Regular stick margarine and stick butter contain the same number of calories: about 36 per teaspoon.

Butter, as an animal fat, contains both saturated fats and cholesterol. Butter’s biggest trouble is its saturated fat content. Saturated fats raise LDL (“bad”) blood cholesterol and total blood cholesterol. While butter does contain cholesterol, the cholesterol found in food has little effect on blood cholesterol in most people.

The controversy with margarine is with the trans fat it contains. Trans fats are formed when hydrogen is added to vegetable oils, making the oil more solid and less likely to spoil. This process is called partial hydrogenation and allows stick margarine to be firm at room temperature. Trans fats have been shown to increase “bad” and lower “good” blood cholesterol levels. The more solid a margarine is at room temperature, the more trans fat it contains. For example, stick margarine contains the most trans fat, approximately 3 grams in one tablespoon. Switch to tub or liquid margarine and you’ve cut that by almost 2/3. Margarine manufacturers are now cutting their trans fat levels even further; to less than 0.5 grams per serving! It’s best to keep the total trans fat as close to zero as possible and saturated fat under 2 grams per serving.

The trans-fat free tub or liquid kind of margarine spreads are recommended over butter. Aim for the growing number of tub or liquid trans-fat free margarines available on the market and know that you are eating in a more heart-healthy manner.

Additional Resources:
http://www.mayoclinic.com/health/butter-vs-margarine/AN00835
http://my.clevelandclinic.org/heart/prevention/askdietician/margarine.aspx
http://www.nlm.nih.gov/medlineplus/ency/article/002114.htm