Use of Dietary/Nutrient Data in the WHI

Marian L. Neuhouser, PhD, RDWHI Data Training Workshop

May 6, 2009

mneuhous@fhcrc.org or mneuhous@WHI.org

Presentation Outline & Objectives

1. Review dietary assessment procedures in WHI

2. Present types of dietary data available for analysis

3. Special examples for using nutrient data

4. Using computed variables from the FFQ line items

5. Summary

6. Q and A

Dietary

How Was Diet Measured (DM)?

Food FrequencyQuestionnaire

All

Food FrequencyQuestionnaire

All

Food FrequencyQuestionnaireRotating 1/3

of participants

Study Start Year 1 Year 2Close-out

4-day food records 4-day food records4.6% of ppts

Repeat (x2)24 hr Recalls4.6% of participants

Year 3,6,9

24 hour recalls1% of participants

Dietary

How Was Diet Measured (OS)?

Food FrequencyQuestionnaire

All

Food FrequencyQuestionnaire

All

Study Start Year 3

Note: CT participants not in the DM only have SV (baseline) FFQ)

Which dietary data are available?

Only FFQ data have been released to www.whiops.org

Food record data have been used in selected publications (including some in process) but these data are not posted.

The focus of this presentation will be on the FFQ data.

FFQ Data Availability & AnalysisFFQ Data Availability & Analysis

1. Analysis by nutrients

2. Analysis by food groups (computed variables)

3. Analysis by individual or grouped line items, adjustment questions and summary questions

Potentially useful for “index” or dietary pattern type analyses (computed variables not yet made)

FFQ analysis by nutrients and FFQ analysis by nutrients and use of nutrient datause of nutrient data

• Standard analysis of FFQ data yields nutrients per person per day

• 135 nutrients/important compounds:Fat, fatty acids protein, carbohydrate, vitamins,

minerals, carotenoids, genestein, daidzein, sugars, fiber, vegetable protein

• Most WHI analyses have used the standard nutrient data

WHI FFQ Structure and FormatWHI FFQ Structure and Format• The WHI FFQ has three parts

• 19 Adjustment Questions– Food preparation, fats added in

cooking/table• 122 line items of foods or food groups

– Frequency and portion size– 122 line items = > 350 foods

• 4 Summary Questions– Overall usual intake of fruits and

vegetables, fats added to foods in cooking

– Used to reduce measurement bias of over-reporting long lists of foods

Processing the WHI FFQ and Processing the WHI FFQ and creation of nutrient outputcreation of nutrient output

• Step 1: FFQ are passed thru a mark-sense scanner. Responses are converted into ASCII data.

• Step 2: ASCII data checked for errors (ie, missing)

• Step 3: Calculating nutrient intake

Processing the WHI FFQ and Processing the WHI FFQ and creation of nutrient outputcreation of nutrient output

1. Processing system estimates annual medium portion sizes by multiplying frequency * portion sizeExample: Medium portion of eggs once a week = 52 annual medium portions. Small portion of eggs once a week = 26 annual medium portions [s = .5(med)]

2. Annual medium servings are multiplied by the nutrient string for the food code (135 possible nutrients)

3. All nutrient results for all foods are summed and divided by 365 = average daily nutrient intake of each nutrient

Processing the WHI FFQ and Processing the WHI FFQ and creation of nutrient outputcreation of nutrient output

Note that many line items have multiple foods

Example: peaches, nectarines, plumsrice, grains and plain noodles

Each food is proportionately represented on the line item. Proportional weights are based on national consumption data and expert opinion.

The processing stream occurs for each food. USDA (NCC) may have several food codes for each item. Careful assignments are made by nutritional epidemiologists.

FFQ analysis by nutrients: FFQ analysis by nutrients: caveats – know what you are caveats – know what you are analyzinganalyzing

Example 1: Folic Acid/Folate

Which variable to use?

• Dietary Folacin• Dietary Folate Equivalents• Dietary Synthetic Folate• Dietary Natural Folate

FFQ Analysis by NutrientsFFQ Analysis by Nutrients

Dietary Folacin “Old” folate values that represent the pre-1998 food fortification values. Approximately equivalent to natural folate PLUS foods already fortified pre-1998 (e.g., some cereals)

Dietary Synthetic Folic AcidThe enriched/fortified portion (post 1997-8)

FFQ Analysis by NutrientsFFQ Analysis by Nutrients

Dietary Natural Folate Folate from natural sources only, such as fruit, vegetables, liver, egg

Dietary Folate EquivalentsCombines synthetic folic acid and natural folate but takes into account the lower bioavailability of natural folate

DFE = [µg of food folate + (1.7 x µg folic acid)]

FFQ Analysis by NutrientsFFQ Analysis by Nutrients

Example 2: Vitamin E

Dietary Alpha-TocopherolDietary Beta-TocopherolDietary Delta-TocopherolDietary Gamma-TocopherolDietary Natural Alpha-TocopherolDietary Synthetic Alpha-TocopherolDietary Total Alpha-Tocopherol

EquivalentsDietary Vitamin E

FFQ Analysis by NutrientsFFQ Analysis by Nutrients

Example 2: Vitamin E

Dietary Alpha-TocopherolDietary Beta-TocopherolDietary Delta-TocopherolDietary Gamma-TocopherolDietary Natural Alpha-TocopherolDietary Synthetic Alpha-TocopherolDietary Total Alpha-Tocopherol

EquivalentsDietary Vitamin E (IU)Use others at your own discretionUse others at your own discretion

FFQ Analysis by NutrientsFFQ Analysis by Nutrients

Example 3: Trans Fats• Many investigators interested in trans

fats due to the purported associations with disease risk

• Caution: not all trans fats are created equal

• Some trans fats are naturally occurring, some are created during food processing (but not hydrogenation) and some created by hydrogenation

FFQ Analysis by NutrientsFFQ Analysis by Nutrients

Example 3: Trans Fats

Which trans fat variable(s) should be used?

Dietary Trans Fatty Acid16:1TDietary Trans Fatty Acid18:1TDietary Trans Fatty Acid18:2TDietary Total TransFattyAcid

Be very cautious about trans16:1T and total trans fats

FFQ Analysis by Food GroupsFFQ Analysis by Food Groups

Food groups are constructed variables made by grouping and summing the line items from the FFQ

Computed variables are available for the following food groups:

Fish Red Meat Poultry

Grains Whole Grains Nuts

Soy Milk Dairy

These have all been created from the line items and are now posted.

Are there other uses of the line items?

New Food Group Example: Cruciferous Vegetables

1. There is no line item called “cruciferous vegetables” so it must be constructed from existing line items

2. Find line items with cruciferous vegetables

3. Summing across yields medium servings per participant per day

So far so good – these are all in the Brassica or Cruciferae Family

But here is a problem since spinach is not in the Brassica family, but theother greens listed are Brassica.

Other uses of the FFQ line items

Dietary Patterns or Indices 1. Diet Quality Index

– Reflects adherence to the 8 Diet and Health recommendations of the National Academy of Sciences

– Estimates of nutrient intakes are scored– Neuhouser et al J Am Diet Assoc 2000 100: 576-579

– Neuhouser et al Pub Health Nutr 2003 6: 703-709

2. High-Fat Snacks/Desserts Index• Potischman et al Cancer Causes Control 2002; 13:937-946

3. Mediterranean Diet4. Healthy Eating Index5. MPEDs (My Pyramid Equivalents)

We don’t have these food groups/indices set-up as constructed variables. Some manuscript writing groups are doing on their own

FFQ Adjustment Questions (newly posted)

19 Adjustment Questions at start of FFQ– Types of cereal

– Types of milk on cereal and in beverages

– Food preparation, fats added in cooking/table

– Types of cookies and pastries

These questions were designed to more precisely adjust the fat content of the line items since fat reduction was a primary goal of the WHI-DM

One response option permitted for this adjustment question

The choice selected in the adjustment question is applied to the response for this question. Thus, is someone marked “regular” then the nutrient string for regular ground beef is used for this question. If someone marked “extra lean” then the “extra lean” nutrient string is used for this question.

And so on …. 5 possible choices. Participants permitted to mark one or two responses.

The adjustment question is used for this line item. If only one option is marked, then the marked option used as 100% of the nutrient string. If two options are marked, ½ of the nutrient string comes from each option. For example, ½ from “highly fortified cereals” and ½ from “granola”.

FFQ Adjustment Questions:

Note: the adjustment questions were not originally designed to be used by themselves.

Therefore, we cannot provide any data on the validity or reliability of using the adjustment questions alone (ie – “did you eat popcorn?” or “What type of salad dressing did you use?”

Caveat emptor!

FFQ Summary Questions

Four summary questions at the end of the FFQ on: Fat used to deep fry or sautéFat added in cookingVegetable intakeFruit intake

Note that these questions are frequency, not “what kinds of fat” so they are different than the adjustment questions

Used to adjust the frequency of fruit or vegetables since respondents may tend to overreport when long lists are provided

The fruit and vegetable summary questions have previously been used to create the fruit and vegetable variables already in the database.

SummarySummary

The FFQ data are posted on whiops.org; recall and food record data are not posted.

The nutrient data are the primary data generated from the FFQ. The output yields average daily intake of 135 nutrients per person per day.

When using nutrient data be careful about which nutrients to use. Know what you are analyzing. Examples: folate, trans fats and vitamin E variables.

SummarySummary

The individual 122 line items, 19 adjustment questions and 4 summary questions are also now posted. No known validity/reliability of using the adjustment questions by themselves.

The 122 line items represent about 350 foods, each with a proportional weight. Don’t deconstruct the line items under the assumption that you know the weights.

Selected constructed variables from the line items are now posted.

SummarySummary

We did not cover:

Measurement error in the FFQ

Use of calibrated estimates of energy, protein or percent energy from protein

Adequacy of the actual nutrient values in the database. Imputation of various nutrients.

Questions?

• Marian Neuhouser, PhD, RD– mneuhous@fhcrc.org or

mneuhous@WHI.org

• Lesley Tinker, PhD, RD– ltinker@WHI.org