One of the themes of public choice economics is the problem of information. One of the most important insights about communist or command economies is that they will fail to discover and use the information needed to use society's resources effectively to deliver a good standard of living for everyone. Or, in ordinary language, government bureaucracies do not know what is going in in people's lives and they will fail to make smart decisions.
Even fulfilling the must basic and fundamental functions of a state, protecting people from force and fraud, requires a great deal of difficult and expensive information collection. If a cop is called because of a fight that leaves someone injured, finding out who is at fault can require an entire courtroom trial to collect the relevant information.
Our instincts do not understand this information problem. The modern world is a far more complex place than the ancestral human environment. In a small band of foragers, everybody knew most of the relevant information about everyone else. In that environment, it was relatively easy to operate a communal economy and enforce moral rules. But in today's world, enforcing a seemingly simple moral rule like 'stop people from selling food that hurts people' requires a lot of work to collect the information needed to make good decisions.
Every day, people introduce dozens of new food products to the market, make changes to hundreds more, and make thousands of changes to farming practices or production processes that might affect the health or safety of food. Asking the government to monitor or approve of all of these changes is like asking the government to have a police officer follow every child around as a bodyguard. It would be impossibly expensive and generate far more problems than it would solve.
Some of the things that people do to the food they sell will kill people. This is a fact of life, just like the fact that children will die because of crime or accidents. We can and should work to prevent bad things from happening and, if necessary, punish the people responsible, but we will never be able to guarantee perfect safety. We should not treat all farmers or food processors as if they were criminals.
This means that you have to work to keep your food safe and healthy the same way you work to keep your children safe and healthy. It is impossible for you to inspect farms and warehouses and processing facilities for safety, but you can inspect the ingredient lists and nutrition information and learn to avoid things that might harm you.
Skepticism and vigilance is especially important when it comes to dietary supplements. Things like energy shots, herbal mixtures, and vitamin pills are regulated like food, not drugs, which means that they have never been subject to any kind of scientific test for effectiveness or even safety. The laws here are incredibly complicated, to match the complexity of the situation, but a rough approximation is that the government can only take action against a dietary supplement if it has claims that are provably false, includes ingredients that are known to be unsafe, or is known to be harmful.
There is an additional rule, which says that supplements can only use substances found in nature, but this does nothing to protect you. Nature is full of toxic chemicals. Plants and insects are in a constant state of chemical warfare. Humans have an amazing ability to digest and tolerate the toxic chemicals that plants produce, and by lucky chance some of these chemicals help us in certain circumstances, but you should never assume that natural means safe or healthy.
It seems like it should be easy to use the 'known to be harmful' rule to remove unsafe things from the market, but the information problem makes it much more difficult. It may seem obvious that you should remove an energy shot from the market if healthy people who drink it start dying from heart attacks. But it is a fact of life that healthy people who take no chemicals have a small chance of dying randomly from heart attacks when they exercise. This means that a few deaths is not enough proof for the courts to shut down someone's business, just like circumstantial evidence is usually not enough to lock someone in jail. There has to be good medical documentation and/or enough dead people to become statistically significant.
As a consumer, you should assume that all dietary supplements are guilty until proven innocent, just like all strangers giving candy to your children are guilty until proven innocent. The laws prevent the cops and FDA from making that assumption, but you should be less tolerant.