Comparative bioavailability to humans of ascorbic acid alone or in a citrus extract

Area of Science:

• Nutritional Science
• Biochemistry
• Human Physiology

Background:

• Ascorbic acid (AA), commonly known as vitamin C, is an essential nutrient.
• Investigating the bioavailability of different forms of vitamin C is crucial for understanding optimal human nutrition.
• Natural sources of vitamin C often contain co-factors like bioflavonoids that may influence absorption.

Purpose of the Study:

• To compare the bioavailability of synthetic ascorbic acid (AA) versus AA naturally present in a citrus extract.
• To evaluate the impact of a citrus extract containing bioflavonoids, proteins, and carbohydrates on plasma ascorbate levels.
• To assess the effect of different vitamin C forms on ascorbate excretion patterns.

Main Methods:

• A single 500-mg dose of synthetic AA, citrus extract ascorbate, and a placebo citrus extract was administered to eight fasting human subjects.
• Plasma ascorbate concentrations were monitored over time to calculate areas under the plasma concentration-time curves (AUC).
• Ascorbate excretion in 24-hour urine was measured in both ascorbate-saturated and non-saturated male subjects.

Main Results:

• The citrus extract demonstrated 35% greater absorption compared to synthetic AA (p < 0.001).
• Absorption of ascorbate from the citrus extract was significantly slower than from synthetic AA (p < 0.001).
• Ascorbate from the citrus extract led to greater urinary excretion in saturated subjects but less excretion in non-saturated subjects compared to synthetic AA.

Conclusions:

• Ascorbate present in a natural citrus extract is more bioavailable in human subjects than synthetic ascorbic acid alone.
• The presence of other citrus components, such as bioflavonoids, may enhance vitamin C absorption and modify its metabolic handling.
• These findings suggest that whole food or natural extracts may offer superior vitamin C delivery compared to isolated synthetic forms.