By Karen Collins, MS, RN, CDN

Q: Have studies proven the safety of low-carbohydrate diets?

A: In the few studies to date, lasting six months or more, low-carbohydrate diets did not cause a rise in LDL (“bad”) cholesterol as many nutrition experts expected. Apparently, the amount of weight loss offset the cholesterol-raising impact of fatty high-protein foods. However, studies have shown possibly negative effects of these diets on the liver, kidney, and the risk of gout. Since people’s responses varied widely in these studies, individuals who choose to follow a high-protein diet should have their physician regularly give them blood tests. Although all the studies conducted so far seem to support the safety of low-carb diets, there are still other health concerns. The risk of heart disease posed by LDL cholesterol is based on the form of this cholesterol, not just its blood level. Antioxidants help keep LDL cholesterol in a form that poses less risk. Yet vegetables, fruits, whole grains and beans, which are the sources for most antioxidant vitamins and phytochemicals, are limited by low-carbohydrate diets. Weight control is an important step toward lower cancer risk, but the nutrients and phytochemicals in plant foods play a crucial role in good health and cancer prevention and should be a part of your meals.

Q: Are wraps lower in calories and carbs than traditional sandwiches?

A: Not necessarily. Portion size has a huge impact on the calorie and nutrient content in wraps. The one-ounce flatbreads and tortillas used for wraps often contain 70 to 90 calories, which is the same as a one-ounce slice of whole grain bread. But some wraps are two to three ounces and contain 110 to 160 calories. Low-calorie bread, on the other hand, is usually about 50 calories, often because it is sliced thinner. Low-carb claims can be deceiving. Breads and tortillas labeled “low carb” don’t actually contain any fewer carbohydrates or calories than regular products. The extra fiber added to low-carb choices is subtracted from the total carbohydrate content, yielding a lower “net carb” amount. The other aspect of any sandwich you should weigh when judging its nutritional value is the contents: The larger the quantity of stuffing, the higher the calories. At fast food restaurants, when wraps are smaller than sandwiches, they are lower in calories. At restaurants where the two are equal in size, wraps can be higher in calories because their fillings may include more mayonnaise, bacon, and other high-fat ingredients.

 

Q: Is red grapefruit more nutritious than white?

A: All grapefruit is an excellent source of vitamin C, but red and pink varieties provide more of the phytochemical called lycopene. Lycopene is a carotenoid, a “cousin” to beta-carotene, as well as a pigment. Although it cannot be turned into vitamin A like beta-carotene, it is a much stronger antioxidant. Consequently, choosing red or pink grapefruit instead of white makes good sense. The darker red flesh signals a higher lycopene content. Lycopene is also found in tomatoes and watermelon. Some studies suggest that people who eat more foods high in lycopene may have a lower risk of prostate and other cancers, and less heart disease. Because phytochemicals like lycopene appear to work best in combination with other phytochemicals, it is preferable to eat them from foods rather than supplements. Some people on certain medications should avoid eating any kind of grapefruit; consult your doctor or pharmacist.

Q: Is it okay for me to rely on frozen dinners for my meals if they are healthy ones?

A: Frozen dinners that limit fat and sodium content are a good start compared to many other frozen meals. Regular versions of these dinners can contain 30 to 55 grams of fat and 700 to 2,100 milligrams (mg) of sodium per serving. You should check the nutrition information on these healthier dinners, however. Some products designed for weight control reduce the fat and calorie content, but sodium content can still be 600 to 800 mg. Depending on your other food choices for the day, this high amount of sodium makes it difficult for a person to stay under the American Institute for Cancer Research’s (AICR) recommended limit of 2,400 mg for the whole day. In fact, the newest Institute of Medicine recommendations say that it’s best to stay under 1,500 mg to prevent and control high blood pressure. If you plan to eat frozen dinners frequently, the health-oriented meals that keep sodium at 400 to 600 mg are better. You should also keep in mind that even the healthier frozen dinners can have small quantities of vegetables. In fact, some products that feature vegetables in their name place cornstarch higher on the list of ingredients than any vegetable. If you create vegetable sides for the healthier kinds of frozen dinners, you can have a delicious meal that is much more nutritious. While convenient frozen meals are heating, open a bag of ready-to-eat salad. Or microwave a bag of microwavable, prewashed spinach, serving it with a splash of balsamic vinegar or a sprinkle of Parmesan cheese. Salad bars at grocery stores can provide either salads or chopped vegetables for a quick stir-fry at home. Many kinds of fully prepared fruits are also available. Since some health-oriented convenience meals can be a little low in calories, eating extra vegetables and fruits can make these meals more satisfying and sustain your energy for several hours.

Q: Is olive oil a source of antioxidants?

A: Yes. There are primarily two kinds of antioxidants in olive oil: phenols and vitamin E. The amount of phytochemicals in olive oil called phenols varies depending on how the oil is produced. Extra virgin oil is higher in these phenols than light olive oils. Olive oil also supplies the antioxidant vitamin E. Although olive oil contains less vitamin E than several vegetable oils that have more polyunsaturated fat, olive oil is mostly composed of monounsaturated fat. This is an important difference. Polyunsaturated fat is less stable and more vulnerable to oxidation reactions than monounsaturated fat. Human studies suggest that olive oil, because of its monounsaturated fat, can help prevent LDL (“bad”) cholesterol from converting to its most damaging form. By raising the antioxidant content of blood, olive oil could possibly lead to less DNA damage that can initiate cancer.

Q: Does the Daily Value amount for potassium on food labels apply to all adults?

A: The Daily Value for potassium, 3,500 milligrams (mg), applies to all adults. This figure comes from old recommendations of the Institute of Medicine (IOM) that formed the basis of the Recommended Dietary Allowances. Some experts still do approve of using this amount as a target for potassium intake. It is substantially higher than the current average intake. But the IOM has revised its recommendation for potassium. The institute now suggests that from age 14 males and females might benefit from a daily potassium intake of 4,700 mg. If you follow the American Institute for Cancer Research (AICR) advice to eat an abundance of vegetables, fruits, whole grains, and beans, a higher potassium intake is one of the many nutritional benefits you will receive.

Karen Collins is a registered dietitian and certified dietitian/nutritionist with the American Institute of Cancer Research.