Professionals, within and outside the medical community, have long believed that a person’s diet might affect acne. Why else, some experts argue, would 9.4% of the world’s population at any given time have acne when some cultures, like the populations of Tanzania, natives of Okinawa Japan, Canadian Intuits, and South African Zulu populations have amounts hovering around 1%? Adding fuel to the fire, scientists have found that acne increases in these populations after exposure to a Western lifestyle, which includes diets consisting of processed foods, dairy, and simple sugars.2
As researchers have attempted to understand the relationship between dietary sugar and acne, increasing amounts of data have accumulated linking the glycemic load of a person’s diet--how much a person's diet spikes his or her blood sugar--to acne development. However, due to the lack of a large, long-term, controlled trial, scientists have been unable to definitively confirm the link between glycemic load and acne. Therefore, doctors have not yet widely implemented diet as an acne preventative or treatment. Still, there is some evidence that shows us that a high glycemic load may be connected with increased acne symptoms.
Let's start by looking at exactly what the glycemic load is, and why, when it comes to acne, it is more important than the glycemic index.
Glycemic Load Defined
Glycemic index and glycemic load are two measures of a food’s ability to spike blood sugar levels. Although similar, each measures a slightly different capacity, and when it comes to acne, it is the glycemic load of the diet that is of concern.
Glycemic Index: The glycemic index (GI) is a number from 1-100 that represents how quickly a particular food will cause a rise in blood sugar levels. When a person eats a food with a GI of 100 (i.e., glucose) it will cause an extremely quick spike in blood sugar, whereas eating a food with a GI of 1 (i.e., bean sprouts), will cause a very slow rise in blood sugar.3
Glycemic Load: The glycemic index of a food only tells part of the story. It tells us how quickly the blood sugar spikes but not by how much - this is where the glycemic load comes in. The glycemic load (GL) is a number from 1-20, which adds onto the glycemic index by taking into account both how quickly the blood sugar rises and by how much when you eat a particular portion size of the food. For instance, watermelon has a high glycemic index (72), but a typical serving of watermelon does not contain a lot of carbohydrates, which means the blood sugar doesn't rise by much, and therefore, the glycemic load is low.4
In other words, sometimes a food, like watermelon for instance, might have a high glycemic index, which means it makes blood sugar rise quickly, but has a low glycemic load, which means it does not cause the blood sugar to rise by much. Ultimately, what matters is how much blood sugar rises. Therefore, glycemic load is what we need to look at when it comes to acne.
Foods both high on the glycemic index and glycemic load include foods like soft drinks, candy, or bread, with large amounts of processed sugar or carbohydrates.
Foods both low on the glycemic index and glycemic load include foods like vegetables, meat, some fruits, and beans.
Foods high on the glycemic index but low on glycemic load include some fruits like watermelon and pineapple, and some vegetables like carrots and pumpkin. You might have heard that these foods are "bad for you" before because they have a high glycemic index, but they are not. They have a low glycemic load, which is what really matters.
The Studies: Research Connecting Glycemic Load and Acne
Scientists have performed seven studies investigating the link between glycemic load and acne. Five of the seven studies concluded that a potential link between high glycemic load diets and acne development may exist, and two studies found no such association. So, the preponderance of the evidence at this point, albeit tentative, seems to point toward a connection.
Studies Showing a Link Between High Glycemic Load Diets and Acne
A 2007 study randomly assigned 43 men to two groups consuming either a high or low glycemic load diet for 12 weeks. After 12 weeks, the researchers concluded that the men consuming the low glycemic load diet had decreased numbers of total and inflammatory acne lesions, as well as an increased sensitivity to insulin, which is a hormone that the body employs to use and store sugars that it consumes. Greater sensitivity to insulin is good because that means that there is less sugar in the blood. Diabetics, who struggle with high blood sugar levels, are generally not sensitive to insulin.5
A 2007 study randomly assigned 43 men to two groups consuming either a high or low glycemic load diet for 12 weeks. After 12 weeks, the researchers concluded that the men consuming the low glycemic load diet had decreased the total number of acne lesions, increased sensitivity to insulin, and decreased levels of androgens (male hormones), which are hormones that cause an increase in sebum (skin oil) production.6
A 2008 study randomly assigned 12 men to consume either a high or low glycemic load diet. After one week, the men on the low glycemic load diet showed increased insulin sensitivity, lower androgen levels, and increased insulin growth factor binding protein-3 (IGFBP-3) concentrations than men on the high glycemic load diet. IGFBP-3 is a protein that has two main functions: (1) to bind insulin growth factor-1 (IGF1) and (2) to stimulate skin cell death. When there are high levels of IGFBP-3, this binds to IGF1, which supports increased insulin sensitivity and stimulates skin cell death, which may decrease pore clogging.7
A 2008 study randomly assigned 31 men to either a low GL diet or a control diet with high amounts of carbohydrates. After 12 weeks, men consuming the low GL diet had decreased sebum production, and less total acne lesions than the men on the control diet.8
A 2012 study randomly assigned 32 men and women to a high or low glycemic load diet for 10 weeks. Patients consuming the low glycemic diet saw an improvement in acne severity as well as decreased sebaceous gland (skin oil gland) sizes.4
Studies Showing No Link Between High Glycemic Load Diets and Acne
A 2010 study randomly assigned 58 men to consume a high or low glycemic load diet for eight weeks. Although men consuming the low glycemic load diet saw greater improvement in acne compared to men consuming the high glycemic load diet, the improvements were not large enough to be considered statistically significant. Therefore, this study concluded that a low glycemic load diet did not result in acne improvements or increased insulin sensitivity.9
A 2014 study interviewed 91 patients about their dietary practices and then assigned them to either a high or low glycemic index group based on what they normally ate. After examining the patient’s acne severity, blood sugar, and insulin levels, the scientists concluded that there were no differences in any of the examined factors between patients consuming a high or low glycemic load diet.2
Although five of seven studies have identified a potential link between glycemic load diets and acne, these studies are not proof that a high glycemic load diet causes acne. This is because all five studies are small (less than 100 subjects), use mainly male research subjects, and have confounding factors like patient weight loss caused from the low glycemic diet. Weight loss can cause the body to become more insulin sensitive and thus improve acne in the short term. These study flaws, among others, prevent researchers from making a general conclusion about high glycemic diets and acne. Therefore, scientists will need to perform additional studies, including at least one large, randomized trial, in order to more definitively claim that high glycemic load diets cause acne.
However, for now, the evidence seems to at least weakly point toward a connection. Let's look now at the science behind exactly why a high glycemic load diet might increase acne.
The Science: How Glycemic Load Might Affect Acne
Eating a high glycemic load food increases the level of sugar in the blood. When the body senses there is a high level of blood sugar it responds by producing insulin, which helps the body use and store the sugar. The presence of insulin then triggers the activation of a variety of responses in the body, which might potentially lead to an increase in acne.
Okay, here comes the deep science...One major response is the insulin-induced suppression of a protein known as FoxO1. The normal activity of FoxO1 is to inhibit androgen activity and also lower production of important sebum components called fatty acids. A rise in insulin leads to a suppression of FoxO1 and therefore increased androgen activity and production of sebum. A second major response to increased insulin is the insulin-induced stimulation of a protein known as mTORC1. The normal activity of mTORC1 is to promote the production of sebum. Therefore, a rise in insulin will increase the activity of mTORC1 and increase the production of sebum.1
Eating a high glycemic load diet leads to an increase of insulin, which suppresses FoxO1 and activates mTORC1 pathways. These pathways may result in an increase in sebum production, making the skin oilier, which could in turn promote the growth of acne bacteria. Therefore, some scientists predict that consuming a low glycemic diet will result in decreased levels of insulin and in turn a decreased amount of sebum, bacteria growth, and acne.10
The Bottom Line
Because it is so hard to study the effects of diet on disease, we still don't know definitely whether eating a low glycemic diet will improve acne. But since the preponderance of the evidence points toward this possibility, and eating a low glycemic diet is healthy regardless, it can't hurt to try to eat more unprocessed, whole foods whenever possible. While you should not expect a dramatic reduction in acne simply from changing your diet, consuming a low glycemic diet might help at least to some degree.
Eating low glycemic means eating more vegetables, whole fruits (not juice), nuts, beans, meats & fish, and unprocessed whole grains.