Chocolate and acne: how valid was the original study?

Recent reviews on “The role of diet in acne: facts and controversies”1 and “Nutrition and acne”2 were interesting but may not have adequately challenged the dogma that chocolate does not exacerbate acne vulgaris. Our Medline search, using the key words “acne and chocolate,” showed that only 3 studies examined the role of chocolate consumption and acne. One clinical trial had 8 patients,3 another did not specify sample size,4 and the third study by Fulton, Plewig, and Kligman (1969) supported the oft-repeated assertion that eating chocolate has no effect on acne.5 While some reviewers acknowledge that few studies exist, they describe Fulton's study among them as “a methodologically stronger trial.”1 As a result, Fulton's (1969) finding that chocolate consumption does not exacerbate acne has continued to remain virtually unchallenged for decades and continues to be cited even in this most recent review. For the first time in over forty years, we thoroughly examined this 1969 classic paper entitled, “Effect of Chocolate on Acne Vulgaris,” published in the Journal of the American Medical Association. It was a crossover study with 65 participants consuming chocolate or placebo bars for four weeks (3-week wash-out period). A 30% decrease or increase in weekly lesion count resulted in “mild to moderate” acne being assessed as improved or worsened, respectively. The authors concluded that chocolate had no effect on acne severity; however, an analysis of this frequently cited paper reveals the following flaws: