David Wood asked:
Hello I'm David from The States and i have 2 questions about the same thing.
I heard that we get vitamin D from the sun if that's true does that mean that to a point we go through a kind of photosynthesis?
And, if so, does sunblock block the Vitamin D getting to us?
We put this question to Dr. Laura Tripkovic from Surrey University, and Professor Richard Cogdell from Glasgow University:
Laura - We need vitamin D to maintain our bones and to make sure we absorb enough calcium from our diet. One of the main sources to humans, radiation from the sun can penetrate the layers of the skin called the epidermis, while there's a chemical called 7-hydrocholesterol and this is observed through UV light and then will produce the pre-vitamin D molecule. And then because the skin is quite warm, this pre-vitamin D3 will spontaneously convert to vitamin D3 and the vitamin D3 will move from the skin, and will be pushed out into the capillary system, and into your blood system, so it can then be activated and used.
Hannah - So, human skin does make vitamin D using a photochemical reaction. How similar is this process to the photosynthesis are carrying in the chloroplasts of plants which uses the sunís rays to convert carbon dioxide into oxygen and carbohydrate?
Richard - My name is Richard Cogdell and I'm the Hooker Professor in Botany at Glasgow University. In vitamin D production, the wavelength of light which triggers that reaction or drives that reaction is the ultraviolet wavelength. So itís the wavelength that actually would burn you if you're out in the sun for too long. The wavelengths of light which drive photosynthesis are the wavelengths that give rise to the blue and red regions in the spectrum because itís light absorbed by chlorophyll. And so, photosynthesis is not driven by ultraviolet light. Itís driven by a visible radiation in the blue and the red regions of the spectrum.
Hannah - So what happens during the winter months when the intensity of all wavelengths of sunlight hitting the UK decreases? Plants enter dormancy phase and use remaining carbohydrates stored up during the summer months but what happens to us humans? Back to Laura.
Laura - We can only have vitamin D3 here in the UK between the months of April and September. We can be out in the sun for about 10 to 15 minutes, three times a week, just around your face. You donít need to strip off, and this will see you through into early autumn. We now know that the half-life of vitamin D can be around a month. Now there are dietary sources of vitamin D that can support your levels during the winter time and they will be things like oily fish, like sardines and mackerel, there's a little in eggs, if you like shitake mushrooms it's in there, and there's also little bits added into breakfast cereals, milk, and soya milk and things. But you need to check the label to see if they're actually in there.
Good Question , ummm... well plants photosynthesis in need of food. Plants obviously won't live if they can't make or have food. For humans vitmain D isnt exactly food. Even though it is a very important vitamin , especially for our bones , we humans can probably live without vitamin D . Our bones might weaken , we might not even be able to move without this very important vitamin. But we could just manage to survive without it , so ... No , making vitamin D isn't human photosynthesis.
In common usage, "photosynthesis" refers to plants producing sugar and oxygen from carbon dioxide and water plus light using chlorophyll.
Photosynthesis is a special biochemical process that uses solar energy to create relatively complex and energy-rich sugar molecules from CO2, a simple and low-energy source of carbon. Essentially, solar energy is stored in the chemical bonds of sugars. Because of this, plants are able to make their own food.