Chapter 2 - Evaluating Nutrition Information

Pellagra

in early 1900’s, pellagra disease common in prions, orphanages, and mental institutions

• more common in South than North

symptoms of pellagra

weakness, diarrhea, skin rash, mental confusion, death

pellagra": 1914 and prevailing hypothesis

physician Joseph Goldberger was assigned to work on pellagra

• prevailing hypothesis: pellagra was infectious disease spread by close contact amongst people living in close quarters

• however, prison guards and others who had close contact with prisoners (orphans, etc) did not get the disease)

the cause of pellagra was most likely…

diet related

pellagra: prison diet vs. wealthier diet

• prison: high in corn bread, hominy grits, molasses, potatoes, cabbage, rice, diet of poor people in South US

• wealthier diet: more meat, milk, vegetables

pellagra: goldberger’s hypothesis

pellagra resulted from some dietary deficiency among the poor, prisoners, orphans etc.

goldberger’s proof for his hypothesis

1. fed better foods to pellagra patients in a mental institution and children in 2 orphanages —> they were cured

2. clinical study: experiment where prisoners were fed the usual corn and molasses-based diet for a few months —> more than half developed pellagra

3. 1916: ‘filth party’: Goldberger applied secretions from a pellagra patient to party invites’ noses and throats, swallowed pills made from skin flakes from pellagra rash, and injected blood from a pellagra patient into each other (UNETHICAL) —> goldberger nor volunteers developed pellagra

pellagra after goldberger

• medical establishment still believed it was infectious, not diet

• 1920: goldberger died

• 1937: Dr. Conrad Elvehjem’s team isolated niacin from liver extracts and showed it cured a pellagra-like disease in dgos

Niacin and pellagra

niacin was tested in humans and found to cure pellagra

• niacin is essential nutrient vitamin

• while raw corn contains niacin, our body cannot use it

• while meat and milk don’t have much niacin, their protein content contains tryptophan, an amino acid we can convert to niacin

• cases like this gave birth to scientific method

Nixtamalization

a process for the preparation of maize (corn), or other grain, in which the grain is soaked in an alkaline solution (limewater aka Cal)

Benefits of NIxtamalization

• nutritional value increases

• Lime is highly aklaline and helps tryptophan in corn proteins become more available for human absorption

• outcome: prevents niacin deficiency (pellagra)

• Corn has niacin not available to us, but if nixtamalized, the niacin becomes available

In the past, nutrition and diet facts based on:

• intuition

• common sense

• conventional wisdom

• anecdote

Intuition

belief acquired without use of reason

common sense

sound and prudent judgement based on a simple perception of the situation or facts

• ‘sounded right’ ex. eating liver is necessary

Conventional Wisdom

traditionally or generally held belief

• what we always did

anecdote

report of personal experience

what do nutrition experts rely on for nutrition recommendations today?

scientific method

• conventional medicine/medical system follows evidence based results

• information that is based on the results of scientific studies

The scientific method

1. make observation that generate questions

2. formulate educated hypotheses to explain events

   1. based on previous research

   2. research costs money, need to ensure experiments we’re doing are justified

   3. research funded by federal grants, grants from taxpayer money

3. review current literature that relate to the questions

4. design studies, perform tests, collect data

5. analyze data and draw unbiased conclusions based on the results

6. share results with peers (peer review! experts in field, have most knowledge about what has been done before, provide feedback)

7. share with public

8. conduct more research, results of which may confirm or refute previous findings

experiment/lab experiments

a systematic way to test a hypothesis

• in vivo or in vitro

in vitro

experiments tested on cells

in vivo

experiments tested on small animals

• small rodents often used in nutrition experiments

• can’t test on humans, rodents next best thing

lab experiments and humans

• human research is last

  • safety and ethical concerns

  • experiments performed with lab animals first

• humans also don’t make the best subjects

  • population variability

  • cooperation

two groups in experimentation

• treatment group

• control group