Vitamin A and Stargardt's - Part 1

The only advice I was given when diagnosed with SD was that vitamin A was causing my vision loss and to not take supplements with Vitamin A. This totally contradicts the widely known fact that Vitamin A is essential for eyes. It's not that this fact is incorrect, it's that it doesn't wholly apply to SD. 

Since I love my science and research, I took it upon myself to spend my spare time reading every published article on SD and vitamin A to find out more about the mechanisms at play in the eye causing problems and what evidence exists to support these theories. The earliest article I found was published in 2008 and all used mouse models for investigations.

A paper published in Cell Death and Disease this year gives a good overview of the mechanism leading to vision loss and how Vitamin A is implicated. Essentially, SD is caused by an accumulation in the RPE of Vitamin A dimers (dimers are two molecules joined chemically), which are known as A2E (shortened version of the chemical name). Using an in vivo model, they found that increased A2E led to greater cell death. A word that always comes up when talking about SD is lipofuscin which is the yellow-brownish pigment deposits seen on a retinal scan used to diagnose the condition. Tying it all together, A2E derived from vitamin A is a retinal lipofuscin which is causing the damage and subsequent vision loss. These findings support earlier studies in mice such as articles n the Journal of Biological Chemistry and Investigative Ophthalmology and Visual Science which both looked at the effects of vitamin A, SD and mice demonstrating that higher doses of vitamin A led to increased lipofuscin development. 

Another paper in the Journal of Biological Chemistry also used a mouse model to investigate the effects of A2E and  also oxidative stress. It was found that A2E increased inflammation in the RPE, which is an important finding for prospective treatment solutions.

 

There are no studies performed in humans on the effects of vitamin A probably because it is not exactly ethical to get a group of SD patients and give them high doses of vitamin A and see whether they deteriorate! Despite this, the research is available to support that vitamin A is indeed causing damage in the eye and leading to vision loss. The continuing research has led to greater understanding on the different components at play and, no doubt, will help in the future to develop therapies. 

So now we know vitamin A is not our best friend, where do we go from here? Part 2 will discuss diet and vitamin A and how we can ensure not to overload vitamin A and contribute to the SD process.

Vitamin A

I came accross an article published in 2010 by Ma, Kaufman, Zhang and Washington from the Department of Opthalmology at the Colombia University Medical Centre about a dose combination acting upon vitamin A in the retina. The article was quite interesting, having been conducted on a mouse model of Stargardt's disease. The study used a dose combination of vitamin A and something called C20D3 directly on the retina.

Lipofuscin, which are the yellowish granules, accumulate in the retina causing permanent damage. I'm no chemistry whiz, but from what I deciphered the study found that if you could stop the chemical reaction occurring that allows two separate vitamin A molecules to combine and cause damage, the retina would not deteriorate. Thus, they made a combination of vitamin A and the C20D3 character to stop this chemical reaction occurring.

The study found this to work in mice, and thus may benefit humans. Although this would not restore sight already lost, but it could prevent further deterioration.

It is early stage research but it is quite promising to know that there is another group of people researching Stargardt's to help find us a cure.

The details of the article are below:
C20-D3-vitamin A Slows Lipofuscin Accumulation and Electrophysiological Retinal Generation in a Mouse Model of Stargardt's Disease.
By Li Ma, Yardana Kaufman, Junhua Zhang and Ilyas Washington

Diet - To eat those carrots or to not?

When I was first diagnosed last year, the only thing I was told was to steer clear of any excess Vitamin A in my diet - so no supplements containing Vitamin A. I then asked, "What about foods with Vitamin A?" and my doctor told me that I can't totally exclude foods with Vitamin A in my diet although I can try to limit and not eat excess of foods high in the vitamin, including carrots, which I happen to love and constantly eat!

I decided to look up what foods are rich in Vitamin A so I can try to limit my consumption of them, hoping this would contribute in some way to maintaining my vision. Foods that are rich in Vitamin A include:
Carrots
Liver
Broccoli
Sweet Potato
Butter
Spinach

Most of these foods I enjoy eating (with exception of liver.. gross) and are foods I will usually pick over other foods!

I was also told to take Lutein supplements, which I did at first, though I found they made me quite nauseous and upset my gastro system (if you catch my drift!). So I scrapped them and looked for Lutein rich foods. Such foods include:
Kale
Spinach
Peas
Zucchini
Bruessel Sprouts
and any other leafy green vegies

Interestingly, spinach is on both lists so how do you eat just what you want and not what you've been told to avoid? Some days I find I avoid eating carrots and other Vitamin A rich foods, but sometimes I just can't help myself.

Thus the only real advice I received at the time of my diagnosis, I can't really use. I still eat carrots sometimes, and try to eat spinach and other leafy vegies and at this stage this is all I can do.

It was also suggested by friends and my optometrist to follow a macular degeneration diet, although the benefits of sticking to such diet has not been proven for Stargardt's.

I guess all we can do is eat healthily and hope for more knowledge on this area.