Effects of Milk and Milk Products Consumption on Cancer: A Review H. Davoodi, S. Esmaeili, and A.M. Mortazavian
Abstract: Milk is considered to be the only foodstuff that contains approximately all different substances known to be essential for human nutrition. In terms of cancer risk, dairy foods have been reported as both protective and occasionally as harmful. The evidence that dairy foods can protect against cancer, or increase the risk of cancer is not conclusive. Overall, the proven health benefits of dairy foods greatly outweigh the unproven harm. Dairy foods should be encouraged as part of a varied and nutritious diet as they are essential to maintain good bone and dental health, to prevent osteoporosis, major cardiovascular disease risk factors, hypertension, type-2 diabetes, metabolic syndromes, as well as some cancers. The Cancer Council and USDA recommend 3 servings of milk and milk products daily. This article reviews the potential of milk and milk products (its indigenous or exogenous compounds) to inhibit different cancer risks. Also reviewed are the reports over the years that have suggested milk and the dairy industry as responsible agents for causing cancer.
Introduction
the most important components of the human diet, particularly in the Western world, and increasingly also in Asia (Tsuda and others 2000). Milk is considered to be the only foodstuff that contains approximately all different substances known to be essential for human nutrition (Goodman and others 2002; Laakkonen and Pukkala 2008). Milk is an important source of protein, calcium, and the B-group vitamins (thiamin, riboflavin, niacin, vitamin B6 , and folate), and provides vitamin A, vitamin C, magnesium, and zinc as well (Jelen 2005; Miller and others 2007). Carbohydrates are found in the form of lactose, which is generally considered to be of low carcinogenicity. Also, approximately 1/3 of the fat in whole milk is monounsaturated and small amounts of essential fatty acids are provided. Milk is one of the major sources of conjugated linoleic acid (CLA) in the diet, although it is a minor component of milk fat (Jelen 2005). Several milk constituents such as vitamin D, proteins, calcium, CLA, butyrate, saturated fatty acids, and contaminants such as pesticides, estrogen, and insulin-like growth factor I (IGF-I) may be responsible for either a prospective or a harmful association between dairy products and cancers (McCann and others 2004; Moorman and Terry 2004; Parodi 2005; Bingham and Day 2006; Cui and Rohan 2006; Laakkonen and Pukkala 2008). The main compounds in milk and dairy products that might affect cancer MS 20121243 Submitted 8/9/2012, Accepted 3/12/2012. Author Davoodi is can be classified in several groups and are shown in Figure 1. with Dept. of Clinical Nutrition and Dietology, National Nutrition and Food Tech- This article reviews the preventive and inductive effects of dairy nology Research Inst., Faculty of Nutrition Sciences, Food Science and Technology, products on the risk of cancers. Cancer is a leading global cause of death and disability, responsible for approximately 7.6 million deaths each year. The fact that only 5% to 10% of all cancer cases are due to genetic defects and that the remaining 90% to 95% are due to lifestyle factors (such as smoking, diet and nutrition, alcohol, physical inactivity, obesity, and sun exposure), infections, and environmental pollutants provides major opportunities for preventing cancer (La Vecchia and others 1991). Within the lifestyle factors, it is globally accepted that nutrition and related factors play an important role in cancer occurrence (Gonzalez and Riboli 2010). Observational evidence suggests that approximately 30% to 40% of cancer cases are potentially preventable via modification of nutritional factors and food consumption patterns (Marmot and others 2007). Milk and milk products are recognized as functional foods, suggesting that their use has a direct and significant effect on health outcomes and their consumption correlates with a reduced risk of numerous cancers (Keri Marshall 2004). Milk and other dairy products were recognized as important foods as early as 4000 BC, evidenced by stone drawings from the Sahara desert. It is one of
Shahid Beheshti Univ. of Medical Sciences, P.O. Box 19395-4741, Tehran, Iran. Author Esmaeili is with Young Researchers Club, Varamin-Pishva Branch, Islamic Azad Univ., Varamin, Iran. Author Mortazavian is with Dept. of Food Science Preventive Effects of Milk and Milk Products and Technology, National Nutrition and Food Technology Research Inst., Faculty of Consumption on Cancer Nutrition Sciences, Food Science and Technology, Shahid Beheshti Univ. of Medical Sciences, P.O. Box 19395-4741 Tehran, Iran. Direct inquiries to author Mortazavian Effects of indigenous milk ingredients on cancer prevention The positive effects of indigenous milk and milk products on (E-mail:
[email protected]/
[email protected]) and Esmaeili (E-mail:
[email protected]). cancers and related mechanisms are discussed below and shown in
Figure 2. C 2013 Institute of Food Technologists®
doi: 10.1111/1541-4337.12011
Vol. 12, 2013 r Comprehensive Reviews in Food Science and Food Safety 249
Dairy products and cancer . . .
Milk compounds
Vitamins Minerals
Exogenous compounds
Indigenous compounds
of milk
of milk
Contaminants
Calcium
Chemical
CLA
Proteins
Omega 3 Functional enriched compounds
Phytochemical Probiotics Synbiotic
Microbial
Vitamin D Dairy additives Fats
Heating Maillard Irradiation Bioactive peptides
Lactose
Process-produced compound Fermentationproduced compound
IGF-1 Estrogens
Figure 1–Main compounds in milk and dairy products that might affect cancer.
Colorectal cancer Colorectal cancer is the 3rd most common type of cancer worldwide with about 1.2 million new cases diagnosed in 2008 accounting for 9.7% of all cancers (Ferlay and others 2010). An increased consumption of milk or dairy products is associated with a significant reduction in colon cancer (Elwood and others 2008). Cho and others (2004a) conducted a large pooled analysis of data from 10 cohorts (n = 534, 536) from 5 countries and found 4992 individuals diagnosed with colorectal cancer at follow-up. Individuals who consumed more than a glass of milk (≥250 g)/d had a 15% reduced risk of developing colorectal cancer (relative risk 0.85, 95% CI 0.78 to 0.94), compared to those who consumed
