Vitamin K is a group of fat soluble vitamins. We can distinguish three types – K1 and K2 which are natural and a synthetic form K3. The vitamin is mostly known for helping us absorb calcium for strong bones and ensuring proper blood coagulation. Synthetic K3 also known as menadione can be toxic for humans and damage cells (especially in kidneys and liver) in larger doses. K1 is found in plants (especially leafy greens) and can be converted to K2 by bacterias that reside in our gut. So it’s best to get our vitamins from natural sources.
Vitamin D, also known as “sunshine vitamin” is a group of fat-soluble compounds. The most important ones for human bodies are vitamin D2 and vitamin D3. D2 naturally is present in plants, while D3 is synthesized by our organisms when we are exposed to sun rays. Actually, vitamin D should be seen more as a hormone than a vitamin. It is synthesized in our skin, but it is actually activated in a different place in our bodies – liver and kidneys.
Vitamin E is a fat soluble vitamin and the main antioxidant present in our bodies. It is a group of compounds that include tocopherols and tocotrienols. It’s probably best known for its free radical fighting properties. We can get this vitamin from natural sources (in which case it works much better), but it is also possible to synthesize it.