At the outset of this lesson, I have to stress that I am not a doctor and that you are responsible for what you choose to do with this information. This information does not constitute medical advice.
I don't know you personally and we've never had a face-to-face consultation. I cannot comment on your specific case or provide you with personalised advice.
If, at any point, you have concerns about your health, you should consult your medical practitioner.
Nutrition Rule #8 tells us to use supplements only as supplements.
That's a very different message to the one promoted by the very expensive marketing of the supplement manufacturers, however. Vitamins are big business, selling billions of dollars worth every year. If you're to believe the hype, our food is deficient and we can't live without supplementing these magical substances. But it wasn't always like that.
Until about 1912, the only place you got vitamins and minerals from was your food (aside from drinking rusty water for anaemia, apparently). Then, a biochemist called Casimir Funk discovered the relationship between the lack of certain compounds in animals and certain diseases. He called these "vital amines" (now shortened to "vitamins"). A bunch of biochemists jumped on this and started isolating substances in food. The vitamin industry was born.
Of course, once vitamins became accepted, this opened the door for the sale of all kinds of supplements, including those that are of questionable safety, dubious efficacy or are simply illegal.
There are a few supplements that you might consider but few, if any are actually necessary.
Possible Supplements
Broad Spectrum Multivitamin
You probably don't need this if you're on a good diet but it can do no harm if you feel better taking one. Some people think of this as an insurance policy. The supermarket version will do, expensive versions are no more effective.
Vitamin D3
You're better off getting your vitamin D by spending time in the sun but this is not always possible. If you are going to take a supplement, make sure it is vitamin D3, not D2. You'll need vitamin K2 to absorb D3 but with a variety of animal foods in your diet, this should not be a problem. There is also some D3 in animal foods.
Fish Oil
DHA & EPA are required for brain function and a number of other body processes. Ideally, you'll get a good dose of this by eating oily fish every week but, if you're not keen on fish (I'd say you don't know what you're missing), 5g of fish oil per day will have you covered. This has to be fish oil. Despite the marketing, flaxseed oil does not contain DHA & EPA, but a precursor that is poorly converted in most, if not all, people.
Magnesium
This is the only supplement that is generally useful. I don't know why it's so hard to get enough magnesium from food - soil depletion? - but it seems to be so. Magnesium citrate or glycinate are the best forms and you know you need magnesium if you are prone to cramping. Also, magnesium before bed seems to help some people sleep better.
Protein Powder
I'd only suggest protein powder if you find yourself unable to get a meal. It breaks both principle #1 and rule # 6 but, because protein is so important, an occasional shake is OK. Look for whey protein isolate, it's the best absorbed & most bio-available. Casein will keep you feeling full for longer but it's not as digestible and some people don't tolerate it well at all.
NSAIDs
These are not a supplement but some athletes take them as if they are one. If you're taking painkillers to cope with your training, stop taking them, take a break from training and find someone to fix whatever is causing the pain. The risk of cardiac and renal issues from chronic use of NSAIDs are real, and the risk is not worth it.
Remember, supplements are just that, supplements. They are never a replacement for good quality daily nutrition.
Lots of people take supplements because they believe it's better than taking pharmaceutical drugs, which is great until you realise that the manufacturers of those supplements are the very same pharmaceutical companies. Yes, even those branded with the name of your favourite high-profile coach and sold as their special formulation, are almost certainly made by the companies whose medications you're trying to avoid.
Tasks for this lesson:
Have a look at any supplements you take regularly and ask yourself whether they're really necessary. Could you get them from real food?