Do Your Antioxidants Suppress Enough Free Radicals?February 2005
By Jim English
Sesame Elevates Gamma Tocopherol, Inhibits LDL
In 2001, researchers from the University of Hawaii Cancer Research Center tested nine subjects by feeding them muffins containing equivalent amounts of gamma tocopherol derived from sesame seeds, walnuts, or soy oil. Eating muffins containing sesame increased serum levels of gamma tocopherol by 20% in as little as three days. No similar benefit was seen in subjects eating muffins containing gamma tocopherol derived from walnuts or soy oil. All of the subjects who consumed muffins containing sesame seeds had detectable levels of the sesame lignan sesamolin in their plasma. According to the study authors, “consumption of moderate amounts of sesame seeds appears to significantly increase plasma gamma tocopherol and alter plasma tocopherol ratios in humans and is consistent with the effects of dietary sesame seeds observed in rats leading to elevated plasma gamma tocopherol and enhanced vitamin E bioactivity.”18
In another study also conducted in 2001, Swedish women who consumed dietary sesame oil saw their gamma tocopherol levels increase 41% from their pre-supplementation levels—without affecting serum alpha tocopherol concentration.19 This effect could be due to the gamma tocopherol or the lignans present in sesame oil, or the interaction of both.
Oxidation of dangerous low-density lipoprotein (LDL) is a primary initiating event in the development of atherosclerosis.20 LDL oxidation occurs when oxidants such as peroxynitrite radical, iron ascorbate, and copper ascorbate modify LDL particles. Once LDL is oxidized, it can no longer be recognized by LDL receptors, but instead is targeted by scavenger receptors on macro-phages, leading to the formation of lipid-filled foam cells observed in atherosclerotic lesions.21
Researchers have found that sesame lignans are highly effective inhibitors of LDL oxidation. In one test designed to measure the ability of various antioxidants to inhibit oxidation, LDL was exposed to a standardized oxidizing agent, such as copper iron ascorbate (CuSO4), and then treated with various antioxidants to determine their potency. Butylated hydroxytoluene, or BHT, is a food preservative that has long been recognized as being among the most potent inhibitors of CuSO4-induced lipid peroxidation. In 1995, researchers at the University of Shizuoka, Japan, found that sesaminol, the most prevalent sesame lignan, effectively inhibited LDL oxidation, outperforming other well-established biological antioxidants, including quercetin, epigallocatechin-3 gallate (EGCG), theaflavin, BHT, and alpha tocopherol. In fact, the lag time to oxidation—the determining factor in antioxidant potency—was greatly increased.22
The lignan sesaminol is thus a strong antioxidant with powerful antioxidant effects.
Sesame Lignans Improve Lipid Profiles
Sesame lignans have been shown to improve lipid profiles in both humans and experimental animals. Unfavorable lipid profiles are a significant risk factor for cardiovascular disease. In one study, re-searchers examined the effects of sesamin on cholesterol metabolism in rats. Their study found that animals fed sesamin (0.5% of their daily diet) for four weeks had significant reductions in serum and liver cholesterol levels, irrespective of the presence or absence of cholesterol in their diet.23 The researchers also noted a significant reduction in liver activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA), the rate-limiting enzyme required for cholesterol biosynthesis. According to the study authors, “since sesamin lowered both serum and liver cholesterol levels by inhibiting absorption and synthesis of cholesterol simultaneously, it deserves further study as a possible hypocholesterolemic agent of natural origin.”23
A study in rabbits showed that sesame helped improve lipid profiles by lowering total cholesterol and triglyceride levels while increasing levels of protective high-density lipoprotein (HDL).24 In addition, sesame decreased susceptibility to oxidative stress in the rabbit study.24 When vitamin E and sesamin were added to the diets of rats, LDL and very low-density lipoprotein (VLDL) levels decreased while beneficial HDL increased significantly, favorably improving the atherogenic index.25
To determine whether sesame lignans affect cholesterol levels in human subjects, Japanese re-searchers recruited 12 male patients diagnosed with hyper-cholesterolemia (high cholesterol). One group of six patients was treated with 32 mg of sesamin per day, while the second (control) group received a placebo. After eight weeks of treatment, the sesamin-treated group was found to have lower total cholesterol, LDL, and apolipoprotein B levels. In the sesamin group, average total cholesterol levels dropped from 270 to 248 mg/dL, LDL levels fell from 187 to 156 mg/dL, and apolipoprotein B levels were reduced from 188 to 168 mg/dL, thus reducing several serious risk factors for cardiovascular disease. By contrast, in the placebo group, levels of total cholesterol, LDL, and apolipoprotein B were unchanged.26
Sesame Lignans Show Antihypertensive Effects
Hypertension is a silent disease that that increases the risk of stroke, heart attack, and other serious disorders. Sesame lignans have demonstrated antihypertensive effects in animals and humans. In both normotensive and hypertensive stroke-prone rats, sesame exerts a mild antihypertensive effect.27 In high-salt diets, sesame prevented the development of hypertension and of histological renal damage such as thickening of the tunica intima and fibrinoid degeneration of the arterial wall.28-33 These findings may have implications for humans because of the high salt content in the American diet.
A recent human study investigated the effects of sesame oil in hypertensive patients who were being treated with a calcium channel blocker (nifedipine). The study enrolled 396 hypertensive patients, including 215 men and 181 women, with an average age of 58. Forty patients were treated only with nifedipine, while 356 patients continued to use nifedipine while switching exclusively to sesame oil in place of other edible oils in their diet. After 60 days, the average systolic blood pressure in the sesame group was reduced from 166 mm Hg to 134 mm Hg, and the average diastolic pressure dropped from 101 mm Hg to 85 mm Hg.34
The nifedipine dosage was then reduced to adjust for the drop in blood pressure observed in patients consuming sesame oil. In the sesame group, plasma levels of sodium decreased, while potassium and chloride levels increased significantly. Levels of lipid peroxidation (thiobarbituric acid reactive substances) also decreased significantly, while activities of enzymic antioxidants (superoxide dismutase, glutathione peroxidase, and catalase) and concentrations of non-enzymic antioxidants (vitamins C and E, beta-carotene, and reduced glutathione) increased in sesame oil group.34
The results led study author Devarajan Sankar, DO, PhD, to observe, “the effect of the oil on blood pressure may be due to polyunsaturated fatty acids . . . and the compound sesamin . . . both compounds have been shown to reduce blood pressure in hypertensive rats. Sesame lignans also inhibit the synthesis and absorption of cholesterol in these rats.”34
Enhanced Actions of Essential Fatty Acids
Essential fatty acids are involved in many of the body’s biochemical processes. One of their most important roles is preventing inflammation.
Dihomo-gamma-linolenic acid (DGLA) is an essential fatty acid produced from the conversion of gamma linolenic acid (GLA), which is found in borage, black currant, and evening primrose oil. DGLA can be directly converted into the anti-inflammatory prostaglandin E1 (PGE-1) at the expense of pro-inflammatory prostaglandin E2. PGE-1 has been shown to normalize blood pressure in hypertensive rats, and to help control inflammation and normalize blood pressure in humans. DGLA is needed to activate the immune system and prevents smooth muscle proliferation of arteries and veins, which leads to hardening of the arteries. DGLA is also needed in the diet to prevent blood-clot formation. DGLA levels are a key factor in human aging, and deficiencies of DGLA have been associated with accelerated aging.