Monday, September 27, 2010

Macular Degeneration and the morality of fats

My great Aunt Dot has macular degeneration and so my family for a while now has been interested in the possible effects of diet on this condition (not only for her but also because there is a genetic component and I sure as hell don't want to go blind).

For ages I have been told that olive oil is the best fat and otherwise we should have butter as it is "pure" whatever that means. Vegetable oils are absolutely prohibited. It seems that the evidence is shaky and inconsistent. What is a vegetable oil anyway if olive oil isn't considered. We were all under the impression that canola oil was bad.

After some internet research I believe we were mistaken. Yes, there was a study in the US which had a link between some vegetable fat consumption and increased risk but it including in that list fats that were partially hydrogenated (particularly nasty industrial procedure) which is not a factor in Australia. Indeed similar studies in Australia did not had the same conclusion. There seems to be conflicting evidence. There is a lack of clarity in what is deemed "vegetable oil".

Anyway, all fat is bad some are worse than others is the only consensus. Factors that were brought up in numerous places is how unsaturated the oil is and whether it contains omega-3 and/or omega-6.

I have included some website links. The first is from the Medical Journal of Australia.

Lots of good stuff there but here is a snippet:

In the Australian Blue Mountains Eye Study, a cross-sectional population-based study, a borderline statistically significant increased risk of early AMD with higher total fat intake (OR, 1.6; P trend = 0.08) and monounsaturated fat intake (OR, 1.5; P trend = 0.05) was found. There was also an increased risk (OR, 2.7; P trend = 0.04) of late AMD with higher cholesterol intake (animal fat).29 Although vegetable fats as a group were not investigated, they found polyunsaturated fats, which are derived mainly from vegetable fats, to be protective (OR, 0.4; P trend = 0.07) for late AMD. More recently, results from another Australian prospective cohort study found no relationship between polyunsaturated fats (vegetable fats) and incident cases of AMD, but found omega-3 fatty acids to be protective for early AMD (OR, 0.4; 95% CI, 0.2–0.8).30

Based on the limited data from the US, there has been publicity in Australia urging people to avoid vegetables oils, particularly margarine, arguing that they cause AMD and encouraging people to eat butter (a saturated animal fat) instead. With the limited, often conflicting, information regarding fats and the risk of AMD, there appear to be no grounds to support any such public health message at this stage. However, it still remains clear that saturated fats are the main dietary cause of high blood cholesterol levels, and groups promoting heart health strongly recommend limiting saturated fat intakes. Saturated fats are found in mainly animal fats and in some plant oils (coconut oil, palm oil, cocoa butter). This message is still particularly pertinent for people concerned about AMD, given the possible links between CVDs and AMD outlined above.

Thus, while it is desirable to advocate a public health message of a low-fat diet in general, a specific recommendation regarding certain fats and AMD is not based on consistent findings at this stage.

Another one this time from America.


Late in 2001, Dr. Seddon and her colleagues at Harvard University reported another startling finding about nutrition and AMD. They found that people whose diets have the right ratio of omega-3 and omega-6 fatty acids have less macular degeneration than those whose diets are skewed. The real bombshell, though, is that most of us are eating skewed diets--very skewed diets. We get five times more omega-6 than we should and hardly any omega-3 at all. Since omega-6 and omega-3 compete with each other in our bodies, what little omega-3 we get hasn't got a prayer of protecting our retinas, which is one of its jobs. It turns out that the rods and cones of our macula need a certain amount of omega-3 to function properly. This may be a major reason that so many of us are winding up with accumulated waste in our maculae and AMD.

Fatty acids are fat molecules found in saturated fats such as butter and in unsaturated fats such as safflower and olive oil. We all know by now that if we eat large quantities of saturated fats, we'll clog our arteries and we'll wind up as candidates for a heart attack. As a result, many people have turned to vegetable oils for a healthier diet. But large quantities of common vegetable oils--like corn, safflower, and soybean oil--may increase our risk of macular degeneration because they are chock-full of omega-6 fatty acids.

You don't have to eat fried food or use lots of vegetable oil in your cooking to be getting too much omega-6, because these oils are key ingredients in just about every commercial food product on the market, especially low-fat foods such as crackers, sports bars, and microwave popcorn. I recently checked every label in a food mart and found that the only products in the whole store that didn't contain omega-6-rich vegetable oils were the ketchup, mustard, and relish. Everything else that came in a box, bag, can, or package contained omega-6 oils, including the Ben & Jerry's ice cream. To reduce your omega-6 consumption, therefore, you need to avoid packaged foods with vegetable oil listed in the ingredients.

Our Heroes: Olive, Canola, Fish, and Flaxseed Oils

The right ratio of omega-6 to omega-3 fatty acids is 3:1, which means that we need to consume approximately three times as much omega-6 as omega-3. So what oils should we use? The answer is monounsaturated oils, such as olive and canola oil for their omega-6 fatty acids, and fish oil and flaxseed oil for their omega-3 fatty acids.


For cooking, use good-quality olive or canola oil. These oils contain high levels of oleic acid, a monounsaturated oil that tolerates heat and light much better than polyunsaturated vegetable oils do, so cooking won't significantly degrade its nutritional content. If you have a recipe that calls for another oil, check with your health-food store. Some of the companies that produce high-quality olive and canola oils also have lines of oleic-rich safflower, sesame, almond, corn, and peanut oils that you can use, especially for baking.

Another American one which had some interesting things to say about dairy and meat (and again says, for omega reasons put canola as "good").
It has:

The Bad
Of the food sources, intake of beef, pork, or lamb as a main dish increases the risk of macular degeneration. More than 1 serving/week of beef, pork, or lamb as a main dish is associated with a 35% increased risk of macular degeneration as compared with less than 3 servings/month. A high intake of margarine is also significantly related to an increased risk of macular degeneration. 1 serving per day of high-fat dairy food (whole milk, ice cream, hard cheese, or butter) increases risk of macular degeneration progression by 1.91 times. 1 serving per day of meat food (hamburger, hot dogs, processed meat, bacon, beef as a sandwich, or beef as a main dish) increases risk of macular degeneration progression by 2.09 times. 1 serving per day of processed baked goods (commercial pie, cake, cookies, and potato chips) increases risk of macular degeneration progression by 2.42 times.

A really good argument to go veg (with no dairy).

1 comment:

  1. Alternatively one can implant tiny telescopes into one's eyes:

    ... Yeah actually, perhaps laying off the meat is a better first shot.