Substances intentionally added to food to produce a desired effect

That is true. For example MSG are added to most Chinese food to make it tasty but actually MSG isn't good for your health because it is an additive that is made chemically. Also juice and many other substances like food coloring are added to food to make it either yummier or prettier but will affect us after years of accumulation. Your question isn't very clear so what are you trying to ask exactly?

Explanation:

to prevent people from getting the ebola virus, countries around the world paid to doctors develop a new vaccine. now that the vaccine has been made, doctors will need to experiment on a large number of people to find out if it works safely.

what is the greatest limitation that scientists are dealing with as they try to figure out how to experiment with the ebola vaccine?

meditation is a practice of sitting still and quiet for minutes or even hours. it has been practiced for thousands of years and is even a part of religious practices for some people. carefully controlled, repeated measurements of brain activity have shown that meditation does increase certain chemicals in the brain and even grows the part of the brain that people connect with their current surroundings and activities.

are claims about the effects of meditation most likely scientific or pseudoscientific?

not pseudoscientific, because people have made claims about it but scientific observations have not been made

i-i-i-i-i-i don't k-k-k-k-know.