Nutritional Effects of Food Processing

FREEZING, DRYING, COOKING, AND REHEATING

Nearly every food preparation process reduces the amount of nutrients in food. In particular, processes that expose foods to high levels of heat, light, and/or oxygen cause the greatest nutrient loss. Nutrients can also be "washed out" of foods by fluids that are introduced during a cooking process. For example, boiling a potato can cause much of the potato's B and C vitamins to migrate to the boiling water. You'll still benefit from those nutrients if you consume the liquid (i.e. if the potato and water are being turned into potato soup), but not if you throw away the liquid. Similar losses also occur when you broil, roast, or fry in oil, and then drain off the drippings.

CONSUMING RAW FOODS

The amount of nutrient loss caused by cooking has encouraged some health-conscious consumers to eat more raw foods. In general, this is a positive step. However, cooking is also beneficial, because it kills potentially harmful microorganisms that are present in the food supply. In particular, poultry and ground meats (e.g. hamburger) should always be thoroughly cooked, and the surface of all fruits and vegetables should be carefully washed before eating. To learn more about preventing common food-borne diseases

GRILLING MEATS

Outdoor grilling is a popular cooking method, primarily because of the wonderful taste it imparts on meats. It can also be a healthy alternative to other cooking methods, because some of the meat's saturated fat content is reduced by the grilling process. However, grilling also presents a health risk. Two separate types of carcinogenic compounds are produced by high-temperature grilling:

• heterocyclic amines (HCAs)
  HCAs form when a meat is directly exposed to a flame or very high-temperature surface. The creatine-rich meat juices react with the heat to form various HCAs, including amino-imidazo-quinolines, amino-imidazo-quinoxalines, amino-imidazo-pyridines, and aminocarbolines. HCAs have been shown to cause DNA mutation, and may be a factor in the development of certain cancers.
• polycyclic aromatic hydrocarbons (PAHs)
  PAHs form in smoke that's produced when fat from the meat ignites or drips on the hot coals of the grill. Various PAHs present in the resulting smoke, including benzo[a]pyrene and dibenzo[a,h]anthracene, adhere to the outside surface of the grilled meat. PAH exposure is also believed to be linked to certain cancers.

HCA and PAH content in meats can be dramatically reduced by slight alterations in your grilling method. In particular, the following practices will reduce the amount of HCAs and PAHs formed:

1. Select leaner meats.
   Leaner cuts of meat are less likely to drip fat on the grill and produce PAH-laden smoke.
2. Marinate meats before grilling.
   Researchers have determined that marinating meat prior to grilling, even for just a few minutes, can reduce HCA formation by 90% or more. It's believed that the marinade forms a protective barrier for the meat juices that prevents the HCA reaction from occurring.
3. Grill at lower temperatures.
   Lower temperature "roasting" also greatly reduces HCA formation.
4. Prevent flare-ups.
   Flames from grill flare-ups cause the formation of both HCAs and PAHs. Keep an eye on your grill and turn meats frequently to minimize the chance of flare-ups.
5. Don't overcook meats.
   While it's important to cook poultry and ground meats thoroughly, be careful not to overcook any meat. Well-done or burnt meats contain higher levels of HCAs than less cooked meats. For thicker cuts of meat, use a meat thermometer to measure doneness rather than just guessing.