Added sugars worsen cholesterol levels

Added sugars hit a new low this week. A study published in JAMA found that people who consume higher quantities of added sugars have worse cholesterol profiles than those who consume less.

First of, what are added sugars? Added sugars simply put are sugars that are added into foods (in contrast to naturally-occurring sugars that you find in fruits). The JAMA article writes that added sugars are “defined as caloric sweeteners used by the food industry and consumers as ingredients in processed or prepared foods to increase the desirability of these foods.”

The most commonly added sugars are sucrose (table sugar) and high-fructose corn syrup, the primary form of sugar in sodas and processed foods. The concept of added sugars is easy to understand. Carbohydrates are more vague. Plenty of carbs are good for you, like those you find in apples or vegetables; others are a mixed bag like whole wheat bread; and then some are just downright bad like Coca Cola. With added sugars you just have to think about where the sugars came from. If they are natural, that’s okay; if they are artificially added, then they should be avoided.

In the study, part of the National Health and Nutrition Examination Survey (NHANES), researchers surveyed 4605 non-pregnant adults ages 18 and older who were not on cholesterol-lowering medications. Each person was asked to describe what he or she ate in the previous 24 hours. Using standardized tables the researchers calculated how many calories in added sugars these foods added up to. They then asked participants a wide-range of questions from their age and weight to whether they had high blood pressure. These were analyzed along with data from blood samples that were taken to measure cholesterol levels.

Besides the bottom line — people who consume more added sugars have worse cholesterol — the study had many important findings.

First is the proportion of the average person’s daily calories that comes from added sugars. The answer: a whopping 15.8%. Put another way, 1 in every 7 calories the average American consumes is from added sugars! For those who still aren’t impressed consider the following. First, for thousands of years, the proportion of our diet that came from added sugars was zero. Zero. This is because up until a hundred years ago we didn’t have the technology to mass produce sucrose and high-fructose corn syrup. And in fact if you go to less “Westernized” parts of the world, as I did a few weeks ago to rural Uganda, this is still true today. Second, added sugars are empty calories. They have absolutely no nutritional value — no vitamins, no minerals, no essential amino acids. Thus 1 in every 7 calories we ingest is nothing but calories.

The investigators divided the participants into groups based on the percent of their total daily calories that came from added sugars. There were 5 groups: people who consumed less than 5% of total calories from added sugars, people who consumed between 5-10% of their calories from added sugars, people with 10-17.5% added sugars, people with 17.5-25% added sugars, and people with over 25% of their total calories from added sugars.

(It’s surprising to see that of the 4605 participants 893 (or 19.4%) had less than 5% of their calories from added sugars whereas 1135 (24.6%) had over 25% of their calories from added sugars. If anything, this shows that it is definitely possible in our modern society to consume low levels of added sugar.)

A few findings stand out. One, whereas 14% of those who consume less than 5% of their calories from added sugars live below the poverty line, 23% of those consuming over 25% from added sugars live below the poverty line. This makes sense because it’s often cheaper to eat processed foods that are loaded with added sugars than fresh foods, not to mention that the difficulty of finding anything but fast food restaurants and convenience stores in low-income urban areas. Still the data offers hope because it shows that 194 people (14%) consumed less than 5% of their calories from added sugars despite being poor.

Two, while the less than 5% group and the greater than 25% group had similar body mass index and waist circumference, the less than 5% group reported losing 0.3 lbs over the past year while the greater than 25% group gained 2.8 lbs. This suggests that over time consuming added sugars leads to significant weight gain.

Finally, let’s look at the core finding of the study. Using the same grouping as above, the investigators looked at the proportion of people in each group who had abnormal cholesterol levels. What they found was that going from the less than 5% group to the over 25% group the proportion of people with low HDL (good) cholesterol increased from 22.4% to 43.9%. Adjusting for potential confounders factors such as age, gender, physical activity, calorie intake and weight, they found that the relationship still held. Looking at other types of cholesterol, they found that consuming higher levels of added sugars increased triglyceride levels (adjusted odds ratio 1.3); however added sugars were not significantly associated with LDL (bad) cholesterol.

This study is not perfect by any means. It is not a randomized controlled trial or even a prospective cohort. It can only tell us about associations; correlations not causation. In addition, it looked at a surrogate marker of heart disease, cholesterol levels, when I am more interested in how added sugars may affect my chances of having a heart attack.

But, to me, the case against added sugars is adding up. At the least, we know that added sugars aren’t doing anything good for our health — they are simply empty calories. But we are increasingly appreciating that besides adding calories they are having other harmful effects on our health. It’s about time that we subtract added sugars from our diets.

Shantanu Nundy is an internal medicine physician and author of Stay Healthy At Every Age: What Your Doctor Wants You to Know.

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