gistfile1.txt

{% set topicsGrouped = craft.entries.section(portal.topicsHandle).limit(null).order('slug') | group('slug | first') %}
			
<div class="index">

	{% for letter, topics in topicsGrouped %}

		<div class="index__item">

			<div class="index__letter">{{ letter | upper }}</div>

			<div class="index__list">

				<ul>

		        		{% for topic in topics %}

		        			{#
		        				{% set group = craft.categories.group(portal.topicsHandle).relatedTo(topic).first() %}
		        			#}

		        			{% set group = topic.businessTopicGroup.first() %}

		            			<li>
		            				<a href="/{{ topic.uri }}">{{ topic.title }}</a>
		            				{% if group is not empty %}<span>{{ group }}</span>{% endif %}

		            			</li>

		        		{% endfor %}

		    		</ul>

			</div>

		</div>

	{% endfor %}

</div>

I would need more information about the entries but my first idea would be -> get one big query outside the for-loop and then only loop throug the results