews. 2012;70(3):153-164.
📚 Rosanoff A, Dai Q, Shapses SA. Essential Nutrient Interactions: Does Low or Suboptimal Magnesium Status Interact with Vitamin D and/or Calcium Status? Advances in Nutrition. 2016;7(1):25-43.
The Calcium-Magnesium Ratio Research
One of Rosanoff's most important and underappreciated areas of research concerns the ratio of calcium to magnesium in the diet — and how a shift in that ratio over the past several decades may be contributing to chronic disease patterns.
Historical Context:
For most of human evolutionary history, calcium and magnesium were consumed in roughly equal amounts — a ratio of approximately 1:1 to 2:1 (calcium to magnesium). The modern Western diet has dramatically skewed this ratio, often exceeding 4:1 or even higher, due to:
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Widespread calcium supplementation and fortification (driven by osteoporosis prevention campaigns)
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Declining magnesium content in food due to soil depletion
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High consumption of processed foods that are fortified with calcium but not magnesium
Why the Ratio Matters:
Calcium and magnesium are physiological antagonists at the cellular level. Calcium triggers muscle contraction; magnesium triggers muscle relaxation. Calcium promotes blood clotting; magnesium inhibits it. At the cellular level, calcium and magnesium compete for the same transport channels.
Rosanoff's research suggests that excess calcium relative to magnesium may competitively impair magnesium absorption and utilization — meaning that even people who are consuming adequate magnesium may be functionally deficient if their calcium intake is significantly higher.
'The increasing calcium-to-magnesium intake ratio in the United States, combined with decreasing magnesium intake, may be contributing to the high rates of cardiovascular disease, type 2 diabetes, and metabolic syndrome observed in Western countries.' — Rosanoff et al., Advances in Nutrition, 2016
📚 Rosanoff A, Weaver CM, Rude RK. Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutrition Reviews. 2012;70(3):153-164.
Implications for Magnesium Supplementation Strategy
Rosanoff's research has direct implications for how we think about magnesium replenishment — including the transdermal approach:
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Because so many people are genuinely deficient from diet alone, supplementation strategies matter. The question isn't whether people need more magnesium — the data is clear that many do. The question is how best to deliver it.
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The GI limitations of oral magnesium (absorption variability, laxative effect at higher doses) make transdermal delivery an attractive complement — particularly for people who cannot tolerate effective oral doses
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The calcium-magnesium competition means that simply eating more calcium-rich foods does not solve the problem — magnesium specifically needs to be replenished
Magnesium and Vitamin D Interaction
Rosanoff has also published on the interaction between magnesium and Vitamin D — a topic of growing clinical interest. Magnesium is required for the enzymatic conversion of Vitamin D into its active form. This means that people who are supplementing with Vitamin D but are magnesium deficient may not be activating that Vitamin D effectively.
This research area is not yet definitive, but it adds another dimension to the case for addressing magnesium status before or alongside other supplement interventions.
📚 Uwitonze AM, Razzaque MS. Role of Magnesium in Vitamin D Activation and Function. Journal of the American Osteopathic Association. 2018;118(3):181-189.
Rosanoff's work makes clear that magnesium inadequacy is not a fringe concern — it is a documented, population-level nutritional gap with real health consequences. Addressing it is not optional for people who want to feel their best.
Frequently Asked Questions
Q: How common is magnesium deficiency in the United States?
A: Research by Andrea Rosanoff and colleagues, published in Nutrition Reviews, found that approximately 48% of Americans consume less than the Estimated Average Requirement for magnesium from diet. This figure likely underestimates true inadequacy because it doesn't account for absorption losses from GI factors, medications, and the inhibitory effect of high calcium intake on magnesium absorption.
Q: What is the calcium-magnesium ratio and why does it matter?
A: The calcium-to-magnesium ratio refers to the relative amounts of these two minerals in the diet. Rosanoff's research shows the modern Western diet has a significantly elevated ratio — often 4:1 or higher — compared to the approximate 1:1 to 2:1 ratio of ancestral diets. Because calcium and magnesium compete for the same cellular transport channels, excess calcium can impair magnesium absorption and utilization, potentially worsening functional magnesium status even when dietary intake appears adequate.
Q: Does taking calcium supplements affect magnesium levels?
A: Research suggests that high calcium intake — including from supplements — may competitively reduce magnesium absorption and utilization. Rosanoff's work on the calcium-magnesium ratio indicates that widespread calcium supplementation (driven by osteoporosis prevention) may have contributed to worsening population-level magnesium status. Anyone supplementing heavily with calcium should consider their magnesium status as well.
Q: Does magnesium affect vitamin D absorption?
A: Magnesium is required for the enzymatic conversion of Vitamin D into its active form. Research published in the Journal of the American Osteopathic Association suggests that magnesium deficiency may impair Vitamin D activation, meaning people with low magnesium status may not fully benefit from Vitamin D supplementation until their magnesium levels are restored.
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