Lifestyle factors & their effect on fertility are difficult to study as it’s challenging to disentangle correlation from causation. Keep this in mind while considering the data presented and be sure to consult the full course for exceptions, explanations, and more detail.
The data is clear: male and female smoking dramatically lowers the likelihood of successfully conceiving.
Data is conflicted around the impact of caffeine on ability to conceive, but most experts agree that 1-2 cups a day likely doesn’t lower the odds of success.
Data suggests that women can have 1-2 alcoholic drinks a day while trying to conceive naturally, however alcohol consumption in the immediate run-up to fertility treatment clearly has a negative effect. Once a person suspects they may be pregnant, all alcoholic consumption should cease.
Male alcoholic intake over 20 - 25 drinks a week appears to harm semen parameters and perhaps fertility.
High male and female BMI and being overweight are correlated with a lower ability to conceive, but delaying treatment in order to lose weight may further decrease the likelihood of success. One exception is for women with PCOS who do not regularly ovulate.
Vigorous exercise for many women is associated with lower ability to conceive, though this did not hold true for women with anovulatory PCOS who did see improvement with vigorous exercise. Men who are sedentary over time are 10 times more likely to suffer from erectile dysfunction. For most patients, an exercise plan with moderate levels of activity is best.
Diets high in fruits, vegetables, legumes, fish are correlated with improved outcomes.
Vitamin D levels can have a significant effect for women undergoing fertility treatment. B9 intake (also known as Folate or Folic Acid) is crucial for both natural conception & fertility treatment.
Soy intake & B9 intake are likely protective against harmful effects of BPA (often found in plastic products.