Milk Consumption Is a Risk Factor for Prostate Cancer: Meta-Analysis of Case-Control Studies

Lactase Persistence, Dietary Intake of Milk, and the Risk for Prostate Cancer in Sweden and Finland

Prostate carcinoma is the most common cancer in men. Its primary pathogenesis is mostly unknown. Dairy products containing lactose have been suggested to be risk factors for prostate cancer. Digestion of lactose is dependent on lactase activity in the intestinal wall. A single nucleotide polymorphism C to T residing 13,910 bp upstream of the lactase gene has been shown to associate with the developmental down-regulation of lactase activity underlying persistence/nonpersistence trait. To find out whether lactase persistence is related to the risk for prostate cancer, we genotyped 1,229 Finnish and 2,924 Swedish patients and their 473 Finnish and 1,842 Swedish controls using solid-phase minisequencing. To explore if dairy products have an association with prostate cancer, we analyzed the milk consumption in the Swedish study consisting of 1,499 prostate cancer patients and 1,130 controls (Cancer Prostate in Sweden I study) using a questionnaire. Only the consumption of low-fat milk was found to be associated with increased risk of prostate cancer [odds ratio (OR), 1.73; 95% confidence interval (95% CI), 1.16-2.39]. A statistically significantly higher (P < 0.01) lactose intake was observed among subjects with high lactase activity (C/T and T/T genotypes) compared with those with low lactase activity (C/C genotype). Lactase persistence did not associate with increased risk for prostate carcinoma in the Finnish (OR, 1.11; 95% CI, 0.83-1.47; P = 0.488) or in the Swedish populations (OR, 1.16; 95% CI, 0.91-1.46; P = 0.23). In conclusion, lactase persistence/nonpersistence contains no risk for prostate cancer. Analysis of different milk products showed some evidence for low-fat milk as a potential risk factor for prostate cancer.

Calcium intake and vitamin D metabolism and action, in healthy conditions and in prostate cancer

An association between Ca intake and the risk of prostate cancer has been reported in some but not all epidemiological studies. Assuming that a pathophysiological relationship would underlie this association, a favoured hypothesis proposes that relatively high Ca consumption could promote prostate cancer by reducing the production of 1,25-dihydroxyvitamin D (1,25(OH)2D; calcitriol), the hormonal form of vitamin D. The present review analyses the plausibility of this hypothesis by considering the quantitative relationships linking Ca intake to 1,25(OH)2D production and action in healthy conditions and in prostate cancer. Changes in the plasma level of 1,25(OH)2D in response to Ca intake are of very small magnitude as compared with the variations required to influence the proliferation and differentiation of prostate cancer cells. In most studies, 1,25(OH)2D plasma level was not found to be reduced in patients with prostate cancer. The possibility that the level of 1,25(OH)2D in prostate cells is decreased with a high-Ca diet has not been documented. Furthermore, a recent randomised placebo-controlled trial did not indicate that Ca supplementation increases the relative risk of prostate cancer in men. In conclusion, the existence of a pathophysiological link between relatively high Ca intake and consequent low production and circulation level of 1,25(OH)2D that might promote the development of prostate cancer in men remains so far an hypothesis, the plausibility of which is not supported by the analysis of available clinical data.

Dairy products and health: a review of the epidemiological evidence

Evidence-based nutrition is essential to move forward in the science of community nutrition. The present study is a review of the epidemiological evidence of dairy products and health. There is an inverse association between the intake of dairy products and hypertension, stroke and colorectal cancer. There is no evidence of an association between the consumption of dairy products and breast cancer. There is some evidence linking high-fat dairy products and an incremental risk of prostate cancer and weak evidence of the protective capacity of dairy products on bone health. More prospective studies should be developed in order to establish better evidence of the relationship between dairy products and health. Due to the importance of dairy products in public health nutrition, quantitative recommendations should be established in the light of the scientific evidence.

Vitamin and mineral supplements for cancer prevention: issues and evidence

Trials of nutritional supplements for cancer prevention must overcome a variety of challenges not shared in the usual paradigm of pharmaceutical agents for prevention of cardiovascular disease. Unlike for cardiovascular disease, for cancer we typically do not have well-established causal risk factors as targets for intervention. Also, for most likely cancer interventions, the expected time to achieve an effect is much longer, more variable, and far less well understood than for cardiovascular disease, and the progression of pathophysiology is much harder-or impossible-to follow, in contrast with imaging for progression of atherosclerosis in cardiovascular disease. Also, cancers at various sites have a wide range of etiologies. The optimal age for intervention, best dose, and duration needed to test nutritional agents for cancer prevention are largely unknown, making null findings hard to interpret. Unlike with drugs, baseline nutritional status can be critical. Moreover, because the nutritional agents are often readily available, adherence in control groups in trials can be impaired. Several gene-nutrient and nutrient-nutrient interactions have been identified that could affect trial results. Some studies suggest that particular nutrients may be effective only in subgroups defined by genotypes or by nutritional status of another nutrient. All these challenges must be considered in planning informative trials. Long-term prospective cohort studies, especially with repeated measures and high follow-up, can provide useful data for planning trials as well as the basis for rational recommendations while awaiting trial results or in settings where trials may be infeasible.

Milk, dairy products and cancer risk (Italy)

BACKGROUND

Inconclusive information is available on the potential role of milk and dairy products on the risk of cancer at several sites.

METHODS

We analyzed data from a large and integrated network of hospital-based case-control studies in Italy on cancers of the oral cavity and pharynx (598 cases, 1491 controls), oesophagus (304 cases, 743 controls), colorectum (1953 cases, 4154 controls), larynx (460 cases, 1088 controls), breast (2569 cases, 2588 controls), ovary (1031 cases, 2411 controls) and prostate (1294 cases, 1451 controls).

RESULTS

Multivariate odds ratio (OR) for the highest consumption level of any type of milk was 0.94 (95% confidence interval, CI: 0.61-1.33) for cancers of the oral cavity and pharynx, 1.20 (95% CI: 0.76-1.90) for oesophageal, 0.77 (95% CI: 0.62-0.96) for colon, 0.80 (95% CI: 0.60-1.05) for rectal, 0.83 (95% CI: 0.56-1.21) for laryngeal, 0.91 (95% CI: 0.76-1.10) for breast, 0.89 (95% CI: 0.68-1.15) for ovarian and 1.08 (95% CI: 0.84-1.37) for prostate cancer. A significant trend in risk was found for colon cancer only. Inverse associations were observed between consumption of skim milk and cancers of colon (OR=0.84; 95% CI: 0.73-0.97), rectum (OR=0.76; 95% CI: 0.64-0.91), breast (OR=0.87; 95% CI: 0.77-0.98) and ovary (OR=0.77; 95% CI: 0.66-0.91). Conversely, whole milk consumption was directly associated with cancer of the rectum (OR=1.22; 95% CI: 1.03-1.44) and ovary (OR=1.25; 95% CI: 1.07-1.46). High consumption of cheese was inversely related to colon cancer risk (OR=0.80; 95% CI: 0.67-0.95).

CONCLUSIONS

There was a modest direct association between milk and dairy products and prostate cancer, and a moderate inverse one for colorectal cancer. However, our findings indicate that milk and dairy products are not strong risk indicators for any of the cancers considered.

A new proposed guidance system for beverage consumption in the United States

The Beverage Guidance Panel was assembled to provide guidance on the relative health and nutritional benefits and risks of various beverage categories. The beverage panel was initiated by the first author. The Panel's purpose is to attempt to systematically review the literature on beverages and health and provide guidance to the consumer. An additional purpose of the Panel is to develop a deeper dialog among the scientific community on overall beverage consumption patterns in the United States and on the great potential to change this pattern as a way to improve health. Over the past several decades, levels of overweight and obesity have increased across all population groups in the United States. Concurrently, an increased daily intake of 150-300 kcal (for different age-sex groups) has occurred, with approximately 50% of the increased calories coming from the consumption of calorically sweetened beverages. The panel ranked beverages from the lowest to the highest value based on caloric and nutrient contents and related health benefits and risks. Drinking water was ranked as the preferred beverage to fulfill daily water needs and was followed in decreasing value by tea and coffee, low-fat (1.5% or 1%) and skim (nonfat) milk and soy beverages, noncalorically sweetened beverages, beverages with some nutritional benefits (fruit and vegetable juices, whole milk, alcohol, and sports drinks), and calorically sweetened, nutrient-poor beverages. The Panel recommends that the consumption of beverages with no or few calories should take precedence over the consumption of beverages with more calories.

A Prospective Study of Calcium Intake and Incident and Fatal Prostate Cancer

Prostate cancer is the most common incident cancer and the second leading cause of cancer mortality in U.S. males. Higher milk intake has been relatively consistently associated with an increased risk of prostate cancer, especially advanced prostate cancer. Some data suggest that high intake of calcium might account for this association, but this relationship remains controversial. We hypothesized that high calcium intake, possibly by lowering 1,25(OH)2 vitamin D levels, is associated with poorer differentiation in prostate cancer and thereby with fatal prostate cancer. We examined calcium intake in relation to prostate cancer risk using data from the Health Professionals Follow-up Study, a prospective cohort study of 47,750 male health professionals with no history of cancer other than nonmelanoma skin cancer at baseline. We assessed total, dietary, and supplementary calcium intake in 1986, 1990, 1994, and 1998, using a validated food frequency questionnaire. We calculated the multivariable relative risk (RR) and 95% confidence intervals (95% CI) using Cox proportional hazards regression. Over 16 years of follow-up, we identified 3,544 total cases of prostate cancer, 523 advanced (extraprostatic) cases, and 312 fatal cases. Higher calcium intake was not appreciably associated with total or nonadvanced prostate cancer but was associated with a higher risk of advanced and fatal prostate cancer [for fatal prostate cancer, compared with men whose long-term calcium intake was 500-749 mg/d (excluding supplement use of <5 years); those with intakes of 1,500-1,999 mg/d had a RR, 1.87; 95% CI, 1.17-3.01; and those with > or = 2,000 mg/d had a RR, 2.43; 95% CI, 1.32-4.48; P(trend) = 0.003]. Dietary calcium and supplementary calcium were independently associated with an increased risk. For high-grade prostate cancer (Gleason > or = 7), an association was observed for high versus low calcium intake (RR, 1.89; 95% CI, 1.32-2.71; P(trend) = 0.005), but a nonsignificant, inverse association was observed for organ-confined, low-grade prostate cancer (RR, 0.79; 95% CI, 0.50-1.25; P(trend) = 0.09). In a sample of this cohort, higher calcium intake was associated with lower circulating 1,25(OH)2 vitamin D levels. Our findings suggest that calcium intakes exceeding 1,500 mg/d may be associated with a decrease in differentiation in prostate cancer and ultimately with a higher risk of advanced and fatal prostate cancer but not with well-differentiated, organ-confined cancers.

Soyfood Intake in the Prevention of Breast Cancer Risk in Women: A Meta-Analysis of Observational Epidemiological Studies

Many studies have suggested that the intake of soy products may protect against the occurrence of breast cancer because of the considerable amount of isoflavones they contain. To review the results of the observational studies, we performed this meta-analysis of the relevant literature. We searched Medline for reports that examined the association between soyfood consumption (or isoflavone intake) and breast cancer risk from January 1966 to April 2006. The random-effects model was used to estimate the pooled relative risk (RR). Twenty-one independent studies (14 case-control studies and 7 cohort studies) were included in the final analysis. The pooled RR of breast cancer for soyfood intake was 0.75 with a 95% CI of 0.59-0.95. As the main types of soyfood in Japan and China, tofu and miso showed clear protective effects. Isoflavone intake resulted in a 20% decrease in risk (RR = 0.81, 95% CI 0.67-0.99). The pooled RR varied little according to study stratification. When the studies published in Japanese and Chinese were added, the inverse associations between soyfood, tofu and breast cancer risk became slightly stronger. The weak association of miso was possibly due to the high concentration of salt in miso soup. In the present analysis, we did not find strong evidence for publication bias in the combination of the studies. This meta-analysis supported the hypotheses that soyfood intake may be associated with a decreased risk of breast cancer due to the isoflavones. Further epidemiological studies need to be conducted with more comprehensive information about the soyfood, and more accurate assessment of the isoflavones.

Role of diet in prostate cancer development and progression

Increasing evidence supports the important role of nutrition in cancer prevention, including prevention of prostate cancer. In this review, we summarize data for some of the most consistently observed dietary associations for prostate cancer incidence, briefly consider possible postdiagnostic effects of nutrition on prostate cancer progression/survival, discuss new but limited data on diet-gene interactions, and comment on current areas of controversy for future research focus. Potential protective dietary elements include tomatoes/lycopene, other carotenoids, cruciferous vegetables, vitamin E, selenium, fish/marine omega-3 fatty acids, soy, isoflavones and polyphenols; whereas milk, dairy, calcium, zinc at high doses, saturated fat, grilled meats, and heterocyclic amines may increase risk. It is important to note that randomized clinical trial data exist only for vitamin E, calcium, beta-carotene, and selenium (all of which suggest inverse or no association). Several genes, such as MnSOD, XRCC1, and GST, may modify the association of specific nutrients and foods with prostate cancer risk; and further research is warranted to confirm these initial observed relationships. Until further clinical trial data are available on specific supplements and prostate cancer prevention, it would be prudent to emphasize a diet consisting of a wide variety of plant-based foods and fish; this is similar to what is recommended (and what is more well established) for the primary prevention of heart disease.

Prospective studies of dairy product and calcium intakes and prostate cancer risk: a meta-analysis

BACKGROUND

The Dietary Guidelines for Americans 2005 recommends that Americans increase their intake of dairy products. However, some studies have reported that increasing dairy product intake is associated with an increased risk of prostate cancer. We conducted a meta-analysis to examine associations between intakes of calcium and dairy products and the risk of prostate cancer.

METHODS

We searched Medline for prospective studies published in English-language journals from 1966 through May 2005. We identified 12 publications that used total, advanced, or fatal prostate cancer as end points and reported associations as relative risks (RRs) with 95% confidence intervals (CIs) by category of dairy product or calcium intake. Data were extracted using standardized data forms. Random-effects models were used to pool study results and to assess dose-response relationships between dairy product or calcium intakes and the risk of prostate cancer. We conducted sensitivity analyses by changing criteria for inclusion of studies or by using fixed-effects models. All statistical tests were two-sided.

RESULTS

Men with the highest intake of dairy products (RR =1.11 [95% CI = 1.00 to 1.22], P = .047) and calcium (RR = 1.39 [95% CI = 1.09 to 1.77], P = .018) were more likely to develop prostate cancer than men with the lowest intake. Dose-response analyses suggested that dairy product and calcium intakes were each positively associated with the risk of prostate cancer (Ptrend = .029 and .014, respectively). Sensitivity analyses generally supported these associations, although the statistical significance was attenuated. The pooled relative risks of advanced prostate cancer were 1.33 (95% CI = 1.00 to 1.78; P = .055) for the highest versus lowest intake categories of dairy products and 1.46 (95% CI = 0.65 to 3.25; P > .2) for the highest versus lowest intake categories of calcium.

CONCLUSIONS

High intake of dairy products and calcium may be associated with an increased risk of prostate cancer, although the increase appears to be small.

The epidemiology of vitamin D and cancer incidence and mortality: a review (United States)

In vitro and animal studies indicate that vitamin D may have anti-cancer benefits, including against progression and metastasis, against a wide spectrum of cancers. Supporting an anti-cancer effect of vitamin D is the ability of many cells to convert 25(OH)D, the primary circulating form of vitamin D, into 1,25(OH)2D, the most active form of this vitamin. No epidemiologic studies have directly measured vitamin D concentrations or intakes on risk of total cancer incidence or mortality. However, higher rates of total cancer mortality in regions with less UV-B radiation, and among African-Americans and overweight and obese people, each associated with lower circulating vitamin D, are compatible with a benefit of vitamin D on mortality. In addition, poorer survival from cancer in individuals diagnosed in the months when vitamin D levels are lowest suggests a benefit of vitamin D against late stages of carcinogenesis. The only individual cancer sites that have been examined directly in relation to vitamin D status are colorectal, prostate and breast cancers. For breast cancer, some data are promising for a benefit from vitamin D but are far too sparse to support a conclusion. The evidence that higher 25(OH)D levels through increased sunlight exposure or dietary or supplement intake inhibit colorectal carcinogenesis is substantial. The biologic evidence for an anti-cancer role of 25(OH)D is also strong for prostate cancer, but the epidemiologic data have not been supportive. Although not entirely consistent, some studies suggest that higher circulating 1,25(OH)2D may be more important than 25(OH)D for protection against aggressive, poorly-differentiated prostate cancer. A possible explanation for these divergent results is that unlike colorectal tumors, prostate cancers lose the ability to hydroxylate 25(OH)D to 1,25(OH)2D, and thus may rely on the circulation as the main source of 1,25(OH)2D. The suppression of circulating 1,25(OH)2D levels by calcium intake could explain why higher calcium and milk intakes appear to increase risk of advanced prostate cancer. Given the potential benefits from vitamin D, further research should be a priority.

Milk Consumption in Relation to Incidence of Prostate, Breast, Colon, and Rectal Cancers: Is There an Independent Effect?

Milk contains a wide variety of ingredients, such as nutrients, hormones, and chemical contaminants. Whether milk consumption is associated with the risk of prostate, breast, colon, and rectal cancers is unclear and was evaluated in this study. Data on milk consumption for 9 time periods (1964-1994) and incidence rates of prostate, female breast, colon, and rectal cancers, mostly around 1993-1997, in 38 countries were obtained from the Food and Agriculture Organization and World Health Organization, respectively. Milk consumption was strongly correlated with incidence rates of prostate cancer (r = 0.65-0.69; all P < 0.0001) and breast cancer (r = 0.64-0.74; all P < 0.0001) in all the nine time periods examined. A modest positive correlation was found for colon and rectal cancers in both sexes (all P < 0.05, except for rectal cancer in the first three time periods). The previous findings remained essentially unchanged after adjustment for vegetable, alcohol, and cigarette consumption but disappeared after further adjustment for non-milk fat consumption, except for breast cancer in the last three time periods. The present study does not support an overall substantial effect of milk consumption on the risk of prostate, breast, colon, and rectal cancers at the population level.

Dietary Intake of Calcium, Vitamin D, Phosphorus and the Risk of Prostate Cancer

OBJECTIVES

A relation of prostate cancer risk with calcium, vitamin D and phosphorus has been suggested, but remains controversial.

METHODS

A case-control study was conducted in Italy in 1991-2002. Cases were 1294 men with incident prostate cancer, and controls were 1451 men admitted to hospital for acute non-neoplastic diseases. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) were estimated using unconditional multiple logistic regression.

RESULTS

Compared to the lowest one quintile of dietary calcium intake the OR was 1.18 for the highest, 1.01 for an increment of 622 mg/day of calcium, and 1.29 (95% CI 0.78-2.13) for 2000 mg/day or more of calcium. The OR of prostate cancer for the highest quintile of dietary intake of vitamin D and phosphorus were 1.33 and 1.20 respectively.

CONCLUSIONS

This study shows no material association of dietary intake of calcium, vitamin D and phosphorus with prostate cancer risk.

Dietary fats, teas, dairy, and nuts: potential functional foods for weight control?

Functional foods are similar to conventional foods in appearance, but they have benefits that extend beyond their basic nutritional properties. For example, functional foods have been studied for the prevention of osteoporosis, cancer, and cardiovascular disease. They have yet to be related to the prevention of obesity, although obesity is one of the major health problems today. The inclusion of foods or the replacement of habitual foods with others that may enhance energy expenditure (EE) or improve satiety may be a practical way to maintain a stable body weight or assist in achieving weight loss; such foods may act as functional foods in body weight control. Some foods that might be classified as functional foods for weight control because of their effects on EE and appetite-including medium-chain triacylglycerols, diacylglycerols, tea, milk, and nuts-are reviewed here. Only human studies reporting EE, appetite, or body weight are discussed. When studies of whole food items are unavailable, studies of nutraceuticals, the capsular equivalents of functional foods, are reviewed. To date, dietary fats seem to be most promising and have been the most extensively studied for their effects on body weight control. However, the weight loss observed is small and should be considered mostly as a measure to prevent weight gain. Carefully conducted clinical studies are needed to firmly ascertain the effect of tea, milk, and nuts on body weight maintenance, to assess their potential to assist in weight-loss efforts, and to ascertain dose-response relations and mechanisms of action for the 4 food types examined.