1/ Half the population may be functionally deficient in vitamin...
William A. Wallace, Ph.D.@WilliamWallace
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Jun 19, 2025
~2 min read
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Half the population may be functionally deficient in vitamin C—despite meeting the RDA.
Recent data suggests the recommended intake is based on outdated models and ignores body weight, tissue saturation, and immune demand.
Let’s break down the new research 🧵
Half the population may be functionally deficient in vitamin C—despite meeting the RDA.
Recent data suggests the recommended intake is based on outdated models and ignores body weight, tissue saturation, and immune demand.
Let’s break down the new research 🧵
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The current RDA for vitamin C is 90 mg/day for men and 75 mg/day for women.
These values were designed to prevent scurvy, not to support optimal health, cognitive function, or immunity.
But modern analyses show these values may be grossly inadequate.
The current RDA for vitamin C is 90 mg/day for men and 75 mg/day for women.
These values were designed to prevent scurvy, not to support optimal health, cognitive function, or immunity.
But modern analyses show these values may be grossly inadequate.
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A 2025 population analysis (PMID: 38845362) found:
At the current RDA, only ~35–50% of adults reach plasma vitamin C levels ≥50 µmol/L—a threshold considered “adequate” for health and immune function.
That’s half the population left behind.
A 2025 population analysis (PMID: 38845362) found:
At the current RDA, only ~35–50% of adults reach plasma vitamin C levels ≥50 µmol/L—a threshold considered “adequate” for health and immune function.
That’s half the population left behind.
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Body weight matters.
For every 10 kg (~22 lbs) above the 70 kg reference weight used to set the RDA, plasma vitamin C drops by ~2.6–3.5 µmol/L—even at the same intake.
That means someone weighing 200 lbs may need ~40 mg more per day than the RDA.
Body weight matters.
For every 10 kg (~22 lbs) above the 70 kg reference weight used to set the RDA, plasma vitamin C drops by ~2.6–3.5 µmol/L—even at the same intake.
That means someone weighing 200 lbs may need ~40 mg more per day than the RDA.
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And here's the kicker:
The assumed variability used to set the RDA was 10%.
But real-world data shows variability closer to 57%—meaning the RDA should be closer to 175 mg/day to cover 98% of people.
The current RDA? It may only cover ~50%.
The assumed variability used to set the RDA was 10%.
But real-world data shows variability closer to 57%—meaning the RDA should be closer to 175 mg/day to cover 98% of people.
The current RDA? It may only cover ~50%.
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Vitamin C status isn’t just about plasma.
Leukocytes (white blood cells) concentrate vitamin C up to 100x higher than plasma and are better indicators of immune function.
Some advanced supplement forms (like Ester-C and liposomal C) increase leukocyte levels more effectively than plain ascorbic acid.
PMID: 39861409
Leukocytes (white blood cells) concentrate vitamin C up to 100x higher than plasma and are better indicators of immune function.
Some advanced supplement forms (like Ester-C and liposomal C) increase leukocyte levels more effectively than plain ascorbic acid.
PMID: 39861409
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Subclinical deficiency—plasma levels between 11–23 µmol/L—can impair:
Mood & cognitive performance
Wound healing
Immune response
Energy metabolism
And it can exist even in people without dietary symptoms.
Subclinical deficiency—plasma levels between 11–23 µmol/L—can impair:
Mood & cognitive performance
Wound healing
Immune response
Energy metabolism
And it can exist even in people without dietary symptoms.
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Bottom line:
✅ RDA values may be outdated
✅ Many people may need 200–400 mg/day
✅ Body size, stress, and illness raise requirements
✅ Supplement form and dosing frequency affect absorption & retention
✅ One-size-fits-all doesn’t cut it
Bottom line:
✅ RDA values may be outdated
✅ Many people may need 200–400 mg/day
✅ Body size, stress, and illness raise requirements
✅ Supplement form and dosing frequency affect absorption & retention
✅ One-size-fits-all doesn’t cut it
