The relationship between acne and diet remains as unclear today as it was 50 years ago. Back then, acne was reputed to be caused by hamburgers, malt sodas, and other foods popular to teenagers. Today, around one in every three teenagers, medical students, doctors, and nurses still believe in a link between acne and diet.

Interest regarding this “link” has been overwhelming due to rising concerns for health and nutrition, but much of what experts know are still largely based on pseudo-scientific hearsay and myths. Actual studies about the link between acne and diet have been hampered by commercial issues, and irrefutable evidence based on good-quality research is still elusive.

At this point, a consensus of popular opinions on the topic is the most reliable source of information regarding the link between acne and diet. While this may be questionable, it is important to note that most medical treatments initially stem from people’s perceptions.

Acne and diet link

The link between acne and diet may have grown from the comparison of western societies with non-western ones. Acne was found in lower incidences in the non-western societies, but was also found to increase that when these societies migrated to a western lifestyle. For instance, the Inuit Indians of Canada had practically no knowledge of acne prior to their adoption of a western lifestyle. When they did, the acne incidence levels soon paralleled those seen in Western Caucasian societies. Similar observations were also noted in other populations undergoing the same migration.

Hyperinsulinemia effect on acne

Chronic hyperinsulinemia (high insulin resistance) may be a key link between acne and diet. It is believed that hyperinsulinemia causes acne by stimulating androgen production and affecting the sebaceous glands and follicular keratinization. It is caused by diets that are high in fat and carbohydrates, which is common in western societies.

SHBG (sex hormone binding globulins) acts against testosterone, binding to free molecules of testosterone and rendering them inactive. More SHBG reduces testosterone, and consequently reduces androgen hormone activity. Testosterone may maintain insulin levels and promote insulin resistance at different levels.

Studies in women with polycystic ovarian syndrome have shown that hyperinsulinemia increases androgen production and decreases SHBG production in the liver. This results in unusually high insulin resistance levels and may prove to be a cause of acne.

Dietary influence on sebum composition and secretion rate

Another possible link between acne and diet was shown in sebum studies on animals and humans. Animals produced more sebum while subsisting on a high-fat or carbohydrate diet, and humans showed changes in sebum composition and a 40% reduction in sebum secretion after subjected to total and prolonged calorie deprivation.

Pappas et al also disproved the once-popular opinion that sebaceous glands produced sebum on their own and did not derive any of its components from the bloodstream. They convincingly showed that the sebaceous glands in fact draw fatty acids from the bloodstream and use it to produce sebum. While this and other discoveries suggest that dietary fat and carbohydrate may have affect sebum production, it still fails to prove the link between acne and diet.

Interventional studies

Several studies have been made in an attempt to prove the relationships between acne and diet, but so far many of these have failed to produce any links. 2,720 soldiers were studied for any link between acne and obesity, and while a link was found in older subjects, adolescents showed no such relation. 16 acne sufferers showed no difference in sugar consumption with those without acne in another study.

Monozygotic and dizygotic twins were also subjects of a large and important study that found no significant differences in weight, height, birth weight, BMI (body mass index), and reproductive factors between acne and non-acne affected twins.

Chocolate - a cause?

A 1969 study on the supposed worsening effects of chocolate on acne suggested relation. Negligible differences in the moderate acne of 65 volunteers were found, even when one part of the group ate a daily candy bar containing ten times the normal amount of chocolate and the other part eating a similar bar with no chocolate.

However, critics have found several serious flaws in the study’s methodology, the most important of which involved the quality of acne lesions. The study only measured the number of lesions (both comedones and pustular flares) combined, but the conversions of comedones to pustular flares were not taken into account. This was a vital hole in the study, as patients with food-related acne complain of pustular flares more imperatively than comedones. Larger, better-designed studies have not been conducted since.

Is there a link between acne and diet? The jury’s still out on this one.