Relation between intake and plasma concentration of vitamin C in elderly women.

Abstract

The plasma concentration of vitamin C is relatively low in the elderly, particularly those in long stay hospitals,' but it is not clear to what extent these low concentrations are due to low intake. We examined the relation between intake and plasma concentrations of vitamin C in elderly women living at home and in long stay hospitals. Patients, methods, and resultsWe studied 101 elderly women: 24 were healthy and living at home (mean age 74), and 77 were long stay patients (mean age 83) in two geriatric hospitals and one psychiatric hospital. Food intake was weighed and noted for five days in the case of the elderly women in hospital and for seven days in the case of those at home. Vitamin C intake was calculated from standard food tables except in the case of vegetables and potatoes delivered to the wards, which we analysed for vitamin C. Each subject's plasma concentration of vitamin C was measured at the end of the period during which intake of food was measured.2The figure shows the relation between plasma concentration and intake of vitamin C. The relation was sigmoidal, not linear, the curve being constructed by plotting the median concentration of vitamin C at the median point for each decile of intake. First and last deciles were split again to give greater detail. When the intake of vitamin C was above 60 mg a day the median plasma concentration was 74 fmol/l (1-3 mg/100 ml), and all but one of the subjects had a plasma concentration above 20 /Amol/l (0.35 mg/ 100 ml). There was a large decrease in the median plasma concentration of vitamin C as the median intake decreased from 60 to 30 mg a day, and most patients with an intake of less than 30 mg a day had a plasma concentration of less than 20 jAmol/l (0 35 mg/100 ml). Conversion: SI to traditional units-Plasma vitamin C: 1 Hsmol/l 17-6 g/ 100 ml. CommentThe sigmoidal relation between intake and plasma concentration of vitamin C has not been reported before. Garry et al3 showed that the relation was not linear, but their study did not include elderly people with low vitamin C intakes. We found that as intake increased from 10 to 30 mg a day the plasma concentration of vitamin C rose only slowly. The rapid change in plasma concentration as the intake increased from 30 to 60 mg a day suggested that a pathway of metabolic utilisation was being saturated. The much slower increase with intakes above 60 mg a day may have been due to a large loss of vitamin C in the urine when the renal threshold of a plasma vitamin C concentration of 51-57 ,umol/l (0 9-1 0 mg/100 ml) was exceeded.4 When we gave a similar group of elderly patients 1 g vitamin C a day for two months their mean plasma concentration reached only 78 umol/l (137 mg/100 ml).5Evidence shows that plasma concentrations of vitamin C should be maintained above 20 timol/l (0 35 mg/100 ml) to ensure against impairment of health. The patient lived at home with an older sister and remained well for a further 20 years. He presented again, when his sister could no longer look after him, with a six month his...

Nutrition Discussion Forum

“…These findings, together with the evidence for the potential role of antioxidants such as vitamin C in preventing free radical damage (Frei et al 1989;Halliwell, 1994), provide considerable, although not conclusive, support for the idea that vitamin C intakes should be significantly higher than those preventing the development of clinical scurvy. Studies in healthy individuals have indicated that intakes above 60 mg/d, with averages around 100 mg/d, will saturate metabolic processes and maximize vitamin C content in white cells (Kallner et al 1979;Newton et al 1983;Levine et al 1996), and could, therefore, potentially maximize protection against diseases such as cancer, atherosclerosis and serious infections. Bates (1997) claims that, within the intake range for potential benefit, neither efficacy nor harm can be accurately gauged because there is insufficient evidence for either, in contrast to folate for the prevention of neural tube defects, where the evidence of benefit is overwhelming.…”

Experimental folate deficiency in human subjects: what is the influence of vitamin C status on time taken to develop megaloblastic anaemia?

“…In their cross-sectional study of an elderly population of 138 males and 166 females on high vitamin C intakes, Garry et al [ 30 ] found that plasma vitamin C concentration increased rapidly up to a daily vitamin C dose of 150 mg, then the rate of increase slowed significantly. Newton et al [ 31 ] also reported a sigmodal relationship between plasma concentration of vitamin C and vitamin C intake in their study of 101 elderly women on lower vitamin C intakes. Jacob et al [ 20 ] also plotted plasma vitamin C concentration against the daily vitamin C dose, for an elderly population of 235 males and 442 females.…”

“… a mean of 7 patients, derived from Levine et al [ 32 ] b estimated from Fig. 5 and table and chart in Additional file 2 c converted from stated concentration of 1.0 mg/dL to SI units using formula provided by Newton et al [ 31 ]: 1.0 μmol/L ≈ 17.6 μg/100 mL …”

“…c converted from stated concentration of 1.0 mg/dL to SI units using formula provided by Newton et al [ 31 ]: 1.0 μmol/L ≈ 17.6 μg/100 mL…”

Nutrition Discussion Forum

“…Studies in healthy individuals have indicated that intakes above 60 mg/d, with averages around 100 mg/d, will saturate metabolic processes and maximize vitamin C content in white cells (Kallner et al 1979;Newton et al 1983;Levine et al 1996), and could, therefore, potentially maximize protection against diseases such as cancer, atherosclerosis and serious infections. Bates (1997) claims that, within the intake range for potential benefit, neither efficacy nor harm can be accurately gauged because there is insufficient evidence for either, in contrast to folate for the prevention of neural tube defects, where the evidence of benefit is overwhelming.…”