High-Sugar/Fat Diet Tied to High Insulin, Subsequent Hypertension

Marlene Busko

November 04, 2015

LOS ANGELES — Most doctors and many laypersons are aware that eating a diet high in sugar and/or fat is unhealthy, but now a new study connects a couple more dots, revealing that such diets are associated with a greater likelihood of having high insulin levels, which in turn seems to be linked with a heightened risk of hypertension and left ventricular hypertrophy.

Specifically, researchers identified this increased risk in participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study who ate a "sweets/fat" diet or a high-sugar (Southern) diet, whereas having a "plant-based" or an "alcohol/salad" diet was associated with a lower risk of these outcomes.

The findings from this cross-sectional, observational study will need to be confirmed in further research, Barbara Gower, PhD, from the department of nutrition science, University of Alabama at Birmingham, cautioned, presenting these results in an oral abstract session at Obesity Week 2015.

"With the [dietary] pattern data, you can't pull out any one thing and say 'this is what caused it,' " she told Medscape Medical News.

For example, a Southern diet contains a lot of fried food plus highly sweetened tea, where a serving may hold more glucose than in an oral glucose tolerance test, she noted. "I think that combination is really toxic, but we would have to dig deeper" in further randomized studies to be able to show true cause and effect.

That said, in the meantime, "I really think that fasting insulin should be looked at more closely," Dr Gower said. Clinicians rarely request this test, and it is generally not reimbursed by insurance, "but if there's one thing that is always going to be bad for any type of cardiometabolic-health outcome, it's going to be high fasting insulin....It's a huge red flag and it probably ought to be measured more," she urged.

The message for patients and the general public is to avoid living on convenience foods made from overly processed carbohydrates, she stressed.

Does Diet Affect Hypertension By Altering Insulin Resistance?

About 29% of American adults and up to 46% of African American women have hypertension. The researchers hypothesized that elevated insulin might account for a portion of this hypertension, since insulin stimulates the absorption of sodium and secretion of vasopressin. In turn, dietary patterns might explain higher fasting insulin levels.

Dr Gower and colleagues analyzed data from 14,729 nondiabetic participants in REGARDS — an observational study of adults older than 45 who lived in 1855 counties across the continental United States.

Earlier data from REGARDS published this summer have already linked routine consumption of a "Southern" diet with a more than 50% increased risk for acute coronary heart disease.

For the new analysis, the researchers examined the Block 98 Food Frequency Questionnaire filled in by the participants, and based on their replies, five diet patterns emerged: convenience (high in Chinese, Mexican, and take-out food), plant-based (high in vegetables and fruit), sweets/fat (high in sugary desserts, bread, and candy), Southern (high in fried foods, eggs, and sugar-sweetened beverages such as tea), and alcohol/salad (high in wine, liquor, and salad dressing).

After researchers excluded heavy drinkers and participants with missing data, this left 13,528 participants for the final analysis. The participants had a mean age of 64.5 and a mean body mass index (BMI) of 28.4; 57% were female.

The researchers determined the prevalence of hypertension and electrocardiographic left ventricular hypertrophy in the participants.

They used logistic regression to examine how diet pattern was associated with odds for high fasting insulin [quartiles 3 and 4 vs quartile 1], after adjustment for covariates. They also used the same method to examine the association between insulin quintile and hypertension or left ventricular hypertrophy.

Participants who had a "sweets/fat" or "Southern" diet pattern or ate more carbohydrates were more likely to have high insulin (P < .05 to < .0001). In contrast, participants who had a "plant-based" or "alcohol/salad" diet pattern were less likely to have high insulin (P < .0001).

Strikingly, participants in the highest quintile of fasting insulin were 3.4 times more likely to have hypertension than participants in the lowest quintile of fasting insulin (odds ratio [OR], 3.4; P < .001).

Similarly, participants in this quintile of highest fasting insulin also had an almost threefold higher risk of having left ventricular hypertrophy (OR, 2.77; P < .001).

Further interventional studies that they performed also support these findings, Dr Gower reported.

Asked to comment, session cochair Gabrielle Jenkins, MPH, a PhD student at the University of North Carolina at Chapel Hill, said that the alcohol/salad group was interesting.

She wondered, given that this analysis excluded heavy drinkers, "how much alcohol [are people with the alcohol/salad] diet pattern [actually] consuming, considering that alcohol is associated with increased hypertension."

Dr Gower and Dr Jenkins have no relevant financial relationships.

Obesity Week 2015; Los Angeles, CA. Abstract T-OR-2108, presented November 3, 2015.

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