Fish Oil
- Contains the lipid docosahexanoic acid (DHA) which is an essential polyunsaturated fatty acid. It's found in the body as a structural component of membranes (1-4%) and is highly concentrated in nerves and photoreceptors (up to 50%).
- The DHA increases membrane fluidity (there's a constant need to make new membranes) and improves the efficiency of membrane functions including phototransduction & synaptic transmission
- Reminder - oxidation is loss of electrons. When biological molecules are oxidised first an unstable free radical results and then the electron is lost/bond is broken.
- Free radicals are caused by high energy light and toxins like the ones in pollution, drugs and smoking. The concentration of free radicals in the body is exacerbated by high oxygen levels, poor diet and ageing.
- Lipids in membranes, proteins (both in enzymes and structural) and DNA (protein synth) are susceptible to oxidation. If the free radicals become too numerous you will get cell damage
- Antioxidants neutralise free radicals and limit oxidative damage
- Examples of antioxidants include carotinoids (fruit/veg), Flavinoids (fruit/bilberries/gingko/tea), Vitamin E (seed oils/fruit), Vitamin C (fruit/veg), Zinc & Selenium (meat/fish/nuts/seeds/cereal)
- Important carotinoids include beta carotene found in carrots and apricots, lutein and zeanthin (found in corn, leafy veg & egg yolk) and lycopine from tomatoes/fruits.
Special protection for the macula is useful because the macula is of course always being bombarded by light, has a high metabolic rate (it's constantly transmitting info) and the highest concentration of oxygen in the entire body.
Antioxidants in the macular pigment xanthophyll are lutein and zeanthin and you can get em from corn, cabbage, kale, egg yolk as well as some other fruits and vegetables. Obviously nutrition alone ain't goin' to save ya - MD is multifactorial - genetic risk, race/pigment, vascular health, oxidative damage.
Four age related studies (see P102 shared care book) showed that high doses of an antioxidant zinc substance reduced progress of nuclear cataract and decreased progression of ARMD in those with intermediate or high risk ie those with large drusen and pigment abnormalities.
Nutritional Advice to Px re: eye disease
- Eat fruit and veg (corn, carrots, spinach)
- Routine supplements aren't justified if your diet is pretty good already
- Supplements may benefit those at high risk. If you aren't then they aren't going to do any harm but don't think subbing them for stopping smoking works
- Other factors like smoking and vascular health may have a greater impact
- Bear in mind that you aren't a nutritionist - if the px is thinking of taking a load of supplements best to refer them to one
- Good articles here
- The foetus/neonate needs a lot of DHA for photoreceptors and synaptic membranes and Vit A for photopigments. These are provided by the mother.
- Preterm infants are especially vulnerable due to low fat levels / limited nutrient stores and receving little or no breast milk
- Fish? WHO now says 3 servings of oily fish are good every week especially if you're pregnant. Pregnant women transfer the DHA to the baby and can leave their own supply depleted. So if the woman takes supplements then they have a good amount of DHA for both them and the baby. The baby takes only as much as it needs so the supplements don't make much difference to them
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