I had once an iron deficiency, so I looked into how to improve my iron intake. Soaking legumes in water overnight reduces the amount of phytic acid and therefore increases the availability of minerals. This article gives a good overview: https://www.healthline.com/nutrition/how-to-reduce-antinutri...
Probably I could spend less and still have a relatively big impact on the climate. I would just buy a lot of methane and release it into the atmosphere. Assuming [1] is correct, I could get 4t of CH4 for less than 4000€. According to the IPCC AR5, 1t of CH4 is equivalent to 28t of CO2. So I could "easily" have a climate impact of 112t CO2e. This is more than 22 times the global average of CO2e emissions per capita.
My point is that one Euro can have a huge or a small impact on the climate. Nevertheless there are some studies that wealthy people produce more CO2e because of their higher consumption. Everyone should reduce their consumption to what's really necessary. For a real change though, we would need better laws, and people that lobby for them. You could help, too! [2]