The Ecology of Humans (59-3) Dietary Fats


The amount of fat isn’t as important as the relative amounts, or ratio, of specific fats in the diet. ~ American biochemist and nutritionist Bruce Watkins

An essential fatty acid is a fatty acid that an animal needs to obtain from the diet. A fatty acid is either saturated or unsaturated.

A saturated fat is a fat molecule with only single bonds between carbon atoms. The carbon chain that forms the backbone of the fat is fully “saturated” with hydrogen atoms.

Saturated fats are needed to produce hormones, stabilize cell membranes, for padding around organs, and for energy. Deficiency can negatively impact the immune system. But a surfeit of saturated fats can clog the arteries and lead to coronary heart disease.

An unsaturated fat has 1 or more double bonds between carbon atoms. A double or triple bond in a fatty acid causes a dimensional kink in the carbon chain which affects the molecular structure in a meaningful way.

Unsaturated fats tend to be liquid at room temperature rather than solid, as the kinks prevent molecules from closely packing together. These fats are termed oils, which are found in plants and fish.

A fat molecule with only 1 double bond is monounsaturated. Molecules of fat with more than 1 double bond are polyunsaturated.

Double bonds in unsaturated fats prevent atomic rotation. This locks the molecule into a specific structure.

There are 2 significant unsaturated fat structures: cis and trans, depending upon how hydrogen atoms are bound to carbon atoms. Cis is Latin for “on the same side.” Trans is Latin for “on the opposite side.”

In a cis configuration, adjacent hydrogen atoms are on the same side of a carbon double bond. In a trans configuration, hydrogen atoms are on opposite sides of the double bond. A trans configuration restricts bending the carbon chain, giving a trans fat a similar structure to a saturated fat.

The human body lacks the enzymes necessary to break down the trans configuration. This allows trans fats to accumulate and clog the system: which is why trans fats are unhealthy.

All fatty foods contain a mixture of saturated and unsaturated fats. Animal fat is mostly saturated, while vegetable fats are unsaturated to varying degrees.

The terms saturated and unsaturated provide a characterization of what the predominant fat content of a food is.

Saturated fat foods include meat, dairy, chocolate, and certain oils: coconut, cottonseed, and palm. Foods high in unsaturated fats include avocado, nuts, and vegetable oils such as canola, soybean, and olive oil. Unsaturated fats provide antioxidants.

Only 2 fatty acids are known to be essential: α-linoleic (alpha-linoleic, ALA), and linoleic (LA). ALA is a ω-3 (omega-3) fatty acid. LA is a ω-6 (omega-6) fatty acid. Both are polyunsaturated.

When ALA and LA were discovered in 1923 they were designated vitamin F. In 1929, research on rats showed that they were fats.

ω-3 and ω-6 interact with each other. Their bioactivity cannot be characterized independently, as the two compete for the same conversion enzymes. ω-6 inhibits the conversion of ω-3 into the desired fatty acids. Meat and dairy are out of balance, with far too much ω-6.

A healthy diet would include roughly equal ratios of these fats, but we’re way off the scale in the Western diet. ~ cytologist Farshid Guilak

Seaweed, seeds (chia, kiwifruit, flax, pumpkin, sunflower, hemp), and walnuts are all rich sources of ω-3 in proper proportion with ω-6. Leafy green vegetables, berries (especially blueberries), mangoes, and wild rice also offer appropriately balanced ω-3.

ALA is susceptible to oxidation, and so becomes rancid more quickly than many other oils. To lengthen shelf life, commercial producers partially hydrogenate oils containing α-linoleic acid. Soybean oil is exemplary.

In the US, soybeans are the largest source of edible oils. 40% of soy oil is partially hydrogenated.

ALA can oxidize at baking temperatures. Therefore, the best source of ω-3 is in natural foods not subjected to prolonged high heat.

A diet with adequate essential fatty acids enhances a sense of well-being, reducing stress and anxiety.

Fats are terribly satisfying to the palette. The common dietary problem with fat consumption comes in eating too much, especially saturated and trans fats.

Eating fatty foods creates a feedback loop that encourages bingeing by creating a surge of endocannabinoids in the gut, stimulating appetite, and so encouraging continued feeding. Endocannabinoids are modulatory lipids intertwined with appetite, pain sensation, mood, and memory. They also mediate the psychoactive effects of marijuana consumption – which explains a lot about pot.