It’s late fall or winter, and for some of us who lives in the northern hemisphere that means little sun exposure. For people living in the southern hemisphere, its the exact opposite, and summertime usually means more sun exposure. Many people know that the sun is a source of vitamin D. However, if you want to optimize your vitamin D levels, especially when you are getting little sun exposure, its not necessairly enough just to supplement with vitamin D orally. How much vitamin D that gets activated is also dependent on our potassium/sodium balance. Our kidneys are responsible for activating oral vitamin D or vitamin D comming from food. How much of the vitamin D the kidneys activate is dependent upon our intake of sodium and potassium. It all comes down to a quite interesting evolutionairy mechanism. Back in our hunter gatherer days our intake of these two minerals varied with which types of foods that were available, and which plants and fruits that were in season. Foods like fruits and different plants like salads etc. that requires more sunlight are high in potassium. Typically the more sunshine a fruit or plant requires, the higher the potassium levels are.
So what does this mean when it comes to optimizing our vitamin D levels.?
If you eat alot of foods containing high levels of potassium, your kidneys will take this as a sign that there’s plenty of sun available, and that alot of vitamin D is produced in your skin, since these foods were only available when in season. So the kidney’s don’t think they need to activate as much vitamin D from food sources.The result is less vitamin D absorbtion when eating alot of high potassium foods and getting little sun exposure. It might not be that problematic for people having acess to adequate sun and eating a diet low in potassium and high in sodium when it comes to vitamin D uptake (although it might lead to other health problems), since the body will interpret this as recieving less vitamin D from the sun. So you’ll recieve more vitamin D from food in addition to the vitamin D from the sun.
The conclusion is: It might be a good idea, especially when vitamin D from the sun is less available, to eat foods that are in season or low in potassium, in order to optimize vitamin D uptake.