Dietary protein and blood pressure : epidemiological studies

Background Elevated blood pressure is a major risk factor for cardiovascular diseases. Diet and lifestyle have a substantial impact on blood pressure, but the role of protein intake is not yet clear. This thesis focuses on total dietary protein, types of protein (i.e. plant and animal), protein from specific sources (i.e. dairy, meat, and grain), and specific amino acids in relation to blood pressure levels and incident hypertension. Methods The associations of dietary protein, protein types, and protein from specific sources with population blood pressure levels were cross sectionally examined in 20,820 Dutch adults aged 25 to 65 y (MORGEN Study). The relation with risk of hypertension was examined in 3,588 of these adults with 15 years of follow-up (Doetinchem Study) and in 2,241 older Dutch adults (≥55y) with 6 years of follow-up (Rotterdam Study). In the latter cohort we also examined the relation of specific amino acids (i.e. glutamic acid, arginine, lysine, cysteine, tyrosine, and essential amino acids) with blood pressure levels and risk of hypertension. As an ancillary Study, a fully controlled randomized cross over trial with different protein-rich diets was conducted to obtain objective biomarkers for dietary protein types that may be used in future epidemiological studies. Finally, we performed several meta-analyses to summarize our findings for dietary protein and protein types in relation to blood pressure and incident hypertension, combined with data from the literature. Results The epidemiological studies presented in this thesis and a meta analysis of observational studies showed no associations of total protein and animal protein with blood pressure or incident hypertension. A meta analysis of 14 randomized controlled trials, however, showed a pooled blood pressure effect of protein supplementation (weighed mean contrast in intake of 41 g/d) of 2.1 mmHg systolic (95%-CI: 2.9 to 1.4) when compared to carbohydrate intake. In the epidemiological studies in this thesis plant protein was significantly inversely associated to blood pressure levels ( 1.8/ 1.0 mmHg with 14 grams higher energy adjusted intake), but not with incident hypertension (all HR per SD ~1.00). Meta-analyses of cross sectional studies showed a small differential association of plant and animal protein with blood pressure (-0.52 mmHg per SD of dietary plant protein versus +0.03 mmHg per SD of animal protein), but this association was not present in meta-analyses of prospective studies and trials. The epidemiological analyses on meat protein and dairy protein in this thesis revealed no consistent associations with blood pressure or incident hypertension. Grain protein was inversely associated with diastolic (but not systolic) blood pressure, and with borderline significant lower risk of hypertension in a general Dutch population (HR: 0.75, 95% CI: 0.73 to 1.00), but this association was absent in older adults. No associations with blood pressure or incident hypertension were found for amino acid intakes. Finally, we identified a combination of 3 urinary amino acids as a potential biomarker for meat protein intake and a combination of 7 plasma amino acids as a potential biomarker for grain protein intake Conclusion Results from this thesis suggest a small beneficial effect of protein on blood pressure if consumed instead of carbohydrates. Plant protein, e.g. from grain, may be more beneficial to blood pressure than animal protein but data are too limited to draw firm conclusions. After validation, future epidemiological studies could make use of biomarkers as more robust estimates for protein from specific sources and amino acid intakes. Randomized controlled trials are warranted to examine the blood pressure effect of specific types of protein, reflecting habitual intakes in western societies, compared to different types of carbohydrate. At present, a prudent diet for the prevention of hypertension with adequate amounts of dietary protein, preferable from plant sources, is recommended. </p

Sources of dietary protein and risk of hypertension in a general Dutch population

Evidence suggests a small beneficial effect of dietary protein on blood pressure (BP), especially for plant protein. We examined the relationship between several types of dietary protein (total, plant, animal, dairy, meat and grain) and the risk of hypertension in a general population of 3588 Dutch adults, aged 26–65 years, who were free of hypertension at baseline. Measurements were done at baseline and after 5 and 10 years of follow-up. Hazard ratios (HR), with 95 % CI, for incident hypertension were obtained in tertiles of energy-adjusted protein, using time-dependent Cox regression models. Models were adjusted for age, sex, BMI, education, smoking, baseline systolic BP, dietary confounders and protein from other sources (if applicable). Mean BP was 118/76 mmHg at baseline. Protein intake was 85 (sd 22) g/d (approximately 15 % of energy) with 62 % originating from animal sources. The main sources of protein were dairy products (28 %), meat (24 %) and grain (19 %). During the follow-up, 1568 new cases of hypertension were identified (44 % of the participants). Energy-adjusted intake of total protein, plant protein and animal protein was not significantly associated with hypertension risk (all HR approximately 1·00, P>0·60). Protein from grain showed a significant inverse association with incident hypertension, with a HR of 0·85 (95 % CI 0·73, 1·00, Ptrend = 0·04) for the upper tertile ( = 18 g/d) v. the lower tertile ( <14 g/d), whereas dairy protein and meat protein were not associated with incident hypertension. In conclusion, higher intake of grain protein may contribute to the prevention of hypertension, which warrants confirmation in other population-based studies and randomised controlled trials

Sources of Dietary Protein in Relation to Blood Pressure in a General Dutch Population

Background - Little is known about the relation of different dietary protein types with blood pressure (BP). We examined whether intake of total, plant, animal, dairy, meat, and grain protein was related to BP in a cross sectional cohort of 20,820 Dutch adults, aged 20–65 y and not using antihypertensive medication. Design - Mean BP levels were calculated in quintiles of energy-adjusted protein with adjustment for age, sex, BMI, education, smoking, and intake of energy, alcohol, and other nutrients including protein from other sources. In addition, mean BP difference after substitution of 3 en% carbohydrates or MUFA with protein was calculated. Results - Total protein and animal protein were not associated with BP (ptrend = 0.62 and 0.71 respectively), both at the expense of carbohydrates and MUFA. Systolic BP was 1.8 mmHg lower (ptrend36 g/d) than in the lowest

National laboratory-based surveillance system for antimicrobial resistance: a successful tool to support the control of antimicrobial resistance in the Netherlands

An important cornerstone in the control of antimicrobial resistance (AMR) is a well-designed quantitative system for the surveillance of spread and temporal trends in AMR. Since 2008, the Dutch national AMR surveillance system, based on routine data from medical microbiological laboratories (MMLs), has developed into a successful tool to support the control of AMR in the Netherlands. It provides background information for policy making in public health and healthcare services, supports development of empirical antibiotic therapy guidelines and facilitates in-depth research. In addition, participation of the MMLs in the national AMR surveillance network has contributed to sharing of knowledge and quality improvement. A future improvement will be the implementation of a new semantic standard together with standardised data transfer, which will reduce errors in data handling and enable a more real-time surveillance. Furthermore, the

Associations of plant and animal protein intake with 5-year changes in blood pressure: The Zutphen Elderly Study

Background and aim The aim of the present study was to investigate the association of plant and animal protein intake with 5-year changes in blood pressure (BP) level. Methods and results Analyses were based on 702 observations of 272 men participating in the Zutphen Elderly Study. Men did not use antihypertensive medication and were initially free of cardiovascular disease, diabetes mellitus and cancer. Physical and dietary examinations were performed in 1985, 1990, 1995, and 2000. Diet was assessed using the cross-check dietary history method. Men were categorised into tertiles according to their plant and animal protein intake. BP was measured twice at each examination. The associations of plant and animal protein intake with 5-year changes in BP level were investigated by a random intercept model with first-order autoregressive (AR [1]) serial correlation and a nugget effect. Adjustments were made for age, examination year, BMI, socioeconomic status, smoking, physical activity, prescribed diet, alcohol consumption and intake of energy and nutrients. In 1985, men were 70.1 ± 4.6 years old and had a mean BP of 147/84 mmHg. Mean protein intake was 15 en%, of which one-third consisted of plant protein. The higher-intake tertiles of plant protein intake were associated with a mean 5-year change of -2.9 mmHg (95% CI: -5.6, -0.2) systolic and -1.7 mmHg (95% CI: -3.2, -0.2) diastolic, compared with the lowest-intake tertile. No associations were observed for animal protein intake. Conclusion Intake of plant protein, but not animal protein, was inversely associated with 5-year changes in BP level in elderly men