By: Marleen van Balkom On: April 20, 2016 In: Metabolite of the month Comments: 0

Spring is here, the sun is shining (we hope!) and everybody talks about Vitamin D. What makes it so incredibly important for our health?

Despite its name, vitamin D does not quite qualify as a vitamin. In fact, it would be more precise to name it a hormone: We are capable of synthesising vitamin D themselves in our skin, liver and kidneys and it is used in various different cell types throughout our body.

For the body to make sufficient amounts of vitamin D, exposure of the face, arms, legs or back to sunlight for 5-30 minutes at least twice per week without sunscreen protection is known to be sufficient.

Nevertheless, seasonal changes in sunlight availability are known to lead to a drop in vitamin D levels during winter. Vitamin D is stored in fat tissue and released gradually over months into the bloodstream as vitamin D production decreases during winter. Hence, vitamin D levels in blood serum are lowest in late winter. Several studies have been conducted in the past to assess this drop in different geographic regions. Commonly, vitamin D levels are estimated by measurement of 25(OH)D, the prehormone of vitamin D produced in the liver that circulates in our blood.


Monthly variation of vitamin D levels in healthy adults (age 45) living in Great Britain. (Hyppönen & Power, 2007)

Some population groups are specifically at risk of becoming vitamin D-deficient, including older people, people living in northern latitudes, dark-skinned people and breastfed babies.

Most importantly, this can affect bone density and is known to cause rickets in children and osteomalacia in adults. Vitamin D metabolism is crucial for bone mineralisation as it regulates uptake and distribution of calcium throughout the body. In addition, vitamin D has been associated with various other conditions: Low serum levels of this compound are thought to increase the risk to develop certain kinds of cancer as well as cardiac diseases including heart failure and stroke. However, most of these associations have not been researched thoroughly enough yet in order to draw conclusions. We hope that knowledge we can gain from Kenkodo will help establish possible connections of vitamin D with overall health!

Unfortunately, uptake of vitamin D through nutrition is mostly ineffective as it is only contained in very few foods including fatty fish. While many dairy products are fortified with vitamin D in the US and Canada, Europeans usually do not obtain sufficient vitamin D through diet alone. Therefore, supplementation, often in conjunction with calcium, can be used to increase vitamin D levels in case of inadequate sun exposure.

Different institutions such as the American Institute of Medicine or the European Food Safety Authority issue recommendations for daily uptake of vitamin D, which usually range between 200-800 IU (= international unit) per day.

If you are a Kenkodo Beta user, check out the progress of your own vitamin D level at! If you have been sampling for a few months you might already see a change. Once you can take up sampling with Kenkodo again in June (we expect the new Kenkodo Kits to be ready by then) you will be able to track your levels over a longer time and compare it to other Kenkodo users! We are curious to see the vitamin D levels change after a year of sampling over all Kenkodo users 🙂

Have a sunny day!

Further Reading:

15 Health Benefits of Vitamin D, According to Science (+15 Best Vitamin D Foods). Jenn Miller, 2018.

Hypovitaminosis D in British adults at age 45 y: nationwide cohort study of dietary and lifestyle predictors
Hyppönen & Power, 2007

Harvard School of Public Health

European Food Safety Authority

Vitamin D and cancer – Vuolo et al., 2012

Deutsche Gesellschaft für Ernährung e. V.