@jamedoc B12 and omega-3's are definitely the biggest offenders, even for non-vegans.
·Vitamin-D as supplementation as there are very few foods that contain them and most of the population suffers from deficiency (even in countries with good climates most of us need supplementation during winter).
·Check for iron defficiency on a blood test, it's especially prevalent in females for any diet, can be solved easily and anemia has some serious consequences.
Plant-based diets offer higher intakes of almost every micronutrient, and a healthier gut flora, so I wouldn't recommend anything else for health if you're following a healthy diet.
Now, given how we are on r/veganfitness, a couple of healthy sport supplements are:
Disclaimer: these are all regarded as ergogenic aids, which boost performance but do not cause serious side effects and are allowed even in professional sports.
·Creatin-monohydrate: the worst side effect is that it can cause episodes diarrhea if taken in excessive quantities, increases performance in strength training and HIIT protocols by boosting the reserves of phosphocreatine up to around a 20%. Dosage is 0,06g/kg daily.
·Nitrid oxide: mainly in the form of beet juice but there are pills nowadays, boosts aerobic performance for long-distance sports by the expansion of the cardiovascular vessels. Has no common side-effects. The only time I've used it, pills didn't even exist and the dosage was two glasses of juice 40 minutes before exercise.
·Caffeine: can boost overall performance by stimulating the sympathetic nervous system, it's effects diminish with repetition so it's typically used only on competition days. Dosage varies from 200 to 400mg 1h before exercise.