MD, PhD, FMedSci, FRSB, FRCP, FRCPEd.

There are many proponents of so-called alternative medicine (SCAM) who advocate the use of high-dose vitamin D for the prevention or treatment of corona-virus infections. Considering that ethnic minorities are disproportionately affected with Covid-19 further research seems justified, especially as there is clear evidence that vitamin D deficiency is particularly common in these ethnic groups.

However, an international team of experts strongly caution against doses higher than the upper limit (4000 IU/day; 100 µg/day); and certainly of very high doses of vitamin D (in some reports, 10 000 IU/day (250 µg/day) of vitamin D are being promoted) unless under personal medical advice/clinical advice by a qualified health professional. Instead, they advocate the following lifestyle strategies for avoiding vitamin D deficiency and ensuring a healthy, balanced diet.

  1. Supplementation with vitamin D according to Government guidelines (eg, 400 IU/day (10 µg/day) for the UK;7 600 IU/day (15 µg/day) for the USA (800 IU/day (20 µg/day) for >70 years) and Europe. These recommendations were established to ensure that 25OHD concentrations in the majority of the population are above 25 nmol/L (UK) in order to protect musculoskeletal health or above 30 nmol/L (USA) to minimise the risk of vitamin D deficiency (the USA recommendation was also established to optimise musculoskeletal health in the population using a 25OHD concentration of 50 nmol/L). Supplementation with vitamin D is particularly important during times of self-isolation associated with limited sunlight exposure. This is in line with the UK Scientific Advisory Committee on Nutrition (SACN) recommendations for vitamin D, and the US Institute of Medicine (IOM) recommendations for vitamin D, both of which were established under the assumption of minimal exposure to sunlight. Thus, re-emphasis of advice on safe sun exposure (below) and reinforcing government advice on supplements especially when sunlight exposure is low would further boost vitamin D status. The UK SACN, US IOM and EU European Food Safety Agency recommend that vitamin D intake (total from both foods and dietary supplements) should be limited to 4000 IU/day (100 µg/day) for adults, and there is broad international consensus that the general public should avoid higher dose supplements that risk total intake from all sources exceeding this level.
  2. Consumption of a nutritionally balanced diet, for example, according to the UK Eatwell Guide and US Food Pyramid including vitamin D rich foods, that is, oily fish, red meat, egg yolk and fortified foods, such as breakfast cereals in the UK, as well as fortified milk in the USA and Canada.
  3. Safe sunlight exposure to boost vitamin D status. Safe sunlight exposure will enable vitamin D production in skin from March through September in the UK, and at most northern latitudes. Dermal synthesis of vitamin D is most efficient with short, regular (daily) exposures when the sun is at its strongest (in the middle of the day). The efficiency of vitamin D synthesis declines well before the threshold for sunburn is reached but the desirable dose is skin-type dependent and so exposure times required differ for different skin types. For the UK about 10 min of exposure at around lunchtime, in-season appropriate clothing, can meet vitamin D needs for white-skinned people; this increases to about 25 min for those of skin type V (ie, South Asian, brown skin tones). What is key is to try to achieve the sunlight exposure without leaving home (eg, in the garden/balcony); and if that is not possible ensure that social distancing is maintained at all times. Increasing the unprotected skin area (skin not protected by clothing or sunscreen) will increase the vitamin D supply from skin while keeping exposure times short and sub-erythemal. Exposing as much skin as temperature and social comfort allow will maximise vitamin D supply through this route. For those of skin type V and VI (brown or black skin) the exposure requirements in UK sunlight are more challenging to achieve than for white-skinned people and oral vitamin D intake is especially important.
  4. Appropriate diet and lifestyle measures, as emphasised by the WHO at this time, including adequate nutrition to protect the immune system.
  5. Targeted nutritional advice, for example, for UK Military personnel as advised by the Defence Nutrition Advisory Service, with specific reference to COVID-19.
  6. Vitamin D—advice for bone health. The Royal Osteoporosis Society provides specific guidelines on the management of vitamin D deficiency in adults with, or at risk of developing, bone disease.

In conclusion, the experts recommend appropriate RCTs to evaluate the effects of vitamin D supplementation on COVID-19 infections. Until there is more robust scientific evidence for vitamin D,  they strongly caution against the use of high vitamin D supplementation (greater than the upper limit of 4000 IU/day (100 µg/day)). Rather, they strongly endorse avoidance of vitamin D deficiency in the population (as per the six points above) and complete adherence to government’s advice worldwide on the prevention of the spread of COVID-19.

I am sure that this will not stop self-appointed SCAM-experts to continue recommending mega-doses of vitamin D. Therefore it is perhaps worth reminding consumers that an excess of vitamin D will lead to a condition called hypervitaminosis D. It is characterised by the following symptoms:

  • Anorexia
  • Dehydration
  • Fatigue
  • Frequent urination
  • Irritability
  • Tinnitus
  • Dizziness
  • Disorientation
  • Confusion
  • Weight loss
  • Muscle weakness
  • Vomiting
  • Excessive thirst
  • High blood pressure
  • Arrhythmias
  • Passing large amounts of urine

It can lead to serious complication, including permanent kidney damage.

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