"I want to become vegan?"
If you want to become a vegan, then the first thing to do is some research, and know what being a vegan means. To become a vegan, is to follow where the diet is concerned the strict vegetarian diet. But first a little bit of myth busting or debunking is in order, with just one immediate qualifier, on my part. That is I eat meat as a part of my diet, before I go any deeper on how to become a vegan.
Now as for the proteins, or amino acids, it's not as hard to find them and in enough amounts to meet the daily needs. However the three that were mentioned for the amino acids/proteins, creatine, carnosine, and taurine are NOT classed as essential, two of the three, are classed as conditionally essential, but creatine is NOT classed as being either essential, or as being conditionally essential. Sulfur while essential, is easily obtained from plant based foods. Some of the various amino acids, contain sulfur, and that aren't classed as either essential, or conditionally essential, can be broken down by the body for sulfur if needed.
Now as far as the omega three fatty acid DHA, or even the other omega three fatty acid EPA, they are NOT currently classed as either essential or semi essential nutrients. Alpha linoleic acid, is the only essential omega three fatty acid. There is a move by some though in the field of nutritional science, to at the least, classify both DHA, and EPA as conditionally essential with a preference for the classification as essential.
Now as for the heme iron, while it's more readily bioavailable, the body can convert the non heme iron, into heme iron. However it requires at least a sufficient intake of vitamin C, for it to first be absorbed, and converted into the preferred form of heme iron. However it's suggested strongly, that the intake be about two times greater. So you're going to need to learn what are the best plant based sources for iron.
Now I'll get into vitamin D, or more accurately, what's known as vitamin D3. While it's true that the human body can produce vitamin D3, most people, and this crosses ALL dietary types, doesn't either get enough sunlight, or for other reasons simply can not produce enough. Vitamin D3 is the leading vitamin, for the overwhelming vast majority of the population, to be at subclinical levels, or even being outright deficient in. To date, there's only only known, and proven plant that produces vitamin D3, a specific type of lichen. Which is now being used by a few companies to produce vitamin D3 supplements. Otherwise the only other source for vitamin D3, comes in small traces from dairy, eggs, and some cuts of meat, with fish being the best source, and more specifically the cold water types, especially what are known as forage fish.
Now vitamin B12 has to date only been found in animal based sources. The most common form of vitamin B12, used for supplements is a synthetic. It's found in supplements, and fortified foods. However his is a micronutrient, that even those of us, are even found to be at subclinical levels. That's even with eating foods that's been fortified with it. However even just meeting, or even surpassing the minimum daily value, can still leave a person coming up short. I won't get into the reasons why, as that's getting more into the medically technical end of things.
Now the first thing to don is learn as stated in another answer how to meet all of the essential nutrients as best possible. To do that though, you will need to go beyond just what's found on the nutritional labels for foods. Now you don't need to know the specifics for each and every nutrient, but it will help to known how, and where to get them. However that means looking up the different types of foods to see what they have or don't have, as well as in what amounts. You can create a simple basic search that will help with that, or use the one I use. Below are a couple of examples.
broccoli cooked nutritional value
broccoli raw nutritional value
Now using modifiers is very important, in that they play a role in the nutrient levels. Now here are just some of the different types modifiers that you can use, baked, broiled, canned, cooked (this includes steamed, dry or moist heat), dried, dry roasted, fried, raw and roasted. The next thing to do, is look for, and find a site, that will give you the most complete breakdown of the various nutrients, at just more than a few select ones, that are commonly found on nutrition labels.
Now there are some micronutrients that are hard to get, beyond the two I mentioned. Now before I list those, while they are a big issue for vegetarians, and vegans, they can be, and often are also an issue for those of us who eats meat as well. I'll even put some numbers or percentages with them, that as I said isn't restricted to one specific dietary type.
Vitamin A (the retinol form) fifty one percent have been found at subclinical levels.
Vitamin B4 (more commonly known as choline) an estimated ninety percent are at subclinical levels.
Vitamin B6 fifteen percent have been found at sub-optimal levels.
Vitamin B9 (also known as folate, folic acid, and folnic acid), thirteen percent, or higher, are at subclinical levels.
Vitamin B12 38 percent to 60 percent percent of the population are below the recommended levels. However the average for those who follow a vegetarian diet, is sixty percent, or greater.
Vitamin D3 eighty one percent to ninety five percent of the population are below recommended levels.
Vitamin E 79 to 93 percent of the population are below the recommended levels.-
Vitamin K2 there are no numbers available at this point for any of the vitamin K2 isomers.
Calcium it's estimated that at least fifty one percent are at subclinical levels.
Copper
Iodine the current estimate that I have is about eleven percent of the population is at subclinical levels.
Iron about eleven percent of the population is at subclinical levels.
Selenium
Zinc about twelve percent is at subclinical levels.
Some of the numbers for the level of being at subclinical levels shocked me, but not necessarily for some of the specific nutrients. These numbers however are NOT for second or third world countries, but they're for the modern industrialized countries.
No my suggestion is and in alignment with a vegan regular, to get A GOOD quality multivitamin with minerals. It's a very cheap form of insurance that can help ton guard against becoming very low in, or even developing a frank deficiency in. If you go vegan, just make sure that they are clear that they're vegan friendly. Now there are at least two though that you will need top but as separate supplements, and a third to strongly consider. The one is choline. The tablets are fairly large in size, and to even put it into a regular vitamin supplement in at about half the daily value would make it quite large. About a three hundred fifty milligram tablet of choline, should suffice.
Next is vitamin K2, and specifically you want vitamin K2-MK7. Vitamin K1 is found in multivitamins but not any of the nine to ten vitamin K2 homologues, or isomers. Vitamin K2 works with vitamin D3, and magnesium with getting calcium to where it needs to go, to the bones. But importantly from building up, where you don't want it, in the arteries as plaque, that could lead to a heart attack or stroke.
Now there are a few maker I have a short list of for vegan suitable vitamin D3, that I'll leave some links to.
http://vitashine-d3.com/
http://www.globalhealingcenter.com/suntrex-d3.html
http://www.countrylifevitamins.com/store/vegan-d3
Now I do take vitamin D3 myself, but what I take, is NOT vegan friendly, as I can get it in any store, that has a selection of vitamins.