If you enjoyed something as a much younger person, and enjoy it as a much older person, it is very unlikely that it is the thing itself that you are enjoying. To test it, you can try giving that thing to someone your age and see if they enjoy it (they will most likely think it's a nuisance). To experience it yourself, you can try what kids are into these days or even better try something that people used to like long before you were born, in which case you will very likely see these things as pointless quite quickly. If you observe these things, it is easy to see that nostalgia is enjoyable because it is about associating your youth and naiveté with the object of nostalgia. If you grew up, you would see that it is just some distraction that merchants brought to you to profit from your stupidity. If you realize this, you'll enjoy not having to deal with that shit a lot more.
If you gain weight during summer (so that excess vitamin D is stored in fat cells) and use body's stored fat in the winter (eat at a deficit, so that your stored fat, rich in vitamin D, is used), you need no supplementation. This is what all animals living in the region do.
Here's my theory: When some people saw that physics could be used to get great power, they decided to keep physics research a secret, in the hands of the few. So, they have been using governments and spies to keep it away from the masses (and hence adversaries). I believe string theory is a result of this.
Wrong! Oil-rich countries have every incentive to not let it happen, and that is exactly what they have been doing. For example, “but the Uighers” is a propaganda tactic (among others) developed by the current oil countries as an attack to the Chinese solar industry.