The European food safety authority (EFSA) was unable to derive a safe maximum daily intake due to a lack of human studies with very high doses of vitamin B1.
There are no reports of adverse effects from excessive intake of vitamin B1 from food or supplements.
In studies, no side effects occurred with a daily intake of 30 mg of vitamin B1 over several years. This amount, at which no negative effects were found, is about 30 times higher than the EU’s recommended daily intake (Nutrient Reference Value, NRV). The intake of 500 mg of thiamine per day, taken over one month, also showed no negative effects.
The data from the NVS II (National Nutrition Survey II, 2008) on the daily intake of vitamin B1 from all sources (conventional diet and supplements) indicate that an amount of 30 mg is far from being reached.
Adverse effects of excessive vitamin B1 intake have been observed after prolonged ingestion of more than 3 g (= 3,000 mg) in isolated cases of cephalgia (headache), sweating, pruritus, tachycardia, drowsiness, and urticaria.
