American Institute for Cancer Research, 1997. World Cancer Research Fund. Food,Nutrition and the Prevention of Cancer: A Global Perspective. Nuts and Seeds. 450-1.
Since the early ‘80s, a number of expert reports have reviewed the literature on diet and cancer and made recommendations designed to reduce the risk of cancer. The report, of which this is a summary, builds on that earlier work. The experts recommend that populations consume nutritionally adequate and varied diets, based primarily on foods of plant origin. They specifically recommend that the public choose predominantly plant-based diets rich in a variety of vegetables and fruits, legumes and minimally processed starchy staple foods. The report notes,“While there are as yet no useful epidemiological data on nuts and seeds, it is biologically plausible that diets high in specific nuts and seeds or these foods as a whole, protect against cancers.”
Blomhoff, R., M.H. Carlsen, L.F. Andersen, D.R. Jacobs Jr, 2006. Health benefits of nuts: potential role of antioxidants. British Journal of Nutrition. 96, Suppl. 2, S52–S60.
A diet rich in fruits, vegetables and minimally refined cereals is associated with lower risk for chronic degenerative diseases. Since oxidative stress is common in chronic degenerative disease, it has been assumed that dietary antioxidants may explain this protective effect. Every dietary plant contains numerous types of antioxidants with different properties. Many of these antioxidants cooperate in oxidative stress reduction in plants, and we hypothesize that many different antioxidants may also be needed for the proper protection of animal cells. To test this hypothesis, it is useful to identify dietary plants with high total antioxidant content. Several nuts are among the dietary plants with the highest content of total antioxidants. Of the tree nuts, walnuts, pecans and chestnuts have the highest contents of antioxidants. Walnuts contain more than 20 mmol antioxidants per 100 g, mostly in the walnut pellicles. Peanuts (a legume) also contribute significantly to dietary intake of antioxidants. These data are in accordance with our present extended analysis of an earlier report on nut intake and death attributed to various diseases in the Iowa Women’s Health Study. We observed that the hazard ratio for total death rates showed a U-shaped association with nut/peanut butter consumption. Hazard ratio was 0.89 (CI . 0.81–0.97) and 0.81 (CI . 0.75–0.88) for nut/peanut butter intake once per week and 1–4 times per week, respectively. Death attributed to cardiovascular and coronary heart diseases showed strong and consistent reductions with increasing nut/peanut butter consumption. Further studies are needed to clarify whether antioxidants contribute to this apparent beneficial health effect of nuts.
Bruce, B., G.A. Spiller, L.M. Klevay, S.K. Gallagher, 2000. A diet high in whole and unrefined foods favorably alters lipids, antioxidant defenses and colon function. J Clin Nutr. 19(1): 61- 7.
OBJECTIVE: Diets rich in whole and unrefined foods, like whole grains, dark green and yellow/orange-fleshed vegetables and fruits, legumes, nuts and seeds, contain high concentrations of antioxidant phenolics, fibers and numerous other phytochemicals that may be protective against chronic diseases. This study compared the effects of a phytochemical-rich diet versus a refined-food diet on lipoproteins, antioxidant defenses and colon function. METHODS: Twelve hyperlipidemic women followed two diets for four weeks starting with a refined-food diet. Subjects then directly crossed over to the phytochemical-rich diet. Duplicate, fasting serum lipids and single, fasting antioxidant enzymes were measured at the end of the four-week refined-food diet period (baseline) and again at the end of the phytochemical-rich diet period. RESULTS: Total energy and total fat intake were similar during both diet periods, but there was a decrease in saturated fat (SFA) of 61% in the phytochemical-rich diet group. Dietary fiber, vitamin E, vitamin C and carotene intakes were 160%, 145%, 160% and 500% more, respectively, than during the refined-food diet period. The phytochemical-rich diet induced a drop of 13% in total cholesterol (TC) (p < 0.05) and 16% (p < 0.001) in low density lipoprotein-cholesterol (LDL-C). Erythrocyte superoxide dismutase decreased 69% (p < 0.01) and glutathione peroxidase dropped 35% (p < 0.01). Colon function was improved on the phytochemical-rich diet. CONCLUSIONS: A diet abundant in phytochemically-rich foods beneficially affected lipoproteins, decreased need for oxidative defense mechanisms and improved colon function.
Gonzalez, C.A., J. Salas-Salvado´, 2006. The potential of nuts in the prevention of cancer. British Journal of Nutrition. 96, Suppl. 2, S87–S94.
Cancer is a disease that is characterized by the loss of genetic control over cell growth and proliferation, mainly as a result of the exposure to environmental factors. Cessation of smoking and a high consumption of fruits and vegetables are the most important means of reducing the risk of cancer in our society. Like fruits and vegetables, nuts are a source of vegetable protein, monounsaturated fatty acids, vitamin E, phenolic compounds, selenium, vegetable fiber, folic acid and phytoestrogens. There are numerous mechanisms of action by which these components can intervene in the prevention of cancer, although they have not been fully elucidated. There are very few epidemiological studies analyzing the relationship between nuts consumption and risk of cancer. One of the greatest difficulties in interpreting the results is that the consumption of nuts, seeds and legumes are often presented together. The most commonly studied location is the colon/rectum, an organ in which the effect of nuts is biologically plausible. Although the results are not conclusive, a protective effect on colon and rectum cancer is possible. Likewise, some studies show a possible protective effect on prostate cancer, but there is insufficient data on other tumor locations. New epidemiological studies are required to clarify the possible effects of nuts on cancer, particularly prospective studies that make reliable and complete estimations of their consumption and which make it possible to analyze their effects independently of the consumption of legumes and seeds.
Hebert, J.R., T.G. Hurley, B.C. Olendzki, J. Teas, Y. Ma, J.S. Ha, 1998. Nutritional and socioeconomic factors in relation to prostate cancer mortality: a cross-national study. J Natl Cancer Inst. 90:1637-47.
Background: Large international variations in rates of prostate cancer incidence and mortality suggest that environmental factors have a strong influence on the development of this disease. The purpose of this study was to identify predictive variables for prostate cancer mortality in data from 59 countries. Methods: Data on prostate cancer mortality, food consumption, tobacco use, socioeconomic factors, reproductive factors, and health indicators were obtained from United Nations sources. Linear regression models were fit to these data. The influence of each variable fit in the regression models was assessed by multiplying the regression coefficient b by the 75th (X75) and 25th (X25) percentile values of the variable. The difference, bX75 − bX25, is the estimated effect of the variable across its interquartile range on mortality rates measured as deaths per 100 000 males aged 45–74 years. Reported P values are two-sided. Results: Prostate cancer mortality was inversely associated with estimated consumption of cereals (bX75 − bX25 = −7.31 deaths; P = . 001), nuts and oilseeds (bX75 − bX25 = −1.72 deaths; P = .003), and fish (bX75 − bX25 = −1.47 deaths; P = .001). In the 42 countries for which we had appropriate data, soy products were found to be significantly protective (P = .0001), with an effect size per kilocalorie at least four times as large as that of any other dietary factor. Besides variables related to diet, we observed an association between prostate cancer mortality rates and a composite of other health-related, sanitation, and economic variables (P = .003). Conclusions: The specific food-related results from this study are consistent with previous information and support the current dietary guidelines and hypothesis that grains, cereals, and nuts are protective against prostate cancer. The findings also provide a rationale for future study of soy products in prostate cancer prevention trials.
Jain, M.G., G.T. Hislop, G.R. Howe, P. Ghadirian, 1999. Plant foods, antioxidants and prostate cancer risk: findings from case-control studies in Canada. Nutr and Cancer. 34(2):173-84.
Epidemiological data on most cancer sites suggest that consumption of plant foods, which contain high levels of antioxidants, might slow or prevent the appearance of cancer. We used data from three case-control studies to test this hypothesis. The total study population consisted of 617 incident cases of prostate cancer and 636 population controls from Ontario, Quebec, and British Columbia. Dietary information was collected by an in-person interview with a detailed quantitative dietary history. Unconditional logistic regression analyses were performed to estimate odds ratios (ORs) and 95% confidence intervals (CIs). A decreasing, statistically significant association was found with increasing intakes of green vegetables (OR = 0.54, 95% CI = 0.40-0.71 for 4th quartile), tomatoes (OR = 0.64, 95% CI = 0.45-0.91), beans/lentils/nuts (OR = 0.69, 95% CI = 0.53-0.91), and cruciferous vegetables (OR = 0.69, 95% CI = 0.52-0.91 for 3rd quartile). Higher intakes of fruit were associated with higher ORs (OR = 1.51, 95% CI = 1.14- 2.01 for 4th quartile), an effect that was seen for total fruit and citrus fruit, as well as for all other noncitrus fruits. Among the grains, refined-grain bread intake was associated with a decrease in risk (OR = 0.65 for 4th quartile), whereas whole-grain breakfast cereals were associated with a higher risk for prostate cancer. Of all the antioxidant nutrients studied, the ORs were higher with higher intakes of cryptoxanthin (OR = 1.44, 95% CI = 1.09-1.89 for 4th quartile). Exposure to certain dietary components of plant origin, which are potentially modifiable, indicates the theoretical scope for reducing the risk from prostate cancer. Future experimental studies or trials are warranted for further understanding.
Jenab, M., et al., 2004. Association of nut and seed intake with colorectal cancer risk in the European prospective investigation into cancer and nutrition. Cancer Epidemiol Biomarkers Prev. 13(10):1595-603.
A link between unsaturated fatty acids or phytonutrients and reduced risk of colorectal cancer has been suggested. However, the effects of higher intake of dietary sources of these nutrients, such as the nuts and seeds food group, are less clear. The objective of this study was to determine the effects of nut and seed intake on colorectal cancer risk within the European Prospective Investigation into Cancer and Nutrition study, a large prospective cohort study involving 10European countries. Total nut and seed intake was determined from country-specific dietary questionnaires. The data set included 478,040 subjects (141,988 men, 336,052 women) with a total of 855 (327 men, 528 women) colon and 474 (215 men, 259 women) rectal cancer cases. A multivariate Cox proportional hazards model, stratified by center and controlled for fruit intake, dietary fiber, energy, height, weight, sex, age, physical activity, and smoking, was used. The data show no association between higher intake of nuts and seeds and risk of colorectal, colon, and rectal cancers in men and women combined, but a significant inverse association was observed in subgroup analyses for colon cancer in women at the highest (>6.2 g/d) versus the lowest (nonconsumers; hazard ratio, 0.69; 95% confidence interval, 0.50-0.95) category of intake and for the linear effect of log-transformed intake (hazard ratio, 0.89; 95% confidence interval, 0.80- 0.98), with no associations in men. It is not evident from this data why there may be a stronger association in women or why it may be limited to the colon, suggesting that much further research is necessary.
Kune, S., G.A. Kune, L.F. Watson, 1987. Case-control study of dietary etiological factors: the Melbourne colorectal cancer study. Nutr Cancer. 9:21-42.
A brief description is given of a large and comprehensive population-based investigation of colorectal cancer with a new study design. The study design allows the simultaneous examination of the incidence pattern, all the hypothesized causes and all the survival determinants of colorectal cancer of a defined population in a single data set. The relevance of this approach to surgeons in the primary prevention of and screening for colorectal cancer is illustrated in relation to the findings. Thus a diet with a low intake of fat and red meat and high intake of plant foods seems the most important factor in the primary prevention of colorectal cancer. In the screening for this cancer, high-risk groups include those with a previous colorectal cancer, a previous adenomatous polyp, a family history of colorectal cancer in first-degree relatives, Jews, those with an unsatisfactory diet and for rectal cancer, also those who are heavy beer consumers.
Mills, P.K., W.L. Beeson, R.L. Phillips, G.E. Fraser, 1989. Cohort study of diet, lifestyle, and prostate cancer in Adventist men. Cancer. 64:598-604.
Dietary and lifestyle characteristics were evaluated in relation to subsequent prostatic cancer risk in a cohort of approximately 14,000 Seventh-day Adventist men who completed a detailed lifestyle questionnaire in 1976 and who were monitored for cancer incidence until the end of 1982. During the 6-year follow-up period, 180 histologically confirmed prostatic cancers were detected among some 78,000 man-years of follow-up. Increasing educational attainment was associated with significantly decreased risk of prostate cancer in this study; age at first marriage was also inversely associated with risk, although this was not significant. There was no relationship between body mass index (as measured by Quetelet's Index) and risk. A history of prostate “trouble” was associated with a 60% increase in risk which was highly significant. Although there were suggestive relationships between increasing animal product consumption and increased risk, these results did not persist after accounting for the influence of fruit and vegetable consumption. Nor was exposure to the vegetarian lifestyle during the childhood years associated with alterations in subsequent risk. However, increasing consumption of beans, lentils and peas, tomatoes, raisin, dates, and other dried fruit were all associated with significantly decreased prostate cancer risk.
Pickle, L.W., M.H. Greene, R.G. Ziegler, A. Toledo, R. Hoover, H.T. Lynch, J.F. Fraumeni, Jr., 1984. Colorectal cancer in rural Nebraska. Cancer Research. 44:363-9.
A case-control interview study of colorectal cancer was conducted in two rural counties of eastern Nebraska to determine reasons for the elevated colon cancer mortality rates during 1950 to 1969. Comparison of the information provided by 86 colorectal cancer cases and 176 matched controls (or their next of kin) revealed an increased risk among persons of Czech background, with persons of Bohemian and Moravian extraction predominating in this area. The data suggest an interaction between Bohemian ancestry and certain dietary patterns in the pathogenesis of colon cancer in this region. Colon cancer risk was elevated among commercial beer drinkers regardless of their ethnic back ground, although Bohemians reported heavier consumption. An excess risk was also associated with intestinal polyps, reported more often by Moravians, and with familial occurrence of gastrointestinal and other cancers. Since 1969, the mortality and incidence rates for colon cancer in this area have declined, possibly as a consequence of acculturation of the American-born descendants of Czech immigrants.
Singh, P.N., G.E. Fraser, 1998. Dietary risk factors for colon cancer in a low-risk population. Am J Epidemiol. 148:761-74.
In a 6-year prospective study, the authors examined the relation between diet and incident colon cancer among 32,051 non-Hispanic white cohort members of the Adventist Health Study California, 1976-1982) who, at baseline, had no documented or reported history of cancer. The risk of colon cancer was determined from proportional hazards regression with adjustment for age and other covariates. The authors found a positive association with total meat intake (risk ratio (RR) for >1 time/week vs. no meat intake = 1.85, 95% confidence interval (CI) 1.19-2.87; p for trend = 0.01) and, among subjects who favored specific types of meat, positive associations with red meat intake (RR for >1 time/week vs. no red meat intake = 1.90, 95% CI 1.16-3.11; p for trend = 0.02) and white meat intake (RR for >1 time/week vs. no white meat intake = 3.29, 95% CI 1.60-6.75; p for trend = 0.006). An inverse association with legume intake (RR for >2 times/week vs. <1time/week = 0.53, 95% CI 0.33-0.86; p for trend = 0.03) was observed. Among men, a positive association with body mass index was observed (relative to the RR for tertile III (>25.6 kg/m2) vs. tertile I (<22.5 kg/m2) = 2.63, 95% CI 1.12-6.13; p for trend = 0.05). A complex relation was identified whereby subjects exhibiting a high red meat intake, a low legume intake, and a high body mass experienced a more than threefold elevation in risk relative to all other patterns based on these variables. This pattern of putative risk factors would likely contribute to increases in both insulin resistance (high body mass, high red meat intake) and glycemic load (low legume intake), a synergism that, if causal, implicates hyperinsulinemic exposure in colon carcinogenesis. The overall findings from this cohort identify both red meat intake and white meat intake as important dietary risk factors for colon cancer and raise the possibility that the risk due to red meat intake reflects a more complex etiology.
Torabian, S., E. Haddad, S. Rajaram, J. Banta, J. Sabate´, 2009. Acute effect of nut consumption on plasma total polyphenols, antioxidant capacity and lipid peroxidation. J Hum Nutr Diet. 22: 64–71.
Background: Nuts have been shown to have beneficial effects on human health due to the healthy fat content; however, the effect of antioxidants (i.e. polyphenols) in nuts have not been fully investigated. The present study aimed to assess the immediate effect of a polyphenol-rich meal (75% of energy from nuts: walnuts or almonds) and a polyphenol-free meal on plasma polyphenol content, antioxidant capacity and lipid peroxidation in healthy volunteers. Methods: Thirteen subjects participated in a randomized, crossover, intervention study. After an overnight fast, walnuts, almonds or a control meal in the form of smoothies were consumed by study subjects. Each subject participated on three occasions, 1 week apart, consuming one of the smoothies each time. Blood samples were obtained at fasting and then at intervals up to 3.5 h after consumption of the smoothies. Results: There was a significant increase in plasma polyphenol concentration following both nut meals, with peak concentrations being achieved at 90 min, and with a walnut meal having a more sustained higher concentration than an almond meal. The plasma total antioxidant capacity reached its highest point at 150 min post consumption of the nut meals, and was higher after the almond compared to walnut meal. A gradual significant (P < 0.05) reduction in the susceptibility of plasma to lipid peroxidation was observed 90 min after ingestion of the nut meals. No changes were observed following consumption of control meal. Conclusions: Consumption of both nuts increased plasma polyphenol concentrations, increased the total antioxidant capacity and reduced plasma lipid peroxidation.
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