A number of nutrients are known to lower plasma concentrations of cholesterol in humans. Garlic and fibre for example, are well studied and have been shown repeatedly to be as effective as pharmaceuticals at lowering cholesterol concentrations. The tocotrienols have perhaps received less attention for their cholesterol lowering ability, which is unusual because they are also very effective within this regard. Tocotrienols are part of the vitamin E group of vitamins which includes the tocopherols. However, unlike the tocotrienols, the tocopherols appear to show no cholesterol lowering ability. Tocotrienols are limited to a small number of foods such as the oils of barley, oats, rice and palm, and must be taken in concentrated supplemental form in order to affect cholesterol. In addition, the tocotrienols may be beneficial to those with metabolic syndrome because they can also have physiological effects on blood sugar concentrations and blood clotting.
For example, one group of researchers1 used a double blind placebo controlled crossover design study to investigate the effect of tocotrienols on the serum lipoprotein concentrations of hyperlipidaemic subjects. For 4 weeks, subjects consumed either 300 mg per day corn oil which contained no tocotrienols, or 250 mg palm oil containing 50 mg of a highly concentrated fraction of tocotrienols made up of 15 to 20 % α-tocotrienol, 12 to 15 % β-tocotrienol, 35 to 40 % γ-tocotrienol and 25 to 30 % δ-tocotrienol. After the initial 4 weeks, subjects crossed over to the opposite treatment. Analysis of the data showed that the tocotrienol treatment was able to significantly lower the serum concentrations of total cholesterol by 15 %, low density lipoprotein cholesterol by 8 % and lower total ApoB particles [made up of very low density, low density and intermediate density lipoproteins as well as apolipoprotein(a)] by 10%.
In addition to the beneficial effects on serum lipoproteins, tocotrienols also significantly lowered thromboxane by 25 % and platelet factor 4 by 16 %, suggesting they may reduce the tendency of the blood to clot. Tocotrienols also reduced the serum levels of blood glucose by 12 %, when compared to the control. In seven subjects with very high cholesterol levels over 7.84 mmol/L, 200 mg of γ-tocotrienol caused a 31 % reduction in total cholesterol. From this the authors concluded that the γ-tocotrienol may be the most potent of the tocotrienol isomers and was probably responsible for most of the effects on serum lipids. Tocotrienols can regulate serum cholesterol concentrations because they are post-transcriptional inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate limiting enzyme responsible for cholesterol synthesis2. Therefore tocotrienols affect the same part of the mevalonate pathway at the statin drug class.