Difference between revisions of "Oil"

Latest revision as of 21:07, 30 May 2021

Oils and health factors to consider

Oils are widely used in cooking, ranging from being simple condiments to being the key ingredient to cooking something a certain way.

However, oils present three major downsides, that vary in severity according to the type of oil, amount used, and cooking way:

Empty calories

Oils have a very poor nutrient profile, consisting mainly of some vitamin E and some essential fatty acids.
Similarly to sugar and white rice, they do not provide anything really useful, and while they do provide very little of a few things, they would be much better off replaced with other--more nutritious--foods.

This is especially true when considering that oils are very high in calories, and that it is easy to use lots of them without realizing because of the ways they are used. For example, when mixing oils in a sauce or to stir fry some vegetables and coating them, you can easily use more than you realize by dropping a little extra oil, and going from 1 tbsp to 2 tbsp can be as simple as inclining the bottle of oil a bit too much or not seeing the quantity of oil precisely due to reflection of light on the pan.
However small of an error this may seem, 1 extra tbsp of olive oil would already present an extra 119 kcal, which is a considerable amount--that is 119 kcal that would give you pretty much nothing, and make you less hungry for nutritious food (therefore, miss more nutrition and be more unlikely to get optimal levels of the nutrients you need), and/or add extra weight to you.

This is not always a concern, as using oil sparsely and in controlled quantities would have a pretty much negligible effect--still net negative to do, but the conveniency of using oil would likely outweigh the damage after a certain point.

It is important to note that oil ends up not being an 'empty calories'-related problem if it actually allows you to eat healthy foods you would otherwise be unwilling to eat. That is, the calories of the healthy food + the oil used to cook it would still be far better than eating some unhealthy food instead.
For example, it would be far better to eat some sautéed broccoli than to eat some white bread instead. Of course, eating steamed broccoli would be even better, but if by sautéing the broccoli you would eat considerably more of them or you would need to sauté the broccoli in order to tolerate eating them (making them more tasty and palatable), then eating sautéed broccoli is better than eating considerably less steamed broccoli or not eating broccoli at all.

High saturated fat content and other fats

High amounts of saturated fats lead to cardiovascular disease by increasing the amount of cholesterol the body produces.
Saturated fats raise LDL cholesterol [1], and LDL cholesterol causes cardiovascular disease (CVD). [2]

Saturated fat in oil is a problem because of the often-high quantity of it. However, oils are very different from each other when it comes to fat profile, and some oils are much better/worse than others.

There are three types of fat:

• Saturated fat
• Monounsaturated fat
• Polyunsaturated fat (which represent the essential fatty acids)

Polyunsaturated fat then can be categorized into another two types:

• Omega3
• Omega6

Both of these have requirements that need to be met daily (RDAs).

When it comes to fat profile, there are essential fatty acids to take into consideration (omega3, omega6), and some oils are quite rich in those--which helps towards getting enough essential fatty acids throughout the day. EFAs (essential fatty acids) become a negative when frying or heating the oil to high temperature, because of instability and oxidization (more explained below).
Polyunsaturated fats also show to have beneficial/protective effects towards CVD, with studies ranging from showing them to be significantly protective, to studies showing them to be somewhat beneficial.

"There is substantial evidence that PUFAs induce significant beneficial cardiovascular effects. One of the interesting aspects concerning this beneficial action is that it is not achieved through one mechanism of action, but appears to be achieved via different effects on the heart, vasculature and blood. This makes PUFAs even more important as a therapeutic modality." [3]

"Increasing polyunsaturated fatty acid (PUFA) intake probably makes little or no difference (neither benefit nor harm) to all‐cause mortality and probably slightly reduces the risk of coronary heart disease events and cardiovascular disease events (all moderate‐quality evidence). Increased PUFA intake may slightly reduce risk of coronary heart disease mortality and stroke (although for stroke the confidence intervals include important harm), but may have little or no effect on cardiovascular disease mortality (all low‐quality evidence). Increasing PUFA does reduce total cholesterol, probably reduces triglyceride, probably has little or no effect on high‐density lipoprotein (HDL) or low‐density lipoprotein (LDL) and probably increases body weight. This suggests that increasing PUFA intake may have beneficial effects on risk of cardiovascular disease events, coronary heart disease mortality, coronary heart disease events and stroke. The mechanism may be via reduction of total cholesterol and triglyceride. However increasing PUFA will probably lead to slight body weight increase." [4][5]

There is also monounsaturated fat, which is empty calories like saturated fats, are less stable then saturated fats at high temperature but more stable than polyunsaturated fats (EFAs), and do not represent the risk of saturated fat in regards to health. On top of that, monounsaturated fat has been shown to have better to significantly lower risk of CHD (coronary heart disease) when replacing saturated fat or trans fats--which may not necessarily mean a protective effect, but a neutral effect (of the monounsaturated fat) having the replacement of a bad effect (of the saturated/trans fats).

"In conclusion, we found largely different correlations of MUFAs (monounsaturated fats) from plant sources and animal sources with PUFAs and SFAs. Significantly lower CHD risk was observed when SFAs, trans fats, or refined carbohydrates were replaced by MUFA-Ps but not MUFA-As. Our findings support a beneficial role of MUFAs in long-term CHD prevention, when plant-based foods such as vegetable oils, nuts, and related products are the primary sources." [6]

"Apart from the fact that several meta-analyses and meta-regressions observed benefits of MUFA on cardiovascular risk factors, it should be noted that most meta-analyses did not report significant negative effects of a MUFA-rich diet on CVD risk factors." [7]

Here below you can see the amount of fats for most common oils per 1 tbsp.

Trans fats with high heat

With high heat, unsaturated fats (which would be otherwise good) can be degraded by oxidization and some can become trans fats [8].

Trans fats are the most unhealthy fats, posing a multitude of risks: increasing cancer risk, causing brain damage, and particularly raising LDL cholesterol and lowering HDL cholesterol, which significantly increases cardiovascular disease risk. [9] [10] [11] [12]

When considering which oil should be used and in which way, trans fats should be the main priority of avoidance, as saturated fats would definitely be the lesser evil between the two.

Stability of different types of fat differs when it comes to their likelihood to degrade into trans fats:

• Saturated fat is the most stable (and therefore the one least likely to degrade into trans fats)
• Monounsaturated fat is less stable than saturated fat but still quite stable, and does not present the CVD risk of saturated fat
• Polyunsaturated fats (EFAs) are the least stable and most susceptible to oxidization, and even though they represent the healthiest fats in normal conditions, they are the ones most likely to become trans fats when exposed to high heat

Best oils for high temperatures (baking/frying)

Using the table above and the information we know about which types of fat present the most risk when exposed to high temperature, we can determine which oils are best (or least bad) for different scenarios.

High heat (deep frying)

When it comes to high temperatures, as explained above, we know that:

• Saturated fat is the most stable to not degrade into trans fats, but pose CVD risk
• Monounsaturated fat is less stable than saturated fats but still stable overall, without the CVD risk
• Polyunsaturated fat (EFAs) are unstable and the ones most likely to become trans fats (trans fats -> worse than saturated fat)

Therefore, when it comes to deep frying and high heat, we can conclude that monounsaturated fat is preferable to saturated fat, which is preferable to polyunsaturated fats (monounsaturated > saturated > polyunsaturated). This is because:
1- the temperature is not (and should not) be high enough for the monounsaturated fat, which is quite stable, to degrade into trans fats
2- saturated fat is stable and would remain the same (similar to the monounsaturated fat), but pose CVD risk, thus being less preferable than monounsaturated
3- polyunsaturated fats (EFAs) are unstable, and would pose a risk of becoming trans fats (which are significantly worse than saturated fat in healthfulness), thus being less preferable than saturated fat

By sorting the table by putting a positive value for monosaturated fat (unlikely to turn into trans fats and no CVD risk), a somewhat positive value for saturated fat (very unlikely to turn into trans fats but CVD risk), and a negative value for polyunsaturated fats (vulnerable to turn into trans fats, which pose the highest risk by far), we can see which oils are best for deep frying, and which ones are the worst.

The equation used to arrive at the 'Final value of safety for high heat cooking' = (saturated fat / 2) + (monounsaturated fat) + (- polyunsaturated fats)
DISCLAIMER: this equation does not give a precise result on how less/more healthy a oil is to use when deep frying, but it is useful to get a good enough idea of it.

On top of these values, it should be taken into consideration that extra-virgin olive oil is known to have protective antioxidative polyphenols (that prevent it further from oxidizing and turning into trans fats)--this together with the high level of monounsaturated fat (and low polyunsaturated fat), makes it not surprising that studies show olive oils to be resistant to frying conditions. [13]

Extra-virgin olive oil and high oleic sunflower oil are the clear winners, followed by avocado oil, cocoa butter, palm oils (which should although be avoided for their problematic impact on the environment), coconut oil, and canola oil.

Low/medium heat (baking, sautéing/stir frying)

Sautéing/stir frying is usually (and better) done quickly and with not-very-high temperatures (so as to avoid as many trans fats as possible, while still being able to fry things).

The more the temperature is high when baking and stir frying, and the more the length of the cooking is prolonged, the more the situation gets similar to deep frying (and the more the table above applies here too).
However, since baking and stir frying is usually done with low or medium temperatures (and not necessarily very high ones such as with deep frying), there is a nuance that needs to be made: while polyunsaturated fats are unstable at high temperatures, cooking them at low heat and for short periods of time likely does not produce a more-than-negligible quantity of trans fats. This is because of two factors:

1- the temperature might be too low to have a significant effect, as high heat is necessary for oxidization
2- polyunsaturated fats have protective polyphenols that help prevent the fats from degradation into trans fats, and at low heat the polyphenols probably have a significant enough effect to prevent the majority of the degradation (depending on the oil and amount of polyphenols), since the oxidization would not be as strong

Considering this, there are two possible scenarios:

• one where the temperature is high enough, and the cooking long enough, that polyunsaturated fats become a negative (trans fats formed from polyunsaturated fats > polyunsaturated fats helping in meeting RDAs and lowering CVD risk)
• one where the temperature is low enough, and the cooking short enough, that polyunsaturated fats remain a positive (trans fats formed from polyunsaturated fats < polyunsaturated fats helping in meeting RDAs and lowering CVD risk)

So if you want to get the best--or least bad--out of frying, by lowering CVD risk as much as possible (polyunsaturated fats help in lowering CVD risk), and/or you are struggling to meet RDAs of omega3 and omega6, using polyunsaturated-rich oils while sautéing/stir frying low heat and for a short amount of time might be best (using the table written in the section below).

However, if you want to be safe, and you are already meeting RDAs of omega3 and omega6, you can apply the table written above for high heat for lower heat too, and not worry too much about making sure the temperature stays low and the cooking is done fast.

Best oils for condiments (salads/topping)

Unlike with methods where high heat is required for cooking, when it comes to condiments and toppings the main things to look out for in oils are different.
The worry shifts away from trans fats (as trans fats are a worry when it comes to high heat), and the main problem of avoidance becomes empty calories and saturated fats.

Empty calories because, as explained at the beginning of this article, are 'useless' calories, or at least calories that could be much better spent--thus eating them would prove a waste of 'caloric space' those empty calories are consumed in, whereas you could spend those calories to eat something better instead, or an extra caloric amount that would increase gain weight.

However, saturated fat does a step further from just being empty calories, as high amounts of it present a CVD risk (as explained above).

So, saturated fat is not only empty calories, but also an increased risk of CVD. Monounsaturated fat is mainly just empty calories instead, providing no RDA, and likely having no effect on CVD by itself, showing a positive effect when replacing saturated fat and trans fats (eliminating the bad with something likely neutral).
Polyunsaturated fats, instead, do provide nutrients as they are essential fatty acids--it is optimal to meet both omega3 and omega6's RDAs daily, and on top of that they have a protective/beneficial effect on CVD (as explained above).

Therefore, when it comes to using oils without heat (and thus without worrying about trans fats), in occasions such as a condiment/topping for a salad, mixing it with a sauce once the heat has been turned off, or making hummus and needed an oil filling to make it smooth, it can be concluded that the priority for what to look for in oils would be: polyunsaturated fats > monounsaturated fat > saturated fat.

By sorting the table by putting a positive value for polyunsaturated fat (provide RDAs and lowered CVD risk), a negative value for monounsaturated fat (empty calories), and an even more negative value for saturated fat (empty calories and increased CVD risk), we can see which oils are best for non-heat uses, and which ones are the worst.

The equation used to arrive at the 'Final value of usefulness for non-heat uses' = (-2 * saturated fat) + (- monounsaturated fat) + (polyunsaturated fats)
DISCLAIMER: this equation does not give a precise result on how less/more healthy a oil is to use for non-heat uses (condiments/toppings), but it is useful to get a good enough idea of it.

Flaxseed and grapeseed oil are the winners, followed by sunflower oil, and walnut oil.