Understanding Dietary Fats
Contrary to what you may think, dietary fat not only does not make you fat, it is an essential component of our diet and needed for optimal health. Fat has many roles including:
- Enables us to absorb fat soluble vitamins and minerals, such as vitamins, A, D, E and K
- Is a hormone precursor and regulator.
- Enables us to regulate enzymes.
- Necessary for emulsifying functions.
- Provides necessary padding and insulation for our organs.
- Are an important energy source.
- Our brains are mostly composed of fats.
- Are the building blocks for cell membranes.
- Fat slows down the rate at which food is absorbed, making us feel full faster and able to go longer without feeling hungry.
Not all fats are the same, you will probably be familiar with the term saturated fat, associated with animal fats, as people have been warned for a long time to avoid this fat, as well as unsaturated fats. There has in more recent years on the fat debate been a common classification of fats as either ‘good’ or ‘bad.’
While this is a broad subject I will attempt to summarize the difference between the different kinds of fats, and where we are on the debate of good and bad fats. This issue until today is unfortunately considered to be controversial as to what fats are good for you, in what quantities and how they are prepared.
Polyunsaturated Fats and Free Radical Damage
These are unsaturated fats, which are generally considered to be healthy, good fats. These are found mostly in oils. They are called polyunsaturated fats because the fatty acids contain double bonds, which unite them to their carbon atoms, polyunsaturated fats contain multiple double bonds between their carbon atoms. This makes polyunsaturated fats the least stable forms of fats as the more double bonds a fatty acid has the higher the chances there are they will break and auto-oxidize. The problem occurs when these fats are attacked by oxygen, creating ‘free radicals’, which is why consuming high quantities of anti-oxidants in our diet, is advisable.
This problem of increased risk of free radical damage with high consumption of polyunsaturated fats is not so with monounsaturated fatty acids, which contain one double bond and saturated fatty acids, which contain no double bonds and are therefore stronger and more stable.
So while unsaturated fats are paraded as being the good fats that we should consume more of, polyunsaturated fats are in fact the most toxic kinds of fats due to their ability to auto-oxidize and saturated fats the most healthy for being resistant to self-oxidation.
All fats, whether from animal or plant sources, are a mixture of both saturated and unsaturated fatty acids, the degree to which a fat is either saturated or unsaturated determines its melting point, its ability to go rancid and its chemical stability and likelihood of self oxidizing.
In our bodies, the presence of saturated fatty acids, prevent and protect the polyunsaturated fats from self-oxidizing. But for those of us who live according to the current guidelines of avoiding saturated fats and eating high amounts of polyunsaturated fats are at great risk of creating free radical damage.
As mentioned earlier, there is an assumption that foods containing fat are either one kind of fat or another, but fatty foods are in fact made up of more than one type of fat. It is even possible that that same food, for example oils to contain different amounts of each kind of fatty acid, depending on the temperature at which the plants are grown. In climates such as the Mediterranean, monounsaturated oils are found, in the tropics, saturated oils are found in oils such as coconut oil and polyunsaturated oils in cooler climates.
The same is the case with animals, the ratio of saturated to unsaturated fats from warm blooded to cold blooded animals as well as the temperature of their environment will determine the degree of saturation, cold water fish for example will produce higher amounts of polyunsaturated fatty acids compared to warm blooded animals which contain a mixture of saturated and unsaturated fats.
Our classification of a food being a certain kind of fat is based on the highest percentage of what that fat is made up of. Below is a breakdown of fats and oils and the saturated to unsaturated fat ratios.
| Fat or Oil | Saturated % | Monounsaturated % | Polyunsaturated % |
| CoconutPalm KernelButter
Human Milk Lamb Beef Pork Human (Body fat) Hen’s Egg Chicken Cod Margarine Soy oil Olive oil Corn oil Sunflower oil Safflower oil Canola Oil |
91
83
60
54
53
45
43
40
39
35
26
24
18
17
13
5-16
9
6
|
6
16
34
39
41
51
48
57
47
48
16
21
24
74
24
14-40
12
67
|
3
1
6
8
5
5
8
3
14
16
59
55
58
9
60
48-74
75
27
|
The animal products we eat today have changing ratios to what they contained on their natural diets, in large part due to modern farming and their not being fed their natural diet. So for example, if cattle are fed grains and soy as opposed to being grass fed, this is creating a change in the ratio of their fat making up their fat tissue. With grass fed beef you would find a more balanced Omega 3-Omega 6 ratio, as well as Conjugated Linoleic acid (CLA), but on grain fed beef as is the custom with modern intensive farming methods would reduce the content of Omega 3 and CLA and increase the Omega 6 content.
With regard to oils, the extraction of oil in itself must be cold pressed oil, such as olive oil. Polyunsaturated fats found in vegetable oils cannot handle the heat pressure, degumming, neutralization, bleaching and processing involved in their extraction and alters the fatty acid profile. This damages the fatty acids and creates toxic Lipid Hydro peroxides.
Trans-Fatty Acids
When the recommendations on dietary fat, pushed for people to avoid saturated fats, things we previously used mostly saturated fats for were replaced with polyunsaturated fats or even trans fats, such as margarine or vegetable oils for frying and cooking.
Margarine we believed was healthier than butter, but later we discovered that margarine was a terrible, unnatural alternative to butter capable of causing harm to our health. Foods used to be fried using saturated fats, such as butter or animal fat. Even McDonalds used to use animal fat to fry their food before pressure forced them to change to polyunsaturated vegetable oils.
The problem with frying using mostly polyunsaturated fats, is that as explained above is that they cannot withstand the hydrogenating process, when this occurs the double bond(s) change from bent to straight, this conversion process is not complete as some of those unsaturated fatty acids do not hydrogenate and instead are converted to trans-fatty acids, these fats inflame the arteries and accelerate disease.
You will probably be aware by now of health warnings of the dangers of hydrogenated oils, yet this process occurs at some point in almost all processed foods produced, including confectionary and sweets, ready meals, cooking oil, not only in things that have been put into the deep fat fryer.
In fact it is highly likely that you may use one of these oils in your own home when you cook eggs for example, or sprinkle it onto pans before you put food in the oven. If those oils in the first place have been extracted through heat and not cold pressed like olive oil, then this can be even more harmful if then reheated or used for cooking. Polyunsaturated oils that have been cold-pressed can be healthy if used for example on top of a salad, but should not be used for cooking or heated.
It is important to look at oils carefully, there are many flavoured oils too, where they may be fused with Garlic or Chilli for example, these may well have been subject to heat in their production, as opposed to having been left for a period of time for the flavour to mesh in at a normal temperature.
A final point to make on oils is that they should be kept in dark, glass bottles, in a dark, cool place to avoid rancidity.
So what should I cook with?
Fats that are predominantly saturated, monounsaturated or both, such as butter, lard or palm or coconut oil. This should all coincide with lowering carbohydrate intake.
Interesterified Fat
Now that you have been made aware of hydrogenated fats and how to avoid them, food companies are too aware that more of us are learning of the dangers of trans-fats and sugars and are finding new ways to create our food, which we are now in fact discovering to be even worse.
Interesterified fat is a new kind of fat that has been developed by the food industry, this is when a fat has been hydrogenated and then molecularly rearranged in order to harden the fat. Research conducted in 2007 published in Nutrition and Metabolism suggests that these fats, used to replace trans fats, may be more harmful. The study compared diets containing saturated palm oil with partially hydrogenated soybean oil and interesterified soybean oil.
HDL (good cholesterol levels) dropped amongst participants in the interesterified fat group as well as a rise in blood glucose levels up by 20% due to the fats suppression of insulin production, whilst levels were relatively constant in the other two groups.
Conclusion
The consensus is that Trans and Saturated fats are bad and that polyunsaturated and monounsaturated fats are good.
However there is compelling evidence to suggest that saturated fat, including animal fats are not to blame for heart disease, obesity or atherosclerosis and a number of studies have shown that when saturated fat is increased and carbohydrate intake decreased that HDL cholesterol goes up, and blood glucose and triglyceride levels go down, lowering your risk of heart disease.
We have evolved on a diet high in saturated fat and it is only in the past century that we have begun to see increases in the rate of heart disease, it is also only in the past century that our carbohydrate intake has increased as well as the introduction of processed foods, artificial sweeteners and hydrogenated oils as well as other non dietary factors contributing to our weight gain and heart disease.
In many cases, we believe we are buying ‘healthy’ polyunsaturated fats but are in fact buying and using trans fats due to the heating involved in the oils processing as opposed to cold pressed oils such as olive oil.
Some polyunsaturated fats have shown to be healthy in numerous studies, particularly CLA found in many meat products, and Omega 3s when in a correct ratio with Omega 6. Even a diet high in these beneficial polyunsaturated fatty acids must be consumed with a diet that has an adequate saturated fat and high anti-oxidant intake to protect them from their vulnerability to self oxidize and free radical damage, which will be less likely to occur provided that factors creating free radical damage be reduced, such as overtraining, alcohol, oxidative stress or a poor diet.
Fats are not the enemy, apart from Trans fats and I’m sure in a few years to come we will all hear a lot more about Interesterified fats. These are in fact not natural fats, and should be avoided, much like refined sugars and processed carbohydrates, but saturated, monounsaturated, polyunsaturated fats do have health benefits, but polyunsaturated fats can be potentially harmful when its intake increased and saturated fat decreased.
Fats will make you thin. If you look at most of the fat loss supplements that are marketed today to those looking to trim down, these will contain the Omega 3 fatty acids, DHA/EPA or ALA, or Conjugated Linoleic Acid. These are all fatty acids, which are found naturally in high quality fatty cuts of meat. But since we have been told to avoid animal fats, lots of people will not eat the fat on their meat and will eat only the lean parts, but by no surprise it is in the fats of these meats that will contain these fatty acids which are not as present in our diets, due to eating more poor quality meats and fish with a poor, less balanced fat profile than found in wild meats and most organic meat.
References:
Volek JS, et al Modiication of lipoproteins by very low carbohydrate diets. J Nutr 2005; 135: 1339-1342.
German JB, Dillard CJ. Saturated fats: what dietary intake? Am J Clin Nutr 2004; 80: 550-559.
Ravnskov U. The questionable role of saturated and polyunsaturated fatty acids in cardiovascular disease. J Clin Epidemiol 1998;51:443-460
Grundy SM. Influence of stearic acid on cholesterol metabolism relative to other long chain fatty acids. Am J Clin Nutr 1994; 60: 986S-990S.
Sundram K, et al. Stearic acid-rich interesterified fat and
trans-rich fat raise the LDL/HDL ratio and plasma glucose relative to
palm olein in humans. Nutr Metab 2007; 4:3.
Berglund L, et al. HDL-subpopulation patters in response to
reductions in dietary total and saturated fat intakes in healthy
subjects. Am J Cl Nutr 1999;70:992-1000.
Hays JH, et al. Effect of a high saturated fat and no starch diet on
serum lipid subfractions in patients with documented atherosclerotic
cardiovascular disease. Mayo Clin Proc 2003;78: 1331-1336.
Seshadri P, et al. A randomised study comparing the effects of a
low-carbohydrate diet and a conventional diet on lipoprotein
subfractions and C-reactive protein levels in patients with severe
obesity. Am J Med 2004; 117:398-405
Wolf RB. Effect of temperature on soybean seed constituents. J Am Oil Chem Soc 1982; 59: 230-232.
Wolfe R. Chemistry of nutrients and world food. Univ of Oregon Chem. October 16, 1986; 121.
Paul AA, Southgate DAT. McCance & Widdowson’s The Composition of
Foods. Fourth revised extended edition of MRC Special Report, No 297.
London:HMSO, 1979.
Lambelet P, et al. Formation of modified fatty acids and
oxyphytosterols during refining of low erucic acid rapeseed oil. J Agric
Food Chem 2003;51: 4284-4290.
Mozaffrian D, et al. Trans fatty acids and cardiovascular disease. N Engl J Med 2006; 354: 1601-1613.
Exercise, Oxidative Damage and Effects of Antioxidant Manipulation (review). Journal of Nutrition 122(3 suppl): 766-73, 1992 Mar.
Groves, B (2008) Trick and Treat, how ‘healthy’ eating is making us ill, Hammersmith Press: United Kingdom
Taubes, G (2010) Why We Get Fat, And What To Do About It, Anchor Books: United States: New York
Harcombe, Z (2010) The Obesity Epidemic, What Caused It? How Can We Stop It? Columbus Publishing: United Kingdom
Enig, M (2000) Know Your Fats, The complete primer for understanding the nutrition of Fats, Oils And Cholesterol, Bethesda Press: USA
Erasmus, U (1993) Fats that Heal, Fats that Kill, Alive books: Vancouver
by
TRAIN WITH WAYNE
No comments:
Post a Comment