Diets High in Refined Grains Increase Heart Attack Risk

Eating a lot of refined carbohydrates increases the risk of:

  • obesity
  • high blood pressure
  • type 2 diabetes
  • stroke
  • heart disease

In a new study, researchers wanted to see how the consumption of refined grains and cereals, whole grains, and rice affects blood pressure, cholesterol levels, and the risk of heart disease and death.

The findings further validate a wealth of previous research linking diets high in refined carbohydrates with negative health outcomes.

“This study reaffirms previous work indicating a healthy diet includes limiting overly processed and refined foods,” says Prof. Scott Lear, a health sciences expert at Simon Fraser University in Canada.

The study, which involves 32 contributing researchers in 21 countries, appears in The BMJ.

‘Simple’ vs. ‘complex’ carbohydrates

Carbohydrates are an essential nutrient. While we associate a diet of certain carbohydrates with health benefits, others raise the risk of health complications.

“Simple” carbohydrates include refined grains and cereals found in foods such as white bread, pasta, and cereals.

Generally speaking, these are considered “bad” carbohydrates because of how their sugars are structured and digested. When grains undergo the refinement process, they lose a nutrient, fiber-rich shell, and endosperm core, so they are quickly broken down into simple sugars when eaten.

These simple sugars are rapidly absorbed into the bloodstream, causing sudden, temporary spikes in blood sugar levels. This explains why most people only experience a short-term energy boost when eating refined carbohydrates.

And because they lack fiber and are quickly digested, most people feel hungry relatively soon after eating simple carbohydrates.

Foods rich in simple carbohydrates also raise blood triglyceride levels, referring to blood fat. In addition, having high blood triglyceride levels increases the risk of diabetes, coronary artery disease, and fatty liver.

Simple carbohydrates also contain many calories but have been stripped of their nutrition. So eating a lot of refined carbohydrates increases the risk of obesity and its associated health complications, as well as malnutrition.

In contrast, “complex” carbohydrates include foods with whole grains and whole grain flours such as whole grain bread, cereal, and rice.

This is because complex carbohydrates contain grains that have their shell and endosperm core intact. These layers are rich in nutrients and fiber, so they take much longer to break down and be absorbed.

Because of this, consuming complex carbohydrates tends to provide a slow, steady release of sugar into the bloodstream, reducing the risk of blood sugar spikes and crashes. The fiber in complex carbohydrates also helps most people feel full for longer.

Therefore, eating whole grain foods is associated with plenty of health benefits, including maintaining:

  • moderate weight
  • sufficient cholesterol levels
  • sufficient blood pressure levels

In the new study, the research team aimed to define the association between refined grain and cereal intake and the risk of heart disease and death. They also set out to assess how socioeconomic and demographic factors influence this link.

Past studies have found conflicting information on the topic. Most previous research has also only taken place in European and North American countries, which tend to be middle-to-high income countries.

Validating previous research

In the study, researchers from 21 countries in North America, Europe, Asia, Africa, and the Middle East analyzed questionnaires from 137,130 participants spread across 21 countries.

The questionnaires asked people to detail their intake of refined grains, whole grains, white rice, and sugar. Researchers also collected the following participant information:

  • lifestyle habits, such as general diet, alcohol intake, smoking status, and physical activity levels
  • socioeconomic status, such as education level, income, and employment status
  • personal medical history, including any history of diabetes, heart disease, high blood pressure, cholesterol and triglyceride levels, and medication usage

Once they completed the baseline questionnaire, the participants conducted a follow-up questionnaire every 3 years for 16 years across 2003–2019. The researchers also tested their blood pressure and blood lipid (fat) levels during these follow-ups.

At the start of the trial, all participants were between 35–70 years of age. In addition, researchers excluded people with preexisting heart disease from the trial.

The participants represented a diverse mix of populations, including those living in urban and rural regions in five low-income countries, five lower- middle-income countries, seven upper-middle-income countries, and four high- income countries.

The study found that eating more than 7 servings of refined grains and cereals, or more than 350 grams (g), increased the risk of early death by 27% compared to eating less than 50 g per day. It also increased the risk of heart disease by 33% and the risk of stroke by 47%.

The researchers also found that people consume much more refined grains and sugars than before. No negative health effects or outcomes were associated with whole grain and white rice consumption.

However, the team stated several shortcomings to their study. Firstly, they did not assess the separate impact of added sugars in foods with refined grains and sugars.

Secondly, given human error, questionnaires that rely on participants’ record- keeping also tend to detail relative — as opposed to absolute — dietary intake. Participants’ diets were also only recorded comprehensively during the first questionnaire. Dietary changes could have taken place in the subsequent 16 years.

The study, whose formal name is the Prospective Urban Rural Epidemiology study, provides further proof that limiting intake of refined carbohydrates helps reduce the risk of negative health complications.

If confirmed by additional research, these findings could help create more precise guidelines concerning the daily recommended consumption of refined grains and cereals.

These discoveries could also help encourage billions of people to make dietary changes to improve their overall health and risk of developing major health complications, including heart disease and stroke.

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