M. Zhang, L. Robitaille, S. Eintracht, L. J Hoffer. Nutrition. 2010. Aug 4. [Epub ahead of print] pub ahead of print]
Why was the study done?
Vitamin C and vitamin D insufficiency are very prevalent in hospitalized patients, and both vitamins have been linked to psychological abnormalities, including abnormal mood states. Researchers suspected that supplementation might therefore improve mood in hospital in-patients.
How was the study carried out?
This was a small double-blind clinical trial in 55 subjects randomized to either vitamin C (500mg twice daily) or vitamin D (1000 IU twice daily). Reasons for hospitalizations were mixed, and ranged from cancer to cardiovascular disease, diabetes, renal failure and gastrointestinal disease. Before and after 5-10 days of supplementation, participants completed a mood assessment questionnaire using a well validated 30-item questionnaire – the Profile of Mood States (POMS-B). Assessments of mood state were carried out at the beginning and end of the study by the same researcher and at the same time of day. Patients had blood samples drawn to assess their Vitamin C and D status.
What were the results?
Patients with plasma total concentrations of vitamin C less than 28.4 μmol/L were considered vitamin C depleted, while those with concentrations less than 11.4 μmol/L was considered deficient. For vitamin D, blood levels of 25-hydroxy D less than 75 nmol/L was considered deficient.
Fifty-six percent of the vitamin C group had plasma concentrations less than 28.4 μmol/L, while 9% were deficient (<11.4 μmol/L). Eighty-one percent of the vitamin D group had 25-hydroxy D levels less than 75 nmol/L. Vitamin C supplementation for an average of 8.7 days more than tripled plasma vitamin C (P<0.0001) and this was associated with a 34% reduction in total mood disturbance scores (P=0.013). Vitamin D supplementation for an average of 7.5 days increased plasma levels by 20% (p<0.0004). However, vitamin D supplements did not raise 25-hydroxy D into the target normal range (75 nmol/L) and had no effect on mood scores.
What conclusions did the researchers come to?
The researchers concluded that treatment of low plasma vitamin C, so prevalent in hospitalized patients, improved their mood state. Because they saw no response to vitamin D supplementation, the effect of vitamin C on mood is likely to be a real effect, and not simply a placebo response.