Are there nutrition related data available for individuals - either in the US or International ?

I am intereested in nutritional intake (calories, protein, carbohydrate etc.), dietary habits, and food choices across the ages.

I am not aware of a specific calorie intake variable available in any IPUMS project. However, for US data you may be able to find related variables in the NHIS data from IPUMS Health Surveys. For international data, you might want to check out the World Bank’s LSMS data.