Some things like B12 and D are only found in fortified foods, which are just foods with supplements added to them. Everyone needs B12 supplements. I don't go out in the sun because of skin cancer risk and also because there is no sunshine in the winter where I live, so I need D supplements. Also, I don't eat any sea vegetables or enough iodized salt so I need to take an iodine supplement. I don't eat enough food containing ALA which your body can convert to DHA and EPA, so I need to to take vegan omega 3 DHA/EPA made from algae.
If you eat a lot of dark leafy greens, you will be getting a lot of K1, which your body can convert into K2. I don't so I take a K2 supplement a few times per week.
Your body can make creatine and carnosine but there may be some reason why it may be helpful to take them in supplement form. I still have to look into that.
Here are the Bernard links that I could find concerning supplements/fortified foods. He is president of PCRM:
http://www.pcrm.org/health/health-topics/what-supplements-should-i-take
http://www.pcrm.org/health/diets/pplate/power-sources
http://www.pcrm.org/health/cancer-resources/ask/ask-the-expert-salt
http://www.pcrm.org/nbBlog/index.php/get-omega-3s-with-ease
http://www.pcrm.org/nbBlog/get-omega-3s-from-plants—not-fish-oil
