Another promising dietary supplement fails to deliver protection against a target disease, this time Alzheimer's. Image courtesy of outcast104.

Another promising dietary supplement fails to deliver protection against a target disease, this time Alzheimer's.

DHA (or docosahexaenoic acid for the geekier among you) is an omega-3 fatty acid that is abundant in the brain. Epidemiological studies have suggested that people who consume more DHA from fish have a lower incidence of Alzheimer's disease. Further, DHA supplementation has improved markers of cognitive impairment in mouse models of Alzheimer's disease.

Scientists speculated that DHA supplementation may be beneficial in treating cognitive decline because previous research has suggested that among all omega-3 fatty acids, DHA was the only one associated with a reduced incidence of impairment. Also, the other major omega-3 fatty acid found in fish, eicosapentaenoic acid (EPA), is not present in the human brain, whereas DHA is abundant.

The study, published in JAMA, was a collaborative effort by scientists from the Oregon Health and Science University, UC San Diego, Yale, UC San Francisco, NYU and others. It was a randomized, double-blind, placebo-controlled trial of DHA supplementation in patients with mild to moderate Alzheimer's disease.

The researchers found no benefit of 2 g/day DHA supplementation on cognitive performance on the Alzheimer's Disease Assessment Scale (ADAS) or Clinical Dementia Rating (CDR) compared to placebo. There was also no measurable benefit of DHA on brain volume, which typically declines with Alzheimer's progression.

Though this research does not rule out a benefit of DHA on cognitive health, it does not bode well for regular supplementation. The treatment lasted for 18 months and cognitive changes were detected in both groups. So if DHA had any effect on the rate of cognitive decline it should have been apparent.

It is possible that beginning DHA treatment after early signs of Alzheimer's have already been detected is too late for any meaningful protection offered by DHA. Maybe some benefit would have been found if the treatment began in healthy adults before symptoms of cognitive decline developed.

It may also be that DHA is beneficial, but is not effective in supplement form. DHA is very vulnerable to oxidative damage, and some research has shown that it provides more cognitive benefit when co-administered with an antioxidant (lutein) to protect it. DHA ingested in the form of food (fish) would not be subject to the same level of oxidative degradation, which may explain the results seen in epidemiological data.

It is not uncommon for supplements to fail to replicate epidemiological benefits seem from foods, and more careful studies are needed to determine the nutritional benefit, if any, of DHA on cognitive aging.

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Organic Fed / Certified Organic

All organic eggs are certified by the USDA. Organic eggs come from hens whose feed is free of pesticides, herbicides, fungicides, and commercial fertilizers. Organic chicken feed contains no animal byproducts and the hens have never been given antibiotics.

Hormones and Antibiotics:

The FDA banned the use of hormones – most notably diethylstilbestrol, or DES – in poultry in 1959, after they not only caused tragic health problems in consumers but also failed to stimulate growth in chickens. "Hormone free" is a misleading bit of marketing that suggests other egg producers are illegally dosing their birds.

Kept in Cages

Some hens are kept in battery cages; enclosures so small the animals can't spread their wings. Battery caged hens are crammed as many as six chickens into a cage at a time, leaving each bird with less personal space than a sheet of ordinary notebook paper. Critics say the battery system causes the spread of disease, requires the painful de-beaking of birds, and restricts natural bird behaviors, such as dusting or nesting.

Have Access to Outside

"Free Range" and "Free Roaming" are terms that bring to mind idyllic barnyard scenes. These labels, which are regulated by the USDA, may be used by a producer if their hens are allowed some access to the outdoors. This does not guarantee constant access, nor is there any specification of the size of the outdoor area (which is, of course, a penned area, not a range).

Beaks Clipped

Also known as debeaking, or beak trimming, is a process by which parts of the beak of a chicken or turkey are trimmed. Many variations of debeaking are used. Most commonly, the beak is shortened permanently, with the lower beak somewhat longer than the upper beak. The goal of this is to reduce cannibalism in stressed-out bird populations, such as in crowded egg-laying hen houses.

Forced Molted

When light and temperature are manipulated so hens lay eggs more than normal.

Omega-3 enriched

Omega-3 is a polyunsaturated fatty acid considered crucial by some for developing brains and preventing heart disease and depression. Farmers boost the omega-3 content of their hens' eggs by adding ground flaxseed, algae, or even fish oil to the birds' feed.

My own kind choice is to stay informed, shop at the local farmers' market and ask questions, and someday, raise my own.

If you have any tips or insights into local egg farms, please do share!

For more egg carton terms, go to:

http://blog.pennlive.com/naturalliving/2007/06/eggs.html

Amy Gotliffe is Conservation Manager at The Oakland Zoo.

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