Joel Evans, MD recommends three studies dealing with obesity, diet and chronic diseases.

by Joel M. Evans, MD 


Overweight/obesity and cancer genesis: More than a biological link
 

Irigaray et al., Biomed Pharmacother. 2007 Dec;61(10):665-78

Abstract

The classical view according to which overweight/obesity is related to cancer considers adipose tissue as an active and metabolic “organ”, acting through endocrine, autocrine and paracrine processes. Consequently, it has been hypothetised, that genesis and progression of cancer may be caused by different biological factors acting through diverse mechanisms including changes in the synthesis and bioavailability of sex hormones, insulin resistance, release of growth factors and/or proinflammatory cytokines and abnormal energetic disposal and expenditure.

We have shown that overweight/obesity can be experimentally induced by benzo[a]pyrene, a universal well characterized chemical pollutant and that overweight/obesity may in fact be caused by several types of chemical pollutants.

In this paper we propose that in addition to the above hypothetical biological mechanisms, adipose tissue acts as a reservoir for lipophilic, liposoluble environmental carcinogens, so that chemical pollution may in fact generate both overweight/obesity and cancer. More precisely, we propose that many carcinogens, be they mutagens or promotors can be stored in the adipose tissue, be released at convenient dose in the blood circulation and therefore target peripheral tissues to induce carcinogenesis.

Such carcinogens mainly include organochlorine pesticides and PCBs. Their association with an increased risk of cancer seems to be demonstrated for breast and prostate carcinoma, as well as for lymphoma, not only in obese patients, but also in normal weight or even leaner patients suggesting that the adipose tissue may act as a reservoir for environmental carcinogens in obese as well as in non-obese patients.

My Comment:

This paper benefits the reader in two important ways. First, it provides an excellent summary of the many cutting edge hypotheses for the link between obesity and cancer which look at the adipose cell as a functioning endocrine organ secreting metabolically active compounds that support the carcinogenic process. Second, it provides a novel theory that environmental toxins can increase cancer incidence by two mechanisms: by being independent promoters of obesity and by their lipophilic nature directly causing carcinogenesis in distant tissues after being released from adipose cells.

That adipose tissue is metabolically active in ways that promote cancer is labeled by the author as “the classical view”.  However, despite a preponderance of data, many holistic practitioners care for cancer patients that are unaware of these important physiological links. This paper provides an excellent up to date summary of the literature on overweight and cancer occurrence as well as the underlying biological mechanisms that, unfortunately, should be but often isn’t “the classical view.”

However, the strength of the paper for those already aware of “the classical view” lies in the case they make for the twofold connection of environmental toxins and cancer. It is not just that toxins change cellular function but that they directly induce obesity and are then stored in body fat, to be released systemically when their concentration kills the fat cell in which they were stored or through other mechanisms. In fact, the conclusion of the paper states that the obesity/toxicity link is likely to be more important in cancer causation than all of the metabolic abnormalities caused by the hormonally active adipocyte.

The authors provide a solid basis for their unique unifying theory on the link between obesity, environmental toxins and cancer that should be read by all.


Intake of whole grains, refined grains, and cereal fiber measured with 7-d diet records and associations with risk factors for chronic disease.

Newby et al., Am J Clin Nutr. 2007 Dec;86(6):1745-53

Abstract

BACKGROUND: Research studies examining foods are important, because they account for biological interactions that might otherwise be lost in the analysis of individual nutrients. Single-nutrient studies are also needed to explore the mechanisms by which foods may be protective. OBJECTIVE: Our objective was to examine associations between whole grains, refined grains, and cereal fiber and chronic disease risk factors. DESIGN: In a cross-sectional analysis of participants in the Baltimore Longitudinal Study of Aging, associations between dietary intakes and risk factors were examined with multivariate linear regression analysis. Dietary intakes were assessed with 7-d dietary records and quantified in g/d. RESULTS: Compared with subjects in the lowest quintile (Q1) of whole-grain intake, subjects in the highest quintile (Q5) had lower body mass index (BMI; in kg/m(2); Q1: 25.5; Q5: 24.8; P for trend <0.0001) and weight (Q1: 75.0 kg; Q5: 72.4 kg; P for trend = 0.004) and smaller waist circumference (Q1: 87.4 cm; Q5: 85.0 cm; P for trend = 0.002). Whole grains were also inversely associated with total cholesterol (P for trend = 0.02), LDL cholesterol (P for trend = 0.04), and 2-h glucose (P for trend = 0.0006). Associations between cereal fiber and anthropometrics and plasma lipids were similar. In subgroup analyses, refined grains were positively associated with fasting insulin among women (P for trend = 0.002). CONCLUSIONS: Similar associations of whole grains and cereal fiber with weight, BMI, waist circumference, plasma cholesterol, and 2-h glucose were observed, suggesting that cereal fiber and its constituents may in part mediate these relations. Refined grains were associated with fasting insulin among women but not men. Additional research should explore potential interaction effects with BMI, sex, age, and genes.

My Comment:

This article is important because it is another scientific paper to contradict the widespread belief in the general population that carbohydrates cause weight gain. By now it is well know that carbohydrates as a class of nutrients do not contribute to obesity and poor health outcome, but that the type of carbohydrate is critically important. Here the authors report that carbohydrate consumption the form of whole grains and cereal fiber, as opposed to refined carbohydrate, was beneficial in many categories important for optimal health, including weight, glucose and lipid profiles. This article reinforces the important concept that foods consumed in the form closest to nature are the healthiest foods.


Mediterranean Dietary Pattern and Prediction of All-Cause Mortality in a US Population: Results From the NIH-AARP Diet and Health Study.

Mitrou et al., Arch Intern Med. 2007 Dec 10;167(22):2461-8

Abstract:

BACKGROUND: The Mediterranean diet has been suggested to play a beneficial role for health and longevity. However, to our knowledge, no prospective US study has investigated the Mediterranean dietary pattern in relation to mortality. METHODS: Study participants included 214 284 men and 166 012 women in the National Institutes of Health (NIH)-AARP (formerly known as the American Association of Retired Persons) Diet and Health Study. During follow-up for all-cause mortality (1995-2005), 27 799 deaths were documented. In the first 5 years of follow-up, 5985 cancer deaths and 3451 cardiovascular disease (CVD) deaths were reported. We used a 9-point score to assess conformity with the Mediterranean dietary pattern (components included vegetables, legumes, fruits, nuts, whole grains, fish, monounsaturated fat-saturated fat ratio, alcohol, and meat). We calculated hazard ratios (HRs) and 95% confidence intervals (CIs) using age- and multivariate-adjusted Cox models. RESULTS: The Mediterranean diet was associated with reduced all-cause and cause-specific mortality. In men, the multivariate HRs comparing high to low conformity for all-cause, CVD, and cancer mortality were 0.79 (95% CI, 0.76-0.83), 0.78 (95% CI, 0.69-0.87), and 0.83 (95% CI, 0.76-0.91), respectively. In women, an inverse association was seen with high conformity with this pattern: decreased risks that ranged from 12% for cancer mortality to 20% for all-cause mortality (P = .04 and P < .001, respectively, for the trend). When we restricted our analyses to never smokers, associations were virtually unchanged. CONCLUSION: These results provide strong evidence for a beneficial effect of higher conformity with the Mediterranean dietary pattern on risk of death from all causes, including deaths due to CVD and cancer, in a US population.

My Comment:

The beauty of this paper is that is again proves what we all know intuitively and intellectually: that a healthy diet is healthy. This study is important because it appears in a major journal that will be read by many mainstream physicians. As I already stated, the findings are of no surprise and corroborate other studies on the effectiveness of Mediterranean Diet. However, they are useful in that they provide recent data that a simple nutritional intervention can have tremendous effects in decreasing all cause mortality as well as deaths from heart disease and cancer.  Certainly any pharmaceutical that could provide those benefits would be utilized by all physicians, and hopefully this article is another step in the direction of all health practitioners discussing the importance of diet with their patients.


Joel Evans, MD, is the author of The Whole Pregnancy Handbook published in 2005.