Food usually tastes bad when you have a cold because you're usually congested or have a stuffy nose when you have a cold.
The stuffy nose prevents you from smelling properly which is one cause of bad taste of food when you have a cold because your sense of taste is linked to your sense of smell.
The loss of taste buds can be caused by several different things such as medical conditions, medicines, aging and even illnesses such as respiratory illnesses.
Even burning your tongue could lead to loss of taste buds.
Someone with no sense of smell cannot usually taste foods.
However it depends on if you have fully lost your sense of smell or just partially lost your sense of smell.
Some people who have lost their sense of smell can still taste some foods at least partially but other people who have lost their sense of smell also lost their sense of taste as well.
Your ability to taste things is linked to your ability to smell.
So when you lose your sense of smell then you can also lose your ability to taste things as well.
Losing your sense of smell can indeed alter your ability to taste certain foods so some foods you eat may not taste as good as they once did when you had a good sense of smell.
Your sense of smell does affect your taste but losing your sense of smell doesn't always completely cause a loss taste.
Most people who lose their sense of smell are still able to tell between salty, sweet, sour, and bitter.
But you do need your sense of smell to taste things correctly but you can still usually taste things even without your sense of smell.