Of all the food we eat daily, oils are probably the least understood, least appreciated, and most often wrongly handled in our cooking practices.
Essential Fatty Acids
Every cell in the body depends on a daily intake of “Essential Fatty Acids”, or EFAs for short, which are abundantly supplied by good quality oils and in most vegetable source foods.
Our muscles, glands, nervous, enzyme, and immune systems, brain, heart, lungs, and skin all need Essential Fatty Acids.
Muscle tissues, for example, need EFAs to recover from the fatigue of use. EFAs help in the transport of oxygen from the lung tissue to the bloodstream and thus to every other cell in the body.
There are only two types of oils/fats essential for health from which our bodies then manufacture all the required EFAs and polyunsaturates it needs. Food chemists call these two oil groups Omega 6 and Omega 3 oils.
Omega 6 oils are most commonly found as vegetable seed oils:
- grapeseed oil
- evening primrose oil
- borage oil
- blackcurrant seed oil
- flax/linseed oil
- rapeseed or canola oil
- hemp oil
- soybean oil
- cottonseed oil
- sunflower seed oil
- corn oil
- safflower oil
- pumpkin seeds
Omega 3 oils occur in:
- linseed (flax)
- pumpkin kernels
- chia seed
- black raspberry
- dark green leafy vegetables
Linseed or flax oil stands out as the best food source of both the Omega 6 and Omega 3 type EFAs. Modern cooks, unfortunately, overlook this highly nutritious oil because good quality, carefully processed, and non-rancid linseed oil, while available commercially, is more expensive than cheaper all-purpose oils such as safflower or sunflower.
The average daily intake for Omega 6 oils is 9 – 30 grams or the equivalent of 2 – 6 tablespoons (if there is no other fat source in the diet). We require less of the Omega 3 type oils, only about 4 – 15 grams or the equivalent of one tablespoon of oil per day.
It is not recommended to exceed a total of 30 grams of fat/oils from all food sources taken daily and if one is on a weight reduction program, then no more than 15 – 20 grams of fat/oil is advised. Men, however, may require up to three times as much EFAs from dietary oils than women owing to greater muscle mass and activity. Obese people require more EFAs than the average but most observe the 15 – 20 grams fat/oil limit.
Not all the fats/oils we use in cooking or eat daily in our foods are of the Omega 6 or Omega 3 essential category. Butter does not fall into these categories and neither does margarine, lard, suet, or coconut oil.
When selecting which vegetable oil to use, it is important to understand what processing that oil has undergone before deciding what to buy. Most fully refined commercial vegetable oils are extracted by high temperature pressing at between 240 – 270 degrees Celsius.
The oils are further extracted by chemical solvents, then degummed, deodorized and bleached. These processes result in a cheaper product (by virtue of the fact that every available gram of oil is bleached out of the seed oil source by the chemical additives), but the end product is also inferior nutritionally and possibly retains undesirable chemical residues.
Vital nutrients such as lecithin, calcium, magnesium, and iron are removed when refined oils are degummed – the process which makes the oil free-flowing and “watery”. Artificial antioxidants such as BHT and BHA are also used to add extended shelf life to cheap oils.
Preferable to these highly refined oils are the so-called “cold-pressed” extracted oils which are extracted at temperatures below 40 degrees Celsius. Less heat generated during the cold-press extraction process means less degrading of the oil’s natural nutrients. Chemical solvents are not used so the particular oil’s characteristic delicate flavor, color, and aroma are not changed.
“Cold-Pressed” oils must be kept refrigerated after opening. You can squeeze a 100 IU capsule of natural Vitamin E into every 500ml new bottle of oil. The added Vitamin E is a natural antioxidant and helps protect the oil from rancidity. Most good quality cold-pressed oils retain their own natural vitamin E too.
Saturated vs. Unsaturated
We often hear the terms “saturated”, “unsaturated” and even “polyunsaturated” when oils or fats are discussed.
“Saturation” is the chemical term that describes the percentage of carbon atoms that are fully bonded with hydrogen atoms in the fat/oil molecule. These “bonds” hold the molecules together. Saturation makes the bonds more rigid and hence the oil or fat is resistant to melting at low temperatures. So, “saturated” fats are solid at room temperature. Think of butter or lard which are solid at room temperature, for example.
When an oil is described as polyunsaturated, this should mean that the oil is unprocessed by hydrogenation so there are few rigid bonds in the product’s molecular makeup, the oil is therefore liquid at room temperature and will stay liquid even in the refrigerator.
Vegetable oils naturally contain both unsaturated and saturated molecules. It is the percentage of the polyunsaturated to the saturated components that determine whether the oil can claim to be “highly polyunsaturated” or “partly unsaturated” or ‘saturated”.