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8 Sodium: Dietary Reference Intakes for Adequacy
Pages 207-244

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From page 207...
... , this chapter describes the committee's review of indicators to inform the sodium DRIs for adequacy and presents its approach and determination of updated reference values for the DRI age, sex, and life-stage groups. The committee's decision was informed by its evaluation of evidence on sodium intake requirements in apparently healthy individuals, as well as its review of the evidence on adverse effects associated with continuing low sodium intakes.
From page 208...
... For context, the committee's findings are preceded by a brief summary of the approach taken to establish the sodium AIs in the Dietary Reference Intakes for Water, ­ otassium, Sodium, Chloride, and Sulfate (2005 DRI Report)
From page 209...
... . This committee interpreted the guidance provided in the Guiding Principles for Developing Dietary Reference Intakes Based on Chronic Disease (Guiding Principles Report)
From page 210...
... Evidence Presented in the 2005 DRI Report The 2005 DRI Report provided an overview of topics related to sodium balance and considered the effects of heat and physical activity on sodium losses. Urinary sodium excretion was characterized as being approximately equal to sodium intake for individuals in a steady state of sodium and fluid balance.
From page 211...
... Although all losses were assessed, the study did not control for environmental parameters, such as humidity or temperature, and urinary sodium excretion showed high intra-individual variability. In addition to incomplete sodium loss measurements, a number of studies did not directly measure total sodium intake, but relied on food composition tables or manufacturers' labeled sodium content (Heer et al., 2000, 2009; Lerchl et al., 2015)
From page 212...
... 212 DIETARY REFERENCE INTAKES FOR SODIUM AND POTASSIUM TABLE 8-1 Sodium Balance Studies Summarized by Completeness of Assessment of Intake and Lossesa Sodium Intake (mg/d) Negative Neutral Positive Reference Population Balance Balance Balance Rigorous Complete Balanceb Palacios et al., 2004 36 white and black 1,300 American adolescent 4,000 females, 11–15 years of age Incomplete Balance -- Limitation on Intake Assessmentc Allsopp et al., 1998 25 British males, 1,525d 1,525e 18–40 years of age 4,004 8,013 Incomplete Balance -- Limitation on Loss Assessmentf Kodama et al., 2005g 109 Japanese males 2,210 6,870 and females, 18–28 years of ageh Consolazio et al., 3 healthy, young 8,729 1963 American adult males, 10,229 ages not reported Holbrook et al., 1984 12 healthy American 4,200 (males)
From page 213...
... from 0800 hours to 1800 hours followed by 14 hours at 25°C (77°F) from 1800 hours to 0800 hours •  Sodium intake analyzed based on nutrient composition data and manufacturer's reported content, but was not directly analyzed •  Series of 11 mineral balance studies of 5–12 days duration with a 2–4-day adaptation period •  Sodium intake directly measured •  Urinary and fecal sodium losses measured; only arm sweat losses during physical activity measured •  Balance determined after a preliminary 8 days at 24°C (75°F)
From page 214...
... . cIncomplete balance studies were limited by the lack of direct measurement of sodium con tent in foods consumed and relied on nutrient composition data from various sources.
From page 215...
... kIncomplete balance studies were limited by lack of direct measurement of sodium content in foods consumed and by lack of assessment of one or more sources of sodium losses as noted for each study. lIntakes were reported as mmol/kg/d and estimated as total mg based on average body weight reported as 71.5 kg.
From page 216...
... However, data from observational studies have suggested an increase in risk of specific chronic diseases at low intake levels of sodium. Therefore, to minimize the potential for harmful health effects beyond deficiency at levels of intake around sodium adequacy, the committee considered the evidence related to the potential for such levels to increase biomarkers of chronic diseases (insulin resistance, blood pressure, and lipid concentrations)
From page 217...
... . The committee identified two randomized controlled trials reviewing the effect of dietary sodium on insulin sensitivity and glucose tolerance (Meland and Aamland, 2009; Suckling et al., 2016)
From page 218...
... The AHRQ Systematic Review made no conclusion on whether lowering sodium intake could increase blood pressure. Committee's Synthesis of the Evidence Based on the committee's assessment of the trials that explored blood pressure as an outcome, there is moderate strength of evidence that the positive linear relationship between sodium intake and blood pressure extends downward to as low as 850–1,800 mg/d (37–78 mmol/d)
From page 219...
... The 2005 DRI Report described the selected sodium AI for adults 19–50 years of age as a level above which some studies had reported increased plasma lipid concentrations. Evidence Provided in the AHRQ Systematic Review The AHRQ Systematic Review did not include plasma lipids in its outcomes of interest but recorded them from studies on an ad hoc basis when measured as an adverse event.
From page 220...
... sodium intake difference of > 40 mmol/day; 3. randomized controlled trials using 24-hour urinary sodium excretion for assessing sodium intake; 4.
From page 221...
... ,d [−0.06, 0.23] ,d I2 = 0% I2 = 0% I2 = 0% I2 = 0% I2 = 0% I2 = 0% I2 = NR LDL Cholesterol, mmol/L Trials (Comparisons)
From page 222...
... . Given these inconsistencies in the results of the three systematic reviews and the likelihood that study duration is affecting results, there is insufficient evidence about the relationship between a low sodium intake and detrimental effects on blood lipid concentrations.
From page 223...
... . A systematic review of the evidence of associations between low levels of sodium intake and status or adverse health outcomes was conducted for the European Food Safety Authority in preparation for establishing dietary reference values for sodium.
From page 224...
... . Instead, the AHRQ Systematic Review concluded that "observational studies had limited ability to control for pre-existing health conditions at study baseline that might have resulted in decreased sodium intakes, contributing to potentially spurious associations of lower sodium intakes with morbidity or mortality outcomes of interest" (Newberry et al., 2018, p.
From page 225...
... However, the review also concluded that there is insufficient evidence to draw a conclusion regarding either linear or nonlinear associations between sodium intake levels and cardio vascular disease mortality or associations between sodium intake levels and risks of combined cardiovascular disease morbidity and mortality. Two studies with overlapping populations reported a J or U shape between sodium intake and cardiovascular disease mortality (­ amelas et al., 2016; O'Donnell et al., 2014)
From page 226...
... The method of sodium intake ascertainment in the observational studies that suggest inverse relationships between sodium intake and chronic diseases is of concern. Six out of seven of the studies that reported higher risk of adverse outcomes at low sodium intake levels in the AHRQ Systematic Review used spot urine sodium measurements converted to estimates of 24-hour urinary sodium excretion by using a formula (e.g., the Kawasaki formula)
From page 227...
... Thus, the paradoxical J- and U-shaped relationships of sodium intake and cardiovascular disease and mortality are likely observed because of methodological limitations of the individual observational studies. 2  From three to seven 24-hour urinary sodium measurements during the trial periods.
From page 228...
... In particular, as summarized in Chapter 9, randomized controlled trials on sodium included in the AHRQ Systematic Review did not reveal a pattern of reported adverse effects among the low-sodium groups, suggesting that levels of sodium intakes studied did not result in sodium deficiency. Furthermore, the committee established a sodium CDRR for adults 19 years of age and older at 2,300 mg/d (100 mmol/d)
From page 229...
... The sections that follow present additional details on the committee's derivation of the sodium AIs for each of the DRI age, sex, and life-stage groups. Infants 0–12 Months of Age Details of the committee's approach to estimating the concentration of sodium in breast milk and the contributions of complementary foods to total sodium intake are provided in Appendix F
From page 230...
... DRI = Dietary Reference Intake; mg/d = milligrams per day. The sodium AI for infants 7–12 months of age is based on estimated sodium intake from breast milk and complementary foods.
From page 231...
... In addition, the AHRQ Systematic Review included eight other randomized controlled trials in which sodium
From page 232...
... . • Consideration of potential harmful health effects: There is insuffi cient evidence that low sodium intakes are associated with potential
From page 233...
... For individuals at high ambient temperature and/or performing high-intensity physical activity, a higher sodium intake level than the AI may be needed, but such a level could not be estimated at this time. Several of the randomized controlled trials included in the AHRQ Systematic Review reported allowing participants older than 70 years of age to be included in the study (Appel et al., 2001; Cappuccio et al., 2006; Howe et al., 1994; Hwang et al., 2014; Meland and Aamland, 2009; Nakano et al., 2016; Nestel et al., 1993; Schorr et al., 1996; Wing et al., 1998)
From page 234...
... . The committee agrees with the 2005 DRI Report that there is a lack of evidence to suggest that sodium requirements of pregnant females differ from that of nonpregnant females.
From page 235...
... DRI = Dietary Reference Intake; mg/d = milligrams per day. TABLE 8-9 Sodium Adequate Intakes, Lactating Females DRI Age, Sex, and Life-Stage Group Sodium Adequate Intake, mg/d Lactation 14–18 years 1,500 19–30 years 1,500 31–50 years 1,500 NOTES: Intake values are presented in milligrams.
From page 236...
... For children and adolescents 1–18 years of age, the committee used sedentary EERs to extrapolate from the adult AI. This extrapolation approach differs from the approach used in the 2005 DRI Report, which used energy estimates from proxy- and self-reported 24-hour dietary recalls to extrapolate.
From page 237...
... AI = Adequate Intake; DRI = Dietary Reference Intake; mg/d = milligrams per day.
From page 238...
... 2014. Methodological issues in cohort studies that relate sodium intake to cardiovascular disease outcomes: A science advisory from the American Heart Association.
From page 239...
... 2011. Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol, and triglyceride.
From page 240...
... 2016. Association of urinary sodium excretion with blood pressure and cardio vascular clinical events in 17,033 Latin Americans.
From page 241...
... 2017. Guiding prin ciples for developing Dietary Reference Intakes based on chronic disease.
From page 242...
... 2001. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH)
From page 243...
... 2012. Dietary sodium loading in normotensive healthy volunteers does not increase arterial vascular reactivity or blood pressure.


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