Tabella Nutrizionale Alimenti Pdf Creator
Tabelle di composizione degli alimenti. Istituto Nazionale della Nutrizione.: Rome.. Google Scholar. O.: The stimulation of insulin secretion in non-insulin-dependent diabetic patients by amino acids and gliclazide in the basal and hyperglycemic state. Tabelle di Composizione degli Alimenti. Roma, Istituto Nazionale della Nutrizione; 1997. View in Article. 10Daugirdas, J.T. Second generation logarithmic estimates of single-pool variable volume Kt/V (An analysis of error). J Am Soc Nephrol. 1993; 4: 1205–1213. View in Article; Abstract; Full Text; Full Text PDF.
Abstract
Micronutrients are of fundamental importance in maintaining health status. However, data on their dietary intake are few particularly in persons with diabetes. The aim of this study was to evaluate in adults with type 1 diabetes (T1DM) attending a tertiary-level diabetes center in Southern Italy the intake of micronutrients (both vitamins and minerals) and the adherence to recommendations. Seven-day food records of 60 T1DM patients were analyzed. Micronutrient intake was evaluated based on the Italian food composition tables and expressed as amount per 1000 kcal of energy intake to adjust for possible underreporting. Adherence to recommendations for vitamins A, B6, B12, and C and niacin was acceptable in both sexes (ranging from 77% to 100%). Half of the patients did not adhere to folate recommendation, even less to vitamin E, and no patient reached the recommended intake for vitamin D. As for minerals, adherence was low for potassium and selenium (0–23%); intermediate for zinc, copper, and magnesium; low and intermediate for calcium in men and women, respectively; and low for iron in women. In conclusion, the diet followed by T1DM patients may not have a sufficient content of different micronutrients. Therefore, an adequate intake of low-fat dairy products, fish, legumes, and vegetables should be encouraged as components of a healthier dietary pattern.
1. Introduction
Besides macronutrients, micronutrients, in particular vitamins and minerals, are of fundamental importance in maintaining health status and in preventing and treating different diseases [, ]. Accordingly, precise dietary recommendations for each vitamin and mineral are issued for the general population. However, this may be even more important in people with diabetes, as different vitamins and minerals play a relevant role in the regulation of glucose metabolism at different levels (insulin action, oxidative stress, and inflammation) and in the prevention of diabetes complications []. In spite of the possible pathophysiological relevance of micronutrient levels, data on their dietary intake are few in the general population and really scant in persons with diabetes, especially those with type 1 diabetes [–].
In patients with type 1 diabetes, insulin therapy is essential for survival. At the same time, adequate nutrition therapy represents a cornerstone for reaching optimal glucose control and for preventing chronic complications. However, in these patients, diet therapy is essentially focused on the amount and quality of carbohydrate in order to regulate the doses of insulin to be injected [, ]. This focus may lead, both in caregivers and in patients, to less attention towards other macronutrients [] and micronutrients. To this respect, while some data are present for diet composition in terms of macronutrients [, –], very little has been reported about micronutrients. In particular, one study refers to children with type 1 diabetes [] and another to a Finnish adult population with type 1 diabetes [].
Therefore, the aim of our study was to evaluate in adult patients with type 1 diabetes attending a tertiary-level diabetes center in Southern Italy the dietary intakes of micronutrients (both vitamins and minerals) and the adherence to the recommended dietary intakes.
2. Materials and Methods
All patients with type 1 diabetes attending the outpatient clinic of the Department of Clinical Medicine and Surgery of Federico II University, a tertiary-level diabetes care, from at least six months and consecutively visited within a period of six months were asked to fill in a seven-day food record, provided that they met the inclusion/exclusion criteria. The exclusion criteria were pregnancy, celiac disease, kidney failure (serum creatinine > 1.5 mg/dL), and other acute or chronic diseases apart from diabetes.
Detailed instructions on how to fill in the food records were given by a dietician. In particular, patients were asked to record for seven consecutive days the following:
The amount of any food or drink consumed using a food scale or household measures
The time of meals (breakfast, morning snack, lunch, afternoon snack, dinner, and evening snack)
The type and, if possible, the brand of the product
The cooking method
When the food records were given back by the patients, the dietician checked the records together with the patients in order to improve the completeness of data. Forms for food recording were given to 140 patients, but only 64 patients (46%) filled in and returned the food records. Of these, four were excluded for incompleteness, and therefore, the food records of 60 patients were analyzed.
The intake of water was not reported on the records by the patients. Since water intake is important especially in relation to calcium and magnesium intakes, we included in the calculations a fixed daily intake of 1000 mL of water for each patient, containing an estimated medium amount of calcium (150 mg) and magnesium (13 mg).
Energy intake and macro- and micronutrient contents were calculated on the basis of the Italian food composition tables of the Center of Research for Food and Nutrition (CREA) [13] utilizing the MetaDieta software (Meteda s.r.l., Ascoli Piceno, Italy).
The macronutrient composition, expressed as percentage of the total caloric intake, was compared with the dietary recommendations for diabetes given by the Italian Diabetes Standards of Care [14] that were mainly based on the recommendations of the Diabetes and Nutrition Study Group of the EASD [].
Taking into account the possible underreporting, the intakes of vitamins and minerals are expressed as amount per 1000 kcal of total energy intake. Intakes were compared to the recommended levels expressed per 1000 kcal assuming an average daily intake of 1800 kcal for women and 2000 kcal for men. The percentage of the patients adhering to the recommendations given by the Italian Society of Nutrition [16] is reported.
Anthropometric measures and blood samples for determination of HbA1c and serum lipid concentrations were taken during the outpatient visit. Body weight measurement was performed using a scale provided with a weighing bar, with a precision of 0.1 kg, according to the standardized methods. The height was detected with a fixed stadiometer, and the measurement was performed with patients barefoot with the shoulders at the stadiometer. The body mass index was calculated by the ratio between the weight (kg) and the height squared (m2). The waist circumference was measured using a nonelastic meter between the inferior rib margin and the anterosuperior iliac spine after a deep expiration avoiding skin compression.
Glycated hemoglobin was measured by high-performance liquid chromatography (HPLC). Serum triglyceride and cholesterol concentrations were assayed by enzymatic colorimetric methods. LDL cholesterol concentration was calculated using Friedwald's formula.
3. Statistical Analysis
Data are expressed as mean ± SD. Differences between women and men were evaluated by t-test for independent samples. A p < 0.05 was considered statistically significant. The statistical analysis was performed according to standard methods using the Statistical Package for Social Sciences software, version 20 (SPSS/PC; SPSS, Chicago, IL, USA).
4. Results
The main characteristics of the participants (n = 60), divided by sex, are reported in Table 1. As expected, women had a lower waist circumference and higher HDL cholesterol levels. More than half of the participants (55%) were on multiple daily insulin injections (MDI) and the remaining ones (45%) on continuous subcutaneous insulin infusion (CSII). No differences for all the parameters considered were detected between MDI and CSII, and therefore, the two groups were combined for analysis. In Table 2, energy intake and diet composition are reported separately for men and women. The energy intake was quite low for both men and women. The intake of macronutrients was, on average, within the recommended dietary intake levels except for fiber consumption that was substantially lower than the recommended level. Sodium intake was lower than recommended, but it must be considered that only NaCl naturally present in foods was evaluated and not the amount added to foods.
Table 1
The main characteristics of the patients with type 1 diabetes participating in the study.
| All (N = 60) | Men (N = 30) | Women (N = 30) | |
|---|---|---|---|
| Age (years) | 35.8 ± 11.3 | 35.5 ± 11.1 | 36.0 ± 11.8 |
| Diabetes duration (years) | 17.3 ± 10.7 | 16.4 ± 10.5 | 18.4 ± 11.1 |
| HbA1c (%) | 7.6 ± 0.8 | 7.6 ± 0.9 | 7.7 ± 0.7 |
| HbA1c (mmol/mol) | 59.9 ± 9.3 | 59.5 ± 10.8 | 60.4 ± 7.8 |
| Body mass index (kg/m2) | 25.5 ± 3.7 | 25.7 ± 3.4 | 25.2 ± 4.0 |
| Waist circumference (cm) | 86.3 ± 10.9 | 90.1 ± 10.4 | 81.9 ± 9.9∗ |
| HDL cholesterol (mg/dL) | 62.7 ± 14.1 | 57.4 ± 13.1 | 67.4 ± 13.5∗ |
| LDL cholesterol (mg/dL) | 99.3 ± 33.2 | 92.3 ± 26.3 | 106.1 ± 37.9 |
| Serum triglycerides (mg/dL) | 82.2 ± 42.9 | 92.5 ± 56.3 | 72.6 ± 22.3 |
Data are expressed as mean ± SD. ∗p < 0.05 versus men.
Table 2
Energy intake and diet composition of the patients with type 1 diabetes participating in the study.
| Nutrient | All (N = 60) | Men (N = 30) | Women (N = 30) | Recommendation§ |
|---|---|---|---|---|
| Energy (kcal/day) | 1653 ± 367 | 1842 ± 364 | 1464 ± 261∗∗∗ | NA |
| Alcohol (TE%) | 14.9 ± 51 | 22.4 ± 60.4 | 7.5 ± 39 | NA |
| Alcohol (g) | 2.1 ± 7.3 | 8.6 ± 1.6 | 5.6 ± 1 | 10 M-20 W |
| Carbohydrate (TE%) | 49.3 ± 5.4 | 51 ± 4.9 | 47.6 ± 5.5∗ | 45–60 |
| Total soluble sugars (TE%) | 14.1 ± 4.2 | 13.3 ± 4.4 | 15 ± 3.8 | NA |
| Added sugars (TE%) | 2.4 ± 2.8 | 2.7 ± 3.6 | 2.1 ± 1.7 | <10 |
| Protein (TE%) | 17.7 ± 2.4 | 17.9 ± 2.7 | 17.5 ± 2.1 | 10–15 |
| Fat (TE%) | 32.8 ± 5.3 | 30.9 ± 5.1 | 34.7 ± 4.9∗∗ | ≤35 |
| Saturated fatty acids (TE%) | 8.8 ± 2.5 | 8.4 ± 2.3 | 9.2 ± 2.7 | <10 |
| Monounsaturated fatty acids (TE%) | 15.2 ± 3.2 | 14.5 ± 3.5 | 15.9 ± 2.7 | >10 |
| Polyunsaturated fatty acids (TE%) | 3.9 ± 0.8 | 3.9 ± 0.8 | 3.9 ± 0.7 | <10 |
| Cholesterol (mg) | 188 ± 65.6 | 206.7 ± 62.7 | 169.3 ± 64.1∗ | <300 |
| Glycemic Index (%) | 55.6 ± 4.6 | 56.4 ± 4.7 | 54.8 ± 4.3 | 45–55 |
| Fiber (g/1000 kcal) | 11.8 ± 4.2 | 11.2 ± 4.2 | 12.5 ± 4.1 | >20 |
| NaCl (g)+ | 4.3 ± 1.5 | 4.9 ± 1.7 | 3.8 ± 1.0∗ | <6 |
Data are expressed as mean ± SD. ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001 versus men. NA = not applicable; TE = total Energy. +Only NaCl present in foods. §Italian Standards of Care ADI-AMD-SID (2013-2014) [14].
The intakes of vitamins and minerals for men and women are shown in Table 3. In this table, also, the percentages of the patients adhering to the recommended dietary intakes are reported. The adherence is acceptable for both men and women for vitamin A, vitamin B6, vitamin B12, niacin, and vitamin C (ranging from 77% to 100%). However, half of the patients did not meet the recommended intake for folate, and the adherence was still lower for vitamin E (20% for men and 43% for women); furthermore, no patient reached the recommended intake for vitamin D. As for minerals, the adherence was extremely low for potassium (7% for men and 0% for women) and selenium (23% for both men and women) and intermediate for zinc, copper, and magnesium. The adherence for calcium and iron differed between men and women being for calcium low in men (50%) and intermediate in women (73%) and for iron high in men (97%) and low in women (57%).
Table 3
Vitamin and minerals intake expressed per 1000 kcal of total energy intake of the patients with type 1 diabetes participating in the study and patients' adherence to the recommendations for the Italian general population∗.
| Men | Women | |||||
|---|---|---|---|---|---|---|
| RI/1000 kcal | Intake/1000 kcal | Adherence (%) | RI/1000 kcal | Intake/1000 kcal | Adherence (%) | |
| Vitamins | ||||||
| Vitamin A (μg) | 250 | 440.9 ± 226.1 | 80 | 222.2 | 537.2 ± 250.7 | 93.3 |
| Vitamin D (μg) | 5 | 1.4 ± 0.9 | 0 | 5.5 | 1.1 ± 0.9 | 0 |
| Vitamin E (mg) | 6.5 | 5.6 ± 1.5 | 20 | 6.7 | 6.5 ± 1.5 | 43.3 |
| Thiamine (mg) | 0.5 | 0.5 ± 0.1 | 66.7 | 0.5 | 0.6 ± 0.2 | 76.7 |
| Riboflavin (mg) | 0.6 | 0.6 ± 0.1 | 40 | 0.61 | 0.7 ± 0.1 | 80 |
| Vitamin B6 (mg) | 0.5 | 0.9 ± 0.2 | 100 | 0.61 | 1 ± 0.3 | 96.7 |
| Vitamin B12 (μg) | 1 | 2.3 ± 1.4 | 96.7 | 1.1 | 2.2 ± 0.9 | 90 |
| Folate (μg) | 160 | 178.1 ± 76.3 | 46.7 | 177.8 | 196.8 ± 67 | 52.3 |
| Vitamin C (mg) | 37.5 | 70.7 ± 52 | 76.7 | 33.3 | 86.3 ± 46.8 | 83.3 |
| Niacin (mg) | 7 | 9.7 ± 2.8 | 80 | 7.8 | 10 ± 2.7 | 80 |
| Minerals | ||||||
| Calcium (mg) | 400 | 403.6 ± 121.3 | 50 | 444.4 | 493.4 ± 79.0 | 73.3 |
| Potassium (mg) | 1950 | 1403 ± 352 | 6.7 | 2166 | 1541 ± 316 | 0 |
| Magnesium (mg) | 85 | 94.5 ± 28.5 | 63.3 | 94.4 | 102.9 ± 24.2 | 60 |
| Iron (mg) | 3.5 | 5.6 ± 1.9 | 96.7 | 5.5 | 6.1 ± 1.5 | 56.7 |
| Zinc (mg) | 5 | 5.1 ± 0.8 | 60 | 4.4 | 5.3 ± 1.1 | 76.7 |
| Copper (mg) | 0.3 | 0.4 ± 0.1 | 66.7 | 0.4 | 0.4 ± 0.1 | 63.3 |
| Selenium (μg) | 22.5 | 18.8 ± 6.5 | 23.3 | 25 | 20.2 ± 8.2 | 23.3 |
Data are expressed as mean ± SD. RI: recommended intake. ∗Società Italiana di Nutrizione Umana. Livelli di Assunzione di Riferimento di Nutrienti ed Energia per la popolazione italiana (LARN–IV review 2014) [16].
5. Discussion
This study shows that the diet composition of our relatively small cohort of patients with type 1 diabetes was on average within the recommended dietary intakes for what concerns macronutrients. Fiber intake was, instead, very low confirming results obtained in patients with type 2 diabetes from the same geographical area [, ].
The main focus of our study was on micronutrient intake. To this respect, the most relevant results are that, even correcting for possible underreporting—a real problem in the evaluation of dietary habits whatever the method used—the adherence was unsatisfactory for some micronutrients.
In particular, as for vitamins, no patient adhered to the recommended intake for vitamin D. The adherence was poor for vitamin E and folate and, at least in women, for riboflavin. For what concerns minerals, the adherence was very poor for potassium, poor for selenium, and unsatisfactory for calcium (at least in men) and iron in women. For the other micronutrients, the adherence was in general not fully adequate but certainly more satisfactory.
Certainly, the most impressing results regard vitamin D as no patient adhered to the recommendations. This is in line with the data reported in the general population from different countries, for example, Italy, Finland, and USA [, , 20], and in Finnish patients with type 1 diabetes []. To investigate about the reasons of this very low intake, we looked at the frequency of consumption of foods that represent the main source of vitamin D, that is, fish and dairy products. In our cohort, the consumption of fish (on average, one portion per week) was very low and that of dairy products (less than 2 servings per day) was lower than recommended (3 servings per day) by the USDA Dietary Guidelines for Americans [20].
The adherence to recommendations for potassium was very poor. This result may be related to the low consumption of vegetables and fruit in our population. For what concerns the other micronutrients for which we found poor or, anyhow, unsatisfactory adherence, intakes were lower compared to the ones reported in the only other study performed in adults with type 1 diabetes [], although the results were quite in line with the results in the general population wherein unsatisfactory intakes for different vitamins (vitamin D, vitamin A, vitamin E, folate, and riboflavin) and minerals (calcium, magnesium, selenium, and iron) have been generally found []. The low intake of the above micronutrients in our population was linked, as for foods, especially to low consumption of fish and dairy products and also of legumes and vegetables as indicated by the low intake of fiber.
The poor adherence for some micronutrients in our population of patients with type 1 diabetes was rather unexpected. These patients receive precise dietary recommendations that should translate into a generally healthy diet. However, it is common that diabetes professionals and, even more, patients with diabetes focus their attention on the amount of carbohydrates on which they balance insulin therapy paying less attention to the overall diet, in particular to foods representing the main source of micronutrients. Furthermore, in order to avoid variations in postprandial blood glucose response, patients prefer to utilize a restricted selection of foods. This may contribute to making the diet not adequate in terms of micronutrient content.
Whatever the reason, the unsatisfactory intake of many important micronutrients in this particular category of patients could lead to a worsening of glucose control, a major susceptibility to micro- and macrovascular complications, and a higher risk of osteoporosis. This means that adequate strategies aiming at improving also micronutrient intake should be implemented in the general population and, particularly, in persons with type 1 diabetes. To this regard, it has been estimated that in the USA, the consumption of the daily recommended intake of dairy products would eliminate inadequacy of calcium intake across all age and gender categories and only partially improve vitamin A and magnesium intake. However, an adequate intake of dairy products would not reduce the poor adherence to vitamin D and potassium recommended intake, for which other strategies are needed such as sun exposure (if possible and with moderation) and increases in other foods rich in vitamin D (in particular fish) and potassium (legumes, vegetables, and fruit) [].
Our study has some strengths, particularly in relation to the use of the 7-day food records that represent the gold standard for evaluating dietary habits at individual level. The limitation of the study is the possible underreporting that is anyway common to all types of food recording methods. In addition, the food record was filled in by the participants on only one occasion, and therefore, this did not allow to take into account the seasonal variability. Lastly, the results observed in this relatively small cohort should be confirmed in larger samples of patients with type 1 diabetes. To this respect, obtaining data on dietary habits in this category of patients may be challenging, as shown by the low percentage of people who filled in the records in the present study, in line with a similar participation rate in a previous study []. It can be speculated that patients who did not agree to participate had on the average a lower consideration for diet and therefore were less likely to be compliant to dietary recommendations. Consequently, if anything, the low participation rate may have hindered an even lower adherence to recommendations than that observed in our study.
In conclusion, our study underlines that the diet followed by patients with type 1 diabetes may not be adequate concerning micronutrient intake and that strategies aiming at solving this problem should be implemented. To this aim, an adequate intake of dairy products—in particular low-fat products in order to avoid an increment in saturated fat—fish, legumes, and vegetables should be encouraged as components of a healthier dietary pattern.
Conflicts of Interest
The authors declare that there is no conflict of interest regarding the publication of this paper.
References
Abstract
Dietary L-arginine supplementation has been proposed to reverse endothelial dysfunction in such diverse pathophysiologic conditions as hypercholesterolemia, coronary heart disease, and some forms of animal hypertension. In particular, chronic oral administration of L-arginine prevented the blood pressure rise induced by sodium chloride loading in salt-sensitive rats. To investigate the effects of L-arginine–rich diets on blood pressure and metabolic and coagulation parameters we performed a single-blind, controlled, crossover dietary intervention in six healthy volunteers. The subjects (aged 39 ± 4 years, body mass index [BMI] 26 ± 1 kg/m2, mean ± SEM) received, in random sequence, three different isocaloric diets, each for a period of 1 week (Diet 1: control; Diet 2: L-arginine enriched by natural foods; Diet 3: identical to Diet 1 plus oral L-arginine supplement). Sodium intake was set at a constant level (about 180 mmol/day) throughout the three study periods. A blood pressure decrease was observed with both L-arginine-rich diets (Diet 2 v 1, SBP: −6.2 mm Hg [95% CI: −0.5 to −11.8], DBP: −5.0 mm Hg [−2.8 to −7.2]; Diet 3 v 1, SBP: −6.2 mm Hg [−1.8 to −10.5], DBP: −6.8 mm Hg [−3.0 to −10.6]). A slight increase in creatinine clearance (P = .07) and a fall in fasting blood glucose (P = .008) occurred after Diet 3 and, to a lesser extent, after Diet 2. Serum total cholesterol (P = .06) and triglyceride (P = .009) decreased and HDL cholesterol increased (P = .04) after Diet 2, but not after Diet 3.
These results indicate that a moderate increase in L-arginine significantly lowered blood pressure and affected renal function and carbohydrate metabolism in healthy volunteers.
Although a few studies have investigated the relationship between dietary protein intake and blood pressure,1 little interest has been paid thus far to the effect of single amino acids. Recently, the identification of nitric oxide (NO) as a product of the metabolism of L-arginine through the NO synthase pathway2 has opened a new avenue of research. L-arginine, a so-called “conditionally” essential amino acid largely present in several food items, plays a central role in a number of major metabolic pathways (3). Its average dietary intake is 5.4 grams/day, assuming a total daily protein intake of 100 grams/day (3). On clinical grounds, interest in the role of this aminoacid has been stimulated by the observation that L-arginine supplementation was able to attenuate the endothelial dysfunction associated with hypercholesterolemia (4) and coronary heart disease (5). Moreover, hypertension induced by sodium chloride loading in Dahl salt-sensitive rats was prevented by chronic dietary L-arginine supplementation.6,–8 Yet in other studies the parenteral administration of large doses of L-arginine acutely lowered blood pressure in normotensive9,11 and in salt-sensitive hypertensive individuals.9,–11 Against this background, the present study was designed to investigate the effects of increased L-arginine dietary intake—in the form of naturally arginine-rich foods or as a pharmacologic preparation—on blood pressure and metabolic and coagulation parameters in healthy humans.
Materials and methods
Six untreated healthy volunteers (aged 39 ± 4 years, body mass index [BMI] 26 ± 1 kg/m2, mean ± SEM) gave their informed consent to the study and, after baseline evaluation, received, in random sequence, three different isocaloric diets each for a period of 1 week.
Dietary intervention
The diets were tailored for each patient by an expert dietitian to keep the caloric intake constant . Diet 1 (control) was a relatively low L-arginine diet (3.5–4.0 g/day). Diet 2 was an L-arginine–enriched diet (10 g/day) based on natural foods; dry legumes (lentils) and nuts (hazelnuts, walnuts, and peanuts) were chosen as major sources of L-arginine, due to their particularly high L-arginine content. Diet 3 was identical to Diet 1 (control diet), but was supplemented with 10 g/day of an oral L-arginine preparation (Bio-Arginina, Farmaceutici Damor s.p.a, Naples, Italy), given three times a day. The nutrient composition of the diets was calculated based upon updated tables of food composition.12 The calculated composition of the diets is reported in Table 1. The three diets were similar with regard to their macronutrient composition, with the exception of fiber intake, which was higher in Diet 2. The dietary content of L-arginine in Diet 2 was more than doubled as compared with the control diet. Sodium intake was set at a constant level throughout the three study periods (about 180 mmol/day). Meals were prepared in the research kitchen of the Institute of Food Sciences and Technology in Avellino. On weekdays, the participants had lunch on site and took their evening meals with them. On Friday, they received their weekend meals to be consumed off site. Two participants started the study with the control diet (Diet 1), two with the Diet 2, and two with the Diet 3.
Calculated compositions of the control diet and the intervention diet
| −6.2 (−0.5 to −11.8) | .03 | −6.2 (−1.8 to −10.5) | .01 | ||
| DBP (mm Hg) | 81.2 (4.6) | −5.0 (−2.8 to −7.2) | .002 | −6.8 (−3.0 to −10.6) | .006 |
| Crea Cl (mL/s) | 2.55 (0.31) | 0.26 (−0.20 to 0.71) | .20 | 0.30 (−0.03 to 0.63) | .07 |
| U-Na (mmol/24 h) | 190 (18) | −8 (−57 to 41) | .69 | −12 (−88 to 65) | .71 |
| U-K (mmol/24 h) | 53 (7) | 22 (−2 to 48) | .06 | 1 (−7 to 8) | .73 |
| S-chol (mmol/L) | 4.86 (0.36) | −0.33 (−0.67 to 0.001) | .06 | 0.07 (−0.15 to 0.31) | .45 |
| S-TG (mmol/L) | 0.93 (0.12) | −0.29 (−0.47 to −0.11) | .009 | −0.21 (−0.48 to 0.03) | .08 |
| HDL-Chol (mmol/L) | 1.21 (0.11) | 0.1 (0.005 to 0.20) | .04 | 0.04 (−0.05 to 0.13) | .32 |
| Plasma insulin (mU/L) | 7.8 (0.7) | 0.3 (−1.5 to 2.1) | .68 | 0.4 (−0.9 to 1.6) | .47 |
| FBG (mmo/L) | 4.81 (0.22) | −0.20 (−0.46 to 0.06) | .10 | −0.44 (−0.71 to −0.17) | .008 |
| −6.2 (−0.5 to −11.8) | .03 | −6.2 (−1.8 to −10.5) | .01 | ||
| DBP (mm Hg) | 81.2 (4.6) | −5.0 (−2.8 to −7.2) | .002 | −6.8 (−3.0 to −10.6) | .006 |
| Crea Cl (mL/s) | 2.55 (0.31) | 0.26 (−0.20 to 0.71) | .20 | 0.30 (−0.03 to 0.63) | .07 |
| U-Na (mmol/24 h) | 190 (18) | −8 (−57 to 41) | .69 | −12 (−88 to 65) | .71 |
| U-K (mmol/24 h) | 53 (7) | 22 (−2 to 48) | .06 | 1 (−7 to 8) | .73 |
| S-chol (mmol/L) | 4.86 (0.36) | −0.33 (−0.67 to 0.001) | .06 | 0.07 (−0.15 to 0.31) | .45 |
| S-TG (mmol/L) | 0.93 (0.12) | −0.29 (−0.47 to −0.11) | .009 | −0.21 (−0.48 to 0.03) | .08 |
| HDL-Chol (mmol/L) | 1.21 (0.11) | 0.1 (0.005 to 0.20) | .04 | 0.04 (−0.05 to 0.13) | .32 |
| Plasma insulin (mU/L) | 7.8 (0.7) | 0.3 (−1.5 to 2.1) | .68 | 0.4 (−0.9 to 1.6) | .47 |
| FBG (mmo/L) | 4.81 (0.22) | −0.20 (−0.46 to 0.06) | .10 | −0.44 (−0.71 to −0.17) | .008 |
SBP, systolic blood pressure; DBP, diastolic blood pressure; Crea Cl, creatinine clearance; U-Na, 24-h urinary Na excretion; U-K, 24-h urinary K excretion; S-chol, serum total cholesterol; S-TG, serum triglyceride; HDL-chol, high-density lipoprotein cholesterol; FBG, fasting blood glucose; M, mean; SEM, standard error of the mean; CI, confidence interval.
Effects of L-arginine–rich diets on blood pressure and metabolic parameters
| −6.2 (−0.5 to −11.8) | .03 | −6.2 (−1.8 to −10.5) | .01 | ||
| DBP (mm Hg) | 81.2 (4.6) | −5.0 (−2.8 to −7.2) | .002 | −6.8 (−3.0 to −10.6) | .006 |
| Crea Cl (mL/s) | 2.55 (0.31) | 0.26 (−0.20 to 0.71) | .20 | 0.30 (−0.03 to 0.63) | .07 |
| U-Na (mmol/24 h) | 190 (18) | −8 (−57 to 41) | .69 | −12 (−88 to 65) | .71 |
| U-K (mmol/24 h) | 53 (7) | 22 (−2 to 48) | .06 | 1 (−7 to 8) | .73 |
| S-chol (mmol/L) | 4.86 (0.36) | −0.33 (−0.67 to 0.001) | .06 | 0.07 (−0.15 to 0.31) | .45 |
| S-TG (mmol/L) | 0.93 (0.12) | −0.29 (−0.47 to −0.11) | .009 | −0.21 (−0.48 to 0.03) | .08 |
| HDL-Chol (mmol/L) | 1.21 (0.11) | 0.1 (0.005 to 0.20) | .04 | 0.04 (−0.05 to 0.13) | .32 |
| Plasma insulin (mU/L) | 7.8 (0.7) | 0.3 (−1.5 to 2.1) | .68 | 0.4 (−0.9 to 1.6) | .47 |
| FBG (mmo/L) | 4.81 (0.22) | −0.20 (−0.46 to 0.06) | .10 | −0.44 (−0.71 to −0.17) | .008 |
| −6.2 (−0.5 to −11.8) | .03 | −6.2 (−1.8 to −10.5) | .01 | ||
| DBP (mm Hg) | 81.2 (4.6) | −5.0 (−2.8 to −7.2) | .002 | −6.8 (−3.0 to −10.6) | .006 |
| Crea Cl (mL/s) | 2.55 (0.31) | 0.26 (−0.20 to 0.71) | .20 | 0.30 (−0.03 to 0.63) | .07 |
| U-Na (mmol/24 h) | 190 (18) | −8 (−57 to 41) | .69 | −12 (−88 to 65) | .71 |
| U-K (mmol/24 h) | 53 (7) | 22 (−2 to 48) | .06 | 1 (−7 to 8) | .73 |
| S-chol (mmol/L) | 4.86 (0.36) | −0.33 (−0.67 to 0.001) | .06 | 0.07 (−0.15 to 0.31) | .45 |
| S-TG (mmol/L) | 0.93 (0.12) | −0.29 (−0.47 to −0.11) | .009 | −0.21 (−0.48 to 0.03) | .08 |
| HDL-Chol (mmol/L) | 1.21 (0.11) | 0.1 (0.005 to 0.20) | .04 | 0.04 (−0.05 to 0.13) | .32 |
| Plasma insulin (mU/L) | 7.8 (0.7) | 0.3 (−1.5 to 2.1) | .68 | 0.4 (−0.9 to 1.6) | .47 |
| FBG (mmo/L) | 4.81 (0.22) | −0.20 (−0.46 to 0.06) | .10 | −0.44 (−0.71 to −0.17) | .008 |
SBP, systolic blood pressure; DBP, diastolic blood pressure; Crea Cl, creatinine clearance; U-Na, 24-h urinary Na excretion; U-K, 24-h urinary K excretion; S-chol, serum total cholesterol; S-TG, serum triglyceride; HDL-chol, high-density lipoprotein cholesterol; FBG, fasting blood glucose; M, mean; SEM, standard error of the mean; CI, confidence interval.
After Diet 3, a significant reduction was observed in fasting blood glucose concentration; a similar trend was also apparent after Diet 2. A decrease in serum total cholesterol and triglycerides and an increase in HDL-cholesterol concentration were observed after Diet 2. Twenty-four–hour urinary sodium excretion was very close to the prefixed value (180 mmol/day) in all dietary periods, whereas a trend toward an increase in 24-h potassium excretion was observed after Diet 2. A trend toward an increase in creatinine clearance was also observed at the end of both Diets 2 and 3, the difference approaching statistical significance versus the control diet after Diet 3.
Body weight, plasma insulin levels, and coagulation factors (ELA, PAI-I, t-PA, fibrinogen) did not change throughout the study.
Discussion
To the best of our knowledge, there are no published data from controlled studies dealing with the blood pressure effects of L-arginine–rich diets in humans. The main finding of our work is that this dietary intervention was associated with a statistically and biologically significant blood pressure reduction, whether L-arginine was provided through natural foods or as a pharmacologic preparation.
A reduction in serum glucose and an apparent increase in renal glomerular filtration rate (as suggested by the higher creatinine clearance) were also observed. To our knowledge, this is also the first report of an effect of dietary L-arginine supplementation on glucose metabolism in humans. An effect of L-arginine on insulin release has been observed in acute experiments using the parenteral route13; it is possible that a similar mechanism accounts for our finding during chronic oral administration, although no significant changes in fasting plasma insulin levels were observed in the present study. The increase in creatinine clearance is consistent with the recognized effects of an oral protein load or an infusion of amino acid mixtures on renal hemodynamics, although here again the available information stems essentially from acute experiments.14,15 As to the improvement in serum lipid profile after Diet 2, this was most likely due to the higher fiber content of that diet.16
The explanation for the blood-pressure–lowering effect of L-arginine administration in our study is not apparent. Modulation of NO production may be critical for blood pressure control, particularly during dietary salt loading,11,17 and L-arginine feeding may actually correct a failure in NO production under these circumstances.6,–8,10,11 A dysfunction in the L-arginine-nitric oxide pathway in the renal circulation has also been advocated by recent studies in patients with mild primary hypertension.9,–11 Interestingly, in two of these studies9,11 the acute infusion of L-arginine reduced blood pressure also in normotensive control subjects, a finding consistent with our results. An unresolved issue, however, is that increased dietary L-arginine availability does not necessarily lead to enhanced NO production, as L-arginine supply is not normally rate limiting for NO synthesis.18 Alternative or additional mechanisms whereby L-arginine may affect blood pressure and renal function need to be investigated (direct effects of the amino acid, release of hormones, prostaglandins, etc.).
A few potential limitations of this study should be considered. First, the short-term duration of the intervention does not allow exclusion of the possibility that the blood-pressure–lowering effect of L-arginine may not be sustained over time. Second, we set out a high level of sodium intake for our experimental diets on the assumption that modulation of NO delivery is critical to blood pressure control during dietary salt loading.10,11,17 Thus we cannot exclude that the response may be limited to (or greater in) subjects eating a high-sodium diet, as we did not study subjects at different levels of sodium intake. Third, the possibility that dietary components other than L-arginine might at least partly explain the effect observed needs to be considered as well. The 24-h urinary potassium excretion of our participants increased after Diet 2, most likely due to the increase in legume and nut intake. In a previous long-term controlled trial we showed that increasing dietary potassium intake improved blood pressure control in hypertensive patients19; however, in the present study, a blood pressure fall similar to the one observed with Diet 2 took place when L-arginine was given as pharmacologic supplementation to the control diet, thus ruling out the confounding influence of dietary components other than L-arginine. Finally, the dietary modifications adopted in our trial are not intended for use in clinical practice. Our dietary modifications were implemented to achieve the goal of consistently increasing L-arginine intake while avoiding, as much as possible, the influence of confounding factors on the experimental results. Interestingly, however, the magnitude of the blood pressure fall observed with both dietary and pharmacologic increase in L-arginine intake was similar to that reported by the DASH Collaborative Research Group20 and by McCarron et al,21 as a consequence of more complex dietary modifications aimed to provide, respectively, a dietary model for the prevention and treatment of high blood pressure20 and for the nutritional management of cardiovascular risk factors.21
In conclusion, the present study indicates that an approximately twofold increase in dietary L-arginine intake had significant hemodynamic and metabolic effects in a group of healthy men. Further studies are warranted to confirm these findings over a long-term period and in a larger population; to evaluate the blood-pressure–lowering effect of oral L-arginine in hypertensive patients; and to elucidate the mechanism(s) involved.3,4,5
Acknowledgments
We thank Rosalba Giacco, MD, and Ms. Anna Maria Palumbo for the generous help with the fieldwork; Angela Giacco, RD, and Delia Pacioni, RD, for valuable dietary advice; and Rosanna Scala for editing the manuscript.
References
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