Understanding Mixed Messaging on Diet and Cancer

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We continue to be inundated with conflicting messages on diet and nutrition. March is National Nutrition Month. Here is Karen Collins, AICR’s Nutrition Advisor, explaining the conflicting nutrition news and headlines, and helping you make sense of them.

I try to follow nutrition research so that I can make smart choices. But I am so overwhelmed by conflicting headlines that I am about to give up. How can I keep up without going crazy?

It can be overwhelming if you expect that you should change your eating habits based on each new study. But that is not what these studies are for. Scientific journals provide a vehicle for scientists to document individual steps in the process of scientific investigation. Scientists know that before accepting results of a study, it needs to be repeated several times by other people to see if findings are consistent.
Even a study that is designed and executed well can lead you astray if you try to use it as a stand-alone guide to reduce your risk of cancer. Problems can stem from several sources:

  • Laboratory studies of individual compounds lay valuable groundwork for additional research, but they can’t reflect the effects of a food in a human being. Looking at individual compounds is necessary to study potential mechanisms, but it misses the influence of other nutrients and compounds in a food.

Example: Whole Grains – Phytates and lectins are sometimes called “anti-nutrients” based on laboratory studies in which they can bind to (and potentially decrease our ability to absorb) some nutrients. And claims are circulating that lectins can attach to gut walls and promote inflammation. Some headlines say that whole grains are major sources of these compounds, so we should avoid them.

Any potential risk from these compounds may be overpowered by the multiple nutrients and protective plant compounds in whole grains and legumes.

However, although phytates can decrease absorption of iron, for example, that can be counter-balanced by eating foods that increase iron absorption, such as fruits and vegetables with vitamin C. Moreover, evidence suggests phytates may yield cancer-protective effects through influence on cell signaling and antioxidant and anti-inflammatory defenses. Lectins are high in uncooked grains and beans, but proper cooking markedly reduces content.

Any potential risk from these compounds may be overpowered by the multiple nutrients and protective plant compounds in whole grains and legumes. AICR/WCRF Continuous Update project report concluded that three standard servings of whole grains per day is linked with 17% lower risk of colorectal cancer. An analysis focused on overall cancer risk found three standard servings of whole grains daily associated with 15% lower cancer risk.

Lower cancer risk is most likely based on what you do eat as well as what you don’t eat, and finding an approach that you can realistically sustain as a long-term habit.

  • Large amounts of a substance in experiments help make sure that scientists don’t miss an effect. But that can mean amounts that are out of proportion to what people get from eating a food, and thus suggest risks or protective effects unlikely to occur.

Example: Coffee – A compound called acrylamide is carcinogenic in rodents. Hearing that acrylamide can form in the process of roasting coffee has led some people to worry that coffee is a cancer risk. However, the dose of acrylamide in these studies is 1,000 to 100,000 times higher than what humans get from diet. And since rodents metabolize the compound differently than humans, their exposure is even further in excess of ours.

Moreover, coffee also contains other compounds, such as polyphenols that may support antioxidant defenses and help reduce cancer risk. Before jumping to conclusions based on laboratory studies, it is important to consider what research shows about coffee consumption in humans.

  • Population studies can’t show cause-and-effect. Observational studies can follow people for many years, which is valuable for learning about a disease like cancer that develops over time. These studies try to adjust statistically for alternative influences on risk. But even after adjusting for factors like family history, smoking and age, we need to consider whether some portion of an association a study shows is really due to something else.

Example: Plant-Based Diets – Eating patterns that emphasize nutrient-rich plant foods like vegetables, fruits, whole grains, and beans are recommended for lower risk of cancer. Vegan diets, which include no animal foods at all, offer one way to eat a plant-based diet. When headlines highlight a lower risk of cancer among vegans, it may sound like that is the necessary choice for cancer prevention.

However, it’s important to note that these studies are often comparing vegan diets with a “Western diet” (high in red meat, refined grains and sweets). They are not providing a comparison to other healthy plant-based eating patterns, which may include modest portions of fish, dairy and/or red meat. Some studies, for example, show lower cancer risk with Mediterranean-style diets (which are not necessarily vegetarian). Lower cancer risk is most likely based on what you do eat as well as what you don’t eat, and finding an approach that you can realistically sustain as a long-term habit.

Seek the Big Picture

The play-by-play of new studies gradually advancing our understanding of eating for better health is fascinating. But it’s important to see these studies in the context of overall research. And since it’s hard for anyone to keep track of all today’s research and evaluate the soundness of methods used, the most reliable way to know that you are making smart choices is to have a few unbiased sources you count on for knowledgeable insights. Knowing the expertise of the team behind the AICR/WCRF Continuous Update Project is what makes it a go-to source for me.

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    How Do I Read Mixed Messaging on Alcohol and Health?

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    Many choices you make to lower risk of cancer pack an extra health-protective punch, because they also lower risk of heart disease. But trying to make a smart choice about alcohol can be confusing. The American Heart Association recently released its first-ever scientific statement on the intersection of cardiovascular disease and breast cancer, and alcohol is singled out as the only lifestyle choice as having somewhat mixed effects.
    Alcohol — especially wine — has an image as a heart-healthy choice, and fewer than 4 in 10 people are aware that alcohol poses cancer risk. But it does, and the link should be of special concern to women, since increased breast cancer risk starts at relatively low amounts of alcohol.

     

    In observational studies that follow large groups of people for many years, those who drink moderate amounts of alcohol have lower risk of heart disease compared to people who drink large amounts and compared to those who don’t drink alcohol. However, in observational studies like these, which can’t establish cause-and-effect, some of the people with little or no alcohol consumption are people who have health problems that led them to avoid alcohol.

    Guidelines focused on heart health emphasize that you should not drink alcohol specifically in hopes of cardiovascular benefits.

    A closer look shows that alcohol actually stands on a thin line when it comes to heart health: Blood triglyceride levels can rise with too much alcohol. People often focus on potential benefit in reports that alcohol can raise HDL (“good”) cholesterol. However, high blood triglycerides raise heart disease risk, and too much alcohol can send these up.

    Blood pressure may rise with excessive alcohol. For most people, one to two drinks a day don’t pose a problem for blood pressure, but drinking more than two or three standard drinks a day can raise it. A healthy blood pressure plays an enormous role in heart health, so if you are having trouble keeping yours under control, discuss with your healthcare provider whether you should try reducing alcohol.

    Weight gain and excess body fat promote chronic low-grade inflammation that threatens heart health (and risk of cancer). People who have major problems with alcohol addiction may skip eating and become underweight. But as a registered dietitian nutritionist, many people I have worked with have found that the extra calories in alcohol lead to weight gain.

    Each standard size alcoholic drink contains at least 100 to 150 calories from the alcoholic beverage itself, and mixers in cocktails can add even more. Many people find that after a drink or two, they are less likely to withstand impulses to indulge in foods or portion sizes that they would normally be more cautious about limiting, leading to a further increase in calorie consumption.

    Binge drinking is not moderate drinking, regardless of whether it “averages out” over the course of a week to the same total amount of alcohol defined as moderate drinking. Binge drinking raises risk of heart disease.

    Alcohol’s Link to Cancer Risk

    Evidence is stronger than ever linking alcohol to increased risk of breast cancer. In the U.S., one standard drink is defined as one providing 14 grams of pure alcohol (ethanol). That is equivalent to 5 ounces of wine, 12 ounces of beer or a 1 ½-ounce shot of 80-proof liquor. Just 10 grams of pure alcohol consumed daily raises the risk of premenopausal breast cancer 5 percent, and risk of postmenopausal breast cancer 9 percent.

    While risk of breast and esophageal cancers increases at even low levels of consumption, alcohol beyond moderation also raises risk of cancers of the colorectum, stomach, liver, mouth, pharynx, and larynx.

    Increased circulating estrogen seems to be an important reason for alcohol’s link to breast cancer, and explains why risk of Estrogen Receptor-positive breast cancer (the most common form) particularly rises with alcohol consumption. Women often ask about whether certain foods may be “estrogenic,” yet completely overlook this effect of alcohol.

    DNA damage can occur from the free radicals formed as alcohol is metabolized, forming acetaldehyde, a recognized carcinogen. Alcohol may also act as a solvent, increasing other carcinogens’ ability to damage cells.

    Finding Common Ground

    What is moderate drinking? The same amount of alcohol poses more risk for women because differences in alcohol metabolizing enzymes and total body water make alcohol more concentrated in the blood and more slowly eliminated.

    The same concerns seem to apply to older adults of both genders. Binge drinking is not moderate drinking, regardless of whether it “averages out” over the course of a week to the same total amount of alcohol defined as moderate drinking. Binge drinking raises risk of heart disease.

    Despite some differences in how alcohol affects risk of heart disease and cancer, there is agreement about a commonsense approach. Guidelines focused on heart health emphasize that you should not drink alcohol specifically in hopes of cardiovascular benefits.

    Whether focused on heart health or lower cancer risk, recommendations agree that for those who choose to drink, it is best if women limit themselves to no more than one alcoholic drink per day, and men to no more than two.

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      Do salads make sense in winter?

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      Salads, although not essential for a healthy meal, do still make sense in winter! It’s an opportunity to try different ingredients than what you use in a summer salad.

      Winter Salads: Rethinking Ingredients
      Greens: Today’s grocery stores stock all types of lettuce year-round, so you don’t have to switch up your greens for winter. For more seasonal fun, however, try kale or the winter versions of spinach, which stand up well to hearty flavors. These greens are high in beta-carotene, lutein, and vitamin C, and spinach is a good source of the B vitamin folate that helps protect our DNA.

      Read more… “Do salads make sense in winter?”

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