Tuesday, December 2, 2008

Coconut Lowers LDL, VLDL and Triglycerides, Raises HDL

All coconut products seem to be beneficial for cholesterol. (Photo by yimhafiz)

There is some confusion over whether coconut products like coconut oil, coconut water and coconut flakes raise or lower cholesterol levels. The traditional wisdom is that all saturated fats raise cholesterol, and as coconut is high in saturated fat, most people expect it to raise cholesterol.

However, in recent years, this theory has been criticized as more and more studies have shown beneficial effects from saturated fats and negative effects from polyunsaturated fats. Coconut especially seems to have positive effects on cholesterol and triglyceride levels. Trinidad et al. report:

This study investigated the effect of coconut flakes on serum cholesterol levels of humans with moderately raised serum cholesterol in 21 subjects. The test foods were as follows: corn flakes as the control food, oat bran flakes as the reference food, and corn flakes with 15% and 25% dietary fiber from coconut flakes (made from coconut flour production).

Results showed a significant percent reduction in serum total and low-density lipoprotein (LDL) cholesterol (in mg/dL) for all test foods, except for corn flakes, as follows: oat bran flakes, 8.4 ± 1.4 and 8.8 ± 6.0, respectively; 15% coconut flakes, 6.9 ± 1.1 and 11.0 ± 4.0, respectively; and 25% coconut flakes, 10.8 ± 1.3 and 9.2 ± 5.4, respectively. Serum triglycerides were significantly reduced for all test foods: corn flakes, 14.5 ± 6.3%; oat bran flakes, 22.7 ± 2.9%; 15% coconut flakes, 19.3 ± 5.7%; and 25% coconut flakes, 21.8 ± 6.0%.

In conclusion, both 15% and 25% coconut flakes reduced serum total and LDL cholesterol and serum triglycerides of humans with moderately raised serum cholesterol levels. Coconut flour is a good source of both soluble and insoluble dietary fiber, and both types of fiber may have significant role in the reduction of the above lipid biomarker.

What this study shows is that oat bran flakes and coconut flakes reduced LDL and triglycerides. Coconut was the most effective in reducing LDL, while oat bran was most most effective in reducing triglycerides. Looking at the full paper, HDL levels were slightly reduced in all subjects, but the authors conclude that this change was insignificant. Corn flakes reduced triglycerides but did not have a lowering effect on LDL (in fact, there was a statistically insignificant increase).

Coconut water seems to have a similar effect, at least in rats. Sandhya & Rajamohan report:

The purpose of this study was to determine the effect of coconut water feeding in cholesterol-fed rats. Male albino rats were fed tender coconut water and mature coconut water at a dose level of 4 mL/100 g of body weight.

Cholesterol feeding caused a marked increase in total cholesterol, very low-density lipoprotein (VLDL) + low-density lipoprotein (LDL) cholesterol, and triglycerides in serum. Administration of coconut water counteracts the increase in total cholesterol, VLDL + LDL cholesterol, and triglycerides, while high-density lipoprotein cholesterol was higher. Lipid levels in the tissues viz. liver, heart, kidney, and aorta were markedly decreased in cholesterol-fed rats supplemented with coconut water.

An increased rate of cholesterol conversion to bile acid and an increased excretion of bile acids and neutral sterols were observed in rats fed coconut water. Histopathological studies of liver and aorta revealed much less fatty accumulation in these tissues in cholesterol-fed rats supplemented with coconut water. Feeding coconut water resulted in increased plasma L-arginine content, urinary nitrite level, and nitric oxide synthase activity. These results indicate that both tender and mature coconut water has beneficial effects on serum and tissue lipid parameters in rats fed cholesterol-containing diet.

Again, LDL and triglyceride levels were reduced. Especially important is that the harmful form of LDL, very low-density lipoprotein (VLDL) was lowered when coconut water was present in the diet. Unlike the previous study, this one also showed an increase in HDL levels.

Cox et al. compared the effects of butter, coconut fat and safflower oil on cholesterol:

Objective: The aim of this present study was to determine plasma levels of lathosterol, lipids, lipoproteins and apolipoproteins during diets rich in butter, coconut fat and safflower oil.

Design: The study consisted of sequential six week periods of diets rich in butter, coconut fat then safflower oil and measurements were made at baseline and at week 4 in each diet period.

Subjects: Forty-one healthy Pacific island polynesians living in New Zealand participated in the trial.

Results: Plasma lathosterol concentration (P<0.001), p="0.04),"> Plasma total cholesterol, HDL cholesterol and apoA-levels were also significantly (P£ 0.001) different among the diets and were not significantly different between butter and coconut diets.

Conclusions: These data suggest that cholesterol synthesis is lower during diets rich in coconut fat and safflower oil compared with diets rich in butter and might be associated with lower production rates of apoB-containing lipoproteins.

The figures in the full paper show that total cholesterol and LDL levels were highest during the butter diet and lowest during the safflower oil diet. On the other hand, VLDL levels were highest during the safflower oil diet and lowest during the butter diet; so even though butter seems to raise LDL, it doesn't raise VLDL, which is the one harmful form of LDL. Coconut oil values were somewhere in the middle between butter and safflower oil values.

As for HDL and triglycerides, coconut oil takes the cake. HDL levels were highest during the coconut oil diet, and lowest during the safflower diet, while triglyceride levels were highest during the butter diet and lowest during the coconut diet.

So what should we make of all this? Based on these studies it seems pretty clear that coconut – regardless of whether it's coconut water, coconut oil or coconut flakes – reduces LDL, VLDL and triglycerides and slightly raises HDL. This is exactly what you'd want to happen with your cholesterol levels.

These results certainly suggest that coconut is good for cholesterol and at the same time cast doubt on the claims about saturated fat always being harmful.

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1 kommenttia:

TedHutchinson September 25, 2011 at 11:56 PM  

Dietary Carbohydrate Modifies the Inverse Association Between Saturated Fat Intake and Cholesterol on Very Low-Density Lipoproteins Free full text at link
We aimed to investigate the relationship between dietary saturated fat on fasting triglyceride (TG) and cholesterol levels, and any mediation of this relationship by dietary carbohydrate intake.
Men and women in the NHLBI Genetics of Lipid-Lowering Drugs and Diet Network (GOLDN) study (n = 1036, mean age ± SD = 49 ± 16 y) were included.
Mixed linear models were run with saturated fat as a predictor variable and fasting TG, very low density lipoprotein cholesterol (VLDL-C), low density cholesterol (LDL-C) and high density cholesterol (HDL-C) as separate outcome variables.
Subsequent models were run which included dietary carbohydrate as a predictor variable, and an interaction term between saturated fat and carbohydrate.
All models controlled for age, sex, BMI, blood pressure and dietary covariates.
In models that included only saturated fat as a predictor, saturated fat did not show significant associations with fasting lipids.
When carbohydrate intake and an interaction term between carbohydrates and saturated fat intake was included, carbohydrate intake did not associate with lipids, but there was an inverse relationship between saturated fat intake and VLDL-C (P = 0.01) with a significant interaction (P = 0.01) between saturated fat and carbohydrate with regard to fasting VLDL-C concentrations.
Similar results were observed for fasting TG levels.
We conclude that, when controlling for carbohydrate intake, higher saturated fat was associated with lower VLDL-C and TGs.
This was not the case at higher intakes of carbohydrate.
This has important implications for dietary advice aimed at reducing TG and VLDL-C levels.

So when is Saturated fat harmful?
When it is associated with higher carbohydrate intakes.

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