The Effects of Caffeine On Human Vision

Daniel SchapiraGrade 11

Central Catholic High SchoolPJAS 2010

Many people consume caffeinated beverages in their every day life to feel more alert, but is it possible that this practice could be hazardous?

Rationale

Independent Variable: Caffeine Tablets (200mg)Active Ingredient: 200mg Caffeine / Tablet.Inactive Ingredients: Cellulose, D&C Yellow 10,

Dicalcium Phosphate, Dextrose, FD&C Yellow 6, Magnesium Stearate, Silica Gel, and Starch.

Dependent Variable: Vision

Introduction

Caffeine:Is a psychoactive (acting primarily on the CNS) stimulant

drug.Widely used in coffee and most soft drinks.Molecular formula C8H10N4O2.In North America, 90% of adults consume caffeine daily.In a regular cup of coffee there are generally 70-135mg of

caffeine.The half-life is approximately 4.9 hours.Absorbed by the stomach and small intestine within 45

minutes of consumption.Has some diuretic properties (increases the rate of urination).

Regular consumers of caffeine develop a tolerance to the diuretic effects.

Active Ingredient

An inactive ingredient or excipient is an inactive substance used as a carrier for the active ingredients in a substance.

Cellulose: A polysaccharide comprised of a long chain of D-glucose monomers. Molecular formula (C6H10O5)n . Cellulose has the appearance of a white powder. Insoluble.

D&C Yellow 10: Known as Quinoline Yellow WS. A yellow food dye. A study by the UK’s Food Standards Agency found that a mixture of food colors

and preservatives increased levels of hyperactivity and decreased intelligence in children.

Dicalcium Phosphate: Also calcium mono-hydrogen sulfate. Mainly used as a dietary supplement in things like breakfast cereals. Practically insoluble in water.

Inactive Ingredients

Dextrose: Better known as glucose. Monosaccharide sugar. Molecular formula of C6H12O6. Important fuel in biological systems.

FD&C Yellow 6: Known as Sunset Yellow FCF. A colourant added to foods, denoted by E Number E110.

E numbers are codes for food additives. It has the capacity for inducing allergic reactions.

Magnesium Stearate: Also called octadecanoic acid or magnesium salt. Has the molecular formula C36H70MgO4. Often used as a diluent.

A filler used to fill out the size of a pill or tablet to make it practical to produce.

Inactive Ingredients (Continued)

Silica Gel: Silica gel, despite its name is a solid. It is a granular, highly porous form of silica made synthetically from

sodium silicate. Silica is the most abundant mineral in the earth’s crust. Silica has the molecular formula SiO2 .

High surface area (around 800 m²/g) allows it to absorb water readily. Effective drying agent.

Starch: A polysaccharide carbohydrate consisting of a large number of glucose

monomers joined through glycosidic (dehyderation) bonds. Molecular formula (C6H10O5)n. Most important carbohydrate in the human diet.

Inactive Ingredients (Continued)

Vision:Visual perception is the ability to interpret information and

surroundings from visible light entering the eye.Action potentials activated by the receptor cells in the retina send a

nerve signal to the cerebral cortex of the brain.From the primary visual cortex, situated a little above the cerebellum,

run two “streams”: the dorsal stream and the ventral stream. Dorsal Stream:

Proposed to be involved in the guidance of actions and recognizing where objects are in space.

Stretches up from the primary visual cortex into the parietal lobe. Ventral Stream:

Associated with object recognition and form representation. Stretches down from the primary visual cortex. Has strong connections with the medial temporal lobe.

The two streams are highly interconnected.

Dependent Variable

The purpose of this experiment was to determine whether caffeine consumption, or the time passed after caffeine consumption, influences visual perception.

Purpose

Null Hypothesis:The different amounts of caffeine and/or the

time passed after consumption will not have a significant effect on the visual perception of the test subjects.

Alternative Hypothesis:The different amounts of caffeine and/or the

time passed after consumption will have a significant effect on the visual perception of the test subjects.

Null/Alternative Hypotheses

200mg Caffeine Tablets Styrofoam Drinking Cups Four 250ml Beakers De-ionized Water Wax Paper Pestle Computer Printer

Materials

1. Four 200mg tablets of caffeine were placed in wax paper, crushed with a pestle, and the crushed tablets were placed in four separate 250ml beakers.

2. De-ionized water was added into each beaker to obtain a total volume of 200ml.

3. The solutions were allowed time for the caffeine to totally dissolve in the water (about 2 hours).

4. From these beakers, different volumes were poured into Styrofoam drinking cups to create solutions with 200mg, 175mg, 150mg, 125mg, 100mg, 75mg, and 50mg of caffeine.

Procedure

5. 13 lines of 12 letters at 4 point font on Microsoft Word were typed using different and randomly selected sequences of letters.

6. Each test subject had 4 seconds to try to read correctly as many of the 12 letters on their assigned line as they could. This was the control test.

7. The caffeine solutions were distributed to 6 consenting test subjects with instructions to drink them at the same time.

8. Every 15 minutes for 105 minutes, each test subject would have 4 seconds to try to correctly read as many of the 12 letters as they could on their assigned line.

The assigned lines were rotated every 15 minutes so that no test subject repeated a line.

The test subjects were not told when the time limit was over to limit competitive influence.

9. Steps 6-8 were conducted two more times on two different days.

Procedure (cont.)

0min 15min 30min 45min 60min 75min 90min 105min9

9.5

10

10.5

11

11.5

12

12.5

Number of Letters Read at 15 minute Intervals

200mg

175mg

150mg

125mg

100mg

75mg

50mg

Time

Nu

mb

er

of

Lett

ers

Read

Data

P-value = 0.4939

0min 15min 30min 45min 60min 75min 90min 105min9

9.5

10

10.5

11

11.5

12

12.5

Number of Letters Correct at 15 Minute Intervals

200mg

175mg

150mg

125mg

100mg

75mg

50mg

Time

Nu

mb

er

of

Lett

ers

Corr

ect

Data (cont.)

P-value = 0.386535

Two double factor ANOVAs were performed on the two sets of acquired data to obtain p-values of 0.4939 and 0.386535 for number of letters read and number of letters correct, respectively. Both p-values are greater than the accepted .05 cutoff.

Based on the statistical analyses, there is no significant data to reject the null hypothesis.

It is accepted that different amounts of caffeine and the time passed after consumption both do not significantly effect visual perception.

Conclusion

Test subjects may have had different levels of tolerance to the effects of caffeine.

Test subjects may have disregarded instructions and had other caffeinated beverages throughout the day.

The precipitate in the bottom of the solutions may have contained some un-dissolved caffeine.The precipitate was assumed to be made of the insoluble

molecules of the inactive ingredients. Only a limited number of people were able to participate and only

for a limited number of days, thus limiting the number of replicates.

Because the experiment was carried out over multiple days, the different lighting from the windows on different days could have influenced experimental results.

A factor outside of the tested variable could have influenced the test subjects, such as sugar content in their diet that day, etc.

Sources of Error and Limitations

More test subjects to increase the number of replicates.

More exact ways to influence the caffeine concentrations given to test subjects.Ex: tablets pre-made with varying amounts of

caffeine. More closely monitor and regulate the diets of the

test subjects leading up to, and during the testing dates.

Perform the test in an area with limited or no windows so as to limit influence of outside weather conditions.

Extensions

http://sxph.org/caffeine/ http://www.cermav.cnrs.fr/glyco3d/lessons/cellulose/index.ht

ml http://www.chemicalland21.com/specialtychem/finechem/QU

INOLINE%20YELLOW%20WS.htm http://en.be-long.com/Chemical-Products-Suppliers/Dicalciu

m-Phosphate-Manufacturers.html http://www.medterms.com/script/main/art.asp?articlekey=70

40 http://www.chemical-industry-india.com/products/stearate.ht

m http://www.southernexposure.com/library/drying-seed-silica-

gel.html http://encyclopedia2.thefreedictionary.com/starch http://ahsmail.uwaterloo.ca/kin356/ventral/ventral.htm

References