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The Health Professionals Follow-up Study (HPFS) questionnaire had the following questions involving chicken skin.

When you eat chicken, is it usually cooked with skin on?
Answer: yes/no

Do you usually eat the skin?
Answer: yes/no

Three chicken/skin combinations were possible:

• chicken cooked and eaten with skin,
• chicken cooked with skin but not eaten with skin,
• and chicken cooked without skin.

The Charred database was developed with questionnaires that asked if the respondent ate skin but did not include the question on whether the chicken was cooked with skin. Therefore, the Charred values are based on a mean of cooked with skin and without skin.

For the HPFS study, heterocyclic amines (HCA) intake and meat derived mutagenicity from chicken was calculated using specific values from the database developed at NCI. This database contained measurements on HCA and meat derived mutagenicity for different types of chicken (white boneless chicken, white chicken meat and bone, dark boneless chicken and dark chicken meat and bone) prepared using different cooking methods (pan-fried, grilled/barbequed and broiled) and doneness levels (just, well and very). In addition, the database contained HCA and meat derived mutagenicity measurements for white chicken skin and dark chicken skin separately.

The three types of chicken/skin combinations, specific examples, and the final values used follow.

1. Chicken cooked and eaten with skin:
   The values can be obtained directly from the Charred Database.
   
   
2. Chicken cooked without skin
   To calculate HCA for chicken cooked without skin we computed a weighted average of the HCA measurements from white boneless chicken and dark boneless chicken. For pan fried chicken the weights used were 1/3 for white meat and 2/3 for dark meat. For broiled and grilled chicken the split was evenly at 1/2 for both white meat and dark meat.
   
   
3. Chicken cooked with skin but not eaten with skin
   HCA values for chicken cooked with skin but not eaten with skin were computed by calculating a weighted average for white chicken with bone and dark chicken with bone using the same weights for white and dark meat as mentioned above for pan fried, broiled and grilled chicken.

The following examples illustrate the three different combinations for pan fried, just done chicken for PhIP.

Chicken Cooked and Eaten with Skin (from Charred database) 

Chicken Cooked without Skin 

Chicken Cooked with skin but not Eaten with Skin 

All Final Values used for the HPFS are also available.

For more information:

Kana Wu, MD, PhD
Harvard School of Public Health
Department of Nutrition
665 Huntington Avenue
Boston, MA 02115
Tel. 617-432-1842
Fax. 617-432-2435
e-mail:kana.wu@channing.harvard.edu