Since I'm not a licensed nutritionist or dietitian I can't make any direct recommendations for you, but I can tell you that I've never been healthier since I adopted a vegan diet centered mainly on whole (non-processed) foods, and there are studies out there that show how a well rounded vegan diet is the healthiest. If you're interested I can find links for you.
I can tell you some of the worst for good health...
You may just want to cut out anything your body can't easily digest naturally. Milk/dairy is the first thing. There's a reason a good percentage of the non-Western world is lactose intolerant; it's not a natural food for humans to be ingesting after infancy.
Processed foods, sugars and flours are other ones. If you can't walk into a garden, pick it off a plant and eat it as-is, then chances are it's not an overly healthy food. If you need a chemistry text to figure out what the ingredient list is, then chances are it's also not very healthy.
Excessive proteins that will raise your body's pH level and cause it to deplete the calcium supply in your bones to compensate should also be avoided. It doesn't take a rocket scientist to figure out the number one source of protein for most Western diets comes in the form of meat. Replace that with the normal amounts found in grains, nuts, legumes and vegetables and the "excessive" part won't be a factor... you also won't have to worry about those pesky little things like Osteoporosis and heart disease.
1. Kale! It is classified as a "super food" for a reason. Kale contains high levels of beta carotene, vitamin K, vitamin C, lutein, zeaxanthin, and is packed full of calcium. You can prepare kale in a variety of ways, so if you are a bit leery about greens, try blending it into a smoothie with a banana. It doesn't have a overpowering taste, has a wonderful texture, and its so good for you!
Second.
I either mix this into my morning drinks or eat the leaves raw if I'm too lazy to bother.
I do as well. Raw kale is great! The other day I added egg-white, lettuce,carrots, radicchio, and zapped it in the microwave. Delish, especially sprinkled with Mrs.Dash garlic blend.
-Anna
I have been interested in diet, nutrition, and health for a long time, and have a background from both Eastern and Western upbringing and their respective food and medicine cultures. In addition, I have had the experience of an eating disorder and recovering from it, gained weight, lost weight, and gained health and lost health.
From my time spent researching and experiencing all of this, I have come to a few conclusions.
1) Eat mostly natural foods -- that is, not from packages, tin cans, or processed.
2) Eat a variety of things, and use moderation. Don't eat too much or too little. Try to keep it balanced.
3) Try to have a lifestyle that is low in stress, and stay physically active. This includes your attitude -- try to be an optimist in addition to being a realist. Health is holistic. It isn't realistic to nitpick and spend a lot of time on what you eat for the sake on health. To do that would be counterproductive and also make you lose sight of other aspects of your body and life.
4) Ask yourself, "Is my diet sustainable long term, both for my willpower and for the health benefits?" If you really want to have a food that is thought to be "unhealthy" once in a while, you might as well have it, or you could go crazy later and binge. I also think eating things that aren't that healthy once in a while won't do much damage anyway. For this reason, I don't believe in "eliminating" any foods (unless you have serious health problems, of course). For example, @Sali is right in that plain sugar has no nutritional value, and you should try to choose natural foods that have more nutrients as part of them. The thing is, "sugar" is a part of healthy foods -- fruits, or root vegetables, for example. In the end, your body converts the energy from such foods into glucose anyway, and this is basically equivalent to plain sugar. Your body runs on the energy from sugars and lipids to survive. It probably helps if you've spent a lot of time looking into this kind of thing, but the point that I'm trying to make is... I don't believe it's useful to take extreme elimination-style attitudes towards certain foods long term (lowering your sugar intake long term if you used to be a junkie is probably a good idea though), unless it's for spiritual/personal reasons, or you have serious health issues and it's doctor's orders or things like that.
Honestly, the human body isn't too needy or picky. You can find a wealth of information online about what "superfoods" are out there, the foods that are high in nutritional value, and about which foods that aren't ... but humans have been able to thrive in a variety of living conditions, and a lot of the "health-guru" introduced stuff out there is all hype for companies to incorporate new exotic products into their foods and make money off of it. I guarantee you, that if your body is deficient in something, your body will let you know somehow.