I've long been fascinated by fat; apparently, as a child I used to sneak sticks of butter instead of cookies. My prescient brothers
used to call me Fathead.
There's no way to miss the basic message that's out there about fats (they're no longer all bad! hydrogenation is really, really bad!) but I've been hankering for an easy-to-understand summary of the role of fats in our diet, a reference guide, if you will. There's good info out there:
The Philly science museum has a great educational piece that takes on both the impact of dietary fats on health and how fat consumption affected brain size from an evolutionary perspective. First off, it gives the basic lowdown about what's what. Eating ALAs (alpha-linolenic acids) found in dark green leafy veggies and flaxseeds, gives our bodies the building blocks for omega-3 fatty acids. Eating LAs (linoleic acids) found in safflower, corn, and soybean oils helps our bodies form omega-6 fatty acids. You want to have ALAs and LAs around to make DHA (docosahexaenoic acid) and AA (arachidonic acid) -- the long-chained fatty acids that make up the membranes of our neurons and the protective myelin sheaths covering them. Your body cannot make ALAs or LAs; you have to obtain them from food. (DHA and AA you can make or get directly from food sources.) Apparently, the balance between omega-3s and omega-6s is important, as well. You want about a 1:1 balance between the two, and our modern diets tend to heavily tilt towards omega 6s. Diets rich in DHA may help prevent the onset of Alzheimer's and may help combat depression and ameliorate developmental delays in kids.
- Eat ALAs and LAs to make omega-3s and omega-6s. Eat lots of omega 3s directly. Don't eat too many omega-6s! The more DHA and AA the better.
Echoing the evolutionary advantage of DHA, it appears that babies also benefit greatly from the right types of fat. Lise Eliot's fantastic book about brain development traces an overview of the role of fats in both neuron myelination and the creation of new brain membranes, both of which happen primarily in the first two years of life. Apparently, human babies need specific lipids (fats) for these brain-growing processes. Some must come from dietary sources, and some are fats that humans can produce later in life but are difficult for babies to produce on their own (hence the evolutionary need for these lipids in breastmilk).
Researchers' close attention to the lipids in human milk (which differs greatly from cow's milk) has resulted in DHA being added to infant formula, but the exact composition of breast milk is still being scrutinized. The lipid content of mother's milk changes over the course of time and even over the course of the day. Good dietary sources (for nursing mothers and for all of us) of DHA and AA (those beneficial long chain fatty acids) are: cold-water fish, shellfish, egg yolks, liver, and organ meats. Soooo...we don't totally understand all of the component parts of breastmilk, but the fats we do know are beneficial point again to eating foods that will help us produce DHA and AA.
How, you might, ask, can we figure out which foods to eat? Harvard School of Public Health's guide to fats and cholesterol has a handy chart that notes the importance of choosing fats wisely rather than avoiding fat altogether and provides actual foods along with definitions (smile). It advocates a shift from "bad" fats to good: from saturated/trans fats (bad) to unsaturated fats (good), which basically entails eating only fats that are liquid at room temperature, along with a soft margarine-type fat that doesn't have trans fats or hydrogenated fats on the label.
- Saturated fats=animal fats (all dairy/meat)
- Trans fats=margarine/shortening, other hydrogenated fats ie frying oil used in fast food, lots of commercial baked goods
- Monounsaturated fats=olive, canola, peanut oils
- Polyunsaturated fats=sunflower, soy, corn oils, fish (includes omega-3s and omega 6s, fyi)
I must caveat all of this info by saying that there is a dissenting point of view, in the person of Sally Fallon and the Weston A. Price Foundation, who believe that animal fats are a healthy part of a traditional diet -- if the animals are treated properly and allowed to eat grass. I won't go into their ideas in great depth but if you haven't read Nourishing Traditions, it's fascinating. They are proponents of fermented foods and raw milk as well. Fallon and Mary Enig have written extensively about fats and Enig's got a book out; I want to read more of both. They have long been suspicious of trans fats -- long before the current labels -- and they, too, support the consumption of omega-3s via fatty fish. It's the saturated fat they're not willing to condemn....
I'm no scientist, and the argument that people for thousands of years have lived well off animal fats rings true, except that our ancestors knew scarcity and moderation as we'll never experience it and had a far lower bar for their dreams of longevity. That said, I *am* a butter lover, and I don't regret dodging the sticks of oleo in my mom's fridge. Research bears out the Fallonites' claims that grass-fed beef is healthier; its ratio of omega-6s to omega-3s is 2:1 rather than the 4:1 ratio found in conventional grain-fed beef.
One final note about fats, per Sandra Steingraber who wrote in Having Faith about the breastfeeding conundrum we face in this day and age: persistent organic pollutants (POPs) like dioxin bind to fat molecules. Many toxins are fat-soluble and concentrate as you head up the food chain, which is why we must buy organic everything that contains fat (dairy, meat, oils), and it's why you should predominantly eat lower on the food chain. Avoiding the toxins altogether seems impossible, because organic or not, pollutants are everywhere. The hope is to make strategic choices when moving up the food chain, as we do with salmon (ie wild over farmed) and to continue getting the fats we need to keep our brains alert enough to choose wisely. Ahem.
Speaking of fats, a quick shout out to Mrs. G at Derfwad Manor, who hooked me for life with this commentary on New Zealand's refusal to allow a woman with (ahem) larger-than-optimal BMI to emigrate, and also turned me on to Saturday's baby laughing video. Thank you, ma'am!