Monday, April 7, 2014

Nutrition Series: In Defence of Fat

Fat is about all
Rabbits have goin' for 'em.
So, as it happens, I forgot to mention that fats were even a part of nutrition, falling into a sort of mental trap my generation has essentially been drip fed - namely, that fat is unhealthy, full-stop.

For the sake of full disclosure I should amend my usual reminder I'm not a medical professional with another reminder that I work in the culinary field, and that my present employer demonstrates particular lack of concern for the fat components of their meals.

With that in mind though, I'm going to articulate what I can about the realities of fats in human nutrition without overall bias, and I'm going to begin by discussing the types of fat.

In chemical terms (and remembering that humans are complicated chemical factories for turning chemicals into other chemicals (primarily those needed to construct other little humans) fats are triglycerides. While the actual chemistry gets pretty complicated, you can basically group fats into three varieties: saturdated, unsaturated, and transfats.

Saturated Fats are, by definition, those fats in which the fatty acid chains making up the overall fat molecule are sufficiently charged with hyrdogen, that is to say they are saturated with respect to hydrogen content. They differentiate from Unsaturated fats in this way (monounsaturated fats have one chain lacking in hydrogen, polyunsaturated have a plural of chains). This changes the melting point of the fats as well as the energy released by their combustion (and though no fire is involved, the metabolism of substances into energy for the body is analogous to a combustion reaction). The differentiation in melting point provides some way to understand the difference between saturated and unsaturated fats at a glance - saturated fats are more likely, in general, to be solid at room temperature, while other fats tend to be oils.

Transfats are fats in which the molecular structure has been somewhat rearranged in a rather complicated-to-explain way, and since my audience isn't a group of organic chemists and I understand it only on the very surface level, I'm not going to try. What is important to remember is that the research currently supports a link between transfat consumption and coronary heart disease. Hydrogenation is one of a few chemical processes that converts cis-fats to trans-fats, and so I usually recommend avoiding hydrogenated products and therefore usually avoid consuming solid margarine - liquid margarine is a bit of a different animal.

Now, fat serves a few roles in the body. It's one of the two components of the production of cholesterol (the other being protein), and no discussion of fat would be complete without mentioning this first-cousin. Cholesterol comes in two main varieties: HDL and LDL (that is, high and low density). Cholesterol is both consumed in some foods (chiefly cheese, eggs, and meats), and synthesized in the body using fat and protein. Cholesterol regulates the permeability and consistency of animal cells, including yours, so there's a good reason to keep it in the system. It's also a precursor for a bunch of other chemicals that keep the manmachine running. Also generalizing, you prefer your body to contain more HDL than LDL. By maintaining the same chalorie intake, you can:

  • replace dietary carbohydrates with unsaturated fats to lower the LDL and overall cholesterol levels (increasing HDL);
  • replace the same with saturated fats raise all levels across the board;
  • replace the same with trans fats to raise LDL and reduce HDL.
Having LDL in excess of LDL increases the risk of cardiovascular disease.

Stewed Beef Heart
In addition, quite a few vitamins (A, D, E, and K) can only be digested, absorbed, and transported in conjunction with fats. Essential Fatty Acids are (obviously) components of Fats which I'll discuss in a moment. Fat insulates body organs against physical shock and is a component of every cell of your body in the phospholipid bi-layer shell that contains them. There is, in fact, an immune response for storing chemical and biological threats in fatty tissue until they can be excreted by other means. For these reason, a fat-free diet is just as dangerous as fat overconsumption.

Going back to the Fatty Acids: there are two essential fatty acids, which we call Omega-3 and Omega-6. These are considered essential in humans because we lack the proper enzymes (desaturase) to produce them ourselves. Both these acids are found in fish and shellfish, flaxseed, hemp seed, soya oil, canola ouil, and quite a few seeds. Some egg products make claims to elevated Omega-3 or Omega-6 acids as well. Your body uses these for all manner of things, and some research which I find particularly interesting has suggested that a high intake of Omega-3 can decrease clinical depression symptoms in humans. The work on the matter was published in the Australia and New Zealand Journal of Psychiatry and was conducted by Reed et al. (Use PMID 15777365).

So, how much fat is enough? I have been taught (and usually use) the measure of 32.5 grams per 1000 calories of intake and the assumption that no more than 10 of those grams should be saturated. Since this is all about optimizing nutrition for optimizing bodily performance, I reiterate my general dislike for trans fats in general and therefore advise you to avoid them.

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