Publications by authors named "D J Naismith"

74 Publications

An investigation into the bioaccessibility of potassium in unprocessed fruits and vegetables.

Int J Food Sci Nutr 2008 Aug;59(5):438-50

Department of Nutrition & Dietetics, King's College London, London, UK.

Epidemiological studies and clinical trials have consistently shown an inverse association between potassium intake and blood pressure. As a means of raising potassium intake within the UK population, an increase in the consumption of fruits and vegetables is strongly advocated. The aim of this study was to determine the bioaccessibility of potassium in these foods. A 10-day crossover feeding trial was performed on 11 healthy volunteers. For 5 days a diet providing most of the potassium in the form of unprocessed fruits and vegetables was followed by a diet in which the potassium was believed to be almost wholly bioaccessible, being derived from animal foods and fruit juices. The potassium and sodium of the diets and the urine were determined by chemical analysis: 96.3% of the potassium in the 'high bioaccessible diet' was recovered in the urine, compared with 76.8% from the diet rich in fruits and vegetables. This difference is attributed to the cellular structure of plant foods. The relatively poor bioaccessibility of potassium diminishes the perceived nutritive value of these foods with regard to potassium intake.
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http://dx.doi.org/10.1080/09637480701690519DOI Listing
August 2008

Partial substitution of sodium with potassium in white bread: feasibility and bioavailability.

Int J Food Sci Nutr 2009 Sep;60(6):507-21

Department of Nutrition & Dietetics, King's College London, London, UK.

A high sodium intake, to which bread makes a major contribution, and a low potassium intake are believed to be important factors in the promotion of cardiovascular disease. Our aims was to determine to what extent salts of potassium could substitute sodium chloride and potassium-rich soya flour could replace wheat flour without detrimental effect on acceptability, and to measure the bioavailability of a potassium salt added to bread. A single-blind organoleptic evaluation was carried out on eight different potassium-enriched breads by 41 panellists. Thereafter, six volunteers consumed standard or potassium-chloride-fortified bread in an 11-day single-blind cross-over feeding trial to determine the bioavailability of the supplemental potassium. Two breads in which 30% of the sodium was replaced by potassium salts, and bread in which 10% of wheat flour was replaced with soy flour, had acceptability scores similar to the standard bread. In the metabolic study a supplement of 22 mmol/day potassium chloride incorporated into the bread was found to be wholly bioavailable. A substantial reduction in sodium and an increase in potassium intake could be achieved by substituting potassium salts for sodium chloride in bread.
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http://dx.doi.org/10.1080/09637480701782118DOI Listing
September 2009

The effect of a dietary supplement of potassium chloride or potassium citrate on blood pressure in predominantly normotensive volunteers.

Br J Nutr 2008 Jun 6;99(6):1284-92. Epub 2007 Dec 6.

Department of Nutrition and Dietetics, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NN, UK.

Blood pressure (BP) shows a continuous relationship with the risk of CVD. There is substantial evidence that dietary potassium exerts an anti-pressor effect. Most clinical trials have used KCl. However, the chloride ion may have a pressor effect and in foods potassium is associated with organic anions. In a double-blind randomized placebo-controlled trial we explored the effect on BP of two salts of potassium, KCl and potassium citrate (K-cit), in predominantly young healthy normotensive volunteers. The primary outcome was the change in mean arterial pressure as measured in a clinic setting. After 6 weeks of supplementation, compared with the placebo group (n 31), 30 mmol K-cit/d (n 28) changed mean arterial pressure by -5.22 mmHg (95% CI -8.85, -4.53) which did not differ significantly from that induced by KCl (n 26), -4.70 mmHg (-6.56, -2.84). The changes in systolic and diastolic BP were -6.69 (95% CI -8.85, -4.43) and -4.26 (95% CI -6.31, -2.21) mmHg with K-cit and -5.24 (95% CI -7.43, -3.06) and -4.30 (95% CI -6.39, -2.20) mmHg with KCl, and did not differ significantly between the two treatments. Changes in BP were not related to baseline urinary electrolytes. A greater treatment-related effect was observed in those with higher systolic BP. Increasing dietary potassium could therefore have a significant impact on the progressive rise in BP in the entire population.
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http://dx.doi.org/10.1017/S0007114507864853DOI Listing
June 2008

The effect of low-dose potassium supplementation on blood pressure in apparently healthy volunteers.

Br J Nutr 2003 Jul;90(1):53-60

Department of Nutrition and Dietetics, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 8WD, UK.

Epidemiological and clinical trials suggest an inverse relationship between dietary K intake and blood pressure (BP). Most trials however have been of short duration, the dose of K was high, and the results have been conflicting. The aim of the present study was to evaluate the effect on BP of a low-dose supplementation (24 mmol/d) for an extended period. A double-blind placebo-controlled trial was conducted on fifty-nine volunteers, randomly assigned to receive 24 mmol slow-release KCl/d (n 30) or a placebo (n 29). Measures of BP, anthropometric characteristics and urine analysis for electrolytes were recorded during a 1-week baseline period. Supplementation was for 6 weeks during which BP and changes in weight were assessed and a second 24 h urine collection made. The primary outcome was the change in mean arterial pressure (MAP); systolic BP (SBP) and diastolic BP (DBP) were secondary outcomes. After 6 weeks of supplementation MAP was reduced by 7.01 (95 % CI -9.12, -4.89; P<0.001) mmHg, SBP was reduced by 7.60 (95 % CI -10.46, -4.73; P<0.001) mmHg and DBP was reduced by 6.46 (95 % CI -8.74, -4.19; P<0.001) mmHg. The reduction in MAP was positively associated with baseline urinary Na:K (P<0.034). A low daily dietary supplement of K, equivalent to the content of five portions of fresh fruits and vegetables, induced a substantial reduction in MAP, similar in effect to single-drug therapy for hypertension.
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http://dx.doi.org/10.1079/bjn2003861DOI Listing
July 2003

Modulating influence of barley on the altered metabolism of glucose and of basement membranes in the diabetic rat.

Ann Nutr Metab 1994 ;38(2):61-7

Department of Nutrition, King's College London, UK.

A study was conducted to explore the effects of different sources of dietary carbohydrate on the altered metabolism of basement membrane proteins (type IV collagen and laminin) that occurs in the streptozotocin-diabetic rat. The substitution of barley for sucrose reduced the elevated plasma concentration of 7-S collagen and of laminin P2, peptide fragments that retain antigenicity of the parent proteins. Similar effects were noted in the liver and kidney content of these peptides. It is suggested that the beneficial property of barley is due to its high content of chromium, as has been demonstrated in the study of glucose metabolism.
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http://dx.doi.org/10.1159/000177794DOI Listing
September 1994
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