Spoiler alert: you’re going to die of something. And, statistically, there’s a good chance that something will be heart disease, as it’s responsible for one in every four deaths in the United States. But if you exercise, don’t smoke, and avoid roller coasters and Jordan Peele movies, you’re doing almost everything you can to minimize your risk of a heart attack or stroke. That just leaves your diet—and the ongoing debate of whether it’s eating carbohydrates or fats that promotes heart disease.

We’ve long suggested that a lower-carb, higher-fat eating approach is best for most people, and new research from the UK just added further support to that stance. Published in February, a meta-analysis of 12 different studies that included more than 300,000 people from around the world found that those following diets comprising foods that are high on the glycemic index (GI), and with a large glycemic load (GL), were at a significantly greater risk for cardiovascular disease.

What Are Glycemic Index and Glycemic Load?

Processed Carbs May Cause Heart Disease

The glycemic index is a reference guide for the effect that the carbohydrate content of a food has on your blood sugar in relation to pure glucose. Foods are assigned numbers according to how quickly they raise blood sugar. For example, pure glucose has a GI of 100 (read: pretty damn high), so fast-digesting, insulin-spiking foods like white bread, pastries, and cornflakes that come in at 70 or above on the index are therefore considered high-glycemic foods.

Foods with high GI scores are often poor choices to eat, as they’re processed and low in nutrients. However, this isn’t always the case, and this is why scientists also take into account a food’s glycemic load. The GL of a food compares its potential to raise blood sugar to other foods that contain the same number of carbs as a way of assessing food quality. It’s calculated by multiplying the GI of the food by the grams of carbs in a serving of it, and then dividing by 100.

For instance, both watermelon and a donut have a GI of 76, but one serving of the melon is only 11g carbs, versus 23g in the donut. Watermelon has a GL of 8, and the donut a GL of 17, so the watermelon is the healthier option. (A glycemic load of around 20 or greater is consider a high-GL food.) Another example is fiber-rich parsnips. They rank higher on the index than pasta, but have a much lower GL.

A person’s dietary GL is the sum of the GL’s for all the foods he/she eats.

Sugar and Disease

Processed Carbs May Cause Heart Disease

Research shows that people who make a habit of eating foods that are both high GI and GL develop health problems. It’s presumed that their insulin is up all day long trying to bring down the blood sugar spikes that their carb-dense foods cause them, and that leads to weight gain and decreased insulin sensitivity. A study that analyzed data from 1909 to 1997 found that the increased consumption of refined carbohydrates (specifically, corn syrup) by Americans, in conjunction with a declining intake of fiber, paralleled the increase in cases of type 2 diabetes in the 20th century. Meanwhile, a 2014 study in the American Journal of Clinical Nutrition reported that consumption of high-GI and GL foods was associated with a roughly 50% greater risk of developing diabetes.

Too many refined carbs is connected to heart trouble too. A meta-analysis of 14 studies determined subjects were at a 13% greater risk of cardiovascular disease when following a high-GI diet, and a 23% greater risk when eating a high-GL diet. Other research indicates that women in particular are more likely to suffer cardiovascular problems when eating high-GI and GL. A 2015 meta-analysis of seven studies found that dietary GL was associated with a 35% increased risk of ischemic stroke.

Based on these findings, most nutrition experts agree that consumption of refined carbs seem to be a common denominator in people who are unhealthy, but they’ve never been sure that carbs themselves are to blame—usually because of confounding factors like smoking, poor overall diet, and other lifestyle choices that make it impossible to determine which contributor is having the biggest impact. The new UK analysis, however, could provide some clarity.

What makes it such a standout is that the researchers used the Bradford Hill criteria, a set of principles used to determine a causal relationship between a presumed cause and an observed effect. In other words, Bradford Hill groups together criteria that can indicate causation from studies that only show correlation. All nine categories for probable causality were met in this case, so the findings didn’t just show that eating refined carbs was a common trait in people who were developing cardiovascular disease—as plenty of research in the past has already done. They actually gave the researchers reason to say that the refined carbs could be the cause of cardiovascular disease. Also worth noting: all of the studies’ subjects were healthy when the research began, and over years of follow-ups, the ones who ate high-GI and GL were determined to be in increasingly poorer health.

How To Eat To Live Longer

To be clear, while the UK study indicates refined carbs as a possible cause of heart attacks and strokes, it does not completely exonerate fat either. It also doesn’t paint all carbs with the same brush. More studies will need to be done, but the researchers concluded that people should pay more attention to the “quality” of carbs they eat. This echoes advice from the Linus Pauling Institute to lower the glycemic load of your diet by eating more nuts, non-starchy vegetables, and whole grains, while avoiding sweets, white bread, and white rice.

Of course, ketogenic diets are always chock full of low-GI and GL foods, and have been shown many times to help reduce the risk of heart disease and many other health woes. Download our FREE ebook to going keto, and see our guide to staying keto at restaurants and fast food windows.