Research and Professional Briefs A Very-Low-Fat Vegan Diet ...

RESEARCH

Research and Professional Briefs

A Very-Low-Fat Vegan Diet Increases Intake of Protective Dietary Factors and Decreases Intake of Pathogenic Dietary Factors

ANTONELLA DEWELL, MS, RD; GERDI WEIDNER, PhD; MICHAEL D. SUMNER, PhD; CHRISTINE S. CHI; DEAN ORNISH, MD

ABSTRACT There is increasing evidence that dietary factors in plantbased diets are important in the prevention of chronic disease. This study examined protective (eg, antioxidant vitamins, carotenoids, and fiber) and pathogenic (eg, saturated fatty acids and cholesterol) dietary factors in a very-low-fat vegan diet. Ninety-three early-stage prostate cancer patients participated in a randomized controlled trial and were assigned to a very-low-fat (10% fat) vegan diet supplemented with soy protein and lifestyle changes or to usual care. Three-day food records were collected at baseline (n42 intervention, n43 control) and after 1 year (n37 in each group). Analyses of changes in dietary intake of macronutrients, vitamins, minerals, carotenoids, and isoflavones from baseline to 1 year showed significantly increased intake of most protective dietary factors (eg, fiber increased from a mean of 31 to 59 g/day, lycopene increased from 8,693 to 34,464 g/day) and significantly decreased intake of most pathogenic dietary factors (eg, saturated fatty acids decreased from 20 to 5 g/day, cholesterol decreased from 200 to 10 mg/day) in the

A. Dewell is a research project coordinator, Stanford Prevention Research Center, Stanford University School of Medicine, Stanford, CA; at the time of the study, she was a research dietitian, Preventive Medicine Research Institute, Sausalito, CA. G. Weidner is vice president and director of research, Preventive Medicine Research Institute, Sausalito, CA. M. Sumner is a research fellow, Thelton E. Henderson Center for Social Justice, University of California, Berkeley; at the time of the study, he was a postdoctoral fellow, Preventive Medicine Research Institute, Sausalito, CA. C. S. Chi is a graduate student at the Department of Nutrition and Food Science, San Jose State University, San Jose, CA; at the time of the study, she was a research and clinical nutrition assistant, Preventive Medicine Research Institute, Sausalito, CA. D. Ornish is founder and president, Preventive Medicine Research Institute, and a clinical professor of medicine, University of California, San Francisco, Sausalito, CA.

Address correspondence to: Gerdi Weidner, PhD, Vice President and Director of Research, Preventive Medicine Research Institute, 900 Bridgeway, Sausalito, CA 94965. E-mail: gerdi.weidner@

Copyright ? 2008 by the American Dietetic Association.

0002-8223/08/10802-0005$34.00/0 doi: 10.1016/j.jada.2007.10.044

intervention group compared to controls. These results suggest that a very-low-fat vegan diet can be useful in increasing intake of protective nutrients and phytochemicals and minimizing intake of dietary factors implicated in several chronic diseases. J Am Diet Assoc. 2008;108:347-356.

T he prominent role of diet and other lifestyle factors in the prevention of chronic disease is widely accepted (1-6). Diet patterns emphasizing plant foods appear to be protective against several types of cancer, cardiovascular disease (CVD), diabetes, age-related macular degeneration, and overall mortality (5,7-15). One benefit of plant-based diets is that they contain very low or negligible amounts of saturated fat and are devoid of cholesterol. However, there is growing evidence that the inclusion of several protective dietary factors inherently present in plant foods (eg, antioxidants, carotenoids, and fiber) may confer benefits that are superior to mere avoidance of pathogenic factors such as saturated fat and cholesterol (7,15-20). For example, a recent ecologic study investigating the association between well-known cardioprotective nutrients (eg, folate, carotenoids, and fiber) and coronary mortality, found that 86% to 90% of the variation in coronary mortality in 19 European countries could be explained by low consumption of folate and fiber and a high n-6:n-3 fatty acid ratio (21).

The aim of this study was to examine intake of protective and pathogenic dietary factors in a very-low-fat vegan diet used in the Prostate Cancer Lifestyle Trial (13).

METHODS

Participants were men with early-stage prostate cancer (active surveillance) enrolled in the Prostate Cancer Lifestyle Trial, a randomized clinical trial investigating the effect of comprehensive lifestyle changes on the progression of prostate cancer. The University of California?San Francisco Committee on Human Research Institutional Review Board approved this study. The intervention, including dietary counseling, and main findings from this study have been reported previously (13,22,23). Briefly, participants in the intervention group were asked to follow an intensive lifestyle program, including an ad libitum very-low-fat vegan diet (22), moderate aerobic exercise, stress management, and social group support. To achieve a fat intake of approximately 10% of energy from fat, participants were instructed by a registered dietitian

? 2008 by the American Dietetic Association

Journal of the AMERICAN DIETETIC ASSOCIATION 347

Table 1. Changes in dietary intake from baseline to 1 year for intervention and control participants (n37 each) in a study of the effects of a very-low-fat vegan diet in men with early-stage prostate cancera

Variable

Baseline

1y

Intervention vs control group

Baseline vs Grouptime

1y

interaction

Energy and macronutrients Energy (kcal) Intervention Control Fat (g) Intervention Control Energy from fat (%) Intervention Control Saturated fatty acids (g) Intervention Control Energy from saturated fatty acids (%) Intervention Control Monounsaturated fatty acids (g) Intervention Control Energy from monounsaturated fatty acids (%) Intervention Control Polyunsatured fatty acids (g) Intervention Control Energy from polyunsatured fatty acids (%) Intervention Control n-3 Fatty acids (g) Intervention Control n-6 Fatty acids (g) Intervention Control n-6:n-3 Intervention Control Trans-fatty acids (g) Intervention Control Polyunsaturated fatty acid:saturated fatty

acid Intervention Control Cholesterolb (mg) Intervention Control Cholesterol to saturated fatty acid index Intervention Control Protein (g) Intervention Control Energy from protein (%) Intervention Control

4 meanstandard deviation 3

2,077512x 2,052482x

6836x 6527x

289x 289x

2013x 2013x

8.14x 8.75x

2516x 2511x

104x 114x

179x 156x

6.83x 6.63x

1.91 2.63

158x 125x

8.65x 6.43x

3.43x 4.14x

2,283603xy 1,942482xz

2710y 6026x

113y 279x

52y 1811x

1.81y 85x

73y 2211x

31y 104x

115y 146xy

4.41y 6.52x

1.61 21

104y 135xy

6.92x 73x

0.81y 3.73x

1.160.6x 1.10.8x

200139x 222150x

3019x 3220x

8021x 7922x

164x 164x

2.460.4y 1.190.7x

1024y 175130x

52y 2717x

11535y 8327x

204y 174x

4TMTMTMTMTMTMTMTMTMTMTMTMTMTMTM P value TMTMTMTMTMTMTMTMTMTMTMTMTMTMTM3

0.058

0.522

0.040

0.003

0.001

0.001

0.001

0.001

0.001

0.002

0.001

0.001

0.001

0.001

0.001

0.001

0.001

0.001

0.001

0.001

0.001

0.581

0.006

0.018

0.026

0.000

0.001

0.029

0.091

0.624

0.877

0.008

0.006

0.080

0.281

0.025

0.004

0.001

0.002

0.001 0.001 0.001 0.001 0.021

0.001 0.001 0.001 0.001 0.001

0.001 0.001 0.001 0.001 0.001

(continued)

348 February 2008 Volume 108 Number 2

Table 1. Changes in dietary intake from baseline to 1 year for intervention and control participants (n37 each) in a study of the effects of a very-low-fat vegan diet in men with early-stage prostate cancera (continued)

Variable

Baseline

1y

Intervention vs control group

Baseline vs Grouptime

1y

interaction

Animal proteinb (g) Intervention Control Vegetable protein (g) Intervention Control Carbohydrate (g) Intervention Control Energy from carbohydrate (%) Intervention Control Total sugars (g) Intervention Control Added sugars (g) Intervention Control Fructose (g) Intervention Control Galactose (g) Intervention Control Glucose (g) Intervention Control Lactose (g) Intervention Control Maltose (g) Intervention Control Sucrose (g) Intervention Control Starch (g) Intervention Control Total fiber (g) Intervention Control Soluble fiber (g) Intervention Control Insoluble fiber (g) Intervention Control Vitamins Vitamin A (g REc) Intervention Control Vitamin D (g) Intervention Control Vitamin E (mg) Intervention Control

3921x 3922x

4017x 4023x

29479x 28695x

5713x 5612x

11949x 11348x

5634 5028

3016x 2813x

0.560.9x 0.330.4x

3114x 2814x

8.48x 9.710x

3.83x 3.73

4626 4428

123.938x 121.447x

3114x 3117x

83x 8.24x

2311x 2213x

26y 3923x

11236y 4328x

430119y 27384x

755y 5712x

14956y 10845x

5131 5231

5426y 2714x

0.180.2x 0.450.8x

4822y 2713x

0.51y 8.88x

6.64y 3.63x

3916 4224

189.854y 117.839x

5924y 3014x

15.67y 83x

4317y 2211x

0.001 0.001 0.001 0.001 0.024 0.651 0.001 0.867 0.001 0.003 0.010 0.970 0.001 0.001 0.001 0.001

1,6811,372x 2,4811,665y 0.751 2,1951,927x 1,7621,357xy

4.43x 6.36x

6.43x 5.24x

0.590

1211x 1417x

189y 1217xy

0.591

0.001 0.001 0.001 0.001 0.041 0.571 0.001 0.208 0.001 0.001 0.001 0.141 0.001 0.001 0.001 0.001

0.321 0.497 0.101

0.001 0.001 0.001 0.001 0.003 0.347 0.001 0.017 0.001 0.001 0.001 0.433 0.001 0.001 0.001 0.001

0.001 0.028 0.012

(continued)

February 2008 Journal of the AMERICAN DIETETIC ASSOCIATION 349

Table 1. Changes in dietary intake from baseline to 1 year for intervention and control participants (n37 each) in a study of the effects of a very-low-fat vegan diet in men with early-stage prostate cancera (continued)

Variable

Baseline

1y

Intervention vs control group

Baseline vs Grouptime

1y

interaction

Vitamin K (g) Intervention Control Vitamin C (mg) Intervention Control Thiamin (vitamin B-1) (mg) Intervention Control Riboflavin (vitamin B-2) (mg) Intervention Control Niacin (vitamin B-3) (mg) Intervention Control Pantothenic acid (mg) Intervention Control Vitamin B-6 (mg) Intervention Control Vitamin B-12 (g) Intervention Control Folate (g) Intervention Control Minerals Calcium (mg) Intervention Control Phosphorus (mg) Intervention Control Magnesium (mg) Intervention Control Sodium (mg) Intervention Control Potassium (mg) Intervention Control Iron (mg) Intervention Control Zinc (mg) Intervention Control Copper (mg) Intervention Control Selenium (g) Intervention Control Manganese (mg) Intervention Control

350 February 2008 Volume 108 Number 2

243199 212160

171109x 202132x

1.90x 1.91x

21x 2.31x

248 249

6.12x 6.22x

2.31x 2.31x

3.92 5.43

440179x 443240x

347274 237254

324149y 184137x

2.81y 21x

2.61y 2.21xy

2711 258

6.53x 5.92x

4.12y 2.41x

3.52 4.73

926380y 477234x

0.107 0.049 0.002 0.500 0.608 0.512 0.001 0.007 0.001

804352x 1,310580y

825327x

825332x

0.003

1,386373x 2,048690y 1,342425x 1,360433x

0.001

418164x 396162x

657249y 412179x

0.001

3,6421,223 4,0691,392 0.841 3,8401,242 3,7711,481

3,6441,037x 5,6042,297y 0.002 3,7251,434x 3,5161,313x

186x 188x

3412y 199x

0.001

114x 114x

186y 114x

0.001

1.91x 1.81x

3.61y 1.81x

0.001

12853 13352

14043 11832

0.276

5.83x 5.53x

114y 5.63x

0.001

0.039 0.001 0.001 0.022 0.089 0.834 0.001 0.198 0.001

0.001 0.001 0.001 0.346 0.001 0.001 0.001 0.001 0.787 0.001

0.202 0.001 0.001 0.003 0.331 0.220 0.001 0.756 0.001

0.001 0.001 0.001 0.192 0.001 0.001 0.001 0.001 0.065 0.001

(continued)

Table 1. Changes in dietary intake from baseline to 1 year for intervention and control participants (n37 each) in a study of the effects of a very-low-fat vegan diet in men with early-stage prostate cancera (continued)

Variable

Baseline

1y

Intervention vs control group

Baseline vs Grouptime

1y

interaction

Carotenoids -carotene (g) Intervention Control -carotene (g) Intervention Control -Cryptoxanthin (g) Intervention Control Lutein and zeaxanthin (g) Intervention Control Lycopene (g) Intervention Control Isoflavones Total isoflavones (mg) Intervention Control Isoflavones from diet (mg) Intervention Control Isoflavones from supplement (mg) Intervention Control

7,2706,956x 12,3608,588y 0.368 9,4229,606x 7,2287,347x

1,9333,410 2,4552,868 0.575 2,2533,692 1,4562,412

287251 361338

551472 0.687 416529

4,8373,769x 8,5888,178y 0.119 4,7614,071x 5,0836,645xy

8,69310,474x 34,46423,108y 0.001 8,9429,987x 9,2928,588x

2030x 1840x

1828x 1739x

1.66x 14x

13361y 2433x

7649y 2229x

56.827y 1.96x

0.001 0.001 0.001

0.135 0.738 0.009 0.012 0.001

0.001 0.001 0.001

0.001 0.112 0.082 0.034 0.001

0.001 0.001 0.001

aSuperscripts (x,y,z) denote comparisons within columns and rows. Means with different superscripts are significantly different from one another (P0.05, Bonferroni adjusted). bCholesterol and animal protein are higher than 0 mg/g in intervention group at 1 year due to a minor deviation from dietary instruction to consume an exclusively vegan diet. cREretinol equivalents.

to avoid all sources of added fat (eg, oils and margarines) and high-fat foods (eg, nuts, peanuts, olives, avocados, chocolate, and coconut). Whole, unrefined foods were emphasized, and added sugar intake was recommended to 20 g/day. In addition, participants were asked to consume one 58-g serving of a fortified soy protein powder (SUPRO SOY, The Solae Company, St Louis, MO, formerly DuPont Technologies) once a day, to provide isoflavones because of their role in inhibiting prostate cancer genesis and growth (24,25). Also, daily consumption of 16 oz low-sodium tomato-based vegetable juice was recommended to provide an additional source of lycopene, considered protective against the progression of prostate cancer (26,27). Intervention participants also received daily micronutrient supplements specific to prostate cancer (eg, selenium), and an iron-free multivitamin, which were excluded from the dietary analyses. Control group participants were under the usual care of their physician, including recommendations for diet and lifestyle.

A registered dietitian instructed participants on how to complete 3-day food records and verified dietary data entry, as a measure of quality assurance. Data were analyzed using Nutrition Data System for Research software (NDS-R) (versions 4.01_29, 1999 and 4.02_30, 2000, Nutrition Coordinating Center, University of Minnesota,

Minneapolis). Final calculations were completed using NDS-R version 2005. The NDS-R time-related database updates analytic data while maintaining nutrient profiles true to the version used for data collection. Isoflavone values specific for the soy protein supplement used in the intervention were provided by the manufacturer and substituted for the isoflavone value estimated by NDS-R. The analyses presented here are based on data from men who had complete 3-day food records at baseline (n85) and 1 year (n74).

Independent sample t tests were used to assess differences between groups at baseline. Group differences in nutrient changes (baseline to 1 year) were analyzed using analysis of variance for repeated measures, with group as a between subjects factor and time as a repeated factor. Bonferroni adjustments were made for multiple comparisons. Statistical analyses were performed using SPSS (version 14.0, 2005, SPSS, Inc, Chicago, IL).

RESULTS AND DISCUSSION

At baseline there were no significant differences between the intervention (n42) and control (n43) groups in age (mean 657 and 677 years, respectively), weight (8013 kg for both), energy intake, or macro- and micro-

February 2008 Journal of the AMERICAN DIETETIC ASSOCIATION 351

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