July 2019 Issue
The Power of Produce
By Carrie Dennett, MPH, RDN, CD
Vol. 21, No. 7, P. 16
Drawbacks of Skimping on Fruits and Vegetables Plus Tips for Boosting Intake
“Eat the rainbow”; “more matters”; “an apple a day keeps the doctor away.” Few would dispute the healthfulness of fruits and vegetables, yet most Americans don’t eat enough of them. According to the 2015–2020 Dietary Guidelines for Americans, vegetable intake is below recommended levels for all age groups, with the largest deficits between ages 14 and 50, and only children age 1 to 8 meet the recommendations for fruit intake.1 Today’s Dietitian explores the impact boosting produce intake could have not just on disease prevention but also on overall health and well-being, and shares RD tips for helping your patients eat more produce.
The Big Picture
Fruit and vegetable intake is associated with reduced risk of several chronic and other noncommunicable diseases. Research tends to focus on the health benefits of antioxidants, flavonoids, and polyphenols in fruits and vegetables; however, increasing fruit and vegetable intake also may alter overall diet profile by displacing less healthful foods, therefore improving total macronutrient, micronutrient, and fiber content in the diet. For example, an analysis that pulled data from four intervention studies involving participants with various health conditions, as well as healthy older adults, found that when fruit and vegetable intake increases, so does fiber, vitamin C, and beta-carotene, while total fat, saturated fat, and starch intakes decrease.2
Many epidemiologic studies have found positive associations between fruit and vegetable intake and reduced risk of chronic disease and all-cause mortality. The strongest associations are for CVD and all-cause mortality,3-5 with weak, limited, or no associations for cancer3,4 and inconsistent findings for type 2 diabetes.3
The quantity of fruits and vegetables associated with maximum risk reduction—the threshold amount—varies from study to study. A 2014 meta-analysis found a 5% reduced risk of all-cause mortality for each daily serving of fruits and vegetables, up to a threshold of around five servings of fruits and vegetables per day.4 A 2017 meta-analysis found that risk reduction maxed out at 800 g/day (10 portions) for CVD and all-cause mortality, and at 600 g/day (7.5 portions) for cancer.5 The Prospective Urban Rural Epidemiology study enrolled 135,335 adults without CVD from 613 communities of varying income levels from around the world. Higher fruit, vegetable, and legume consumption was associated with a lower risk of noncardiovascular and total mortality. Maximum benefits for reduction of noncardiovascular and all-cause mortality appear to be at 375 to 500 g/day.6
When interpreting observational study data, it’s important to remember that higher fruit and vegetable intake is associated with other characteristics that benefit health, such as nonsmoking status, higher socioeconomic status, and higher levels of physical activity.7
Specific Health Benefits
Improving diet and lifestyle is important for prevention of CVD, and data from observational studies suggest that increasing fruit and vegetable consumption may lower CVD risk, primarily by reducing established risk factors such as high blood pressure and chronic inflammation. However, the mechanisms aren’t clear and findings aren’t consistent from study to study.8
A 2017 meta-analysis with 1,498,909 participants found that higher fruit and vegetable consumption was associated with a lower risk of CVD. Specifically, the groups that ate the most fruits and vegetables had a 17% lower relative risk than the group that ate the fewest. Individuals who ate 800 g of fruits and vegetables per day had the lowest risk of CVD.9
The Dietary Approaches to Stop Hypertension (DASH) diet, which is rich in fruits, vegetables, and low-fat dairy foods with reduced levels of saturated and total fat, has been shown to substantially lower blood pressure,10 and a 2009 study randomizing hypertensive participants to consume one, three, or six servings of fruits and vegetables daily found significant improvements in an established marker of arterial health as produce consumption increased.11 This is in line with current research about the protective role of polyphenols in cardiovascular health, specifically how they affect the health of the endothelium (ie, the lining of the blood vessels).12
The Polyphenol Intervention Trial randomized 102 participants aged 45–60 with hypertension to either a low-polyphenol diet (fewer than two servings of fruits and vegetables daily and no berries or dark chocolate) or a high-polyphenol diet (six portions of fruits and vegetables, including one of berries, plus 50 g dark chocolate) for eight weeks. The high-polyphenol group showed a significant improvement in microvascular function, specifically endothelium-dependent vasodilation, and a significant reduction in total cholesterol.13 Microvascular dysfunction, which includes atherosclerosis, increases the risk of CVD.
A two-week crossover study randomized 22 healthy men aged 18–32 to their usual healthful diet or to a low-polyphenol diet with fewer than two servings of fruits and vegetables per day and no cocoa products, coffee, or tea. After just two weeks, the low-polyphenol diet resulted in impaired vascular biomarkers, including a decrease in nitric oxide and an increase in inflammatory markers. While these changes didn’t reach statistical significance, it’s notable that any difference was detected in healthy young men after only two weeks of a low fruit and vegetable diet.14
Observational research on fruit and vegetable consumption and type 2 diabetes is inconsistent. Some studies find that fruits, but not vegetables, are significantly associated with a lower risk of diabetes.15 Some find a specific positive association with leafy green vegetable intake,15-17 while others find no association.18 A 2015 meta-analysis found that two or three daily servings of vegetables and two daily servings of fruit was associated with a lower risk of diabetes than other levels of vegetable and fruit consumption,19 yet other studies have found no association or a very weak association with higher overall fruit and vegetable consumption.16,17
In a few studies that compared the DASH eating pattern with a control diet with similar macronutrient ratios, women with polycystic ovary syndrome (PCOS) saw significant improvement in several PCOS-related biomarkers. These included a reduction in insulin resistance, C-reactive protein, triglycerides, very LDL cholesterol, abdominal fat,20,21 and androstenedione, a steroid precursor for testosterone and estrogen, of which most women with PCOS have too much.22
A 2017 randomized controlled trial found that giving two servings of fresh fruits and vegetables to young adults who had habitually low produce intake garnered psychological benefits—reported increases in vitality, flourishing, and motivation—during the brief 14-day study.23 A 2016 meta-analysis found a 14% lower relative risk of depression for the highest vs lowest category of fruit intake, and an 11% lower risk for highest vegetable intake. The authors said that while the exact biological mechanisms underlying fruit and vegetable intake and depression risk aren’t fully understood, various minerals and vitamins present in produce have known effects on the mechanisms of depression. For example, depression is related to chronic inflammation, and magnesium intake could reduce plasma concentrations of C-reactive protein, which is a marker of low-grade inflammation, and antioxidants such as vitamin C, vitamin E, and folic acid could dampen the adverse effects of oxidative stress on mental health. In addition, vitamin B12 and zinc have neurological roles.24
Researchers discovered a significant association between higher consumption of fruits and vegetables and healthier bones in the late 1960s, prompting recommendations to eat a diet rich in fruits, vegetables, and vegetable-based protein to help reduce bone loss. Since then, several population-based studies also have found associations between fruit and vegetable intake and bone health. Diets rich in vegetables and fruits contribute to a favorable ratio of sodium to potassium, which may reduce urinary calcium loss. They also contain magnesium, calcium, and vitamins A, C, E, and K, all of which have benefits for bone health. In addition, increased polyphenol and fiber intake may decrease the age-related chronic inflammation that can exacerbate bone loss.
A 2015 New Zealand study randomized 50 healthy postmenopausal women to eat at least nine servings of different combinations of vegetables, herbs, and fruits for three months. This included six servings of vegetables—with at least two servings of leafy greens—and one serving of culinary herbs. One group emphasized specific vegetables, herbs, and fruits with properties that inhibit bone resorption (breakdown and absorption), including citrus, prunes, lettuce, broccoli, tomatoes, cucumbers, green beans, onions, garlic, parsley, sage, rosemary, and thyme. This group experienced improvements in markers of bone health.25,26
Looking at cognitive health, a 2017 systematic review and meta-analysis of six prospective cohort studies involving a total of 21,175 participants found that intake of fruits and vegetables was inversely associated with the occurrence of cognitive disorder, including Alzheimer’s disease, dementia, and cognitive decline/impairment. Compared with the lowest level of consumption, the risk was 26% lower at the highest level of fruit and vegetable consumption. The authors said this was likely due to antioxidants in fruits and vegetables, such as vitamin C, vitamin E, flavonoids, and carotenoids, along with phytoestrogens and polyphenols.27 The MIND diet (Mediterranean-DASH Intervention for Neurodegenerative Delay), which singles out green leafy vegetables and berries, has been shown to reduce age-related cognitive decline.28
Busting Through Barriers
Barriers to achieving recommended intakes of fruits and vegetables include inconvenience, cost, and preference for other foods.29 Fruit consumption, already low, may be taking an additional hit from popular diets that restrict it due to its natural sugar content, including the ketogenic diet, Paleo diet, pegan (ie, Paleo/vegan) diet, and many low-carb diets. Here are some top RD tips for helping your patients boost their produce intake.
“For those who think they don’t enjoy vegetables, often times it’s due to being unfamiliar with a vegetable’s taste or texture vs an actual dislike,” says Philadelphia-based Kelly Jones, MS, RD, CSSD (www.kellyjonesnutrition.com). “While our profession focuses a lot on produce exposure for infants and kids, this can also be an important topic when addressing adults. Encouraging them to prepare vegetables in new ways and then mix them into foods they already enjoy is a great way to disassociate from undesirable past experiences with the foods and start fresh.”
Layne Lieberman, MS, RDN, CDN, LDN, author of Beyond the Mediterranean Diet: European Secrets of the Super-Healthy, became creative with a veggie-averse client. “I have a college-age client who hates most vegetables and is actually proud of it. However, she loves sweets and most fruits,” she says. “The way we’ve overcome the ‘hate’ is to hide them in sweet-tasting smoothies, using dates and bananas in combination with one to two vegetables each day. She also committed to including an additional serving of the vegetables she likes: corn (with a Chipotle bowl), carrots (with hummus), broccoli (only when mixed in a bowl), or edamame (with weekly sushi).”
Bumping up the vegetables in existing dishes is a way for patients to “sneak” in more vegetables, even when they do like them. Joan Salge Blake, EdD, RDN, LDN, FAND, a clinical professor at Boston University and host of the Spot On! Podcast, likes to “beef up” homemade or jarred spaghetti sauce in the jar with grated carrots. “You can grate them yourself or buy them preshredded,” she says. “Simmer the sauce until the carrots are tender. The texture of the carrots will mimic ground beef in the sauce. It’s a great way to add veggies for flavor, texture, and delicious nutrition to your pasta dishes.”
Northern California–based cookbook author and culinary educator Jill Nussinow, MS, RDN, aka The Veggie Queen, says her best tip is to add vegetables to most things that you make. “Add a big handful of spinach or arugula to a bowl with grains, or on top of your bowl of soup. And eat a salad every day. If you don’t want to make it, buy it. You can buy almost everything already done; you pay for it, but if you don’t want to do it yourself, it works.”
Keeping produce prepped and ready to eat increases the odds that it will get eaten. North Carolina–based Hope Warshaw, MMSc, RD, CDE, BC-ADM, FAADE, owner of Hope Warshaw Associates (www.hopewarshaw.com), is an advocate of prepping. “I prepare about once, maybe twice, a week ‘salad accessories’ for salads—which I eat nearly every day for lunch—and cut up fresh fruit that we have for breakfast each morning with a dollop or two of Greek yogurt.”
Judy Simon, MS, RDN, CD, CHES, FAND, owner of Mind Body Nutrition (www.mind-body-nutrition.com) in Bellevue, Washington, encourages her patients to chop up onions, peppers, and celery; prepare a soup, chili, or stew with several vegetables; and roast a large pan of vegetables to use in several meals each week. She says her patients find it easier to increase their fruit and vegetable intake when they sign up for a community-supported agriculture program or ugly produce box. “They order produce they know they like and work it into their weekly menu planning. It also gives them a chance to try new things.”
Guilt over once-fresh produce rotting in the refrigerator also can be a barrier, so starting with produce that isn’t fresh may be a way to boost intake. Amy Gorin, MS, RDN, owner of Amy Gorin Nutrition (www.amygorin.com) in the New York City area, recommends reaching for dried fruit. “Not all produce that you consume needs to be the fresh kind, and the bonus is that dried fruit stays fresh for a very long time!”
Illinois-based Stephanie Wagner, RDN, LDN, founder of Stephanie Lee Nutrition (stephanieleenutrition.com), suggests stocking the freezer with frozen vegetables. “Frozen veggies come in handy all year round. First and foremost, frozen vegetables are about as economical as they come. They can hang out in the freezer for months if stored properly,” she says, also pointing to their versatility. “Frozen vegetables can be easily steamed in the microwave, tossed in a soup, or added to pasta and stir-fries. Lastly, frozen vegetables are often frozen at peak freshness, locking in all the nutrients.”
Getting off on the right foot can encourage produce intake all day. Cheryl Mussatto, MS, RD, LD, author of The Nourished Brain: The Latest Science on Food’s Power for Protecting the Brain From Alzheimers and Dementia, advises her patients to start early in the day to boost their intake of fruits and veggies. “This might mean adding berries to yogurt, sliced bananas to cereal or oatmeal, or vegetables to an omelet,” she says. “Keep the momentum going by having at least one fruit and/or veggie at each meal and snack.”
To boost produce intake at dinner, Gorin suggests adding crudité to appetizer plates. “It sounds so simple, but instead of including just crackers or pita chips as dippers with hummus and pairings for crackers, add in sliced carrots, bell peppers, and even radishes,” she says. “This is an easy way to take in more veggies. You can even slice up a bunch and keep them front and center in the fridge so you see them first thing when you’re looking for a snack.”
Kellie Blake, RDN, LD, IFNCP, CMHIMP, co-owner of NutriSense Nutrition Consulting, LLC, goes even further: “I recommend salad dinner nights where the salad is the entrée. I challenge clients to get creative with healthful toppings and teach them to make their own healthful dressings.”
— Carrie Dennett, MPH, RDN, CD, is the nutrition columnist for The Seattle Times, owner of Nutrition By Carrie, and author of Healthy for Your Life: A Holistic Guide to Optimal Wellness.
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