Milk chocolate and dark chocolate

Milk Chocolate for Dark Chocolate
Dark chocolate (look for at least 60 percent cocoa) is a concentrated source of antioxidants, which protect cells from age-related damage; milk chocolate contains significantly smaller amounts. And chocolate's fat doesn't raise cholesterol. Preliminary results from my lab show benefits to blood vessels two hours after eating dark chocolate or drinking it in cocoa. Nibble an ounce, sip a small cup—the calories still add up.

— David L. Katz, MD
White wine and red wine

White Wine for Red Wine
Compared with white, red wine, like dark chocolate, provides more antioxidants, in this case from the skin of grapes. And alcohol in general can keep platelets from sticking together, possibly preventing blood clots. Moderation is the key here, too; one glass of wine a day, according to studies, appears optimal for most women.
White bread and whole grain bread

White Bread for Whole Grain Bread
Whenever you replace white flour with whole grains—in bread, cereal, pasta—it's a strike against aging. Soluble fiber, found in oats and barley, has been linked to lower levels of insulin and bad cholesterol (think: diabetes and heart disease), and insoluble fiber in whole wheat reduces risk of gastrointestinal maladies like diverticulosis. Check out bread made with the new albino whole wheat—it tastes like the real white thing.
Soda and tea

Soda for Tea
A cup of tea infuses you with antioxidants instead of the wallop of sugar you get in a can of soda. Green, black, and especially white—drink it hot or iced: All offer the powerful nutrients and a boost of caffeine.
Sugar and non-fat powdered milk

1/4 Sugar in a Baking Recipe for the Same Amount of Non-Fat Powdered Milk
Reducing sugar in cakes, cookies, and bread will start retraining your taste buds to prefer less sweetness in your entire diet—a good anti-aging goal, because in addition to weight gain and diabetes, chronically high intake of sugar can lead to glycosylation. This is a process in which sugar molecules adhere to protein molecules, potentially damaging cells, increasing inflammation, and contributing to the blockage of arteries.
Diet soda and water

Diet Soda for Water
There is no better beverage than water to help you stay hydrated, which is important in keeping body systems running well. Diet soda quenches thirst, but some experts still worry that its artificial sweeteners—officially considered safe—may be linked to cancer. My main concern with them is that they propagate a sweet tooth, which leads to more sugar intake and the overall deterioration of the diet.
Meat and lentils

1/4 of Your Meat for Lentils
Saturated fat (which meat tends to have a lot of) can gum up arteries and speed you toward heart disease. Too little fiber (meat has zero) can accelerate the aging of the gastrointestinal system. Beans and lentils are the opposite of meat: lots of fiber and no saturated fat—and they provide protein. How can you lose?
Regular yogurt and low-fat or fat-free yogurt

Regular Yogurt for Low-Fat or Fat-Free Yogurt
Dairy foods are a great source of calcium and vitamin D, which help keep bones from thinning. But the saturated fat in whole milk, cheese, and yogurt contributes to artery clogging. Switching to low- or no-fat dairy gives you all the benefits without the risks.
Meat and fish

1/4 of Your Meat for Fish
Fish is an ideal lean protein source, low in saturated fat. Certain varieties such as salmon are also high in omega-3 fatty acids—vital for heart and possibly brain health. Unfortunately, some species also contain contaminants: If possible, eat wild versus farm-raised salmon and limit albacore (white) tuna to one meal a week. If you're pregnant or nursing, check out the guidelines at epa.gov/ost/fishadvice/advice.html.
Potato chips and an apple

Bag of Potato Chips for Slices of Apple
An apple has no fat, few calories, lots of soluble fiber, and antioxidants. What does a potato chip offer? Pretty nil on the valuable nutrients score, and it's a great source of oil, calories, and salt. A good rule of thumb is to go with foods that come packaged by Mother Nature, i.e., apple (skin) versus chips (plastic bag), banana (peel) versus candy bar (wrapper). Both you and the environment will be around longer to enjoy each other.
As a reminder, always consult your doctor for medical advice and treatment before starting any program.