Monday, December 15, 2014
Eggs and Eye Health
A brief health spot on television showed a nutritionist recommending eggs in the diet of seniors to prevent age-related macular degeneration (AMD). This was news to me, so I started to do some research and found interesting results.
AMD is the primary cause of blindness among older people. The macula of the eye depends on certain anti-oxidants to remain healthy.
The first reference was from 2006 from the University of Massachusetts at Lowell. They designed a study to see if eating eggs would increase lutein and zeaxanthin in the blood. These substances are found in egg yolks (and in several other foods) and are thought to lead to healthier eyes. The study concluded that eating an egg a day both increased levels of these important nutrients in the blood and did not adversely affect cholesterol levels. The headline read: “According to research from the University of Massachusetts Lowell and the University of New Hampshire, regular consumption of eggs … may help stave off macular degeneration, the leading cause of blindness among seniors.” [Emphasis added]
Near the bottom of the story was this disclaimer. “But even the researchers say it's still too early to make a sound prediction about eggs' impact on eye health. And those familiar with the link between carotenoids and ophthalmology remain skeptical about the study until a larger sample size is documented and the report is officially published.”
That comment about the need for more research led me to other, more recent sources. The National Institutes of Health (NIH) had reports of several additional studies. In 2013 they presented a review of the current literature on the subject. This centered on lutein and zeaxanthin, pointing out that they are carotenoid pigments that impart yellow or orange color to various common foods such as cantaloupe, pasta, corn, carrots, orange/yellow peppers, fish, salmon and eggs. So it’s not just eggs. The primary study cited in this review showed a link between them and eye health, but no firm connection. It was old, however, from 1994 – “CONCLUSION--Increasing the consumption of foods rich in certain carotenoids, in particular dark green, leafy vegetables, may decrease the risk of developing advanced or exudative AMD, the most visually disabling form of macular degeneration among older people. These findings support the need for further studies of this relationship.” Again they are not sure until further studies are done.
A 2014 review by the NIH showed, without further detailed information, only this headline: “Consuming a buttermilk drink containing lutein-enriched egg yolk daily for 1 year increased plasma lutein but did not affect serum lipid or lipoprotein concentrations in adults with early signs of age-related macular degeneration.” As of this year, it sounds like the jury is still out on any scientific confirmation of the eggs-good-for-the-eyes hypothesis.
From this I conclude that eggs are good for you. They contain some important nutrients and the cholesterol scare about eggs from several years ago should not be a concern. It is probably still too early to say definitely that eggs help prevent AMD, and important to note that several other dietary sources of the same nutrients are also available.
This is pretty good evidence that information from these short television pieces (and other sources of news), even from apparent experts, should not be relied upon as being either complete or totally accurate.
This is further reinforced by my favorite source for jumping to the conclusion they want to believe in, Natural News, who in 2006 right after the initial U-Mass egg study with the clear disclaimer about more research needed, concluded their web write-up with this quote from one of their experts: " ‘This study once again shows the power of natural medicine found in wholesome foods,’ says Mike Adams, author of The Honest Food Guide.” Though there is nothing wrong with good food, this appears to be more about wishful thinking than an accurate report on the science. (I have found other instances in these types of websites where the source information contains disclaimers not mentioned in the article.)
It’s very easy to see, though, how these health beliefs get started and how they continue to persist even when not confirmed or after contrary evidence comes to light.