Southern-Fried Trouble: Some Diet 'Patterns' Raise CHD Risk

Deborah Brauser

August 13, 2015

BIRMINGHAM, AL – So-called "comfort food" may not be so comforting for the heart.

In what is sure to sadden fans of fried chicken, mashed potatoes, and piles of breakfast bacon, new research suggests that consuming a diet predominantly made up of traditional home-style cooking may increase risk for coronary heart disease (CHD)[1].

After examining data from more than 17,000 participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, investigators found that those who routinely ate the fat-filled and fried foods often found in Southern states of the US had a 56% higher hazard rate for acute CHD compared with the participants who mostly stayed away from this type of diet.

In all multivariable models, no other dietary patterns showed significant heart hazards or benefits. This included a pizza- and pasta-heavy convenience pattern, a sweets-based pattern, and an "alcohol-and-salad" pattern.

"I think this shows that patients should be questioned about what they're eating," lead author Dr James M Shikany (University of Alabama at Birmingham) told heartwire from Medscape.

However, he noted that clinicians shouldn't tell patients to completely cut out a certain type of food, but instead recommend that they cut down. "I never suggest that people entirely stop eating something. They don't like those recommendations, and they won't maintain it, especially if they've been eating this way all their lives," said Shikany.

The findings were published online August 10, 2015 in Circulation.

Five Food Patterns

The investigators report that although past research has shown links between increased CHD risk and certain food items, such as red meat or saturated fat, associations with diet combinations have not been as well studied.

"There's been a movement over the past few years to look at dietary intake that's more relevant to how people actually eat. Instead of concentrating on specific nutrients, it's looking at overall patterns and how that relates to disease," said Shikany. "Most of us don't eat isolated foods. We eat a whole diet."

The original REGARDS trial enrolled 30,239 adults over the age of 44 years between 2003 and 2007.

For this analysis, data were examined for 17,418 of the participants with no history of CHD (59% women; 65% white, 35% black). Of these, 56% lived in states the investigators referred to collectively as "the stroke belt"—Alabama, Arkansas, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, and Tennessee.

All participants completed telephone and in-home interviews. They also anonymously reported type and amount of dietary intake on the Block 98 food frequency questionnaire, which included 110 separate food items.

Five general subgroups were formed based on the main dietary patterns that emerged organically from answers on the questionnaire. These included:

  • Convenience diet—Pasta, pizza, Mexican food, Chinese food.

  • Plant-based diet—Vegetables, fruits, cereal, beans, fish, yogurt.

  • Sweets diet—Added sugars, chocolate, desserts.

  • Alcohol-and-salad diet—Beer, wine, leafy vegetables, tomatoes, salad dressing.

  • Southern diet—Fried food, eggs, organ meat (including bacon), processed meat, sugar-sweetened beverages (including sweet tea).

"Each person wasn't pigeon-holed into just one of these diets. Generally people have adherence of different levels to all five of these groups," Shikany explained.

When asked how the alcohol-and-salad diet came to be, he said that that was just what occurred in their factor analysis. "In that diet, the foods that were loading most heavily happened to be various types of alcohol as well as salad greens, etc. It's an odd combination, but that's what the data gave us."

Risky Diet

After a follow-up of 5.8 years, 536 members of the study population developed CHD. The hazard ratio (HR) for having acute CHD, after adjustment for lifestyle and demographic factors, was 1.56 for those who consumed the most Southern-diet-pattern foods vs those who consumed the least (95% CI 1.17–2.08, P for trend=0.003).

This association was lessened but still significant when medical history, body-mass index, and waist circumference were added into the measure (HR 1.37, 95% CI 1.01–1.85; P=0.04).

The individuals who had the highest consumption of the Southern-pattern diet were significantly more likely to be men, black, younger than 65, a stroke-belt resident, a current smoker, and have an annual household income less than $20,000 compared with those who had a lower consumption of the diet. They were also more likely to have diabetes, hypertension, and dyslipidemia (all comparisons, P<0.001).

Additional analysis showed that those with the greatest Southern-diet intake had lower acute CHD-free survival probability than those who had the highest intake of the other four dietary patterns.

Shikany noted that although he wasn't surprised to find an association between CHD risk and consumption of the Southern dietary foods, the magnitude of the risk was eye-opening.

The biggest surprise, however, was that there was no inverse association for the plant-based dietary pattern. "A lot of the main components of that pattern have been believed to be protective against heart disease," said Shikany. "But there was no significant association at all, in either direction."

He reported that the investigators also expected to see a positive association between the convenience diet and CHD risk. "Overall, I'd say some of the negative findings were the most surprising."

However, he noted that limitations included that it was an observational study with food data self-recorded by the participants. "This was a rigorous trial in a well-characterized population. But you have to keep in mind its observational nature."

Standardization Needed

Drs Susan M Krebs-Smith, Amy F Subar, and Jill Reedy (National Cancer Institute, Bethesda, MD) write in an accompanying editorial that the investigators are adding to an ever-growing body of literature on diet and health outcomes[2].

"Understanding the drivers of health disparities is critically important, and the topic of dietary patterns is of increasing interest," they write.

The editorialists note, though, that the factor-analysis method used in the study presented several limitations, including subjectivity both when determining the food groups and when naming the food patterns.

"Unless methods of collecting the data are comparable and food-group construction is standardized, results are not comparable across studies," they write. In addition, "factor names are determined by the researcher and, given that they tend to be short, often fail to adequately convey what the underlying factor is."

This is illustrated by the plant-based pattern including nonplant foods such as fish, poultry and low-fat milk. So those findings should not be interpreted as individuals who eat a high-quality plant-based diet, as evaluated with a standardized index, have the same risks as individuals who eat other types of diets, they note.

"Questions remain regarding how those factors [identified in the study] relate to the overall pattern of eating, whether those factors could be identified in other samples, and whether those factors are the most important with regard to CHD," write the editorialists.

"Without restricting innovation, there is a need to identify ways to standardize dietary patterns analyses."

The study was funded by the National Institute of Neurological Disorders and Stroke and by the National Heart, Lung, and Blood Institute. The study authors and editorialists report no relevant financial relationships.

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