In an attempt to lead a healthier life and get in daily greens a lot of people are turning to green smoothies as a replacement for breakfast. But just how beneficial are these drinks for you and do they have a down side?
Sugar content of your green smoothie
By blending greens with fruit the majority of the calories come from simple carbohydrates, if using fruits high in sugar like watermellon and banana you could be consuming up to 32 grams of sugar, depending on the amount of fruit you are adding. A can of coke has 33 grams of sugar, however you are not getting any of the fibre that you get with the smoothie and fibre slows down the release of sugar into the bloodstream and counteracts some of the side effects of high sugar to the body. For example a ‘healthy’ smoothie might contain:
- 1 cup of spinach
- 1/4 cup of water
- 1/4 cup of coconut water
- 3/4 cup of strawberries
- 1/2 cup of blueberries
- 1 banana
The smoothie above contains 218 calories (Calculated using www.myfitnesspal.com), with only 6% of the calories coming from spinach and 59% coming from sugar, that makes a total 32 grams of sugar. Now if this is your only intake of fruits and simple carbohydrates then this would not be a problem, however if you are trying to lose weight or if you have some metabolic problems such as being diabetic, you may want to use less sugar and more green in your green smoothie eg.
- 1 cup of spinach
- 1/4 cup of water
- handful of mint
- juice of one lemon
- 1tsbp ginger root
This smoothie contains 75 calories and less than 4 grams of sugar. A major benefit from green smoothies is the abundance of minerals such as calcium, magnesium, potassium and phosphorus and vitamins, and is also the only way to increase dietary fibre and vegatables for some people.
Liquid vs Solid
Some studies have shown that if you take the same amount of energy (in calories) 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 solid food1. This was the case regardless of the food group, ie whether a protein source, carbohydrate or fat, if a liquid the participant, whether lean or overweight, consumed more calories over the day.
Oxalic acid and Goitrogens
Leafy green vegetables contain phytochemicals that help the plant defend itself from predators. In large amounts they can be harmful to those with pre-existing health conditions, such as effecting the thyroid of people with thyroid disease or, in rare conditions (primary hyperoxaluria, enteric hyperoxaluria) where people should reduce the level of high oxalate foods. Using these greens in a smoothie poses little threat to the average person as the amount is minimal and the nutritional benefits outweigh them. Even so it is important that you rotate your greens often this gives you the variety of nutrients and reduces the toxic elements2.
For me I enjoy my green smoothie, I make sure it has some fat and protein included (often as almond milk ) and I find that my blood sugar is stable and I am satiated till lunchtime. I also like to have eggs and greens for breakfast and very rarely have an all carbohydrate meal for breakfast as this is often what sets me up to continually want to eat all day. As we have said everyone is different and you need to find what works for you whilst being mindful of the downsides.
1.Mourao, D.M., Bressan. J., Campbell, W.W., & Mattes RD. Effects of food form on appetite and energy intake in lean and obese young adults. International Journal of Obesity, 2007;31:1688-95.
2. Braun, L., & Cohen, M. (2011). Herbs & natural supplements an evidence based guide (3 ed.). Chatswood, NSW 2067, Australia: Churchill Livingstone Elsevier.