Inclusion Criteria:

• Have a diagnosis of any type of NHL and =< 5 years from the last treatment
• In remission (complete remission [CR], partial remission [PR], or stable disease based on clinical, not necessarily radiologic, assessment) and currently being observed and with no current cytotoxic chemotherapy planned; patients may be on rituximab maintenance
• No international travel planned during the next 4 months
• Able to eat a full range of solid food and liquids and tolerate seeds/nuts
• Maintain a consistent general diet without significant variation
• Able to deliver four fresh (within 24 hours) stool samples to Mayo Clinic Rochester over a four month period
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0, 1, or 2
• Provide informed written consent
• Able to recollect dietary intake for the prior 24 hours in order to complete a one-day food record with assistance from a dietician at each study visit
• Willing to complete the food frequency questionnaire (FFQ) at baseline and at 16 week visits with assistance from a dietician
• Willing to be seen at baseline, 6 weeks, 12 weeks, and 16 weeks for the study time points
• Willing to provide blood and stool samples at baseline and study time points for correlative research purposes

Exclusion Criteria:

• Cannot eat normal table food by mouth; NOTE: patients with any form of feeding tube or a swallowing disorder are not eligible
• Have taken fish oil, another dedicated n-3 supplement, or SH seed from another source within the last 28 days; patients on multivitamins that contain n-3 are eligible
• Co-morbid systemic illnesses such as active infection or other severe concurrent disease which, in the judgment of the investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and toxicity of the prescribed regimens; NOTE: patients with significant gut malabsorptive conditions (such as inflammatory bowel disease or others at the discretion of the investigator) will be excluded
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, uncontrolled cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements
• Receiving any other investigational agent that would be considered as a treatment for the lymphoma; NOTE: rituximab maintenance and patients participating on Mayo Clinic vitamin D study are allowed
• Active other malignancy requiring treatment that would interfere with the assessments of this study
• Major surgery other than diagnostic surgery =< 4 weeks prior to registration
• On prophylactic antibiotics, such as trimethoprim-sulfamethoxazole for pneumocystis prophylaxis or post-transplant penicillin prophylaxis
• Have taken antibiotics =< 7 days prior to registration