Similarly, a trial in hypertensive men and women that examined the long-term daily consumption of beetroot juice ingestion observed a significant increase in FMD [ 15 ]. Moreover, supplements and juice extracts containing beetroot are popular alternatives to fresh beetroot and are a popular ergogenic aid among competitive athletes [ 18 ]. For these reasons, it is important to examine whether these ergogenic aids can improve cardiovascular health. In contrast to other beet juice preparations or beet supplements, FVS sources its nitrates from additional nitrate-rich vegetable extracts beyond beets.
Secondarily, because previous studies have demonstrated increased risk for cardiovascular disease, and hence impaired FMD, in individuals with depressed mood, fatigue, or reduced sleep durations [ 19 — 21 ], we also measured mood and sleep quality.
Finally, we explored whether self-reported athletic status modified the physiologic responses to the supplement since some research has demonstrated that athletes have improved FMD [ 22 ] or alterations in FMD caused by vascular remodeling [ 23 ]. Women were excluded because: 1 the change in progesterone across the menstrual cycle influences FMD [ 25 , 26 ] and 2 women have more compliant blood vessels less likely influenced by acute dietary changes compared to men in the targeted age range [ 26 ].
Additional exclusion criteria were cigarette use within the past year, any food allergies, use of specific medications with vasoactive effects nitroglycerin, beta-blockers, calcium channel blockers , or unwillingness to consume juice concentrates daily or follow study restrictions. The study was reviewed and approved by the Institutional Review Board at Arizona State University and all participants provided written consent to participate in a study examining the effects of juice supplementation on blood pressure and blood vessel function.
Additional ingredients included stevia leaf extract Stevia rebaudiana and a blend of fruit and vegetable extracts green tea leaf, red grape, white grape, bilberry, carrot, grapefruit, papaya, pineapple, strawberry, apple, apricot, cherry, orange, broccoli, green cabbage leaf, onion, garlic, black current, asparagus, tomato, olive, and cucumber. Prune juice was selected as it has been used as a placebo in prior studies of beetroot juice because it has a similar consistency, caloric, fiber and sugar content, high antioxidant, and phenolic profile, but a low nitrate content [ 29 , 30 ] Table 1.
All nitrate and total polyphenol analyses were performed by Eurofins Scientific Inc. The subjects were asked to consume one bottle at approximately the same time each morning for 14 consecutive days and to record compliance on a two-week calendar provided on the first study visit.
Study compliance was determined as the percent of study days that the supplement was consumed. Participants were additionally asked to report any discomfort or adverse responses to their assigned supplement.
Participants met with investigators on four occasions: screening, baseline week 0 , and study weeks 1 and 2. Since some antimicrobial mouthwashes disrupt the reduction of dietary inorganic nitrates to nitrites by commensal bacteria in the mouth [ 31 ], participants were also asked to refrain from using antiseptic mouthwashes for 21 consecutive days starting one week prior to initiation of the 2-week intervention.
In addition, participants were asked to abstain from caffeine for 24 hours and exercise for 48 hours prior to testing. Blood pressure was recorded for three consecutive measurements with the 2nd and 3rd measurements averaged for the final value. Next, flow-mediated vasodilation in the brachial artery was measured by a trained sonographer as described below.
Waist circumference was measured in cm at the midpoint between the lowest palpable rib and the iliac crest using a flexible tension tape according to guidelines from the World Health Organization [ 32 ]. Height was measured using a wall-mounted stadiometer. All measurements were performed by the same study investigator. Physical activity was assessed using a validated questionnaire that quantifies physical activity in terms of metabolic equivalents METS [ 24 ]. Images were recorded during the final 60 seconds of the occlusion to measure the minimum occlusion diameter after which the cuff was rapidly deflated to elicit a reactive hyperemic stimulus that is considered predominantly endothelium-mediated and NO dependent [ 13 ].
The position of the probe was recorded for each participant to ensure that it was placed at the same location for each testing. Intraclass correlation coefficients for this technique in our laboratory for baseline and peak diameter are 0. Plasma total nitrates and nitrites were measured using a commercially available colorimetric assay kit Cat.
The assay uses nitrate reductase to convert sample nitrates to nitrites, which are then complexed to Griess reagent forming a purple azo compound detected spectrophotometrically. At each testing visit, participants completed a Profile of Mood States POMS questionnaire, a validated measure for assessing six mood states: tension, depression, anger, vigor, fatigue, and confusion [ 38 ]. Participants were told to report their feelings during the past week, and a total mood score was calculated the sum of the tension, depression, anger, fatigue, and confusion scores minus the fatigue score.
Based on an age, gender, and race-stratified sample of healthy adults representative of the U. Higher POMS scores indicate greater affect. To assess sleep quality, participants completed the Pittsburgh Sleep Quality Inventory PSQI , a validated measure composed of seven component scores sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medications, and daytime dysfunction that are summed to produce a global PSQI score [ 40 ].
Differences in baseline characteristics were examined by independent T -test, and the two-week change in outcome variables by group were examined using univariate analyses controlling for baseline values. Data were checked for normality and transformed when necessary. Age and physical activity level were not related to outcome variables; however, since markers of adiposity were related to the outcome variables, body mass was entered as a covariate in all analyses.
Alpha was set at 0. Of the volunteers who were prescreened for eligibility, 57 participants met the inclusion criteria and were enrolled in the study; however, three participants were withdrawn prior to the start of the study based on exclusion criteria and an additional six participants did not initiate the study Figure 1.
While 48 participants initiated the study, three participants did not complete the two-week intervention due to personal conflicts two in the PRU group and one in the FVS group; Figure 1. Data are reported for the 45 participants who completed the trial Figure 1. Baseline characteristics did not differ by group Table 2 ; furthermore, athletic status did not relate to any of the outcome measures at baseline and was not associated with changes in any of the outcome variables after the 2-week intervention.
By week one, plasma nitrates and nitrites rose markedly in the FVS group in comparison to the PRU group and levels remained elevated at week 2 Changes in diastolic blood pressure and plasma nitrates and nitrites for individual participants are shown in Figure 2.
Total mood state and sleep quality did not vary between treatment groups over the course of the study Table 3.
There were no differences between groups at baseline. It is possible that a direct comparison between effects of beet juice per se and the FVS evaluated in the current study may not be equivalent since the nitrate-rich sources in FVS include not only beet but also celery and red spinach extracts.
In this context, Bondonno et al. Although not entirely consistent with previous reports, the hypotensive effect of the FVS provides additional support for the inclusion of nitrate-rich foods or supplements as potentially safe and effective nutritional strategies for regulating normal blood pressure.
Blood pressure levels are a strong predictor of both vascular and nonvascular diseases, and their predictive power for vascular disease is stronger than that for blood cholesterol concentration or cigarette use [ 42 ]. Hence, the value of identifying strategies to lower blood pressure is clear.
Although chlorogenic acid, a component of prune juice, has been shown to reduce blood pressure according to a recent meta-analysis [ 46 ], no such blood pressure-lowering effects were observed in subjects consuming PRU in the present study. The daily consumption of a dietary supplement, e. Interestingly, the observed hypotensive effect of the FVS did not correspond with an effect on FMD, a commonly used, noninvasive assessment of vascular endothelial function.
This discordance has previously been noted in other human intervention trials with beet juice. For example, while some investigations noted a lack of influence of dietary nitrates on FMD [ 28 , 49 ], others found a greater FMD in response to dietary nitrate consumption [ 1 , 50 ]. Therefore, it is possible that acute changes in FMD may have occurred following immediate supplementation but these effects resolved by the following days' analysis.
Moreover, the assessments evaluated FMD in healthy subjects without additional dietary treatments. Therefore, it is possible that any beneficial effect of the supplement may have required experimentally-induced endothelial dysfunction to demonstrate an effect such as that observed postprandially after a high-fat meal [ 14 ].
The average baseline FMD values for participants were below those reported in recent reviews [ 22 , 23 ]; hence, a ceiling effect was not likely in this study. For example, Lara et al. This was most likely explained the by lower concentration of dietary nitrates provided by FVS compared with dosages chosen in previous studies.
Furthermore, participants were instructed to restrict dietary nitrate consumption to only that provided in the FVS. Thus, the hypotensive effect of the FVS towards diastolic blood pressure was most likely due to the supplement's nitrate content, although it is possible that other biologically active components may have contributed to or altered the blood pressure-lowering effects of FVS.
For example, a study comparing blended apples enriched with additional apple skins rich in flavonoids and spinach rich in nitrates found both increased plasma NO and FMD resulting in lower systolic blood pressure compared to a control [ 41 ].
In fact, increases in FMD were greater with the consumption of apples as compared to spinach, even though plasma NO was increased more in response to spinach supplementation [ 41 ].
Surprisingly, when apples and spinach were consumed together, there were no additive effects on blood pressure. Bondonno et al. Polyphenols can also improve conversion of dietary nitrates to NO in the gut [ 5 ]. Foods rich in flavonoids include tea, citrus, berries, red wine, apples, and legumes. Thus, it is possible that a similar reduction of nitrite in the gut by flavonoids or polyphenols in the FVS may have limited the effects of the supplement on systolic blood pressure and FMD.
Prune juice was chosen as a control since this beverage has a very low nitrate content, yet similar caloric and sugar content as FVS, and has functioned as a placebo in a previous study [ 29 ]. Fruit and vegetables are a rich source of potassium, and the possible impact of potassium intake on reductions in diastolic blood pressure cannot be ruled out since the potassium level in FVS is not known.
There are additional limitations to the study results. First, healthy male subjects were specifically recruited due to their greater risk of developing cardiovascular disease, and women were excluded to avoid potential menstrual cycle-influenced fluctuations in progesterone known to influence vascular reactivity.
Therefore, it is unknown whether the supplement would have provided a similar hypotensive response in women.
Another limitation is the use of a parallel arm study design which may have limited the power of the study and contributed to the number of confounding factors such as dietary intake. While any physiological pathway that may link endothelial function with either sleep or mood status is uncharacterized, several researchers have reported strong inverse correlations between FMD and impaired mood or sleep states [ 58 — 60 ]. Therefore, we assessed influence of a potential nitrate-induced enhancement of FMD toward these parameters of overall well-being.
However, mood and sleep scores were not altered by daily ingestion of FVS despite a significant elevation in plasma nitrates and nitrites. As discussed above, the nitrate dose of the supplement may have been insufficient to change endothelial function as measured by FMD; hence, any influence of FMD on mood and sleep could not be demonstrated. While the implications of these results will require further evaluation, this study adds to a growing body of evidence suggesting that even small amounts of dietary nitrates may be an effective nutritional strategy to regulate healthy diastolic blood pressure and provide cardioprotection.
The authors thank Ginger Hook, Veronica Zamora, and Roman Mayek for technical assistance with the assays and Theresa Jorgensen for assessing flow-mediated vasodilation. Gumpricht was not involved in the collection, analyses, or interpretation of data. All other authors report no conflicts of interest. National Center for Biotechnology Information , U. Journal List J Nutr Metab v. J Nutr Metab.
Published online Sep Karen L. Sweazea , 1 , 2 Carol S. Johnston , 1 Brendan Miller , 1 and Eric Gumpricht 3. Carol S. Author information Article notes Copyright and License information Disclaimer.
Corresponding author. Nitrite and nitrosyl compounds in food preservation. View Article Google Scholar 3. Determination of nitrates, nitrites and oxalates in food products by capillary electrophoresis with pH-dependent electroosmotic flow reversal.
Food Chemistry. View Article Google Scholar 4. Nitrate and nitrite quantification from cured meat and vegetables and their estimated dietary intake in Australians. View Article Google Scholar 5. A high performance liquid chromatography method for determining nitrate and nitrite levels in vegetables.
Journal of Food and Drug Analysis. View Article Google Scholar 6. Effect of cultivars, harvesting time and level of nitrogen fertilizer on nitrate and nitrite content, yield in Romaine lettuce. Asian Journal of Plant Sciences. View Article Google Scholar 8. Effect of organic and inorganic fertilizers applied during successive crop seasons on growth and nitrate accumulation in lettuce.
Scientia Horticulturae. View Article Google Scholar 9. Survey of nitrate and nitrite levels of fresh vegetables in Turkey. J Food Technol. View Article Google Scholar Prasad S, Chetty AA. Nitrate-N determination in leafy vegetables: Study of the effects of cooking and freezing.
Workgroup report: Drinking-water nitrate and health-recent findings and research needs. Environmental health perspectives. Food sources of nitrates and nitrites: the physiologic context for potential health benefits. The American journal of clinical nutrition. The changing structure of food retailing in Europe: the implications for strategy.
Long Range Planning. A study of nitrate contamination in soil and vegetables in dezful. Tabande L, Taheri M. Preparation of climate map of Kurdistan province using GIS. Sepehr Geographical Information Journal.
The study of effects of some characteristics of the soil habitat on total alkaloids in Leontice leontopetalum and L. Armeniaca tubers from four different regions of Iran. Energy use and economic analysis of NPK 8: 15 fertilizer granulation process in Iran. Journal of the Saudi Society of Agricultural Sciences. Journal of Food Science and Technology Iran. Wood R III. A comparison of the extraction methods used in the UK nitrate residues monitoring program.
Journal of the Association of Public Analysts Online. Molina V. Health risk assessment of selected heavy metals bioaccumulation in Laguna de Bay [Philippines] fish products. Evaluation of nitrate concentration in soil, groundwater and potato tubers on different farm size levels in Fereidan city of Isfahan.
Nitrates and nitrites in vegetables and vegetable-based products and their intakes by the Estonian population. Food additives and contaminants. Authority EFS. EFSA Journal. Bill H. Determination of nitrate concentration of consumed vegetables and fruits in Ardabil. Journal of Ardabil University of Medical Sciences. Tabande L, Safarzadeh Shiraze S. Evaluation of nitrate accumulation and factors affecting it in some leafy vegetables in Zanjan Province.
Iranian Journal of Soil Research. Fytianos K, Zarogiannis P. Nitrate and nitrite accumulation in fresh vegetables from Greece. Bulletin of environmental contamination and toxicology. An assessment of the total external costs of UK agriculture. Agricultural systems. Nitrite and Nitrate content of fruits and vegetables in Kermanshah Nitrate in vegetables and their impact on human health.
A review. Acta alimentaria. Pate J. Transport and partitioning of nitrogenous solutes. Annual Review of Plant Physiology. Nitrate accumulation in vegetables and its relationship to quality. Annals of Applied Biology. Santamaria P. Nitrate in vegetables: toxicity, content, intake and EC regulation.
Journal of the Science of Food and Agriculture. Nitrate and nitrite contents of some fresh and processed Egyptian vegetables. Bednar C, Kies C. Nitrate and vitamin C from fruits and vegetables: Impact of intake variations on nitrate and nitrite excretions of humans.
Plant foods for human nutrition. Critical Reviews in Toxicology. Determination of nitrate contents of lettuce, tomatoes and potatoes on sale in Tehran central fruit and vegetable market by HPLC. Seasonal changes in tissue nitrate levels in fall-planted spinach Spinacia oleracea.
Asian J Plant Sci. Evaluation of nitrate and nitrite content of Iran Southern Ahwaz vegetables during winter and spring of Study on the effect of boiling and freezing process on nitrate and nitrite levels in abundant consumed vegetables. Nitrate and nitrite levels in fresh and frozen broccoli.
Effect of freezing and cooking. Chetty AA, Prasad S. Flow injection analysis of nitrate-N determination in root vegetables: Study of the effects of cooking. Hill MJ. Nitrates and nitrites in food and water: CRC Press; Risk assessment on nitrate and nitrite in vegetables available in korean diet. Journal of Applied Biological Chemistry. Gruszecka-Kosowska A, Baran A. Concentration and health risk assessment of nitrates in vegetables from conventional and organic farming.
We also know that this may be particularly important in older people, since natural nitric oxide production via arginine tends to drop with ageing. Nitrates in leafy greens are less likely to form cancer-causing nitrosamines and have plenty of health benefits Credit: Getty.
So when most of the nitrates in our diets come from vegetables — and in turn encourage nitric oxide formation — they are probably good for us. But the report also noted that people of all age groups can exceed this ADI quite easily. Nitrite intakes are generally much lower one estimate of average intake in the UK being 1. As always, dose makes the poison, and levels of grams mg of nitrate can be acutely toxic, causing changes in haemoglobin that present as a blueish tinge to lips and skin.
The upshot? If you want to eat the right kinds of nitrates and nitrites and avoid the potentially carcinogenic ones, then eat a widely varied diet with at least five servings a day of fruit and vegetables, and avoid nibbling on processed meats too often. That way, the benefits of nitrates and nitrates will almost certainly outweigh the downsides.
Correction: A previous version of this story stated that the International Agency for Research on Cancer categorises processed meat as a probable carcinogen, when it categorises it as a carcinogen.
We regret the error. If you liked this story, sign up for the weekly bbc. The truth about the nitrates in your food. Share using Email.
By Angela Dowden 13th March Usually associated with processed meats, nitrates and nitrites are potentially cancer-causing compounds.
0コメント