Objectives: The hypothesis tested was that menstrual discomfort, e.g. dysmenorrhoea, known to be prostaglandin-mediated, can be influenced by the dietary ratio of n-3 and n-6 polyunsaturated fatty acids. The prostaglandins derived from marine n-3 fatty acids are normally less aggressive and therefore expected to be associated with milder symptoms.
Design: The question was surveyed in an epidemiological study based upon self-administered questionnaires concerning menstrual history, present symptoms, general health, socioeconomic factors, and general dietary habits. Two (prospective) 4-day dietary records were used to estimate average daily nutrient intake.
Subjects: The subjects were recruited by advertising (about 220 volunteered); 181 healthy Danish women were selected, aged 20-45 years; they were not pregnant and did not use oral contraceptives.
Results: No correlations were found between socioeconomic or anthropometric data and menstrual problems. On the contrary certain dietary habits, e.g. low intake of animal and fish products, and intakes of specific nutrients, were correlated with menstrual pain. The average dietary n-3/n-6 ratio of women with menstrual pain was 0.24. It was significantly higher among those with low intake of B12 coincident with low intake of n-3 (0.42, P < 0.001) (chi-square), with low n-3 intake coincident with low n-3/n-6 ratio (0.42, P < 0.005), and finally with low intake of B12 coincident with low n-3/n-6 ratio (0.47, P < 0.001).
Conclusion: The results were highly significant and mutually consistent and supported the hypothesis that a higher intake of marine n-3 fatty acids correlates with milder menstrual symptoms.