Butter does have some health benefits and in moderation butter is healthy for you.
However eating too much butter can be bad for your heart and health in general and could raise your cholesterol levels.
Butter is rich in nutrients and beneficial compounds like butyrate and conjugated linoleic acid.
The high-fat dairy products like butter have been linked to a reduced risk of obesity, diabetes, and heart problems.
But also butter is high in calories and saturated fat and should be enjoyed in moderation.
Margarine is healthier than butter as Margarine is made from vegetable oils which means it contains unsaturated "good" fats — polyunsaturated and monounsaturated fats.
These types of fats in Margarine help reduce low-density lipoprotein (LDL), or "bad," cholesterol when substituted for saturated fat.
Margarine is healthier for your heart than butter is as well.
Butter will last in the fridge for up to 9 months before it goes bad although it's best to use the butter within 3 to 6 months of refrigerating it for best taste and texture.
Eating old butter will not make you sick as long as the old butter is actually not bad.
If the butter is just old and expired and has no bad smell to it or has no mold on it then the old butter is safe to eat and should not make you sick.
However if you have doubts it's best to throw the old butter out and avoid getting sick.
Butter that has gone bad will have a rancid smell or sour smell to it and the butter that has gone bad may also have mold on it and the butter may get hard and crumbly as well.
Expired butter is safe to eat unless the expired butter has actually gone bad.
The expiration date on butter does not mean it's actually bad or unsafe to eat and as long as the butter smells good, tastes good and has no mold, maggots etc in the butter then it's safe to eat.
Most butter lasts up to 6 to 9 months in the fridge before it goes bad.
You can freeze the butter to make it last longer and when frozen the butter will last for up to a year.
However when frozen the butter loses it's texture and the taste can change as well.
Some signs that butter has gone bad is a rancid smell or sour smell to the butter and the butter may also become hard and have mold growth on it as well.
If the butter smells rancid, sour or has mold on the butter then you should throw it out as it's no longer safe to eat.