Related Terms

• Food nutrients, food nutritional value, food retention factors, nutrient retention factors, nutritional value calculation, refuse factor, USDA Table of Nutrient Retention Factors.

Background

• Retention factors are a way of calculating the amount of nutrients in foods that may have been lost or gained during the process of cooking and preparation. A change in nutrient value almost always occurs when a food is cooked. The process of calculating a retention factor typically involves using a protocol determined by the Association of Official Analytical Chemists (AOAC).

• A majority of the available nutritional information is based on uncooked and unprepared food. This information can generally be found on the packaging of the food product. Many grocery stores have this information available in the store for produce. However, the nutritional content of ingredients typically changes according to the methods of food storage and preparation. Many foods are cooked before they are eaten, and vitamin and mineral levels tend to decrease as food is cooked. However, depending on the ingredients, recipe, and the way that the food is prepared, some nutrients, such as fat, may actually increase during the cooking process.

• The USDA Table of Nutrient Retention Factors, Release 5, is a popular source of information on retention factors. This table lists common foods, cooking techniques, and the retention factor for vitamins and minerals associated with each. Multiplying the retention factor by the uncooked nutrient level yields the actual nutritional value of the consumed food.

• Patient groups that frequently make use of retention factors include athletes, diabetics, pregnant women, vegetarians, and those being treated for anorexia, bulimia, and individuals with high cholesterol. Individuals in these categories often must make sure that they are getting enough nutrients from their food. Nutritionists and other health care professionals may use retention factor calculations to advise patients on the best ways to prepare their favorite foods.

Technique

• The nutritional content of foods is altered due to heating or other means of food preparation, such as pickling, soaking, and fermentation. The retention factor is the percentage of the food component remaining after preparation. To calculate this, researchers measure the vitamins and minerals in foods before and after cooking. The fraction of vitamins, minerals, fat, and other nutrients that changes during this process is expressed as the retention factor.

• Components measured in retention factors include zinc, copper, potassium, calcium, and most other common vitamins and minerals. The retention factor of each of these is calculated for most popular foods. The retention factor for two different vitamins in one food may vary considerably, depending on the method of preparation. For instance, cured picnic ham has a calcium retention factor of 100%, while the retention factor for thiamin is 40%. This means that the cured picnic ham does not lose any of its available calcium during the preparation process when compared to the uncured meat, but only 40% of the thiamin is available compared to the uncured meat.

• Refuse factor is a term that describes the part of a food that is inedible. For instance, the bone on a pork chop or the cob in corn would be a refuse factor.

Theory/Evidence

• Retention factors are a very popular area of nutritional research. In the future, retention factors expressed as percentages may be incorporated into the labels of processed foods in order to help consumers more accurately assess nutritional intake.

• Although retention factors assess changes in the nutritional value, they do not relate to how much of a nutrient is absorbed or available to be absorbed after it is eaten. So, although a high nutrient food may change very little in its nutritional value after preparation, factors such as large intestinal health and interactions with other nutrients may affect the availability of the food's nutrients.

Author Information

• This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

1. Association of Official Analytical Chemists (AOAC). www.aoac.org.

2. Food and Drug Administration. www.fda.gov.

3. United States Department of Agriculture. www.usda.gov.