Not medical advice. I am not a doctor or dietitian. This is what I learned from reading the NHS page, written down in plain English. For advice about your own health, speak to a GP, pharmacist or registered dietitian.
Vitamin A turned out to be the one with the most warnings attached, which surprised me. Here is what the NHS page says, in my words.
What it does
The NHS lists three jobs. Vitamin A supports the immune system, helps vision in dim light, and keeps the skin and the lining of some parts of the body, such as the nose, healthy.
Where it comes from
There are two routes. The first is ready-made vitamin A (retinol) from animal foods, and the NHS names cheese, eggs, oily fish, fortified low-fat spreads, milk and yoghurt. Liver and liver products such as pâté are a particularly rich source. The second is beta-carotene, which the body turns into retinol. That comes from yellow, red and green leafy vegetables such as spinach, carrots, sweet potatoes and red peppers, and from yellow fruits such as mango, papaya and apricots.
How much adults need
For adults aged 19 to 64 the NHS gives 700 micrograms a day for men and 600 micrograms a day for women. It says most people can get enough from a varied diet, and the body stores what it does not use straight away, so it is not something you need to eat every day.
The part about having too much
This is where the NHS page gets careful. It mentions research suggesting that averaging more than 1.5 mg (1,500 micrograms) a day over many years may make bones more likely to fracture in later life. Liver is so rich in vitamin A that eating liver or liver pâté more than once a week may mean getting too much. Many multivitamins contain vitamin A, and fish liver oil is particularly high in it, so the 1.5 mg figure applies to food and supplements combined. The page also says pregnant women should avoid liver and liver products.
I am not going to turn that into a rule for anybody. If you take supplements or eat liver regularly, the NHS page and your pharmacist are the right places to check.
What I have not found out yet
The page I read shows a review date of August 2020, so I want to check whether the guidance has changed since. I also have not looked at what the other sources say about beta-carotene and diet, and I will cover that in a later post if I find something worth sharing.