As a general rule, never add sweetened products to a smoothie, as this can increase the calorie count and sugar content without adding nutritional value. Other ingredients, such as nut butter or protein powder, may need to be limited, either because they are high in fat or increase the risk of gastrointestinal side effects like bloating or diarrhea.

1. Processed Fruit Juice

Most fruit juices are naturally high in sugar. Those that are heavily processed have even higher sugar concentrations and are largely stripped of their fiber and nutritional value during pasteurization and filtration.

The worst are those to which sugar has been added, such as commercial fruit punches and cranberry cocktail drinks. Even 1/2 cup of Minute Maid Berry Punch can add 12 grams of sugar to an otherwise “healthy” smoothie.

If you like fruit-flavored smoothies, try replacing processed juices with a combination of fresh fruit and fluid bases like water, coconut water, or low-fat milk.

2. Flavored or Sweetened Yogurt

Yogurts are the cornerstone of many smoothies, but there are healthy and less-healthy options. Among the least healthy are sweetened or flavored yogurts—particularly those with stir-in fruit at the bottom.

By way of example, a standard 6-ounce container of Yoplait Original Low-Fat Strawberry Yogurt delivers 13 grams of added sugar (or between 36% and 52% of your daily recommended intake).

To avoid unwanted calories and sugar, choose unsweetened, low- or non-fat yogurt over triple-cream yogurt, high-fat Greek yogurt, and whole-milk traditional yogurt.

3. Syrups

A tablespoon of syrup—whether chocolate, caramel, fruit, or maple—can add a punch of flavor to any smoothie, along with more calories and sugar than you might expect:

• 1 tablespoon of Hershey’s chocolate syrup contributes 45 calories and 10 grams of sugar,
• 1 tablespoon of Torani strawberry syrup delivers 40 calories and 8 grams of sugar.
• 1 tablespoon of honey, while not officially a syrup, clocks in at around 64 calories and 17 grams of sugar.

As an alternative, try unsweetened cocoa powder (instead of chocolate syrup), fresh fruit (instead of fruit syrup), natural sweeteners like applesauce or dates, or spices and extracts like cinnamon or vanilla.

4. Highly Processed Protein Powder

Protein powders are a convenient way to boost the protein content of smoothies, adding as much as 20 to 30 grams per scoop. However, you need to check the ingredient label, as many commercial brands are high in sugar and other additives.

While some protein powders contain only a little added sugar, others deliver as much as 23 grams per scoop and can turn a glass of milk into a 1,200-calorie beverage.

They can also contain artificial sweeteners, lactose, and thickeners like guar gum, which can cause side effects such as gas, bloating, and diarrhea.

If you want to increase your protein intake, consider using whole-food-based protein powders derived from whole foods like peas, brown rice, beef, chicken, or eggs.

5. Ice Cream

Nothing adds more creaminess to a smoothie than ice cream. At the same time, few ingredients add more calories or fat:

• 1/2 cup plain vanilla ice cream delivers around 137 calories, 14 grams of sugar, and 4.5 grams of saturated fat.
• 1/2 cup full-fat frozen yogurt does little better, contributing less saturated fat (2.3 grams) but adding 110 calories and over 17 grams of sugar to the mix.

Instead of ice cream, try blending in a frozen banana or a combination of low-fat yogurt and a couple of ice cubes to achieve similar richness and creaminess.

6. Nut Butters

A tablespoon of nut butter (including peanut, cashew, and almond) can add between 3 and 4 grams of protein to a smoothie, as well as a very appealing nutty taste. On the downside, they deliver around 95 calories per tablespoon.

Those made with honey, like Jif Honey Creamy Natural, may contain as much as 6 grams of sugar per serving.

Worse yet are nut spreads like Nutella, made with hazelnuts, cocoa, and skimmed milk powder, which contribute 100 calories and 11 grams of sugar per tablespoon.

If you can tolerate the extra calories, opt for natural nut butters with no added sugar or salt. If it’s butteriness you’re seeking, try blending some avocado or silken tofu into your smoothie.

7. Alcohol

People will sometimes add alcohol, such as amaretto, rum, or Tia Maria, to a smoothie to enhance flavor or turn it into an adult beverage.

Beyond adding calories and sugar—Kahlua, for instance, adds 100 calories and 15 grams of sugar per shot—alcohol can increase hunger and cravings, contributing to overeating and weight gain.

If you like the taste of rum or bourbon, try substituting rum and bourbon extracts used for baking. There are also non-alcoholic liquors you can try, including coffee “liqueurs” similar to Tia Maria or Kahlua.