A tomato's good for the body, but it turns out a tomato eaten with an avocado is even better. Lycopene, that much-touted antioxidant found in tomatoes, is more readily available to the body when paired with a little fat, such as the healthy unsaturated kind found in an avocado. That's not the only example of how certain food pairings can augment or diminish food's nutritional properties, according to Janet Tietyen, a food and nutrition specialist in the School of Human Environmental Sciences at the University of Kentucky.

"Lycopene is more readily available in cooked tomato products, so sauce, chili and soups are great ideas -- and by the way they all contain fat," she said.

This idea applies to most vegetables. A little fat helps to release their fat-soluble nutrients, meaning a spinach salad is nice, but a spinach salad drizzled with a little olive oil-based dressing is even healthier, because the oil helps release lutein, thought to protect against age-related eye diseases.

Add a few orange slices to that salad and the body will get more out of the spinach. The vitamin C in the orange alters the structure of the iron in spinach, making it more accessible. Mixing in a little meat, such as chicken, with the spinach does the same thing. Without one of those pairings, most of the iron from that spinach salad is wasted.

Of course, every coin has two sides. The flip side to food pairings are foods that inhibit nutrients from being absorbed. Coffee is one of the offenders. The polyphenols in coffee and tea are thought to reduce the body's ability to absorb iron; so coffee and eggs in the morning aren't the best combination to access all the iron in those yolks. And caffeine? Well, the bones don't get much benefit from milk in a cup of that morning brew.

"Caffeine inhibits calcium and other things from being absorbed, but frankly are you going to give up coffee? Let's be realistic," Tietyen said, laughing.

The point is all things in moderation. A little coffee probably won't hurt, but overindulging might not be the wisest choice.

And foods that are good sources for calcium? Tietyen says yogurt and cottage cheese are a good option, because they're more concentrated sources of calcium than milk. Separating that cup of coffee from a bowl of yogurt by an hour or so is enough time to get full use of the calcium in the dairy product.

If it all sounds like too much to worry about, Tietyen says a balanced diet is a natural and easy way for the body to get the nutrients it needs, without a lot of extra calories.

"If we eat fresh fruit, salads, whole grains, vegetables, fresh meats and dairy, then we're much more likely to get the nutrients we need without extra calories. If it's processed - even a bit, like yogurt - extra calories are very likely added," she said.

She suggests making that New Year's resolution a simple one - vow to shop the outer walls of the grocery store. Staying with fresh, whole foods and filling a plate with a variety of colors rather than an excess of calories is a great way to drop pounds and increase energy for the year ahead.