How much vitamin c can the body absorb
Pro Research Analysisby 
Searched over 200M research papers
Vitamin C Absorption in the Human Body
Absorption Capacity and Efficiency
The human body has a limited capacity to absorb vitamin C, which is influenced by several factors including dose, body weight, and muscle mass. The absorption process follows a saturation kinetics model, where the efficiency of absorption decreases as the dose increases. For instance, at doses above 200 mg, the bioavailability of vitamin C declines, and excess amounts are excreted in the urine 15. This means that while small doses are almost fully absorbed, larger doses result in diminishing returns.
Recommended Daily Intake
The recommended daily intake (RDI) of vitamin C varies based on several demographic factors. For healthy adults, the RDI is generally set at 40 mg for men and 30 mg for women to maintain a suitable body pool of vitamin C . However, some studies suggest that higher intakes, up to 200 mg per day, may be more beneficial for achieving optimal plasma and tissue concentrations 58.
Influence of Body Weight
Body weight significantly impacts vitamin C absorption and plasma levels. Individuals with higher body weight require more vitamin C to achieve the same plasma concentration as those with lower body weight. It is estimated that an additional intake of 10 mg of vitamin C per day is needed for every 10 kg increase in body weight . This adjustment is crucial for ensuring adequate vitamin C status in overweight and obese individuals.
Formulation and Muscle Mass
The form in which vitamin C is consumed also affects its absorption. Liquid formulations, such as vitamin C drinks, have been shown to result in higher plasma concentrations compared to tablets and capsules. Additionally, individuals with higher muscle mass tend to absorb vitamin C more efficiently . This suggests that both the formulation of vitamin C supplements and the individual's muscle mass should be considered when determining the most effective way to increase vitamin C levels.
Safe Upper Limits
While vitamin C is generally safe, there is a threshold beyond which no additional benefits are observed, and potential adverse effects may occur. The safe upper limit for daily vitamin C intake is considered to be 1000 mg, with doses above 400 mg showing no additional value 58. Excessive intake can lead to increased urinary excretion and potential issues such as oxalate and urate excretion.
Conclusion
In summary, the body's ability to absorb vitamin C is influenced by dose, body weight, muscle mass, and the formulation of the supplement. While the RDI for vitamin C is relatively low, higher intakes may be beneficial for certain populations, particularly those with higher body weight or muscle mass. However, it is important to stay within the safe upper limits to avoid potential adverse effects.
Sources and full results
Most relevant research papers on this topic