Professor of Cardiology, AIIMS, New Delhi
With the multitude of options and even more claims and counter-claims by the cooking oil manufacturers, patients and even lay public are often at a loss as to which oil is heart-healthy and ideal one for day-to-day cooking needs. In case of doubt, who to turn to other than the treating physician in specific or the good old doctor in general. However, majority of the physicians are unable to answer this simple question. Very often they give rather unconvincing answers or at best refer the patients to a dietician, which leaves the patients pretty dissatisfied. The ambivalence of physicians in this context is rather justified because of huge amount of commercial and technical jargon in this field: MUFA / PUFA, trans-fat, smoke point, rancidity, N3:N6 ratio, so on and so forth. This opinion piece is an attempt to address some of these issues.
GENESIS OF CONTROVERSY
This whole confusion started with the change in our lifestyle and herald of new-age technology. Hydrogenation of vegetable oil to Vanaspati Ghee was a food revolution; it led to development of oil which resembled desi ghee (which was preferred oil in India since ages) but from commercial standpoint had enormous storing capacity. However, what really clinched the deal was that at the same time it was very cheap. But history concurs that widespread use of this oil coincided with a sudden epidemic of Coronary Artery Disease (CAD). By this time it was realized that oils rich in saturated fat (SFA) may be bad for health at least in context of heart disease. This led to another massive shift in cooking practice where virtually over-night consumers shifted from vanaspati ghee to oils which were low in SFA such as sunflower oil or safflower oil.
Later, researches revealed that these oils by themselves (while very low in SFA) were also not very healthy perhaps because they were unbalanced (they had a high content of polyunsaturated fats (PUFA) to exclusion of all other types as also unhealthy N3: N6 ratio. By this time it was realized that an oil rich in monounsaturated fat (MUFA) or at least balanced (SFA: PUFA: MUFA=1:1:1) may be the ideal choice. This led to another shift in cooking practice of oils used. Now Western oils supposedly high in MUFA started being used (extra-virgin Olive oil or Canola), in at least those who could afford them.
However, later it was realized that these oils had a very low smoke point (point where any oil started smoking and denaturizing as soon as the temperature was raised) and thus perhaps not suited to Indian style of cooking which involves cooking at high heat, stir and deep-frying. At high temperatures these “Western Oils” may break down / denature into toxic end-products which could be even more harmful than any other oil. Currently, there is some evidence that SFA by itself (if used in moderation) may not be all that bad, rather it is the trans-fatty acid (TFA) which is the worst culprit. Further apart from fatty acids other components of oil like anti-oxidants may be protective factors.
TACKLING THE JARGON
TYPES OF FATTY ACIDS
Saturated fat: The fatty acids in oils occur in the form of carbon chain connected to each other by either single “carbon bond” or sometimes one or more double bonds. When connected by a double bond there is a possibility to accommodate an extra hydrogen ion and thus this oil is unsaturated. On the other hand when all the double bonds are taken and only single bonds remain between carbon atoms, there is no more space to add hydrogen ions, and it is termed ‘saturated’ fat. When only one double bond is available, the fat is called mono-saturated fat (MUFA). However, when more than one double bond is available it is called polyunsaturated fat (PUFA). Saturated fats are generally solid at room temperature whereas unsaturated fats are liquid. Health-wise balanced oils (MUFA / PUFA / SFA; 1:1:1) or oils with high MUFA content are considered the best like blended oils or mustard oil, olive oil or rice bran oil. These are better than oils predominantly PUFA; sunflower oil or safflower oil which are in turn better than oils rich in SFA like desi ghee, butter, coconut oil or palm oil. However the worst oils are some unsaturated oils wherein during the process of reuse or hydrogenation, some carbon chains twist at the double bonds becoming trans fatty acid (TFA). Vanaspati ghee or any multiple reused oil is a good example of this type. The predominant FA types of some commonly oils used in Indian cooking are given in the Table.
OMEGA 6 AND OMEGA 3
Both are types of PUFA; with omega 3 fatty acids, the first double bond is located at the 3rd carbon atom (when counted from the methyl end of the chain) whereas it is at the 6th carbon atom with omega-6FA. There is some evidence that oils rich in predominantly omega-6FA may be worse off than even SFA. The Sydney heart study revealed that replacing SFA with Linoleic acid (an omega 6 FA) could increase the risk of death in patients with CAD. Sunflower oil, safflower and corn oil are also rich source of omega 6. On the other hand oils with high omega-3 FAcontent like fish oils may prevent heart attacks.
Once oil is heated, the temperature rises and after a certain point it starts emitting smoke which is known as the “Smoke Point.” Chemically, at this point first the triglycerides break down to fatty acids and glycerol, and then the glycerol further breaks down further producing fumes and unhealthy free radicals. Thus health benefit of any oil is lost once it reaches the smoke point. Indian type of cooking involves high heat especially when deep-frying and thus only those oils with high smoke point can be used for it. Virgin / extra virgin olive oil and butter with low smoke point is thus completely unsuited to Indian cooking and could even be harmful. The smoke point of some commonly oils used in Indian cooking are given in the Table.
TIPS AND TRICKS FOR INDIAN COOKING
1. Reuse of oils is extremely harmful. It involves conversion of unsaturated FA to TFA which is the most harmful fatty acid.
2. Blended oils or mixture of 2-3 oils is a good choicewith at least one oil rich in MUFA.
3. If single oil is to be chosen, oils rich in MUFA are good. Rice bran oil, Mustard oil, groundnut oil are good options
4. Hydrogenated oils or vanaspati ghee is the worst kind of oil because it is rich in TFA. Thus foods cooked in vanaspati ghee; street food, dhaba food, bhujiyas, biscuits etc should be avoided.
5. Natural (unprocessed oils) are better than processed oils.
6. Dietary cholesterol consumption is no longer a matter of great concern. Thus eating eggs is not harmful.
7. Olive oil which has a low smoke point is not ideal for Indian style of cooking which involves bhunoing (deep frying) but can be used for sprinkling on salads.
For healthy Indian type of cooking oils rich in MUFA and those with a high smoke point should be used: Rice bran oil, mustard oil or ground oil are a good option. Another smart way is to use 2-3 oils separately or blended as one. Trans fat is the major culprit and therefore reuse of oils and vanaspati ghee should be avoided at all costs.
Table Characteristics of some oils used in Indian Cooking
Oil Predominant Fatty Acid Smoke Point Range
Butter SFA <200?C
Vanaspati Ghee TFA <200?C
Extra Virgin / Virgin Olive Oil MUFA <200?C
Canola MUFA 200 - 229?C
Sunflower Oil PUFA 200 - 229?C
Ground Nut Oil MUFA 230 - 250?C
Corn Oil PUFA 230 - 250?C
Coconut Oil SFA 230 - 250?C
Palm Oil SFA 230 - 250?C
Soyabean Oil PUFA 230 - 250?C
PomaceOilve Oil MUFA 230 - 250?C
Ghee SFA >250?C
Mustard Oil MUFA >250?C
Rice Bran Oil MUFA >250?C
Safflower Oil PUFA >250?C