Chia seed does not promote weight loss or alter disease risk factors in overweight adults

Abstract

The objective of this study was to assess the effectiveness of chia seed (Salvia hispanica L) in promoting weight loss and altering disease risk factors in overweight adults. The hypothesis was that the high dietary fiber and α-linolenic (ALA) contents of chia seed would induce a small but significant decrease in body weight and fat and improve disease risk factors. Subjects were randomized to chia seed (CS) and placebo (P) groups, and under single-blinded procedures, ingested 25 g CS or P supplements mixed in 0.25 L water twice daily before the first and last meal for 12 weeks. Ninety nondiseased, overweight/obese men and women between the ages of 20 and 70 years were recruited into the study, with 76 subjects (n = 39 CS, n = 37 P) completing all phases of the study. Pre- and poststudy measures included body mass and composition (dual energy x-ray absorptiometry), inflammation markers from fasting blood samples (C-reactive protein, interleukin 6, monocyte chemoattractant protein 1, and tumor necrosis factor α), oxidative stress markers (trolox equivalent antioxidant capacity and plasma nitrite), blood pressure, and a serum lipid profile. Plasma ALA increased 24.4% compared to a 2.8% decrease in CS and P, respectively (interaction effect, P = .012). No group differences were measured for changes in plasma eicosapentaenoic acid and docosahexaenoic acid (interaction effects, P = .420 and .980, respectively). Pre-to-post measures of body composition, inflammation, oxidative stress, blood pressure, and lipoproteins did not differ between CS and P for both sexes. In conclusion, ingestion of 50 g/d CS vs P for 12 weeks by overweight/obese men and women had no influence on body mass or composition, or various disease risk factor measures.

Introduction

The essential fatty acid, α-linolenic acid (ALA; 18:3n-3), is present in various seeds, nuts, and vegetable oils such as flaxseed, linseed, canola, and soy oils. α-Linolenic acid can be metabolically converted to long-chain n-3 polyunsaturated fatty acids (n-3 PUFAs), including eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3), although the efficiency is poor [1], [2].

The reluctance of adults in the United States to increase fish intake and concerns over heavy metal accumulation in fish have accelerated interest in botanical sources of n-3 PUFAs such as flaxseed, walnuts, and algae [3], [4]. Plant n-3 PUFAs are abundant and readily available, and are often contained in foods that are high in dietary fiber and other components with potential health value. The cardioprotective effect of ALA in humans, however, is uncertain, and studies differ widely regarding influences on blood lipid profiles and measures of inflammation [5], [6], [7].

Chia seed (Salvia hispanica L) is an oilseed native to southern Mexico and northern Guatemala [8], [9], [10], [11], [12], [13]. Chia seed has 4.4 g ALA and 9.4 g of dietary fiber per 25 g serving [11]. In chickens fed chia seed, the ALA content of light and dark meat was increased and saturated fat decreased, with a reduction in overall poultry body mass [10]. In rats, consumption of chia seed and oil counters dyslipidemia and visceral adiposity and has been touted as an alternative n-3 source for vegetarians and people allergic to fish and fish products [8], [9]. The high fiber content of chia seed may improve satiety, decrease energy intake, and promote weight loss [10], [14]. Howarth et al [14] determined that although the influence of dietary fiber on energy regulation remains controversial, consumption of an additional 14 g/d soluble or insoluble dietary fiber when energy intake is ad libitum should promote a 10% decrease in energy intake and body weight loss of 1.9 kg over 3.8 months. The consumption of 37 g/d of chia seed in one human showed a decrease in C-reactive protein (CRP) and no change in body weight or blood lipid profiles over 12 weeks in 20 type 2 diabetic subjects [12].

Supplementation with n-3 PUFAs from both fish and plant products is a recent strategy to help control disease risk factors in overweight and obese individuals [15]. Given results from animal studies, we hypothesized that the high dietary fiber and ALA content of chia seed would induce a small but significant decrease in body weight and fat and improve disease risk factors. Specifically, our objective was to investigate the effectiveness of a large chia seed supplement (50 g/d split into 2 daily doses) compared to placebo in promoting weight loss, altering body composition, decreasing blood lipids, and modifying inflammation in 90 overweight men and women during a 12-week period. The 50-g chia seed supplement provided 19 g dietary fiber and 8.8 g ALA per day for 12 weeks. We reasoned that this quantity would be sufficient to test our hypothesis based on other research.