Transcript Whole grain, fiber, and health

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
What is a whole cereal grain?
Go to Fulcher slide show
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
<2 g
white rice
<2 g
How can we tell whether whole
grain consumption is good for
health?
1. Epidemiology
1.
2.
3.
4.
Cross-section
Case-control
Prospective
Long term clinical trial
2. Feeding study
Overview of Study Design, 1
• Cross-section
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Everyone sampled at one time
Can’t 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
Overview of Study Design, 2
• Case-control
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Sample separately from cases and
from controls
Can’t 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)
Overview of Study Design, 3
• Prospective
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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)
Overview of Study Design, 4
• Long term clinical trial
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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)
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)
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)
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
Common epidemiologic
representations of whole grain
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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 can’t tell you about it
Norwegian example using bread
(1) how many slices of bread do you usually eat per day?
(<2 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; <1/4
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.
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
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
Whole grain and cancer: casecontrol 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 3;77(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.
1998;30(2):85-96. Review.
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
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 Nov;6(6):415-23.
Review.
Whole grain confounding with
other behaviors
Iowa Women’s Health Study
34,492 postmenopausal Iowa women, 1986;
levels adjusted for age and energy intake
Whole grain intake
Quintile
Quintile
Health Behaviors
Current smoker, %
Vitamin supplement use, %
Physical activity
% engaging in regular activity
Hormone replacement therapy
% ever
Refined grain intake
Quintile Quintile
1
5
1
5
24.7
53.7
12.1
68.7
16.0
70.9
17.1
54.4
30.3
45.5
49.5
30.0
34.0
42.6
40.4
34.7
34,492 postmenopausal Iowa women, 1986;
levels adjusted for age and energy intake
Whole Grain
Quintile
Quintile
1
5
Refined Grain
Quintile
Quintile
1
5
Other Aspects of Diet
Fruits and vegetables, no juice
mean, servings/week
Red meat, mean, servings/week
34.1
6.6
39.9
5.1
45.5
6.0
28.6
5.4
Keys score, mean, mg/dl
Sucrose, mean, g/day
45.7
42.2
38.9
38.8
42.8
37.6
41.0
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
270.7
332.3
342.1
264.7
Folate, mean, µg/day
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
Iowa Women’s Health Study:
Fiber in 2 groups with similar total grain
fiber
71% grain fiber from whole
77% grain fiber from refined
Sample size
grain
grain
3.6 - 6 g / 2000 kcal whole fiber
<3.6 g / 2000 kcal whole fiber
<3.6 g / 2000 kcal refined fiber 3.6 g / 2000 kcal refined fiber
7481
3559
Whole grain fiber
4.7 ± 0.7
1.3 ± 1.0
Refined grain
1.9 ± 0.8
4.5 ± 0.9
Total grain fiber
6.6 ± 1.0
5.8 ± 1.2
Total dietary
23.3 ± 5.3
19.2 ± 4.5
fiber
fiber
Jacobs DR, Pereira MA, Meyer KA, Kushi LH. J Amer Col Nutr 2000
Iowa Women’s Health Study:
11-year relative risk of mortality in 11040 women:
cereal fiber in itself does not predict death
Hazard Rate Ratio (95% CI)
in 71% whole grain fiber
eaters relative to 77%
refined grain fiber eaters
Total mortality
0.83 (0.73, 0.94)
Coronary heart disease
0.89 (0.66,1.20)
All cancer
0.92 (0.75,1.12)
All other mortality
0.83 (0.71, 0.97)
Which direction from here?
Problems with whole grain theory, 1
• Supported by selected feeding
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and supplement studies
Reliability
Validity
Residual confounding
A synergy model is consistent
with the complexity of biology
In vitro studies also suggest
synergy
Which direction from here?
Problems with whole grain theory, 2
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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
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
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
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
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.
Examples of dietary component at each synergy level
Food 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
Specific nutrients or phytochemicals
single phytochemical
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