Vanguard Neurologist

From ScienceDaily.com:

For the past century, changes in the Western diet have altered the consumption of omega-6 fatty acids (w6, found in meat and vegetable oils) compared with omega-3 fatty acids (w3, found in flax and fish oil). Many studies seem to indicate this shift has brought about an increased risk of inflammation (associated with autoimmunity and allergy), and now using a controlled diet study with human volunteers, researchers may have teased out a biological basis for these reported changes.

Anthropological evidence suggests that human ancestors maintained a 2:1 w6/w3 ratio for much of history, but in Western countries today the ratio has spiked to as high as 10:1. Since these omega fatty acids can be converted into inflammatory molecules, this dietary change is believed to also disrupt the proper balance of pro- and anti- inflammatory agents, resulting in increased systemic inflammation and a higher incidence of problems including asthma, allergies, diabetes, and arthritis.

Floyd Chilton and colleagues wanted to examine whether theses fatty acids might have other effects, and developed a dietary intervention strategy in which 27 healthy humans were fed a controlled diet mimicking the w6/w3 ratios of early humans over 5 weeks. They then looked at the gene levels of immune signals and cytokines (protein immune messengers), that impact autoimmunity and allergy in blood cells and found that many key signaling genes that promote inflammation were markedly reduced compared to a normal diet, including a signaling gene for a protein called PI3K, a critical early step in autoimmune and allergic inflammation responses.

This study demonstrates, for the first time in humans, that large changes in gene expression are likely an important mechanism by which these omega fatty acids exert their potent clinical effects

While valid debates rage over declining fish stocks, where should consumers look to find omega-3s?

From 2Canada.com:

It’s been a controversial couple of weeks for our friends from the deep blue sea. Two weeks ago, the Journal of the Canadian Medical Association published an analysis that not only called into question the purported benefits of omega-3 fatty acids, but also criticized the use of fish oils as ecologically unsustainable. Just days later, the International Society for the Study of Fatty Acids and Lipids (ISSFAL) issued a research summary confirming that omega-3s from plant sources such as flaxseed cannot be converted efficiently enough in the human body to offer any significant benefit, making marine sources of omega-3s our best bet for fighting disease.

Unfortunately, this kind of contradictory advice tends to generate frustration for consumers, who end up feeling pulled in different directions (“When will you people get your stories straight?” is a common complaint). The odd thing about this story, though, is that it turns out both sides make a good point. (Life is never simple, is it?) So let’s sift through all the talk and see if health-conscious consumers can have their omega-3s and keep eating them, too.

A QUICK REFRESHER ON OMEGA-3S

Omega-3 fatty acids are an essential type of fat thought to confer a variety of health benefits. Along with their counterparts, omega-6 fatty acids, omega-3s need to be consumed through food, as they cannot be manufactured in the body. Once inside the body, omega-3s are incorporated into cell membranes, making them more fluid, while also sending signals that reduce inflammation throughout the body. Ultimately, they seem to make our joints less stiff, our arteries more flexible and our brains healthier.

It’s generally accepted that our diet contains both lower levels of omega-3s than those of our ancestors, as well as higher levels of omega-6s. Since omega-3s are largely obtained from fish, while omega-6s are available through numerous types of plant oils (such as sunflower and safflower oils) that are commonly used in food processing, it has been estimated that we consume far more omega-6 than omega-3 fatty acids. The result, in theory, is a higher proportion of pro-inflammatory signals being sent through our body, making us more prone to heart disease, cancer, diabetes and other chronic ailments.

Within the family of omega-3s, there are actually different sub-types, which — at least in theory — can be interconverted. One, known as alpha-linolenic acid, or ALA, is found primarily in plant sources, such as flaxseed, walnuts and canola oil, while others, known as eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DHA, are generally only available from fish and marine-derived sources.

ALA TO DHA: LOST IN TRANSLATION

The controversy addressed in the ISSFAL statement surrounds the conversion of ALA to DHA (DHA is essentially the endpoint of omega-3 metabolism in humans). For years, evidence has been mounting that our bodies simply do not convert ALA to DHA, even though we theoretically have the enzymes to do so. In reality, the amount of ALA that finally becomes DHA — and therefore can be useful to our bodies –is estimated to be close to zero. While ISSFAL wasn’t breaking any new ground with their statement, their point is that the evidence is convincing enough that we should be focusing on consuming “pre-formed” DHA, rather than relying on ALA sources to get us our omega-3s. (Note, however, that ground flaxseed can potentially provide numerous other health benefits from its fibre and lignan content — in other words, it’s worth more to us than just its ALA.)

BUT WHAT ABOUT THE FISH?

If we go by the recommendations of numerous internationalhealth-related organizations, not only do we need to get our omega-3s from the sea, we need to get a couple of servings per week to prevent heart disease, and even more if we already have heart disease or high triglycerides. Since eating that much fish is not palatable for everyone, the next step for many is to take a fish oil supplement.

This is where the CMAJ analysis takes exception: Its authors argue that, with global fish stocks on the brink of collapse, it is irresponsible to recommend an increase in fish consumption, especially since (as they argue) the evidence to support the benefits of fish is not clear. They point to numerous large-scale analyses of fish and fish oil use that have shown an inconclusive or marginal benefit of fish to heart health, in particular, not to mention other medical conditions.

ALTERNATIVES — FOR TIMES WHEN THERE AREN’T ENOUGH FISH IN THE SEA

While getting into the details over the various analyses of the benefits of fish is beyond the scope of this column, there are still enough researchers and medical organizations that believe omega-3s are good for us that it makes sense to look into alternatives to reduce pressure on the fish population. As author Taras Grescoe outlined in his acclaimed 2008 book, Bottomfeeder, smaller, bottom-feeding fish, such as sardines, herring and anchovies are not only rich sources of omega-3 fatty acids, but their rapid reproduction rates allow their populations to regenerate faster than larger fish. While not the most popular choices for North American eaters, Grescoe maintains that there are plenty of ways to enjoy these more eco-friendly fish.

Beyond the bottomfeeders, there is another, growing alternative to fish-based omega-3s: DHA from algae. Now available in supplemental form, as well as added to various food products, algal DHA is considered a far more sustainable means of getting your omega-3s while bypassing fish entirely. Having said that, there is limited research in algal DHA (we assume it works just as well as the fish form), but for now, it looks to have a bright future.

Finally, I think it’s worth mentioning again that, just because some of something is good, does not mean that more is better. While eating fish a couple of times per week seems to be good for your health, eating large, predatory fish on a regular basis or eating fish on a daily basis and taking vast amounts of fish oil supplements puts more pressure on our fish stocks, likely outweighing any health benefits the fish provide you. As always, exercising moderation is likely the best path to follow.

- Jennifer Sygo is a dietitian in private practice at Cleveland Clinic Canada (clevelandcliniccanada.com), which offers executive physicals, prevention and wellness counselling and personal health care management in Toronto.