October 2015 Issue
Taking On Information Overload: Helping Patients Find Evidence-Based Messages About Antioxidants, Weight Loss, Soy, and Cancer Risk
By Karen Collins, MS, RDN, CDN, FAND
Vol. 17 No. 10 P. 54
Patients and health care professionals are inundated with information about nutrition. However, much of what clients and patients read and hear about is based on anecdotal evidence or single studies. Many dietitians say that clients and patients who are armed with too much information pose an even greater challenge than those armed with too little.
Through practical examples, this article explores ways to deal with this deluge of information regarding antioxidants, weight loss, soy, and cancer, and how to help clients and patients understand the facts amid a sea of misinformation.
Unstable molecules, often referred to as free radicals, appear to play a role in chronic diseases such as cancer, heart disease, type 2 diabetes, and dementia. High concentrations of free radicals can cause harm through a resulting chronic low-grade inflammation and direct cell damage. Antioxidants, dubbed "free radical scavengers," neutralize free radicals in laboratory studies, which have generated strong interest in their role in protecting health.
Q: Can Individuals Identify Healthful Food Choices Based on Antioxidant Scores?
A: Several different laboratory assays test antioxidant capacity. The antioxidant most commonly seen in advertisements and nutrition-related books or articles aimed at the public is Oxygen Radical Absorbance Capacity (ORAC). However, in 2012, the USDA withdrew its online database of foods' ORAC values. The USDA stated that there's no evidence that the beneficial effects of foods rich in polyphenols and other bioactive compounds are due to their antioxidant properties, and that ORAC values are routinely misused by food and supplement companies to promote their products and by consumers to guide food and supplement choices.1
The actual effects of compounds in the body vary with their absorption, metabolism, half-life in circulation, and cellular uptake. Many of the phytochemicals responsible for high antioxidant scores in laboratory studies can't be absorbed from the digestive tract. Yet, the colon microbiota breaks them down in varying degrees to bioavailable compounds that circulate through the body in low concentrations.2
Q: Are Antioxidants the Key to Disease Prevention?
A: Antioxidant defenses play a vital role in promoting health. The body's antioxidant defense system entails a complex network of endogenous antioxidants (including enzymes, nonenzymatic compounds such as glutathione and ubiquinol, and metal-binding proteins) that interact with one another and with dietary antioxidants. As defined by the Institute of Medicine and the FDA, a food is considered rich in antioxidants only if it meets criteria as an excellent source of nutrients known to directly inactivate free radicals or block the reactions they initiate within the body, which includes vitamins C and E, selenium, and carotenoids.3,4
In other words, a food providing phytochemicals that may be converted to compounds with antioxidant function or that support the body's endogenous antioxidant defenses shouldn't be called "rich in antioxidants" unless it also contains at least 20% of the DV for one of the defined antioxidant nutrients. It may not be as simple a message as talking about antioxidants, which can include comparisons to rusty cars or apple slices turning brown, because potential health benefits of foods rich in nutrients and phytochemicals extend well beyond antioxidant effects. For example, research is identifying effects on cell signaling pathways that control inflammation, blood vessel function, and cell growth.2
Q: Is More Always Better for Antioxidant Protection?
A: Free radicals and other reactive species commonly are viewed as bad guys to be eliminated, but at low levels they play important roles in cell signaling, immune response, and gene transcription. They also appear to play a role in triggering apoptosis, the self-destruction of abnormal cells that's vital in the body's defense against cancer, and in stimulating the body's endogenous antioxidant defense system.5,6
Oxidative stress develops when reactive species accumulate and create damage by overpowering body defenses. Antioxidants are critical in preventing this oxidative damage. Nevertheless, at excessively high levels, antioxidants can be harmful if they prevent the beneficial levels of reactive species required for optimal cell function, or if they reach levels where they become pro-oxidative. The level of antioxidants needed from the diet to achieve a healthy homeostasis depends on the gap between the level of free radicals to which the body is exposed and the capacity of the endogenous antioxidant system. Randomized controlled trials that used high-dose supplements of antioxidant nutrients such as selenium, beta-carotene, and vitamin E generally have failed to show any health protection, and several demonstrate U- or J-shaped curves, in which excessive intake has led to increased cancer risk or all-cause mortality.7-9
Messages that encourage people to embrace healthful eating patterns help them shift from reductionist views focused on single nutrients or health functions. An eating pattern that supports health might be compared to a symphony, in which food choices work through many pathways to promote health. Each component plays a role, and amounts that promote health are realistically attainable. Dietitians can remind clients and patients that cell and animal studies aren't solid ground for making changes in eating habits, and RDs can encourage them to turn to reliable sources (see sidebar) for information about antioxidants and help them understand what's behind the studies in the news.
Just as there's confusion about antioxidants and health protection, questions persist about how much of a calorie deficit is necessary for 1 lb of weight loss.
Q: Does Cutting 3,500 kcal Produce 1 lb of Weight Loss?
A: The equation in which 3,500 kcal equals 1 lb of weight has been the basis for advice for decades: "Cut 500 calories a day from your current eating habits and you'll lose a pound a week." This equation, known as "Wishnofsky's Rule," is based on research published in 1958 that involved a relatively limited group of subjects in short-term studies without data on long-term outcomes or use of today's computer-generated calculation models.
Current research tracking changes in weight, calorie consumption, and calorie expenditure shows that most people lose less weight than expected based on the "3,500 Calorie Rule." Individual differences in metabolic rate, differences in sedentary time and forms of physical activity, and metabolic adaptation during weight loss each play a role in highly inconsistent weight loss results following equal changes in calorie intake and intentional physical activity.10,11
Research has led to a new model for predicting weight loss following change in calorie consumption. Computer-dependent calculations adjust for multiple adaptations that occur during weight loss. Based on age, height, weight, and gender for a specific time period, the model gives a far more accurate prediction of how weight will change over time for any specific level of calorie consumption or change in calorie consumption.12 This model is available as the Body Weight Planner on the National Institutes of Health website (see sidebar).
Evidence-based recommendations still support health professionals recommending individuals cut 500 kcal per day for weight loss.13 However, the new model provides a basis to explain that individual rates of weight loss vary and to demonstrate the need for people to continue a change in the balance of calorie intake and expenditure to avoid weight regain.
Soyfoods and Breast Cancer
The association between soy and breast cancer risk has been controversial for several years and has confused many people, even dietitians, due to conflicting information.
Q: Does Soy Play a Role in Breast Cancer Risk?
A: From some sources, individuals have heard that studies on Asian women show that soyfoods potentially can help lower breast cancer risk. Other sources report that studies identify soy's isoflavones as reasons to avoid soy, especially in women who've had estrogen receptor-positive (ER+) breast cancer.
Since those earlier studies, scientists have found that rodents metabolize isoflavones differently than humans, so the studies in which genistein (the predominant soy isoflavone) promoted growth of ER+ breast cancer relate to much higher blood levels than what would result from humans consuming soyfoods.14 As for potential protection, population studies linking soy consumption with lower breast cancer risk come mainly from Asia, where most women consume moderate amounts of soy throughout life.15 Research now suggests that hormone-related protection against breast cancer may relate to soy consumption before or around puberty as breast cells are in transition to their mature form. Differences in individual genetics and microbiota may mean that some people benefit more than others.16
We now can base answers to questions about ER+ breast cancer survivors on more than hypothetical concerns. Multiple population studies are consistent in demonstrating that there's no increased risk, and limited evidence shows potential for decreased recurrence or decreased overall mortality related to moderate soyfood consumption.17,18
Reliable sources are important for the public and health professionals to stay current on when new research becomes strong enough to merit changes in nutrition recommendations. For updated recommendations on particular eating choices without reading through a slew of studies, it's helpful to refer patients to unbiased sources that provide evidence-based reviews and recommendations. For example, the American Institute for Cancer Research (AICR) provides detailed background (see sidebar) supporting moderate consumption (considered one to two standard servings daily of whole soyfoods in the United States) as a reasonable choice in a healthful diet, noting that studies show up to three servings per day are safe for survivors.
Eating to Lower Cancer Risk
Amid today's information about creating lifestyle habits that help reduce cancer risk, people also may hear messages that can hinder their motivation to make changes, with claims that cancer risk is hereditary or random bad luck. Other information people may hear supports changing the diet to lower risk but suggests this requires adherence to restrictions that many find unacceptable.
Q: Is Cancer Largely Random Bad Luck?
A: A headline-making study claimed to show with a mathematical model that the rate of genetic mutations in different tissues is strongly correlated with the number and frequency of cell divisions, indicating that many are thus spontaneous rather than inherited.19 Media coverage often interpreted this as proof that cancer risk is largely due to random mutations—or bad luck.
However, that oversimplifies the complex process of cancer development. Even when DNA is damaged, the body has mechanisms to repair it, as well as ways to recognize abnormal cells and trigger their destruction through apoptosis. Moreover, epigenetic changes in gene expression occur without change in DNA itself. Nutritional factors could affect all these processes.20
Q: Is Cancer Risk Hereditary?
A: People without an adequate science background mistakenly may interpret the terms "genetic" and "hereditary" as interchangeable. Cancer is genetic in that it develops due to changes in genes, primarily in those that regulate cell growth and reproduction. However, inherited genetic mutations directly increase risk of only about 5% to 10% of all cancers.20 Genetic changes also accumulate throughout life due to spontaneous mutations and damage from exposure to various carcinogens, and some of these changes can come together to begin or promote cancer development. Cancer that appears to "run in the family" can indicate a syndrome involving inherited genetic mutations, but also can represent the effects of a shared environment or lifestyle choices.
Research is also identifying a wide variety of single nucleotide polymorphisms, variations in DNA sequencing occurring with recognized frequency, that could make some people more strongly affected than others by lifestyle choices that increase or decrease cancer risk. Even for people who have inherited one of the identified high-risk genes, research suggests that cancer-protective lifestyle choices can be beneficial.21,22 However, more research is needed in both of these areas.
Q: Does a Cancer-Protective Diet Need to Be Perfect?
A: While many people have heard that diet is important in cancer prevention, some information they see targets strict eating patterns that require changes many may consider too demanding. Creating even more confusion, standards by which different sources define a healthful diet sometimes conflict with one another. In many cases, these messages are based on cell or animal studies, or single human studies with a research design insufficient to support dietary recommendations.
Based on an expert panel's systematic review of thousands of studies, the World Cancer Research Fund (WCRF) and the AICR say that Americans can prevent about one-third of the most common cancers by reaching and maintaining a healthful weight, engaging in regular physical activity, and eating healthfully.20 The WCRF/AICR Expert Report includes 10 recommendations to reduce cancer risk, which are to be part of a lifestyle that also includes cancer-protective choices such as tobacco avoidance.
Ongoing review of the reports in the WCRF/AICR Continuous Update Project database continues to support a predominantly plant-focused eating pattern, which can be accomplished in a variety of ways. Vegan and other vegetarian diets, as well as Mediterranean and other patterns, can meet these recommendations. A prospective cohort study that scored eating patterns for adherence to the WCRF/AICR recommendations showed lowest cancer mortality in those who most closely meet the recommendations, with some reduction in risk linked with each recommendation met.23 In other words, it's not all or nothing.
For clear messages to help people set priorities for eating choices with the greatest potential to lower cancer risk while promoting overall health, the AICR has developed an approach called the New American Plate. It addresses both the link of several cancers to excess body fat and diet through attention to proportions of foods and portion sizes. Recipes, free downloadable brochures, and other materials to teach the New American Plate approach are available through the AICR website (http://www.aicr.org/new-american-plate). People can be empowered to fact-check information they hear about decreasing cancer risk by going directly to reliable sources rather than doing random, unrestricted Internet searches.
Dealing With the Deluge
It's a given that, as research progresses, evidence-based messages sometimes change. With widespread access to the Internet, where old information never completely goes away, people can get confused when searching for answers and finding apparently sound messages that conflict with one another. The same holds true for health professionals, who often find it challenging to distinguish between findings that are emerging but premature as a basis for recommendations and research consistent enough to merit changes in educational messages.
With information available everywhere, it's more important than ever that people understand that not all information is equally credible, and that simply being published in a journal doesn't make a study a sound foundation for decisions about healthful eating. Helping people identify red flags that can signal misinformation is one aspect of dealing with too much information. For people who don't have time or the background to do more than scan headlines and abstracts, the best approach is to turn to sources with recognized expertise in developing evidence-based recommendations and reports.
— Karen Collins, MS, RDN, CDN, FAND, is nutrition advisor to the American Institute for Cancer Research. She promotes healthful eating as a speaker, consultant, syndicated columnist, and through her blog Smart Bytes, which dietitians can access through her website, www.karencollinsnutrition.com.
1. Oxygen radical absorbance capacity (ORAC) of elected foods, release 2 (2010). United States Department of Agriculture website. http://www.ars.usda.gov/nutrientdata/ORAC. Updated May 16, 2012. Accessed August 7, 2015.
2. Del Rio D, Rodriguez-Mateos A, Spencer JP, Tognolini M, Borges G, Crozier A. Dietary (poly)phenolics in human health: structures, bioavailability, and evidence of protective effects against chronic diseases. Antioxid Redox Signal. 2013;18(14):1818-1892.
3. Institute of Medicine. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, D.C.: National Academies Press; 2000.
4. Guidance for industry: food labeling; nutrient content claims; definition for "high potency" and definition for "antioxidant" for use in nutrient content claims for dietary supplements and conventional foods; small entity compliance guide. US Food and Drug Administration website. http://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/
LabelingNutrition/ucm063064.htm. Updated May 4, 2015. Accessed August 6, 2015.
5. Bouayed J, Bohn T. Exogenous antioxidants—double-edged swords in cellular redox state: health beneficial effects at physiologic doses versus deleterious effects at high doses. Oxid Med Cell Longev. 2010;3(4):228-237.
6. Valko M, Leibfritz D, Moncol J, Cronin MT, Mazur M, Telser J. Free radicals and antioxidants in normal physiological functions and human disease. Int J Biochem Cell Biol. 2007;39(1):44-84.
7. Kristal AR, Darke AK, Morris JS, et al. Baseline selenium status and effects of selenium and vitamin E supplementation on prostate cancer risk. J Natl Cancer Inst. 2014;106(3):djt456.
8. Rayman MP. Selenium and human health. Lancet. 2012;379(9822):1256-1268.
9. Goodman GE, Thornquist MD, Balmes J, et al. The beta-carotene and retinol efficacy trial: incidence of lung cancer and cardiovascular disease mortality during 6-year follow-up after stopping beta-carotene and retinol supplements. J Natl Cancer Inst. 2004;96(23):1743-1750.
10. Hall KD, Heymsfield SB, Kemnitz JW, Klein S, Schoeller DA, Speakman JR. Energy balance and its components: implications for body weight regulation. Am J Clin Nutr. 2012;95(4):989-994.
11. Thomas DM, Martin CK, Lettieri S, et al. Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Commentary on a commonly accepted rule. Int J Obes (Lond). 2013;37(12):1611-1613.
12. Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837.
13. Jensen MD, Ryan DH, Apovian CM, et al. 2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and The Obesity Society. Circulation. 2014;129(25 Suppl 2):S102-S138.
14. Setchell KD, Brown NM, Zhao X, et al. Soy isoflavone phase II metabolism differs between rodents and humans: implications for the effect on breast cancer risk. Am J Clin Nutr. 2011;94(5):1284-1294.
15. Dong JY, Qin LQ. Soy isoflavones consumption and risk of breast cancer incidence or recurrence: a meta-analysis of prospective studies. Breast Cancer Res Treat. 2011;125(2):315-323.
16. Nagata C. Factors to consider in the association between soy isoflavone intake and breast cancer risk. J Epidemiol. 2010;20(2):83-89.
17. World Cancer Research Fund International, American Institute for Cancer Research. Continuous Update Project Report: diet, nutrition, physical activity, and breast cancer survivors. http://www.wcrf.org/sites/default/files/Breast-Cancer-Survivors-2014-Report.pdf. Published 2014.
18. Nechuta SJ, Caan BJ, Chen WY, et al. Soy food intake after diagnosis of breast cancer and survival: an in-depth analysis of combined evidence from cohort studies of US and Chinese women. Am J Clin Nutr. 2012;96(1):123-132.
19. Tomasetti C, Vogelstein B. Cancer etiology: variation in cancer risk among tissues can be explained by the number of stem cell divisions. Science. 2015;347(6217):78-81.
20. World Cancer Research Fund, American Institute for Cancer Research. Food, Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective. http://www.dietandcancerreport.org/cancer_resource_center_/downloads/
second_expert_report_full.pdf. Published 2007.
21. Botma A, Vasen HF, van Duijnhoven FJ, Kleibeuker JH, Nagengast FM, Kampman E. Dietary patterns and colorectal adenomas in Lynch syndrome: the GEOLynch cohort study. Cancer. 2013;119(3):512-521.
22. Manders P, Pijpe A, Hooning MJ, et al. Body weight and risk of breast cancer in BRCA1/2 mutation carriers. Breast Cancer Res Treat. 2011;126(1):193-202.
23. Hastert TA, Beresford SA, Sheppard L, White E. Adherence to the WCRF/AICR cancer prevention recommendations and cancer-specific mortality: results from the Vitamins and Lifestyle (VITAL) Study. Cancer Causes Control. 2014;25(5):541-552.
• National Center for Complimentary and Integrative Health of the National Institutes of Health on antioxidants and health: https://nccih.nih.gov/health/antioxidants/introduction.htm
• National Cancer Institute on antioxidants and cancer prevention: www.cancer.gov/cancertopics/causes-prevention/risk/diet/antioxidants-fact-sheet
Weight Loss Expectations
• National Institutes of Health Body Weight Planner: www.niddk.nih.gov/research-funding/at-niddk/labs-branches/LBM/integrative-physiology-section/body-weight-simulator/Pages/body-weight-simulator.aspx
Soyfoods and Cancer Risk—Information From the American Institute for Cancer Research
• Foods that fight cancer: soy: www.aicr.org/foods-that-fight-cancer/soy.html
• Cancer research update on soy and breast cancer survivors: www.aicr.org/cancer-research-update/2012/november_21_2012/cru-soy-safe.html
• Continuous Update Project report—breast cancer survivors (2014): www.aicr.org/continuous-update-project/breast-cancer-survivorship.html
Eating and Physical Activity Choices to Reduce Cancer Risk
• American Institute for Cancer Research recommendations for cancer prevention: www.aicr.org/reduce-your-cancer-risk/recommendations-for-cancer-prevention
• Food, Nutrition, Physical Activity and the Prevention of Cancer (2007 Report) & Continuous Update Project—American Institute for Cancer Research: www.aicr.org/continuous-update-project
• American Cancer Society Guidelines on Nutrition and Physical Activity for Cancer Prevention: http://onlinelibrary.wiley.com/doi/10.3322/caac.20140/pdf