The Role of Nutrition in AMD Flashcards
List 4 examples of antioxidants that help to prevent AMD
vitamins C, E, carotenoids, minerals (selenium, zinc)
How are antioxidants thought to prevent/delay AMD
by reducing photo‐oxidative damage e.g. from sunlight exposure, and smoking.
what did a systemic review inc 5 RCTs find about people who took supplements to prevent AMD
People who took supplements were not at decreased or increased risk of developing AMD
“Taking vitamin E or beta carotene supplements will not prevent or delay onset of AMD. The same is probably true of vitamin C and the multivitamin (Centrum Silver).”
what does a systemic review state about multivitamins, lutein, vitamin E, zinc about slowing the progression of AMD
Strongest evidence came from AREDS and AREDS2
People who took supplements were not at decreased or increased risk of developing AMD
“People with AMD may experience some delay in progression of the disease with multivitamin antioxidant vitamin and mineral supplements. This finding was largely drawn from one trial, in a well nourished American population…”
what did the AREDS study show about slowing the progression of AMD
Significant reduction in OR (~20% risk reduction) for development of advanced AMD with zinc + antioxidants
Effect increased (~25%) if people with early AMD excluded
“Those [people over 55 years] with extensive intermediate size drusen, at least 1 large druse, noncentral geographic atrophy in 1 or both eyes, or advanced AMD or vision loss due to AMD in 1 eye, and without contraindications such as smoking, should consider taking a supplement of antioxidants plus zinc such as that used in this study.”
name the 3 cases of increased risk of people takin: beta carotene zinc and vitamin E
beta carotene: Increased risk of lung cancer
zinc: Increased genitourinary complications
vitamin E: Increased risk heart failure in people with vascular disease
name 2 carotenoids that form macula pigment
Lutein (L) and zeaxanthin (Z)
Only carotenoids that concentrate in macula
which parts of the macula do lutein and zeaxanthin each accumulate
Z predominates at fovea
L in parafovea
which 5 layers of the retina are L & Z found in
fibres of Henle choroid RPE PR outer seg plexiform layers
what is the peak absorption of L and Z and which type of light does this represent
~ 450nm
Blue Light protection
Hence MP protects against hazardous photochemical effect of short wavelength light
They also act as antioxidants
name 3 ways in which L and Z act as antioxidants
Quench singlet oxygen
Scavenge free radicals
Inhibit lipid peroxidation i.e. prevent oxidative damage by reactive oxygen species
name 4 ways in which the xanthophyll L and Z protect against AMD
Blue Light protection
Antioxidant
Anti-inflammatory
Vascular protection
how does L and Z have an anti inflammatory affect
Thought to scavenge reactive oxygen species produced by inflammatory response
This may affect expression of pro-inflammatory molecules
how does L and Z provide vascular protection
L and Z may prevent thickening of arteries and help maintain healthy retinal and choroidal vasculature
what food is a main source of xanthophylls in diet
Green, leafy vegetables e.g Kale (raw)
what provides the highest bioavailability of dietary Xanthophylls within the body
Xanthophylls consumed with fat more easily solubilised and processed by enzymes
2x higher plasma response to lutein supplement taken with high fat spread compared to low fat spread
how does lutein uptake differ from plants compared to eggs
Esterified lutein (from plants) has 20% lower effect on serum lutein than free lutein (found in eggs)
Eggs has a greater affect on serum levels and it also contains fats which helps absorption
how is the bioavailability of dietary xanthophylls affected in smokers
Smokers have lower levels of serum lutein and MP
what does evidence state regarding effectiveness of xanthophyll in diet (rather than supplements)
High intake of L/Z and β-carotenes associated with reduced risk of developing advanced AMD, but not associated with the risk of developing early or intermediate AMD
name the omega-3 fatty acids and fish oil found in high concentrations in brain & eye
Docosahexaenoic acid (DHA) an omega-3 long chain polyunsaturated fatty acid (PUFA)
Deficiency may initiate onset of AMD
Name a Short chain omega-3 more prevalent in plant oils/ nuts and seeds
alpha-linolenic acid (ALA)
and can be converted into long chain DHA
what is the possible benefits of long chain PUFAs and name a disadvantage it may have
Protection against oxidative, inflammatory, and age-related retinal
damage
PUFAs are very prone to oxidation themselves due to double bonds, and may propagate free radical damage in the retina
what did the AREDS 2 study reveal about L and Z and omega 3 fatty acids with the progression of AMD
Addition of L+Z, Omega 3, or both had no additional effect on risk of progression to advanced AMD when added to AREDS formula
Omega 3 fatty acids had no beneficial or harmful effect in any subanalysis
name 3 aspects of diet that has an increased association with AMD
Western diet pattern had increased association with AMD prevalence
Vegetable oils and animal fats containing omega-6 fatty acids, and red/processed meat should be consumed minimally to reduce the risk of AMD progression
High glycaemic index diets and alcohol consumption of greater than two drinks a day had increased association with AMD
