"Eat to Live, Not Live to Eat"
John H Weisburger, 2000
In recent years there's been increased world-wide emphasis on prevention of health problems rather than what has been the more traditional practice of medicine, viz. attempting to cure or ameliorate them once they've developed. Lifestyle plays a large part in the prevention story, and diet is one factor that can be modified. However identifying life-long healthy diets is a complex affair, and application of the reductionist strategy that has been so successful in drug therapy and nutritional deficiency states has usually been found to be ineffective. So although vitamins, minerals, fibre, essential fatty acids, antioxidants etc all play a role in long-term well-being, adding particular compounds or supplements into the diet is not the way to go.
Even individual foods with their many contained nutrients have been found inadequate, and nowadays there's a recognition that it's only whole dietary patterns that can provide the full spectrum of required nutrients. The Mediterranean Diet which focusses on fruit, vegetables, nuts, cereals, legumes, fish and olive oil and minimises consumption of red meats, saturated fats and dairy is one such proven approach. The thousands of nutrients in plant foods, which we still do not fully understand, can act synergistically in the body to produce their beneficial effects, so selecting a few of them for supplementation is virtually doomed a priori. Consequently prudent diets embrace diversity of nutritious foods as a guiding principle. Research over several decades has convincingly shown that fruits and vegetables (F&V) are very important components of healthy diets, but consumers in developed countries generally eat so few of them that public health promotion programs have concentrated mainly on encouraging people to increase their total intake with choice of which food types make up the servings largely left to the consumer. As a consequence, studies on the importance of F&V variety as opposed to quantity have been of lower priority, resulting in less being known on this question.
The following study (American Journal of Clinical Nutrition (2011) 93, 37–46) on Puerto Rican adults from a USDA Nutrition group is one of the few that has specifically addressed the question of F&V variety. They used a semi-quantitative Food Frequency Questionnaire (FFQ) specifically developed and validated for this population, to assess dietary intake over a 12-month period. The food list for the questionnaire was developed using the format of the National Cancer Institute/Block food frequency, but with data from the Hispanic Health and Nutrition Examination Survey (HHANES) dietary recalls for Puerto Rican adults and tested in Puerto Rican participants aged more than 59 years in Massachusetts.
The Puerto Rican population has a typical diet that differs considerably from both the general US population and from Mexican Americans, so foods such as plantains and specific soup and rice-dish recipes were added to the FFQ. Reported servings of individual F&V were summed to obtain the mean servings consumed per day. Variety in F&V intake was defined as the total number of unique F&V consumed at least once per month over the past 12 months. Fruit included apples, pears, bananas, oranges, grapefruit, peaches, apricots, nectarine, plums, grapes, avocado, kiwi fruit, papaya, mangoes, prunes, cantaloupe, honeydew melon, watermelon, cherries, strawberries, blueberries, raspberries, cranberries, pineapple, olives, and 100% fruit juice. Vegetables included lettuce, spinach, tomato, carrots, string beans, peas, corn, peppers, broccoli, cauliflower, cabbage, beets, asparagus, mushrooms, eggplant, onion, squash, cucumber, radish, celery, cilantro, garlic, parsley, zucchini, basil, and 100% vegetable juice. Starchy vegetables (including potato, plantains, and cassava), beans, and legumes (including lima beans, pinto beans, white beans, black beans, pink beans, kidney beans, cowpeas, soybeans, split peas, and lentils) were excluded.
Before reading the summary of their findings, a few words on inflammation might be helpful. It's a normal response to injury/infection and the subsequent healing/repair process, provided it's not excessive or uncontrolled. Localised and transient inflammation, such as from a bee sting, is very different to chronic systemic inflammation, which if sustained over time can increase the risks of almost all of the non-infectious chronic diseases increasingly found in Western societies. There are a number of valuable markers of systemic inflammation and one of these is C-reactive protein (CRP). Its importance can be gauged by just considering the cardiovascular diseases (CVD) where it's also a mediator, is independent of the traditional risk factors of age, smoking, cholesterol levels, blood pressure and diabetes, and is a stronger predictor of future risk than elevated levels of LDL-cholesterol and most other markers. Results from studies in >15 different populations and >40,000 people (when transient inflammation can be excluded) have shown that the top tertile of CRP levels is associated with a 2-fold relative increased CVD risk. Weight loss, diet, exercise and cessation of smoking all reduce CRP levels and reduce vascular risk.
Puerto Rican adults have prevalent metabolic abnormalities but few studies have explored F&V intake and coronary heart disease (CHD) risk in this population. We tested the hypothesis that greater F&V intake and variety are associated with a lower 10-y risk of CHD and CRP concentrations. In a cross-sectional study of approximately 1200 Puerto Rican adults aged 45–75 y, we assessed F&V intake with an FFQ. The 10-y risk of CHD was assessed with the Framingham Risk Score (FRS, a long running US public health study) in participants free of cardiovascular disease. CRP was measured in fasting serum. Variety, but not quantity, of F&V intake was significantly associated inversely with FRS after adjustment for the following: sex; waist circumference; perceived stress; alcohol use; intakes of energy, trans and saturated fatty acids, use of supplements, cardiovascular medications, and diabetes medications. However, the association was attenuated just above the significance level after adjustment for income. Variety, but not quantity, was significantly associated with a lower serum CRP concentration after adjustment for age, sex, smoking status, alcohol use, servings of F&V, white blood cell count, diastolic blood pressure, diabetes, nonsteroidal anti-inflammatory medication use, intakes of energy and vitamin B6, waist circumference, perceived stress, and income. The adjusted odds of a high CRP concentration for those in the highest compared with the lowest tertile of F&V variety was 0.68. F&V variety, but not quantity, appears to be important in reducing inflammation. Although the results are suggestive, larger studies are needed to confirm a possible association with CHD risk score.
Public media reports of individual 'magic or super foods' or 'the 5 fruits you must eat' that purportedly engender superior health should not be blindly followed to the extent where they unduly dominate others, but instead should be considered in the context of possibly making a contribution to the wide variety of healthy foods in your balanced diet.