|Coconut and cholesterol some hard facts
Dr. U. P. de S. Waidyanatha
Excerpts of a speech made at the Seminar on "Improving the Coconut Oil Industry" of the Hotel Lanka Oberoi on 13 February, 2001
The press has recently been replete with contradictory articles and letters to the editor on the subject that the public must be thoroughly confused. And to those who suffer from excess cholesterol in their minds rather than in their blood, coconut has become synonymous with cholesterol!
The confusion is caused by loads of misinformation and ignorance - unfortunately, even among some doctors, who apparently are not updated on the subject. Rhetorical and emotional statements have also added to the confusion. What I proposed to do today is to briefly discuss five or six pieces of research published in reputed journals on the subject. A candid appraisal of such experimental evidence has been long overdue and our judgement must necessarily rest on such evidence.
An example of the anti-coconut oil campaign by the soya oil lobby!
"Warning: Foods containing imported coconut and palm oils can be hazardous to your health"
"To reduce your risk of heart disease look for foods made with pure low-in-saturated fat soyabean oil"
Some understanding of the three types of fats in our diet is useful before we discuss matters further. Table 1 gives the composition of several dietary fats and it is seen that all of them have varying proportions of the three types of fatty acids. No fat or oil is totally saturated or unsaturated. Coconut oil is called a saturated fat (SFA) as it has 92% saturated fatty acids. Corn, soya and sunflower oils are examples of polyunsaturated fats (PFA) - containing over 60% polyunsaturated fatty acids. Olive oil which is believed to give protection against heart disease is a monounsaturated fat (MFA). It is interesting to note that avocado has a fat composition closest to olive oil and hence should be heart-friendly. The WHO prescription of a healthy diet is that it should contain less than 30% total fat of which less than 10% should be SFA, 3-8% PFA and 10-12% MFA.
Broadly speaking, SFAs increase blood serum cholesterol (BSC), and PFAs decrease it and MFAs have a neutral effect or decrease BSC.
However, the effect of SFA on BSC depends on the chain length, or the number of the carbon atoms in the SFA molecule. There are many studies that have confirmed that SFAs fewer than 12 carbon atoms in the molecule have a neutral effect on BSC, and that oleic acid (MFA) decreases it. Together such fatty acids comprise 27.5% of the coconut fat. Palmitic and stearic acids (12.5% of coconut fat) are reported as not raising BSC significantly. The 14-C myrstic acid (17%) is definitely known to raise BSC. There is disagreement with regard to effect of lauric acid (12-C) on BSC, which is the most predominant fatty acid (48%) in coconut. Some researchers argue that lauric acid may either be transported from the intestine in the portal vein direct to the liver leading to metabolic degradation, or take the lymphatic route and is circulated in the blood before reaching the liver. In the latter situation it should elevate BSC.
A deficiency of coconut oil is its low essential fatty acid (EFA) content. The human body cannot synthesise EFA which should come exclusively from the diet. Our diet should contain about 3% (about 8 grams) SFA out of the total daily calorie intake. Furthermore, it is reported that cholesterol - elevating effect of SFA is countered to some degree by dietary linoleic acid which is known to increase LDL receptor activity. A wholesome diet of cereals, pulses, fish, fruit and vegetables should provide adequate levels of EFA as invisible fats. PFA such as corn, soy and sunflower oils contain high quantities of essential fatty acids (EFA), alpha-linolenic and linoleic acid, and are nutritionally beneficial when taken in moderation (3-8%). Excessive consumption of SFA is however reported to cause several maladies. SFA can also be easily oxidized (when heated) leading to the formation of free radicals which are implicated in many degenerative diseases including coronary heart disease (CHD).
Let us now examine some of the research evidence relating coconut consumption and cholesterol (BSC). In a study by Dr. Shanthi Mendis and others, reported in the Nutritional Reports International (1989, Vol. 40 (4) 773-82) with a group of young Sri Lankan adults, each subject was fed a daily diet containing 100g coconut (about 1/3 of a coconut) and 10ml of coconut oil for 6 weeks, followed by an identical diet replacing coconut and coconut oil with 10gm of cows milk powder and 10ml corn oil. Data adapted from this study are shown Table 1. Although coconut consumption has increased the total, HDL (good) and LDL (bad) cholesterols, the total cholesterol (TC) remained well within levels prescribed as safe. What is significant is that the HDL-C was 69% more compared to LDL-C which was only 32% more during the coconut phase leading to a more desirable TC to HDL-C ratio. The increase in the plasma levels of platelet 4 factors during the coconut phase that had been observed, however, is undesirable.
In a further very similar study by Dr. Shanthi Mendis and co-workers, reported in the British Journal of Nutrition: 1990 63, 547-552, in which 70% of the fat energy was either from soya or coconut, the HDL-C decreased by 15% when the PFA/SFA in the diet ration was 4:1. The authors have discussed this data as follows: "The undoubted cholesterol-lowering effect of soya-bean fat with its implied benefits must be weighed against the potentially harmful reduction of HDL-C. The mean plasma HDL-C concentrations of Sri Lankans have been found to be low compared with Caucasians.
This may be due to the low fat and high complex carbohydrate content of the diet.. Therefore, further reduction of HDL-C as a result of replacement of coconut fat with polyunsaturated (soya) fat may have undesirable effects." However, in other studies, diets with PFA to SFA ratios closer to one have been shown to have no effect on HDL-C.
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