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The effects of dietary nitrate supplementation on endurance exercise performance and cardiorespiratory measures in healthy adults: a systematic review and meta-analysis.
Gao, C, Gupta, S, Adli, T, Hou, W, Coolsaet, R, Hayes, A, Kim, K, Pandey, A, Gordon, J, Chahil, G, et al
Journal of the International Society of Sports Nutrition. 2021;18(1):55
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The ability to increase endurance to improve their physical fitness is of great interest to athletes. Several dietary components have been shown to increase endurance especially those which contain nitrates. It is thought that nitrates, which are found in beetroots, pomegranates, green leafy vegetables, collard greens, lettuce and spinach, aid endurance through their action on improving blood flow to the muscles, helping to improve contraction of the muscles, through increased energy production, through improved oxygen flow and through sugar and nutrient balance. However, studies in humans on the effects of nitrates on exercise endurance have been conflicting. This systematic review and meta-analysis aimed to summarise the research on the use of nitrates during exercise. The results showed that nitrate supplementation improved muscle power, time to exhaustion and distance travelled, although no difference was found to perceived exertion, time trial performance and work done. It was concluded that nitrate supplementation is of benefit to improve exercise endurance, based on very low to moderate quality evidence. This study could be used by health care professionals to recommend a nitrate rich diet and possibly a nitrate supplement to improve exercise performance.
Abstract
BACKGROUND Nitrate supplementation is thought to improve performance in endurance sports. OBJECTIVE To meta-analyze studies evaluating the effect of nitrate supplementation on endurance sports performance among adults. DATA SOURCES We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Web of Science and CINAHL without language restrictions. METHODS We included studies that: 1) compared nitrate supplementation with placebo; 2) enrolled adults engaging in an endurance-based activity; and 3) reported a performance measure or surrogate physiologic outcome. We evaluated risk of bias using the Cochrane Collaboration tool and pooled data with a random-effects model. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to evaluate confidence in estimates. RESULTS We included 73 studies (n = 1061). Nitrate supplementation improved power output (MD 4.6 watts, P < 0.0001), time to exhaustion (MD 25.3 s, P < 0.00001), and distance travelled (MD 163.7 m, P = 0.03). We found no significant difference on perceived exertion, time trial performance and work done. Nitrate supplementation decreased VO2 (MD - 0.04 L/min, P < 0.00001) but had no significant effect on VO2max or blood lactate levels. CONCLUSION The available evidence suggests that dietary nitrate supplementation benefits performance-related outcomes for endurance sports.
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A randomized, double blind, placebo controlled, multicenter clinical trial to assess the efficacy and safety of Emblica officinalis extract in patients with dyslipidemia.
Upadya, H, Prabhu, S, Prasad, A, Subramanian, D, Gupta, S, Goel, A
BMC complementary and alternative medicine. 2019;19(1):27
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Emblica officinalis (Amla or Indian gooseberry) is a fruit that has been traditionally used in Ayurvedic medicine. It has been shown to be effective in the management of dyslipidemia (abnormal fat metabolism), a risk factor for heart disease, in animal models and in pilot clinical studies without major side effects. This multicenter, randomised, placebo controlled, double blind clinical trial was designed to evaluate the efficacy and safety of a proprietary full spectrum amla extract (containing pulp and seeds) in patients with dyslipidemia. 98 patients were enrolled and all completed the 12 week study. None of them were taking any medication for their dyslipidaemia. All the patients enrolled in the study were also asked to initiate lifestyle changes (healthy diet with exercise at least 4 days a week). Apart from conventional lipid parameters, the investigators also measured a number of other parameters relevant to heart disease, including the atherogenic index of plasma (AIP, a marker of heart disease risk). Compared to the placebo group the amla group had significantly greater reductions in triglycerides, LDL-cholesterol, VLDL-cholesterol and the atherogenic index of plasma (AIP, a better predictor of heart disease risk). There were no significant changes in HDL-cholesterol, CoQ10 (lowering of CoQ10 is a concern with many cholesterol lowering drugs), homocysteine, thyroid stimulating hormone (TSH) or fasting blood glucose. Four non-serious adverse events were observed: mild headache, mild fever, two times gastritis (all resolved with standard treatment), three were in the placebo group, one in the amla group. There were no changes in routine blood tests and vital signs (blood pressure, heart rate, temperature, respiratory rate). The authors conclude that the amla extract has significant potential to improve dyslipidaemia without side effects commonly seen with cholesterol lowering drugs.
Abstract
BACKGROUND Dyslipidemia is one of the most frequently implicated risk factors for development of atherosclerosis. This study evaluated the efficacy of amla (Emblica officinalis) extract (composed of polyphenols, triterpenoids, oils etc. as found in the fresh wild amla fruit) in patients with dyslipidemia. METHODS A total of 98 dyslipidemic patients were enrolled and divided into amla and placebo groups. Amla extract (500 mg) or a matching placebo capsule was administered twice daily for 12 weeks to the respective group of patients. The patients were followed up for 12 weeks and efficacy of study medication was assessed by analyzing lipid profile. Other parameters evaluated were apolipoprotein B (Apo B), apolipoprotein A1 (Apo A1), Coenzyme Q10 (CoQ10), high-sensitive C-reactive protein (hsCRP), fasting blood sugar (FBS), homocysteine and thyroid stimulating hormone (TSH). RESULTS In 12 weeks, the major lipids such as total cholesterol (TC) (p = 0.0003), triglyceride (TG) (p = 0.0003), low density lipoprotein cholesterol (LDL-C) (p = 0.0064) and very low density lipoprotein cholesterol (VLDL-C) (p = 0.0001) were significantly lower in amla group as compared to placebo group. Additionally, a 39% reduction in atherogenic index of the plasma (AIP) (p = 0.0177) was also noted in amla group. The ratio of Apo B to Apo A1 was reduced more (p = 0.0866) in the amla group as compared to the placebo. There was no significant change in CoQ10 level of amla (p = 0.2942) or placebo groups (p = 0.6744). Although there was a general trend of FBS reduction, the numbers of participants who may be classified as pre-diabetes and diabetes groups (FBS > 100 mg/dl) in the amla group were only 8. These results show that the amla extract used in the study is potentially a hypoglycaemic as well. However, this needs reconfirmation in a larger study. CONCLUSIONS The Amla extract has shown significant potential in reducing TC and TG levels as well as lipid ratios, AIP and apoB/apo A-I in dyslipidemic persons and thus has scope to treat general as well as diabetic dyslipidemia. A single agent to reduce cholesterol as well as TG is rare. Cholesterol reduction is achieved without concomitant reduction of Co Q10, in contrast to what is observed with statins. TRIAL REGISTRATION Registered with Clinical Trials Registry- India at www.ctri.nic.in (Registration number: CTRI/2015/04/005682 ) on 8 April 2015 (retrospectively registered).