The Food Safety Authority (FSA) has advised people over 65 to only drink tea between meals and not during meals as it interferes with the absorption of iron and zinc.
Dr Mary Flynn, a chief specialist in Public Health Nutrition with the FSA, said these nutrients are key for keeping us physically and cognitively at our best.
Speaking on RTÉ's News at One, she urged this age group to take plenty of fluids as this can impact how fibre works in the body.
She said women should consume at least 1.6 litres of water as drinks alone, while men should take about two litres of water every day.
Dr Flynn said people should not cut back on this water intake if they are on medication such as diuretics.
She also urged people over 65 not to try crash diets.