sometimes it's hard to distinguish 'because of capitalism' from 'because of industrialization' and 'because of humans', but fossil-fuel-emissions deaths under communist regimes seem to have been higher than under capitalism (because of worse pollution controls, which was in turn because of less accountable governments), which strongly suggests that they're not due to capitalism but due to industrialization

but we know that industrialization generally results in a dramatic increase in life expectancy at birth, not a decrease. not much of a comfort if you're dying of mesothelioma from the combination of smoking (also historically higher in the non-capitalist parts of the industrialized world) and working with asbestos in a factory, which is pretty directly caused by industrialization, but i think it's reasonable to weigh diffuse, probabilistic risks against each other. for example, dying of an infected wound that wasn't treated properly because of inadequate resources, versus dying of an asthma attack aggravated by industrial nitrogen oxide emissions

with respect to famines, my claim and source are extremely thoroughly documented, and it is obviously correct to blame famines on non-democratic governance. there may have been historical famines that were not caused by government oppression, but simply due to population reaching the carrying capacity of the existing arable land with the available farming practices. but that hasn't happened since the advent of capitalism, because agricultural productivity has grown more rapidly than population

consequently there has never been a famine in a country whose economy was organized along capitalist lines (from wikipedia: an economic system based on the private ownership of the means of production and their operation for profit, whose central characteristics include capital accumulation, competitive markets, price systems, private property, property rights recognition, voluntary exchange, and wage labor)

democratic non-capitalism is certainly possible — i live in a non-capitalist democratic country that is struggling to return to capitalism, and we have never had a famine, though during the dictatorships we came close — but in practice nobody has ever succeeded in 'repealing' capitalism democratically, which is to say, eliminating it through government fiat. here our historical loss of capitalism was accompanied by a historical loss of democracy

if we want to steelman the 'deaths from capitalism' claim, we could focus on access to healthcare, which is generally better under socialist governments than in capitalist systems (though the usa for some reason runs its healthcare under a weird socialism/capitalism hybrid that gives the worst of both worlds). historically, for example, communist cuba had better health than the much richer and more industrialized usa. but other countries with actually capitalist healthcare systems such as switzerland, germany, sweden, and japan always exceeded both, because they were richer than cuba (due to capitalism) and did healthcare worse than cuba but better than the usa (again, due to capitalism). and of course the non-communist alternatives to capitalism, such as corporatism and medieval-style guild production (sadly still dominant in many countries) fare even worse by these measures

still, capitalism does produce obvious shortfalls in healthcare access, and hypothetical alternatives to capitalism that haven't been tried yet could certainly do much better