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Our Immune System

The immune system or immune system is the defence system of an organism against disease.

There are many parts of the body involved in this task, such as:

  • Throat tonsils
  • Thymus (sweetbread)
  • Bone marrow
  • Lymph nodes
  • Spleen
  • Appendix (small intestine)

The function of the immune system is to fight both external and internal pathogens.

The Latin term immunis means exempt, referring to protection against intruders from outside.

The term 'immune system' refers to the immune response in multicellular organisms, in which a large number of cells and molecules work together to ward off invaders.

In addition to the protection against viruses, bacteria, fungi and parasites the immune system is also used to clear away waste products or diseased body cells such as cancer cells.

Supporting our immune system

We can have a great influence on the quality of our defences.

healthy lifestyle, A healthy and varied diet with plenty of vegetables, sufficient water, exercise and a good quality night's sleep are essential.

Also various vitamins and minerals contribute to the normal functioning of the immune system:

  • Vitamin A
  • Vitamin B12
  • Vitamin B6
  • Vitamin C
  • Folic acid
  • Zinc
  • Iron
  • Copper
  • Selenium

In addition, of course Vitamin D a positive influence on our immune system.

It is important to consider the role of Vitamin D because the blood values of Vitamin D can vary greatly from season to season

The role of vitamin D

It is a well-known fact that we Vitamin D is produced by exposing our skin to sunlight.

We also get vitamin D from food, but our own production under the influence of sunlight is by far the most important source.

But the in-house production of Vitamin D from cholesterol under the influence of sunlight is by far the most important source.

In order to keep up the vitamin D levels, it is therefore important to sufficient sunshine be with a sufficiently bared body.

However, this only for part of spring and summer.

During the autumn and winter the sun is not strong enough to encourage the body to produce sufficient vitamin D.

This applies even more to people of ageThis is because the production of vitamin D in the body decreases with age.

Vitamin D values

In a 1998 study became a Sample taken from the population of a small southern German town, in people between the ages of 50 and 80.

This study shows that the vitamin D levels in the population in the period from October to May low are.

On the other hand, the Vitamin D levels high in the summer months.

It is concluded that the seasons a huge effect on vitamin D levels. 

Seasonal variation of vitamin D values in a sample of inhabitants of a small southern German town [age range 50-80 years].

Bron: Article ‘Epidemic influenza and vitamin D’, J.J. Cannell, R. Vieth, J.C. Umhau, M.F. Holick, W.B. Grant, S. Madronich, C.F. Garland, E. Giovanucci [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2870528/?utm_source=Vit+D+Flu+by+Month+Fri+3%2F27&utm_campaign=Newsletter&utm_medium=email]

Peak months of flu activity

The figure below shows the Peak influenza activity in the United States per month for the influenza seasons 1982-1983 to 2017-2018.

The "peak month of flu activity" is the month with the highest percentage of positive tests for influenza virus infection.

During this 36-year period flu activity peaked most often in February (15 seasons), followed by December (7 seasons), January (6 seasons) and March (6 seasons).

In Netherlands peak months are similar to those in America.

This is made clear in the following graph. 

The horizontal axis shows the weeks of the year and the vertical axis the numbers of people with influenza-like illness, IAZ, (influenza = flu) per 10,000 inhabitants.  

For the 2016/2017 to 2019/2020 influenza seasons, the most influenza takes place between week 50 (December) and week 15 (April).

Source: Centers for Disease Control and Prevention https://www.cdc.gov/flu/about/season/flu-season.htm

Source: Nederlands Tijdschrift voor Medische Microbiologie: 'Influenza season 2019/2020 in the Netherlands - A mild short influenza A epidemic' [https://www.nvmm.nl/ntmm/artikeloverzicht/december-2020/ingezonden-influenza-overzicht-20192020/].

Relationship between the flu and vitamin D

An American research group has combined the two graphs above into the following graph.

Then it becomes clear that there is an inverse relationship exists between vitamin D levels and the occurrence of influenza.

When the vitamin D values high are, there is no or hardly any flu.

And when the vitamin D values low are, comes flu is common.

Source: GrassRoot Health Nutrient Research Institute, https://www.grassrootshealth.net [http://campaign.r20.constantcontact.com/render?m=1102722411090&ca=6eff568e-8949-4d47-b810-8ee08e9c170d].

* Source: National Institute of Health 'Low Vitamin D Levels Associated with Colds and Flu' by William Duval, Ph.D. [https://www.nih.gov/news-events/nih-research-matters/low-vitamin-d-levels-associated-colds-flu].
* Source: The Harvard Gazette 'Study confirms vitamin D protects against colds and flu' [https://news.harvard.edu/gazette/story/2017/02/study-confirms-vitamin-d-protects-against-cold-and-flu/].


"Those who wish to investigate medicine should proceed as follows:

First, look at the seasons of the year and what effect each one has."

Greek physician
Approximately 460 - 377 B.C.


There are, of course, many factors that determine the likelihood of catching the flu.

However, these and other* studies suggest that in order to reduce the minimise the risk of flu that it is important to High vitamin D levels in the body to keep.

Because it Sunlight too weak in autumn and winter months is for proper production of vitamin D in the skin, vitamin D will have to come from food or supplements.


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