Uppdaterat: 18 juni 2020
I am definitely a proponent of a healthy lifestyle and diet as being the best (preventative) medicine. However there are some areas where supplementation should be considered to optimise your immune system. Vitamin D is one of these areas, especially if you live in a country that is far from the equator such as Sweden. Vitamin D is not only a Vitamin but an important hormone for the body and studies indicate that deficiency is very common in the western world. Many experts on the subject say that 20-30 minutes exposure to the sun in the middle of the day is adequate to produce an optimal amount of D vitamin to maintain a strong immune system during the summer months (April to September in Northern Europe as an example) with as much skin exposed and without sun screen. During the winter half of the year however a supplement of around 50-100 mcg which is equivalent to 2000-4000 IU (International Units) can be required depending on your skin colour and how far you live from the equator. Studies show that the darker your skin is the higher the dosage the may be required. Older and overweight people also often have deficient levels and may require higher dosages. These are higher levels than the recommended daily intake in most countries and is at the maximum level under EU guidelines of 100 mcg or 4000 IU. However there are doctors and studies indicating that these guideline are often conservative. There are foods you can eat to bolster Vitamin D as well - fatty fish such as salmon, cod and egg yolks but it is very difficult to come up to the levels you can get from sun exposure during the summer through diet alone.
There are also indications that Vitamin D has a positive effect on mood as well which is yet another reason to consider taking it as a supplement during the darker winter months.
Be well. David