(If you know your fats well, skip to the end for the bit on Omega-3s)
Fat, also called lipid (and sometimes referred to by its liquid name "oil"), really describes a large and diverse group of substances that share a similar chemical structure of carbons linked together. Because of this similar structure, fats all are packed with energy, making them excellent storehouses for energy in the body. Fats are also a critical part of every single cell in our body and serve innumerable functions beyond that of simply providing energy.
There are groups of specialized fat storage cells called "adipose tissue" (when people talk about someone's fat, or love handles, or junk in the trunk, etc. they are talking about adipose!). A recent explosion in scientific research has begun to uncover Adipose tissue's hundreds of novel functions -- scientists are so impressed that they are calling for Adipose to be classified as a separate organ system.
Did I say I was going to be brief? Ok, so let's talk about fats from a vegan perspective according to the way we classify and organize fats:
Saturated Fats - saturated refers to the fact that all the carbons in these fats are full (i.e. saturated) with hydrogens. That's why I'll include partially hydrogenated and hydrogenated vegetable oils in this category. These fats are still a grouping of many types of fats, some of which are worse than others, but in general, these are the guys that raise blood cholesterol and contribute to heart disease and a very large host of atherosclerotic diseases. Yes, most saturated fat in the American diet comes from dairy and other animal foods.
But hefty amounts of saturated fat can creep their way into the vegan diet in the form of margarines, baked and processed foods (which contain hydrogenated vegetable oils, or palm oil, cocoa butter and coconut oil) and a few whole foods like avocado, chocolate, Brazil nuts or coconut.
Are all of these foods bad for us? No. For example, dark chocolate contains ample saturated oils but many studies point to the net benefit of daily intake of a small amount of dark chocolate. Similarly avocados are not enemy number one in health circuits and contain beneficial fat soluble vitamins and nutrients.
The biggest question of debate is palm oil (now gaining infamy for its role in rain forest destruction). Palm oil is ~50% saturated fat and Palm Kernal oil is ~88% saturated fat. Palm oil can be further hydrogenated or fractionated to get a more saturated fat rich product. It seems clear that hydrogenated palm, partially-hydrogenated palm and palm kernal oil are plain terrible for you and your heart. Avoid these in any quantity. So the question is about raw or unrefined palm oil, which is touted to have lots of beta-carotene, vitamin E and other antioxidants. Here studies show mixed results - some reporting a beneficial effect on blood lipids (cholesterol, etc.) and other showing detrimental effect. The differences may have to do with who was selected for the study (e.g. it may have a worse effect on men and people predisposed to bad lipids), on the type of palm oil (red palm may be better than regular palm), how "crude" or unrefined the oil is (in the same way that unfiltered extra-virgin olive oil is far superior to "light" olive oil), or on other factors that are not clear to me. Part of the argument for palm oil not being bad is that the saturated fat is mostly in the 2nd position of the 3 fatty acids on the glycerin backbone - and that this is much less bioavailable (i.e. digested/absorbed) and that palm also contains beneficial mono and polyunsaturated fats.
So in sum, my sense is the verdict is still out on unrefined palm oil. I'll chose to keep my intake small until more is known.
Trans Fats - Most often these are the news-savvy by-product of hydrogenating and modifying oils and contain a chemical structure not often found in things we eat. Until recently, about 80% of trans-fat in the US diet came from hydrogenated soy oil. There is now plenty of science revealing how toxic these critters are... thus the ban on trans-fats now in place in several cities. Do not buy anything with trans fat and be aware of products that say "now trans-fat free" - check to see if they've replaced their trans fat with palm kernal oil or other not-so-good oils.
Unsaturated Fats - we typically divide these into mono-unsaturated oils (think: olive oil, mmm) and poly-unsaturated oils (think: most vegetable-based oils). I won't talk much about mono-unsaturates, except to say they seem to be good for us.
Polyunsaturates can be further divided into categories based on their chemical structure (for you chemistry lovers: the position of the first double bond in the carbon chain), the main groups being Omega 3, Omega 6 and Omega 9.
Omega 3 and Omega 6 are the "essential fatty acids" because if you don't eat any you'll die! You'd be guessing right if you thought that both have beneficial properties. But omega-6s are in so many foods you eat that you don't have to worry about getting enough. Omega-3s are much harder to find and there is growing recognition of the theory that the balance of Omega 3's to Omega 6's in the diet is important. And that our ratio is wayyyy out of whack - we eat way way more omega 6's than 3's (roughly 10x more, rather than the 2-4x more that may be 'ideal').
Where are the Omega-3's hiding?
Well there are modest amounts in some common vegan foods, most notably tofu and other regular fat soy products (excluding soy-oil). So all of us do eat some omega 3's. But given the abundance of Omega 6's in our diet, a strong argument can be made for getting more of the 3's.
Papa Omega 3 and the important fine print of omega 3s:
The parent of the omega 3 family is a fat called alpha-linolenic acid (LNA). The main vegan sources of omega 3 (such as flax oil, canola oil, tofu, walnuts) are mostly alpha-linolenic acid. From LNA our bodies can make some other omega-3s special kiddies called EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). EPA and DHA are the omega 3's most well studied that lower the risk of dying from heart disease. It's thought that large amounts of omega 6 can suppress our ability to convert LNA to DHA and EPA, which may be a particular disadvantage to the common vegan diet at present. So the major question still unanswered is can we make enough EPA and DHA by eating predominantly LNA? And if not, how much does this matter?
I'll skirt these questions by saying this: My hunch is that the modern vegan will get meaningful benefits from improving fat intake - through the combination of reducing harmful fats, increasing omega 3s (especially by replacing omega 6 dominant oils with omega 3s) and likely added benefit from supplementing with DHA (vegan EPA can be extracted from some plant seeds but is still hard to come by right now, and our bodies likely find it easy to convert DHA to EPA...so the main issue is getting or making enough DHA).
Who should pay particular attention to omega 3's?
Those at risk for heart disease and stroke (ok that's most of us); those with depression and women during their childbearing-potential years, especially if you are pregnant or breast-feeding (omega-3s are critical for normal development of the brain).
How to get your omega 3s & improve your balance of 3 to 6:
1. have a daily source of concentrated omega 3s, e.g. 1-3 tablespoons of Flax oil. Flax meal (ground flax seeds) is also an excellent choice because you get the other benefits of the seed, but obviously you need to eat more to get the same amount of omega-3s in the oil. NOTE: whole flax seeds will pass straight through you so are not a viable source (watch out for this in products that claim to have omega-3s from flax).
2. for cooking and baking - switch from generic vegetable oils to canola or extra-virgin olive oil. Do not use shortening or margarine at all. Experiment with flax meal+water as an egg replacer in baking. Pay close attention to the ingredients in those vegan baked goods we love so much.
3. for spreads - again throw out the typical margarine. Use an oil like olive, canola or flax. Or look for specialty margarine-like spreads that boast omega 3s, or at least no hydrogenated, partially hydrogenated oils or palm kernal oils (and thus don't have trans fat or excess saturated fat).
4. Consider a daily source of vegan DHA. These are typically made from algae (precisely where the fishees get theirs) and come in supplement form (e.g. Omega Zen, Health from the Sea and Neuromins (if you don't mind gelatin)) and are now being added to some soymilks (e.g. Silk special formula).
5. Read your labels. Most of us eat an extraordinary amount of packaged and processed foods - try to minimize the junk - stuff with refined grains, hefty sugar helpings and bad oils...
6. Look for fun foods - e.g. refrigerated dark chocolate truffles made with omega-3 rich oil.
7. Focus on the minor sources too. There are plenty of vegan foods that have small amounts of omega-3 (like leafy greens) and or decent amounts but we don't eat them often (like walnuts, hemp and pumpkin seeds). Of course, there are lots of other good reasons to eat these foods too. A recent study on walnuts suggest that daily intake of ~2 ounces offers the same cardiovascular protection as fish.
8. Keep your eye open for more plant based EPA and DHA. These compounds are being discovered in a decent handful of plants (often in the seeds of plants we don't commonly eat) and are sure to make their way to us in functional foods or supplements in the near future...
