I searched on pubmed for studies looking at the effects of flax seed oil on testosterone levels in men.
This study found here ( https://www.ncbi.nlm.nih.gov/pubmed/22394170
) reviews the literature and provides the results of a RCT that found no association between consumption of alpha-linolenic acid and changes in testosterone in men.
"The intake of the n)3 fatty acids alpha-linolenic acid (ALA), acid (EPA) anddocosahexaenoic acid (DHA) has been related to testosterone levels in epidemi-ological analyses. The aim of this study was to assess whether the n)3 fattyacids affects testosterone levels in post-myocardial infarction (MI) patients,who are at risk of testosterone deficiency. In a double-blind, placebo-controlledtrial of low-dose supplementation of n)3 fatty acids, we included 1850 malepost-MI patients aged 60â€“80 years who participated in the Alpha Omega Trial.Patients were randomly allocated to margarines that provided 400 mg â„ day ofEPAâ€“DHA (n = 453), 2 mg â„ day of ALA (n = 467), EPAâ€“DHA plus ALA(n = 458), or placebo (n = 472). Serum testosterone levels were assessed atbaseline and after 41 months using whole day blood samples obtained at thesubjectsâ€™ home or at the hospital. Subjects were on average age of 68.4 (SD5.3) years old and had baseline mean serum total testosterone of 14.8 (SD5.6) nmol â„ L. The four randomized groups did not differ for baseline character-istics. ALA, EPAâ€“DHA, and EPAâ€“DHA plus ALA supplementation did notaffect serum total testosterone compared to placebo. Moreover, n)3 fatty acidsupplementation did not affect the risk of incident testosterone deficiency(n = 76 with total testosterone <8.0 nmol â„ L). We conclude that n)3 fattyacids supplementation did not affect serum total testosterone in men who hadhad a MI."
It might be question of dosage as the study above demonstrates no effect on testosterone with 2 g of alpha-linolenic acid. On a personal note, I should mention that while I follow OMS in terms of sticking to a vegan diet, vitamin D supplementation, regular exercise, and meditation, my general approach to fish oil / flax seed oil is to not to go too far beyond what is recommended as healthy for the general population. However, I do so because I have been treated with alemtuzumab, so I don't really need to maximize whatever positive immune system modulation may be provided by omega-3 supplementation.