Breakfast smoothies seem to be the in thing. So many people are having smoothies that they can't be the wrong choice can they?

The traditional smoothie that the buzz has been created from isn’t that which you go down to your local boost juice, its your “green” smoothie that is designed to have endless benefits, with the main being weight loss.

Surely a smoothie with all the good stuff in it must be good for you?

Yes it is good for you. But, there is one small problem. Green smoothies taste terrible! So we add to them ingredients such as fruit to make it taste palatable. The energy density of the fruit far outweighs that of the energy density of the greens. Therefore these smoothies usually end up being quite high in sugar.

Lets take the following smootie recipe as an example:

• 1 cup spinach, fresh
• ¼ cup water
• ¼ cup orange juice
• ¾ cups strawberries
• ½ cup blueberries
• 1 banana

This recipe contains about 218 calories

In colour this is still a green smoothie. Unfortunately, only about 6% of the calories come from the greens (spinach). The remaining products in this smoothie are all fruit. The fruit listed above contains a total of 32 grams of sugar. 59% of the total calories in this smoothie come from sugar.

Now some may ask the question of why am I still hungry after my breakfast smoothie? Consider that by consuming your breakfast as a liquid you may be less satisfied, less full, and therefore feel the need to eat more calories during the day. Lets go back to the recipe we used for the smoothie and consider whether eating these ingredients whole would keep you more satisfied for a longer period of time. There is research to show that if you take exactly the same energy as a liquid instead of a solid, you will consume more calories later because the liquefied energy doesn’t satisfy your appetite as well as the solid food. (1)

Another point that you may wish to consider is that by having these foods as a liquid you may be altering your blood sugar levels rapidly, causing a rather significant spike followed closely by a rapid fall. Any food that you consume, that has been altered in to a more rapidly digestible product before consumption, will react with a significantly sharper and faster spike in blood sugar, along with a more rapid fall. (2)

Smoothies that are made with healthy ingredients like soy milk, fresh or frozen fruit, skim milk, or yogurt quite often feature plenty of high-fat and/or high-sugar items like ice cream, peanut butter, or chocolate. Instead of your healthy intentions, you end up with a drink that has in excess of 600 calories, enough saturated to take on a double cheeseburger, and enough carbohydrates to reach triple figures in grams.

Yet, for convenience, some may wish to still pursue the direction that they have chosen and have their delicious smoothie for breakfast or another snack.

If you are going to consider having a smoothie in place of a meal, look for a smoothie with at least 5 grams of protein and a similar amount of fiber. This will be more likely to sustain your appetite for more than a couple of hours.

Your best bet is usually to keep it simple, i.e. banana, strawberry, nonfat milk, and protein. Any smoothie that includes nonfat milk, soy milk, or yogurt will likely have a handy helping a of protein. This method will likely keep the carbohydrate content as low as possible.

If you are having the smoothie as a snack, you’re better off having half the quantity of that you may purchase at a retail store, and keep the calories below 300.

 

References

1. Mourao DM, Bressan J, Campbell WW, Mattes RD. Effects of food form on appetite and energy intake in lean and obese young adults. Int J Obes (Lond) 2007;31:1688-95.
2. Crapo PA, Henry RR. Postprandial metabolic responses to the influence of food form. Am J Clin Nutr 1988;48:560-4.