  Large Language Models (LLMs), with their flexible generation abilities, can
be powerful data sources in domains with few or no available corpora. However,
problems like hallucinations and biases limit such applications. In this case
study, we pick nutrition counselling, a domain lacking any public resource, and
show that high-quality datasets can be gathered by combining LLMs,
crowd-workers and nutrition experts. We first crowd-source and cluster a novel
dataset of diet-related issues, then work with experts to prompt ChatGPT into
producing related supportive text. Finally, we let the experts evaluate the
safety of the generated text. We release HAI-coaching, the first
expert-annotated nutrition counselling dataset containing ~2.4K dietary
struggles from crowd workers, and ~97K related supportive texts generated by
ChatGPT. Extensive analysis shows that ChatGPT while producing highly fluent
and human-like text, also manifests harmful behaviours, especially in sensitive
topics like mental health, making it unsuitable for unsupervised use.
