Oils, Water, Produce

Salad Dressings
Your healthiest bottled-dressing options are vinaigrettes made with olive oil, but if you have a weak spot for creamy dressings you can make them last longer (and eat fewer calories) by thinning them with milk, mild rice vinegar, or herb tea. Tossing a salad with dressing before serving it is the key to using less.

Mayonnaise
Go for low-fat mayonnaise rather than the low-cholesterol kind. Regular mayo doesn't have a lot of cholesterol to begin with, but it does have a great deal of fat.

Drinks
Keep filtered water or seltzer in the refrigerator and you'll always have a cold, refreshing, healthy drink on hand. (Soda consumption in the United States surpassed milk consumption in 1994 and is still shooting upward.)

Leftovers
Spoon leftovers — even the take-out kind — into glass or plastic containers that are microwave-safe. Some take-out trays and yogurt tubs are made from a kind of plastic that can leach chemicals into food at high temperatures. Avoid reheating in plastic containers that aren't designated microwave-safe.

Bagged lettuces and vegetables
Consider bags of baby spinach and other salad greens a shopping-list staple. For longest shelf life, buy prewashed greens in single-variety bags (the fragile leaves in salad mixes spoil first and can ruin the whole package). Combine them with more economical lettuce, such as iceberg, as needed.

Produce
Put produce in its place. That generally means either out of the fridge entirely (tomatoes and tropical fruits) or in one of the bottom bins, where the humidity is controlled. When vegetables lose moisture, they get limp and may lose vitamins. Spinach can lose as much as 50 percent of its vitamin C if left out overnight.

Oils
Olive, canola, and sesame oil are your healthiest options. If you have all three, you'll be ready for just about any kind of cooking. All are best kept in the refrigerator, because they oxidize when exposed to heat and light. Oxidized oils taste rancid and may release free radicals, which are linked to many health risks. Chilled oils may become cloudy, but they'll clarify at room temperature.