There's an article by Chris Kesser that has resurfaced and is doing the rounds.
It was first written in 2014. In it, Chris Kesser tells us why you should think twice about Vegan and Vegetarian diets. It lit up a few of the vegan forums recently, sending people into a frenzy. You can check out the orginal article in the link below.
I hadn't read the article before, so I did my due dilligence and waded through his carefully crafted rather redundant piece.
Yep. I said it - redundant. Now before I explain why, I'll recap briefly Chris Kessers main points in his article
The whole article was basically hinged on the fact that if you are vegan or vegetarian you are going to struggle to get some essential nutrients due to
He then goes on to list potential deficiencies, I'll give you a a quick run down, you can read his article for the "Why"
The crux of his argument is that you would have to eat a lot of vegetables or take supplements to get sufficient intake.
That's his argument.
I mean like seriously? You would have thought that after around 700 words or more he would have had a meatier argument than that (I know, I know).
I'm not sure if you are aware of this but in the UK there was a was a campaign called "5 A day" which was based on the World Health Organisation's recommendations, that eating 5 80g portions of vegetables and fruit per day was associated with a lower risk of health problems such as heart disease, stroke, obesity and type 2 diabetes.
The guidelines for health are 5 portions of vegtables and fruit a day minimum. Not an upper limit but a minimum. In Australia the guidelines are actually 2 PLUS 5 a day (two helpings of fruit, 5 of vegetables).
While research is inconclusive, it has also been suggested that 10 a day rather than 5 is optimal. You can check out the meta-analysis by The University College London [here] 
So you know, getting more more vegetables and fruit in your diet may not be such a bad thing for your health.
Now don't get me wrong, everything Chris said about nutrient deficiences and the potential side effects I agree with. He was spot on. Plus some nutrients you will struggle to get from a vegan diet alone [the vegan society make this pretty clear] It's his actual reasoning was a bit redundant. Let me explain,
If you took a good multi-vitamin/ mineral and Algae oil (for EPA/ DHA) you'd be pretty much covered. Now how hard was that? So how many supplements in total?...
Count them people.....
And let's not pretend that Vitamin D deficiency is exclusive to vegans or vegetarians because that is not proven in the science literature.
Vitamin D is a fat soluble nutrient and is critical for human survival. While most people are not deficient in vitamin D, often vitamin D levels are not optimal either.
So what's it good for? Benefits include greater immune health, improved cognition, improved testosterone levels. Vit D can also help reduce the risk of cancer, heart disease, diabetes and MS.
Now while the body produces Vitamin D from cholesterol provding there is adequate amount of UV light from sun exposure, often the amount and level of sun exposure can be inadequate in less sunny climates and especially in winter months.
Here's a fun fact for you:
The correct UV levels of an index of 3 or higher only occur year round near the equator, between the 37th parallels.
Vitamin D supplementation is encouraged if optimal levels are not present. [2}
How many supplements we up to now?
That's 3 supplements (if your multi doesn't have adequate Vitamin D3 in it)
Whether it be to a condition like Crohn's, Ulcerative Collitis or IBS, nutrient absorbtion can be problematic for many whether you are vegan, vegetarian, eat meat or somewhere in between.
There are many protocols that can aid you in absorbing adequate macronutrients and micronutrients. If this is something you struggle with, see a specialist.
Plus medical condition not withstanding, you'd be hard pressed to prove that vegans and vegetarians as a group, absorb less nutrients from their food than ominvores due to their dietary intake alone (rather than genetic, epigenetic or other factors)
Oh what about the protein?
To be fair Chris didn't cover this in his article. Now before the Omnivores start hitting up the comments section talking about essential amino acids, bio-availability and the like.
Let me just ask you this, if a diet rich in animal protein is sufficient, what's with all the whey protein supplements bruh?
That post workout recovery super shake? Them BCAA's (Branch Chain Amino Acids) and EAA's (Essential Amino Acids) that you're guzzling down?
So let me get this straight, it's ok for Omni's to stack up on supplements, but as soon as a vegan or vegetarian begins to supplement it's used as proof that clearly Vegans, plant based or vegetarian diets don't work?
Let's just keep it real. The 9 essential amino acids can be obtained with plant based nutrition provided you rotate your sources of protein, and get it in adequate amounts [1 - 2g per kg of bodyweight]. 
Plus if you supplement with a plant based protein powder that has a complete amino acid profile (just like Ominvores supplement with protein powders) you'll have it covered.
So contrary to what Chris Kesser would have you believe, it can be done. You can be healthy with plant based nutrition just as you can as an omni. It all boils down to this, it requires is a little education and preparation.
Chances are, if you are not prepared to do that, you probably don't value your health that much in the first place.