1.28.08 What is good research in our field?

Nutrition
1.28.08

Nutrition is a very research oriented profession.
What is good research?

Experimental Research
The only type of research that looks at cause and effect relationships.

1. Must have a control group
2. Must have a treatment group

There must be at least two groups, a control who gets a placebo, and a treatment group. The treatment should be the only difference between the two groups of people. Other variables should be controlled for.
Placebo is an inert substance that will have no physiological effect on the subjects.

3. Large n size (large sample size)
Technically, to be statistically significant, you only need 6 ppl. in your study. But we give more weight to groups of three thousand, instead of groups of three.

4. Double blind- none of the subjects nor the testers know who gets the placebo. The only person who knows is the person running the study who keeps it a secret.

5. Statistical significance
6. Reproducibility- must be done hundreds of time by many labs and many researchers.
7. Must appear in a peer reviewed journal? Still question this.

Epidemiological Research
The study of large populations to determine relationships between two or more variables.

Example: Divide group into ppl. who smoke and ppl. who don't. Shows the relationship (correlation) between smoking and lung cancer. Establishes relationship but NOT a cause effect relationship. To get a cause effect relationship you would have to use unethical study practices which cannot be performed. (forcing one group to smoke and one group not to..)

pg. 1 of pkt. International Journal of Sports Medicine
One question on test:

pg. 3 Anatomy and Physiology of the digestive tract:

Digestion: mechanical and chemical breakdown of foods into smaller components making them absorbable.
-Chewing
-Saliva, stomach acid

Absorption: assimilation of nutrients into the body.

1. Mouth- chewing- by jaws and teeth or gums
salivary glands: moisten food, enzymes start digestion- esp. complex carbs.

2. Esophagus-passage between mouth and stomach. Peristalsis- muscular contractions that ensure the food goes into the stomach from the mouth even against gravity. Food is called bolus one it's in the esophagus.

3. One way sphincter valve - Lower Esophageal sphincter (LES)
-Gastro-esophageal reflux (GES) occurs when it doesn't close fully, allowing food the flow the wrong direction.
4. Stomach-about the size of your fist when empty.
2 containers
a. 1st 2/3s is called the body (storage) churns and adds enzymes
b. 2nd Pyloric (food is now called chyme)- still undergoing digestion NOT absorption yet.

5. One way sphincter valve -Pyloric sphincter

6. Small intestines
a. duodenum
-pancreas, liver and gallbladder start at this point. The vast majority of absorption of nutrients happens in the duodenum and jejunum.
b. jejunum
c. ileum (not ilium)

7. Cecum
8. Large intestines
a. ascending colon
b. transverse colon
c. descending colon
d. sigmoid colon
Vast majority of water and electrolyte absorption happens in the large intestines.

9. Rectum
10 Anal Canal

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CHO (C6H12O6)
(Carbon, Hydrogen, Oxygen)

pg. 4 pkt.

Carbs are organic compounds- contain carbon
Most abundant nutrient by far
most critical nutrient to physically active person by far

1. Monosaccharides (Simple CHO)
Significantly different than refined sugar.
a. Glucose (only one the body can use)
b. fructose
c. galactose (body converts fructose and galactose into glucose

Fructose is significantly sweeter than either a or b so manufactures don't have to use much thus saving money. Plus, fructose is processes slowly by the body giving the body energy over a longer period of time instead of a rush. The problem is (esp. with sports drinks) is that as they sit in the GI tract the fructose draws water out and may cause diarrhea.

2. Disaccharides (simple CHO)
-sucrose (gructose and glucose)
-lactose (glucose and galactose)
-maltose (glucose and glucose)
All must be broken down into glucose.

3. Polysaccharides (complex CHO &/or glucose polymers)
Must be broken down even more times.
a. starch- highly branched glucose stored in a plant.
b. glycogen-highly branched glucose stored in the muscle and liver
c. fiber-cannot be broken down by human body.

When you eat any CHO it will be converted to glucose & put into the blood. Healthy blood glucose levels are 70-100 mg/d.

GRAPH

Pancreas senses too much glucose in the blood -releases insulin (postperandial)
insulin is a hormon that acts as a key to open muscles and fat cells in order to absorb excess glucose. Usually, the pancreas overproduces insulin and blood sugar will drop too low ( reactive hypoglycemia)
Pancreas then produces glucagon (opposite of insulin) -starts leveling and returning to 70-100mg/d.
If it takes longer that 2-3 hours to level out, you may be suffering from diabetes.

10-15min. before a race eat refined sugar so there will be no up and big crash- body does not need to produce insulin because you will be using it as energy.

Fate of Blood Glucose (3 fates in order of priority)
1. Provide energy
2. Store in muscle & liver as glycogen
3. Store as fat/adipose

1st priority of body is to provide needed energy because blood only stores 5 grams of glucose (20kcals). The liver stores 70-100 g (400 kcals) to replenish the blood to keep it at 5 g. Muscles total 300-400 g (1200-1600 kcals0
Only health concern with eating CHO? Cavities
There is no research to back up eating too many CHO causes diabetes.

CHO in the form of Grain

1. Bran
a. Protective covering of the seed.
b. not digestable in humans (insoluble)
c. high in fiber, B vitamins, minerals

2. Germ
a. embryo portion of the seed
b. high in B vitamins, Vitamin E, minerals, essential fatty acids

3. Endosperm
a. internal, edible part of the seed
b. 95% starch
c. high in Fe, protein, niacin

Grain Preperation Terms

1. Whole-contains all bran, germ, and endosperm (healthy, expensive, short shelf life)
2. Refined-removal of all bran and most of germ (increased shelf life, healthy)
3. Enriched-refined grain w/ added thiamin, riboflavin, niacin, folate (1996), iron
4. Fortified-refined grain w/vitamins and minerals added above those levels occurring naturally.
-may not be present naturally (eg Calcium)

Dietary Fiber
1. Insoluble
-source: wheat bran, veggies
health benefits: lower rish of colon cancer, rectal cancer
lower rish of diverticulosus ( condition when large intestine has extra pockets where food gets trapped and then gets infected)

2. Soluble
-Source: oat bran, fruits, legumes
-health benefits:slows glucose absorption which helps maintain blood glucose levels, lowers total cholesterol

Actual intake (average person) 6-8g per day
Nat. Cancer Inst. recommendation 24-40g per day
-add to diet slowly (no suppliments-natural food)
-drink plenty of water
-may bind minerals

Glycemic Index (GI)

History of GI

conceived of by Jenkins, et al. (1981) as management tool for IDDM (type 1 diabetes)
-new sugar busters
-atkins
-zone
-south beach diet
-new glucose revolution

What is GI?
Ranks CHO food on how quickly they elevate BG levels
-over a 2hr. pd.
-compaired to either pure glucose or white bread (reference food given a 100 value)

High GI 70 and up
Moderate GI 56-69
Low 0-55

Factors that affect GI:
1. cooking method
2. processing method
3. fiber contents (inverse relationship)
4. type of sugar (glucose:100, sucrose:68)
5. Fat content (inverse relationship)

French fries: 75
Potato chips: 58 (lowest GI because of fat content)
Baked potato: 85

Criticisms:
1. highly variable -cooking method -vary w/i same and different ppl (diff. times of the day)

2. does not take into consideration serving size -based on 50g of CHO (which is 1.5 lbs. of raw carrots)

3. fat lowers GI -high fat foods seen as good dietary choices

4. Meals are mixed diets - GI loses its usefulness in a mixed meal
5. No standardization of testing. - best measured in the morning after overnight fast.

6. Use of two referance foods
glucose (new glucose revolution)
white bread (south beach diet
conversion to compare diets: (white bread based)(.7)=(glucose based)

7. Some nutritious foods are not allowed while less nutritious foods are encouraged. (fruit is high GI)

GI and Obesity

Many popular diets blame high GI foods for obesity
1. high insulin levels facilitate fat storage

Conflicting Research:
1. short term studies
2. small populations
3. based on animals (atkins)

Many factors contribute to a person’s body weight:
1. genetics
2. activity level
3. dietary habits
4. psychology
5. social
6. cultural
7 GI (1 additional factor to consider)