Analyses of U.S. health survey data link diets that include apples or rice to reductions in metabolic and physical factors known to raise diabetes and heart risks
by Craig Weatherby
According to two new analyses of the leading U.S. health survey, people who eat apples or rice enjoy a reduced risk of developing metabolic syndrome (MetS).
However, rather than suggesting that apples and rice are particularly powerful preventive aids against MetS, the new findings indicate that the diets of people who eat apples or rice are healthier overall.
Metabolic syndrome (MetS) is a cluster of health characteristics associated with a substantially greater risk of developing diabetes and/or heart disease.
The question is whether apples and rice separately help prevent MetS, or whether people who eat apples or rice tend to have healthier diets and lifestyles, overall.
It seems plausible that both possibilities may be true.
Apples and rice both possess properties that should militate against MetS.
And people who eat apples or rice regularly probably have healthier diets and lifestyles, compared with peers who rarely eat either food.
With this in mind, let’s take a look at a recent analysis of data from the National Health and Nutrition Examination Survey (NHANES).
Most epidemiological studies involve only interviews or, more commonly, lifestyle questionnaires and/or diaries mailed in by participants.
NHANES is unique in that it combines interviews and physical examinations.
A team led by consulting researcher Victor Fulgoni, Ph.D., analyzed the self-reported dietary habits of about 5,000 adults, collected by NHANES researchers from 1999 to 2004.
Their analysis, which was funded by the U.S. Apple Association and USA Rice Federation, showed positive associations between apple and rice consumption and various measures of metabolic health.
Here’s what they found.
How NHANES takes America’s pulse
NHANES began in the early 1960s and has been conducted as a series of surveys
focused on different population groups or health topics. In 1999, the survey became a continuous program that has a changing focus on a variety of health and nutrition measurements.
The survey examines a nationally representative sample of about 5,000 people annually across the country.
The NHANES interview includes demographic (age, gender, ethnicity), socioeconomic (income, work history), dietary, and health-related questions.
The examination component of NHANES consists of medical, dental, and physiological measurements, as well as laboratory tests administered by trained medical personnel.
Findings from this survey will be used to determine the prevalence of major diseases and risk factors for diseases.
Apples and apple sauce/juice linked to h reduced metabolic risksDr. Fulgoni’s team scrutinized the association between consumption of apples and apple products and the several bodily traits that together define metabolic syndrome (MetS).
Compared with people who reported eating no apples, the 968 people who reported eating apples, apple juice, or apple sauce—were 27 percent less likely to have developed metabolic syndrome by the end of the 5-year survey period (Fulgoni VL et al. 2008).
(Participants were only asked about their diet over the 24 hours prior to the interview, to ensure accurate recall. But in a population this size, the common 24-hour-recall survey method has enough statistical strength to paint a reasonably reliable picture of people’s dietary habits.)
As Fulgoni said in the apple association’s press release, “We found that adults who eat apples and apple products have smaller waistlines that indicate less abdominal fat, lower blood pressure and a reduced risk for developing what is known as the metabolic syndrome.”
Apple eaters tested healthier than their peers with regard to several key markers for MetS:
- 21 percent less likely to have gained inches of belly girth.
- 36 percent less likely to have a high systolic blood pressure.
- 30 percent less likely to have a high diastolic blood pressure.
- Significantly lower levels of the inflammation-indicator called C-reactive protein.
As you might expect, eaters of apples and apple products were healthier overall, compared with other study participants.
Apple eaters reported eating more fruit and less total fat, saturated fat, and added sugars.
In addition to being a marker for healthier overall diet, apples are intrinsically able to tilt metabolisms in a healthier direction.
Anyone who’s eaten them knows that apples take the edge off an appetite.
They are high in anti-inflammatory antioxidants (associated with multiple metabolic benefits), filling fiber, and pyruvate: a phyto-factor seen to aid weight control slightly in clinical trials (Stanko RT, Arch JE 1996).
Neither the abstract nor the press release mentioned whether Dr. Fulgoni’s group analyzed eaters of whole apples separately from those who only consumed apple sauce or apple juice… especially the latter, which lacks any filling starch or fiber.
Correlation vs. causation: Epidemiology provides evidence, not proof
Most of the nutrition and health findings reported in the media come from epidemiological studies.
By definition, epidemiological studies are ones in which researchers collect lifestyle and health status information about a group of people, looking for statistical associations between the participants’ self-reported lifestyle habits (diet, exercise, etc.) and their health status.
Unlike large, well-controlled clinical trials, epidemiological studies cannot prove a causal relationship between people’s lifestyle habits and their health outcomes.
For example, if a study shows that people who eat apples have less risk of metabolic syndrome (MetS) this doesn’t prove that apples help prevent MetS.
However, epidemiological evidence like this points to possibilities that warrant further exploration via experimental (animal or test tube) research and, ultimately, clinical trials.
Accompanying analysis puts rice in positive light
Dr. Fulgoni’s team conducted a similar analysis with regard to NHANES participants who reported eating rice or rice products.
They defined “rice consumers” as people who reported consuming at least 14 grams (1/2 ounce) of white rice, brown rice, or rice flour during the 24 hours prior to completing the NHANES survey (Fulgoni VL et al. 2008).
As with apples and apple product consumers, the analysis linked being a rice consumer to having lower blood pressure, lower body weight, a smaller waist… and a consequently lower risk of metabolic syndrome.
Rice eaters tested healthier than their peers with regard to several key markers for MetS:
- Significantly lower body weight
- Significantly smaller waistlines
- Significantly lower blood pressure (systolic and diastolic)
- 21 percent lower risk of metabolic syndrome.
And, compared to non-consumers, rice consumers had healthier diets overall:
- More fruits and legumes (beans)
- Less fat and added sugar
- Higher (estimated) intake of certain nutrients, including iron, folate, vitamin B6, and niacin
It would be interesting to know whether there were any associations between rice consumption and ethnicity, as these could explain in part the differences in overall diet patterns.
For example, Asians and Latinos eat more rice than most Americans, and their ethnic cuisines feature more vegetables and beans than the average U.S. diet does.
Note: Dr. Fulgoni's nutrition consulting firm exists to develop evidence that specific foods enhance health, so these results must be confirmed by independent research.
- Fulgoni VL, Fulgoni SA, Haaga S, Ebert A. Apple consumption is associated with increased nutrient intakes and reduced risk of metabolic syndrome in adults from the National Health and Nutrition Examination Survey (1999–2004). FASEB J. 2008 22:1081.7
- Fulgoni VL, Fulgoni SA, Upton L, Moon M. Rice consumption is associated with a greater nutrient density, lower blood pressure, decreased body weight, smaller waist circumference and a reduced risk for metabolic syndrome in adults. FASEB J. 2008;22:1081.3
- Stanko RT, Arch JE. Inhibition of regain in body weight and fat with addition of 3-carbon compounds to the diet with hyperenergetic refeeding after weight reduction. Int J Obes Relat Metab Disord. 1996 Oct;20(10):925-30.
- U.S. Apple Association (USAA). Adults Who Eat Apples, Drink Apple Juice Have Lower Risk for Metabolic Syndrome. April 8, 2008. Accessed online April 12, 2008 at http://www.usapple.org/media/newsreleases/cnr040808.cfm