By who? Cordoba University in Spain.
What did scientists study? 50 Covid-19 hospital patients with Covid-19 were given vitamin D. Their health outcomes were compared with 26 volunteers in a control group who were not given the tablets.
What did they find? Only one of the 50 patients needed intensive care and none died. Half of 26 virus sufferers who did not take vitamin D were later admitted to intensive care and two died.
What were the study’s limitations? Small pool of volunteers. Patients’ vitamin D levels were not checked before admission. Comorbidities were not taken into consideration.
By Who? University of Chicago.
What did scientists study? 500 Americans’ vitamin D levels were tested. Researchers then compared volunteers’ levels with how many caught coronavirus.
What did they find? 60 per cent higher rates of Covid-19 among people with low levels of the ‘sunshine vitamin’.
What were the study’s limitations?
Researchers did not check for other compounding factors. Unclear whether or not volunteers were vitamin D deficient at the time of their coronavirus tests. People’s age, job and where they lived – factors which greatly increase the chance of contracting the virus – were not considered.
By Who? Tehran University, in Iran, and Boston University.
What did scientists study? Analysed data from 235 hospitalized patients with Covid-19.
What did they find? Patients who had sufficient vitamin D – of at least 30 ng/mL— were 51.5 per cent less likely to die from the disease. They also had a significantly lower risk of falling seriously ill or needing ventilation. Patients who had plenty of the nutrient also had less inflammation – often a deadly side effect of Covid-19.
What were the study’s limitations? Confounding factors, such as smoking, and social economic status were not recorded for all patients and could have an impact on illness severity.
By Who? Tel Aviv University, Israel.
What did scientists study? 782 people who tested positive for coronavirus had their vitamin d levels prior to infection assessed retrospectively and compared to healthy people.
What did they find? People with vitamin D levels below 30 ng/ml – optimal – were 45 per cent more likely to test positive and 95 per cent more likely to be hospitalised.
What were the study’s limitations? Did not look at underlying health conditions and did not check vitamin D levels at the time of infection.
By Who? Brussels Free University.
What did scientists study? Compared vitamin D levels in almost 200 Covid-19 hospital patients with a control group of more than 2,000 healthy people.
What did they find? Men who were hospitalised with the infection were significantly more likely to have a vitamin D deficiency than healthy men of the same age. Deficiency rates were 67 per cent in the COVID-19 patient group, and 49 per cent in the control group. The same was not found for women.
What were the study’s limitations? Independent scientists say blood vitamin D levels go down when people develop serious illness, which the study did not take into consideration. This suggests that it is the illness that is leading to lower blood vitamin D levels in this study, and not the other way around.
By who? Inha University in Incheon, South Korea.
What did scientists study? 50 hospital patients with Covid-19 were checked for levels of all vital vitamins and compared to a control group.
What did they find? 76 per cent of them were deficient in vitamin D, and a severe vitamin D deficiency (<10 ng/dl) was found in 24 per cent of Covid-19 patients and just 7 per cent in the control group.
What were the study’s limitations?
Small sample size and researchers never accounted for vitamin levels dropping when they fall ill.
By Who?. Independent scientists in Indonesia.
What did scientists study? Checked vitamin D levels in 780 Covid-19 hospital patients.
What did they find? Almost 99% of patients who died had vitamin D deficiency. Of patients with vitamin D levels higher than 30 ng/ml – considered optimal – only per cent died.
What were the study’s limitations? It was not peer-reviewed by fellow scientists, a process that often uncovers flaws in studies.
By Who? University of Glasgow.
What did scientists study? Vitamin D levels in 449 people from the UK Biobank who had confirmed Covid-19 infection.
What did they find? Vitamin D deficiency was associated with an increased risk in infection – but not after adjustment for con-founders such as ethnicity. It led to the team to conclude their ‘findings do not support a potential link between vitamin D concentrations and risk of Covid-19 infection.’
What were the study’s limitations? Vitamin D levels were taken 10 to 14 years beforehand.
By Who? University of East Anglia.
What did scientists study? Average levels of vitamin D in populations of 20 European countries were compared with Covid-19 infection and death rates at the time.
What did they find? The mean level of vitamin D in each country was ‘strongly associated’ with higher levels of Covid-19 cases and deaths. The authors said at the time: ‘The most vulnerable group of population for Covid-19 is also the one that has the most deficit in vitamin D.’
What were the study’s limitations? The number of cases in each country was affected by the number of tests performed, as well as the different measures taken by each country to prevent the spread of infection. And it only looked at correlation, not causation.
By Who? Northwestern University.
What did scientists study? Crunched data from dozens of studies around the world that included vitamin D levels among Covid-19 patients.
What did they find? Patients with a severe deficiency are twice as likely to experience major complications and die.
What were the study’s limitations? Cases and deaths in each country was affected by the number of tests performed.