Whole grain, fiber, and health

1
Whole grain, fiber, and health

• David Jacobs, PhD
• Professor of Epidemiology, School of Public
  Health, University of Minnesota
• Guest Professor, Department of Nutrition,
  University of Oslo
• University of Class lecture September 23, 2005
• University of Oslo, Norway

2
What is a whole cereal grain?

• Go to Fulcher slide show

3
Fiber amounts in different whole cereal grains

• Fiber per 100 g of grain
• wheat 12 g
• oats 10.6 g
• rye 14.6 g
• corn 7.3 g
• brown rice 3.5 g
• refined wheat lt2 g
• white rice lt2 g

4
How can we tell whether whole grain consumption
is good for health?

1. Epidemiology
2. Cross-section
3. Case-control
4. Prospective
5. Long term clinical trial
6. Feeding study

5
Overview of Study Design, 1

• Cross-section
• Everyone sampled at one time
• Cant define whether exposure or disease comes
  first (temporality)
• Any disease has already happened, so disease can
  cause changes in exposure
• Effect measures risk difference, relative
  prevalence

6
Overview of Study Design, 2

• Case-control
• Sample separately from cases and from controls
• Cant define whether exposure or disease comes
  first (temporality)
• Any disease has already happened, so disease can
  cause changes in exposure
• Effect measures prevalence odds ratio
  (approximately relative risk if disease is rare)

7
Overview of Study Design, 3

• Prospective
• Cross-sectional sample excluding prevalent
  disease
• Exposure stated before disease is known
  (temporality well-defined)
• Disease has not happened, so it can not cause
  changes in exposure
• As in cross-section and case-control, level of
  nutritional exposure is naturally occurring and
  correlated with demographics and other behaviors
• Effect measures risk difference or relative risk
  or relative hazard (if time to event is
  considered)

8
Overview of Study Design, 4

• Long term clinical trial
• Cross-sectional sample excluding prevalent
  disease, randomly assigned to different
  nutritional exposures
• Temporality well-defined
• Assigned nutrition exposure uncorrelated with
  other factors, but other nutrition exposures are
  naturally occurring and correlated with
  demographics and other behaviors
• Effect measures risk difference or relative risk
  or relative hazard (if time to event is
  considered)

9
Overview of Study Design, 5

• Long term clinical trial (continued)
• Very difficult to carry out over years
• Successful examples include Lyon Diet Heart Study
  and PREDIMED (in recruitment phase)

10
Overview of Study Design, 6

• Feeding study
• Short term (hours, days or weeks)
• Exposure assigned randomly
• All food provided or supplemental food only
  provided
• Excellent for study short term effects such as
  changes in body weight or plasma insulin (disease
  intermediaries)

11
How do we know what people are eating?

• Epidemiology
• Ask questions about diet
• Short term recall (detailed, not representative
  of long term)
• Long term frequency (intuitive, less detailed,
  representative, guess work)
• Study what people actually eat
• Feeding
• Provide all or some food
• Study what the researcher is interested in

12
Common epidemiologic representations of whole
grain

• Dark bread
• Brown bread
• Whole wheat bread
• Brown rice
• Usual breakfast cereal
• Hot cereal
• Must ask about food in terms the participant
  understands, so if whole grain is not understood,
  the participant cant tell you about it

13
Norwegian example using bread

• (1) how many slices of bread do you usually eat
  per day? (lt2 slices per day 2 4 5 6 7 8
  9 12 13)
• (2) what kind of bread do you eat most often?
  (store bought home-baked)
• (3) If you buy, what type most often? (white
  bread, fine or light bread, whole grain or dark
  bread)
• (4) If you bake at home, what proportion of the
  flour is whole grain (dark)? (don't use whole
  grain flour lt1/4 whole grain flour 1/4- 1/2
  whole grain flour more than 1/2 whole grain
  flour).
• Based on a 24 hour recall, store bought whole
  grain bread was overestimated and used a recipe
  with less whole grain
• Whole grain bread score the number of slices of
  bread eaten per day times the proportion of whole
  grain flour.

14
American example using breakfast cereal

• Ask usual breakfast cereal
• Refer to coding list for whole grain content of
  several hundred brand name products
• Does not account for people eating multiple
  products

15
American example using bread

• The term whole grain bread is not well known and
  is confused with organic (which is irrelevant)
  and multigrain (which be all refined)
• Dark bread in US and brown bread in UK identify
  most whole grain breads, but misclassifies breads
  containing dark color, such as molasses

16
Whole grain and cancer case-control experience

• Chatenoud L, Tavani A, La Vecchia C, Jacobs DR
  Jr, Negri E, Levi F, Franceschi S. Whole grain
  food intake and cancer risk. Int J Cancer. 1998
  Jul 377(1)24-8.
• Jacobs DR Jr, Marquart L, Slavin J, Kushi LH.
  Whole-grain intake and cancer an expanded review
  and meta-analysis. Nutr Cancer. 199830(2)85-96.
  Review.

17
(No Transcript)
18
Meta-analysis of case-control studies of whole
grain food intake and cancer, 1998

• Cancer Site
  Studies Reduced Risk? Pooled Odds Ratio
• Gonadotrophic hormone-related
• Prostate 1 1 0.9
• Breast, endometrium, ovary 6 6 0.85
• Aerodigestive
• Upper aerodigestive 15 14 0.6
• Colon, rectum, and polyps 13 10 0.8
• Pancreas 4 4 0.7
• Other
• Brain 3 2 0.7
• Lymphoma 3 3 0.5
• Soft tissue sarcoma 2 2 0.3
• Bladder 1 1 0.5
• Myeloma 1 1 0.5
• Liver 1 1 0.6
• Thyroid 1 1 0.6

19
Whole grain and heart disease/type 2 diabetes
prospective study experience

• Jacobs DR Jr, Gallaher DD. Whole grain intake
  and cardiovascular disease a review. Curr
  Atheroscler Rep. 2004 Nov6(6)415-23. Review.

20
Whole grain confounding with other behaviors

• Iowa Womens Health Study

21
34,492 postmenopausal Iowa women, 1986 levels
adjusted for age and energy intake Whole
grain intake Refined grain intake
Quintile Quintile Quintile
Quintile 1 5 1
5 Health Behaviors Current smoker,
24.7 12.1 16.0 17.1 Vitamin supplement use,
53.7 68.7 70.9 54.4 Physical
activity engaging in regular
activity 30.3 45.5 49.5 30.0 Hormone
replacement therapy ever 34.0 42.6 40.4
34.7
22
34,492 postmenopausal Iowa women, 1986 levels
adjusted for age and energy intake Whole
Grain Refined Grain

Quintile Quintile Quintile
Quintile 1 5 1
5 Other Aspects of Diet Fruits and
vegetables, no juice mean, servings/week 34.1 39
.9 45.5 28.6 Red meat, mean,
servings/week 6.6 5.1
6.0 5.4 Keys score, mean,
mg/dl 45.7 38.9
42.8 41.0 Sucrose, mean,
g/day 42.2 38.8 37.6
47.3 Constituent Nutrients Dietary
fiber, mean, g/day 16.3
22.3 21.7 17.1 Vitamin E,
mean, IU/day 8.9
10.1 10.2 9.0 Folate,
mean, µg/day 270.7 332.3 342.1
264.7
23
Whole grain and cancer Norwegian and Iowa
prospective studies

• Unpublished talk give in Montreal, American
  Association of Cereal Chemists, 2002
• Findings much less clear than in case-control
  studies
• Same questions and design as for heart disease
  and diabetes

24
Iowa Womens Health StudyFiber in 2 groups with
similar total grain fiber
?
Jacobs DR, Pereira MA, Meyer KA, Kushi LH. J
Amer Col Nutr 2000
25
Iowa Womens Health Study11-year relative risk
of mortality in 11040 women cereal fiber in
itself does not predict death
26
Which direction from here? Problems with whole
grain theory, 1

• Supported by selected feeding and supplement
  studies
• Reliability
• Validity
• Residual confounding
• A synergy model is consistent with the complexity
  of biology
• In vitro studies also suggest synergy

27
Which direction from here? Problems with whole
grain theory, 2

• Fiber not the whole answer
• Myriad phytochemicals coexist with fiber in all
  plant foods
• These include enzymes, pesticides, antioxidant
  defense, signal transducers
• Though the nutrient model has some value, it
  seems more helpful to think of foods and food
  combinations than of nutrients.
• Other plant foods are broadly similar fruit,
  vegetables, nut, legumes, spices
• Plant-based food patterns are more reliably
  ascertained epidemiologically and less prone to
  dietary confounding, inverse to many chronic
  diseases

28
Nutrients vs Foods

• Fiber is probably not as active as its
  accompanying phytochemicals
• The value of carbohydrate depends on whether it
  is fiber rich (with accompanying phytochemicals)
  or fiber poor
• The value of fat depends on saturation and
  location of the double bond if unsaturated

29
Some single nutrient conditions

• A single nutrient deficiency disease would be
  alleviated by introduction of an isolated
  nutrient in the form of a supplement
• Scurvy and vitamin C
• Pellagra, beri-beri and B-vitamins
• Rickets and vitamin D
• Neural tube defects and folate
• Trans fatty acids, increased cholesterol and
  coronary heart disease
• Hypertension and salt

30
Nutrition in the etiology of disease

• Focus on food and the synergy of its components
  may be a method for better understanding
  nutrition and disease etiology
• Reductionism looks for simple, biochemically-based
  associations
• Some diseases are the result of deficiency or
  excess of single nutrients
• Food synergy is defined as additive or more than
  additive influences of foods and food
  constituents on health
• Chronic diseases such as atherosclerosis,
  ischemic heart disease, and cancers, are complex
  with multiple etiologies and not simple
  deficiencies

31
The food synergy approach
A hierarchical structure of dietary patterns,
foods, and nutrients for study of food synergy.
Top down research begins with the higher
levels, searching for combinations of foods and
their constituents that influence health Bottom
up research begins at the lowest level,
searching for individual constituents that
influence health.
Food synergy level Examples of dietary component at each synergy level
Level 5 Dietary pattern Prudent diet, Western diet, other combinations of food groups
Level 4 Food groups Whole grain, dairy, fruit, vegetables, meat
Level 3 Whole grain Whole wheat, brown rice, rolled oats
Level 2 Whole wheat Bran, germ, endosperm extract of fat soluble portion
Level 1 Bran or a single phytochemical Specific nutrients or phytochemicals
32
Maximize nutritional value per bite

• We are increasingly inactive
• We are getting fat from positive energy balance
• Even so, energy intake is less than it used to be
• We cannot afford to waste bites eaten food with
  low nutritional value, such as nutrient-poor
  carbohydrate
• Eat a varied diet rich in plant foods