Very interesting article. I agree that nutrition as a vegan is tricky- there can be limits to supplementation (although relatively cheap b vitamins and vegan omega-3 supplements are available online in my experience). I’d mildly disagree with you that gaining muscle as a vegan is ‘much harder’, pea-isolate protein powder and tofu (if you know where to get it) can be a nutritionally complete protein source, price competitive with even with chicken.

I do have a few issues with your list of (potentially) ethical aninal products:

1. Bivalves: I agree that these are likely to be unconscious. However, a lack of certainty could make this a problem given how many animals are necessary to make a meal, and given that the means of preparation often involve boiling said animals alive. Additionally these are small and expensive foods which probably couldn’t meet the nutritional needs of a large number of people cheaply.
2. Wild caught fish: The issue with this again is the number of animals involved. Some fish may have small brains, but you need a large number of individuals to make a meal. Given the extent of uncertainty around consciousness in the animal kingdom it feels morally risky to do so. I see the argument that these animals could die worse deaths from hunger or predation in nature, however I think there is a useful acts of commission/omission distinction in morality which holds up when talking about wild animal suffering. There is also uncertainty about whether animals lives in nature are net negative, if not then catching wild fish on an industrial scale is  pretty bad.
3. Cattle: I think your argument is stronger here (cows are large indeed!). I think particularly in relation to dairy. An omnivore could probably eat one cow a year in expectation, but may take 2-3 times as long to consume enough dairy to separate a calf and a cow. Personally I consume dairy for this reason, without going so far as to eat beef, but I realise the two industries are connected.

4. Eggs: I think it’s hard to know if an egg is ethically produced or not, given how poorly enforced and vague a lot of ‘free range’ standards are in reality. Also, without in-ovo sexing consumption of eggs necessarily involves a lot of killing male chicks which doesn’t sit right with me.

   Additionally, I’m not entirely convinced of the argument that vegans have worse mental health because of their nutrition. I think it’s as likely that vegans are more likely to be neurotic, self-critical, and politically liberal, all of which are highly correlated with anxiety and depression.

Far-future effects are the most important determinant of what we ought to do

Time, like distance, has no relevance for moral judgement. 

Completely agree with this analysis. For readers interested in a high impact career in the UK civil service I recommend checking out Impactful Government Careers. We offer 1:1 discussions and a weekly job mailing list of high impact roles in government.

I'd be doing less good with my life if I hadn't heard of effective altruism

my decisions to give 10% of my salary to effective causes, and my decision to work in AI were both strongly influenced by EA

Morality is Objective

Like this slider- objectivity is a spectrum. The most subjective thing possible is a pure taste satement 'I like ice-cream'. A pure objective statement is '1+1=2'. 

In the world of inter-subjectivity there are statements like 'Democracy is superiour to dictatorship'. This has elements of both objectivity and subjectivity. 

I think morality is an intersubjective agreement (hence the influence of culture) but supported by biological roots (we possess a biological distaste for suffering and injustice, and a biological capacity for abstract reasoning). These intersubjective agreements combined with objective biological dispositions result in something which is not as objective as mathematics or natural sciences, but possesses a degree of objectivity.

I buy into MacAskill's argument that the 20th-21st centuries appear to be an era of heightened existential risk, and that if we can survive the development of nuclear, AI and engineered biology technologies there will be more time in the future to increase the value where we survive.