As an update to my most recent post about the recent Engle and Stockart fiasco, I’d like to call attention to the comment posted on said post, (also on Reddit), and a post on the Logo Factory. It’s impossible to know the real story, and who’s really at fault, but at least both sides are now being represented more fairly online. It’ll be interesting to see how this all plays out; this drama is not as black and white as it first appeared.
Medium: conte crayon – unusual for medical illustrations, but I wanted to try it out. It’s less finicky than carbon pencil but still gives really rich blacks. My only wish is that conte came in greys as well– I haven’t seen them in the stores.
Intestinal Mesentery Dynamics: color variation
Check out this snowy terrain image – looks like what I saw flying from Minnesota to Atlanta a few weeks ago. This image was taken far away from the midwest, however.
Tibet from above, NASA/Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center
This image via Boston.com’s Big Picture feature.
More satellite images via NASA: http://earthobservatory.nasa.gov/NaturalHazards/category.php?cat_id=11
Regarding recommended intakes for omega-3 and omega-6 fats, research has focused on relative, not absolute, amounts. The reasons for this are historical; currently Americans are consuming an approximate ratio of 15:1 (omega-6 : omega-3). Generations and generations ago, our ancestors consumed a ratio much closer to 1:1 and a ratio of 4:1 is what is recommended today based on the latest research. The theory goes that we’re not feeding our bodies as evolution designed us to eat, and this is the reason the onslaught of many new health issues has arisen – type 2 diabetes, heart disease, asthma, and others. For a brief discussion and some data about this ratio, visit the Whole Health Source blog.
Not all researchers agree that relative amounts should be the only focus. Two Harvard papers, both written in part by WC Willett, concluded that the issue is more about raising omega-3′s, and that lowering omega-6′s showed no appreciable benefits. But still, even though there’s disagreement over the ratio, everyone seems to agree that omega-3′s have importance. Abstracts here and here.
So finally, what food sources contain which kinds of fats? These two PUFA’s come from a range of meats, vegetables, nuts, and their oils, often both in one kind of food. But still there are certain foods that are clearly dominated by one and not the other.
Good sources of Omega-3′s:
ALA: flaxseed and oil, walnuts and walnut oil, canola oil, leafy green vegetables like broccoli and spinach, grains
EPA/DHA: wild fish (especially salmon), grass fed beef, eggs. In general the more natural the animals eat, the better.
Good sources of Omega-6′s:
LA: safflower, sunflower seeds, vegetable oils, corn oil
AA: animal meats, farmed fish, eggs. In general, animals that have a heavily processed and corn derived diet have higher omega-6 to 3 ratios.
The bottom line behind all this research and nutrition hype seems to be that we should eat what evolution carved us out to eat. More omega-3′s, less omega-6′s. More real food, less processed and overly preserved.
Research into omega-3 and omega-6 fatty acids for a recent project has given me much more awareness about these molecules than recent health headlines and food package claims ever could.
Starting with basics, both omega-3 and omega-6 fatty acids are essential polyunsaturated fatty acids (PUFA’s). The ‘essential’ term refers to the fact that even though our bodies need both these fats for healthy functioning (all cells are surrounded by lipid membranes), they can’t manufacture them on their own. There’s another PUFA – omega-9 – that isn’t nearly as well known, and is not an essential fatty acid.
Nothing in the body is simple; there are several types of omega-3 and omega-6 fatty acids, both involved in a lovely web of reactions, at times competing for the same enzymes. For a poorly designed but accurate diagram, go here.
The major types of omega-3 fatty acids are ALA (alpha linolenic acid), EPA (eicosapentaenoic acid), and DHA (docosahexaenoic acid). All of these are found in foods, but to a small extent ALA helps produce EPA and DHA.
Both EPA and DHA are antiarrythmic (keep the heart beating steadily), decrease triglycerides, decrease VLDL cholesterol, increase HDL cholesterol, and decrease cytokines (short messengers between or within cells, usually involved in inflammation). EPA also decreases platelet aggregation, vasoconstriction, and other inflammation mediators. DHA is also well known for its importance in brain functioning and development, making up a significant amount of infant brain mass.
Omega-6 has two well known stars: LA (linoleic acid) and AA (arachidonic acid). Like the Omega-3 acids, both of these are found in food sources, but to an extent the body also makes AA from LA. AA has been shown to lower LDL cholesterol. AA acts more strongly opposing the omega-3 EPA by increasing platelet aggregation, vasoconstriction, and inflammation.
All the actions listed above are healthy body responses, in certain situations. The issue is that you can have too much of a good thing. Inflammation, for instance, is how the body rightly deals with cuts and some foreign invaders. However, when kicked into overdrive, it is also a symptom and/or cause of many modern diseases – heart disease, arthritis, type 2 diabetes, some cancers, and asthma.
More on this topic to follow, including which fats are found in which foods, and reasons behind recommended intake amounts.
Some sources:
Dietary n-6 and n-3 polyunsaturated fatty acids: From biochemistry to clinical implications in cardiovascular prevention.
Metabolic Pathways of Omega-3 and Omega-6 Fatty Acids
