Puzzled Over ProduceMy mother-in-law wouldn't eat chicken skin. Something about salmonella, or maybe it was the fat. Freda visited us in Boston every few months and, in between, sent cautionary clippings. One detailed the perils of eating undercooked meat; another warned of cancer-causing hydrocarbons in grilled foods. I read them all with a patronizing chuckle.Maybe paranoia takes root in midlife. Because, even without my mother-in-law around, rustling up a meal is beginning to feel like a stroll through a minefield.Fish and chicken, long staples of my menus, are rampant in the news: They contain everything from cancer-causing PCBs to arsenic. I could go vegetarian and eat sprouts and tofu. But bean sprouts harbor dangerous bacteria. And isn't the soy in tofu genetically engineered? Sharing a meal with someone I love should be one of life's great pleasures -- which leads me to registered dietitian Patricia Vasconcellos. Pat agrees to meet at my local Stop & Shop. I'm about to get a midlife nutrition lesson -- and a new set of priorities. Puzzled Over ProduceWe begin in the produce section: Corn, strawberries, apples, cantaloupe, zucchini, and salad greens are on my grocery list. My worry: What's the real story with bioengineered corn? And should I be concerned about whether those apples' red-red skin is courtesy of nature or additives? The real issues: "I'm more concerned about bacteria and pesticide residue," Pat says. "Even thorough rinsing may not eliminate all pesticide residue." To lower exposure to pesticides, which some studies have linked to nerve damage and cancer, buy organic.She picks up a basket of organic strawberries and tells me that even organic has a catch: "Although these are grown without chemical pesticides, you still have to wash them -- any produce that's been picked by hand can have sickening pathogens." She urges me to wash all vegetables and fruits (even melons) with soap and running water before eating.Her take-home trick: I ask Pat how I can be sure that produce -- which isn't always labeled "USDA organic" -- is organically grown. She directs me to check the PLU (Price Look-Up) sticker -- that's the little round one with a code number. There's a PLU sticker on virtually every piece of produce sold retail. If it's got five digits, starting with "9," then the produce is organic. Just four digits? It's conventionally grown.Salmon, Bacon, and Snack TricksBring Home the Bacon?We head to the meat and fish section, because I have salmon on my list. Farmed or wild? Wild, Pat says. "It has fewer PCBs and the same amount of omega-3 fatty acids, which are good for heart health."My bad: I grab a pound of bacon. "Do I need to get worked up about the nitrates and nitrites?" I ask, thinking of my mother-in-law. Pat rolls her eyes. "Sure, but aren't you concerned about saturated fat and salt? Bacon is loaded with both." I put the bacon back.Okay, I can do low-fat, low-sodium protein -- chicken. When I ask about arsenic levels in chicken, Pat tells me she's concerned about the antibiotics and hormones they're fed. Organic chickens have neither.Her good (advice): I hold a plump, conventionally farmed bird in one hand, and a skinnier, organic one that costs three times as much in the other. I could go broke eating healthy. "Is organic worth the extra cost?""It's a personal choice," she says."Do you shop organic for your own family?" I press.She admits she often does. I drop the organic chicken in my cart. It's at around this point in the shopping expedition that a lightbulb goes on in my head: I've been worrying about all the wrong things.Sugar, Salt, and SnacksOther than the occasional chicken stock or cranberry sauce, I rarely buy food in cans, for which Pat gives me high marks (canned foods can have added sugar and salt). But I confess to a craving for potato chips. Do I have to give them up? Her advice: "It's all about serving size." And here's the rub: For most potato chips, a "serving" is one handful. That meager amount contains about one-eighth of my daily fat allowance, and 5 percent of the maximum amount of salt (4,000 mg.) I should eat in a day. For heart health, she says, a good guide is not to exceed the 140 mg.