Amy Campbell, CDE, is a registered dietitian and the author of several books about diabetes, including 16 Myths of a Diabetic Diet and Staying Healthy with Diabetes: Nutrition and Meal Planning.

Balancing out your blood sugars is a never-ending task when you live with diabetes. Sure, you’ve heard or been taught that eating a certain amount of carbs, taking the “right” dose of medication, and carefully planning your physical activity should help you keep your blood sugars within your target range. But the reality is that it’s just not that simple. A multitude of factors can affect your blood sugar—food, medication, illness, stress, and even the weather! How do you make sense of it all? In this article, let’s start with one of the more challenging factors: food.

Carbohydrate

No surprise here. Carbohydrate, or carbs, are a major driving force when it comes to blood sugars. Specifically, some carb foods will raise your blood sugar very quickly after you eat them. However, that doesn’t mean that carbs are bad or that you need to ban them from your eating plan. What it does mean, though, is that you might be more thoughtful in the amount and types of carbs that you consume on a day-to-day basis.

Actions: As much as possible, forgo carb foods that have a high glycemic impact (carbs that tend to sky-rocket blood sugars). These foods include:

  • Bagels
  • English muffins
  • White bread
  • Refined cereals
  • Instant oatmeal
  • White rice
  • Instant mashed potatoes
  • Sweetened, sugary drinks, including some sports drinks

Instead, go with lower-glycemic-impact carbs. These foods will provide you with energy and important nutrients (including fiber) without significantly raising your blood sugars:

  • Steel-cut oats
  • Whole-grain breads
  • High-fiber cereals, such as All Bran
  • Barley
  • Brown rice
  • Dried beans and lentils
  • Apples
  • Peaches
  • Oranges
  • Berries
  • Broccoli
  • Green peas
  • Leafy greens, such as spinach

Low-glycemic carbs will provide you with energy and important nutrients without significantly raising your blood sugars.

Fat

Fat isn’t bad to eat, either. The jury is still out on saturated fat, but there’s plenty of evidence supporting the benefits of unsaturated fats, including vegetable oils, nuts, avocados, and olives. Not all that long ago, the belief was that fat had little effect on blood sugar levels. And while that’s still somewhat true—small amounts of fat don’t seem to affect them—researchers and people who have diabetes have realized that moderate to high intakes of fat can, like carbs, raise blood sugars. The difference, though, is that the effect usually isn’t seen until hours later. Example: You eat a fatty meal, such as a double cheeseburger and fries. A couple of hours later, you test your blood sugar or check your continuous glucose monitor (CGM) and your glucose levels seem right on point. But then the slow creep begins over a number of hours. You might even wake up the next morning with a higher-than-usual reading. What gives?

High-fat meals raise blood levels of free fatty acids which can cause insulin resistance. Free fatty acids may reduce the amount of insulin released from the pancreas. Insulin resistance means that you may need to inject or bolus more insulin. Apart from insulin resistance, fat takes longer to digest than carbohydrate—at least four to six hours, if not longer. And it can slow down the digestion of carbohydrate as well. If you take a fast-acting insulin (Humalog, Novolog, Apidra), you may not have enough coverage when the fat and some of the carb finally impact blood glucose.

Actions: First and foremost, limit the number of fatty meals that you eat. They’re not good for your waistline or your diabetes control. If you take mealtime insulin, talk with your healthcare provider or diabetes educator about splitting that mealtime insulin dose when you eat a fatty meal. Pump users can use an extended bolus or even a temporary basal rate to more effectively cover high-fat meals. If you take oral medication, make a point to do some physical activity after eating a greasy meal (actually, good advice for everyone).

Coffee

Judging from the lines at Starbucks and Dunkin’ Donuts every morning, coffee is not going away anytime soon. Coffee contains caffeine, the world’s most commonly used drug, which stimulates the nervous system and keeps us mentally alert. No wonder many of us can’t start our day without it. Interestingly, caffeine is somewhat of a dual-edged sword when it comes to diabetes. On one hand, studies show that drinking coffee may lower the risk of developing type 2 diabetes. On the other hand, research has linked coffee intake with an increase in insulin resistance and higher blood sugar levels.

Actions: The effect of coffee on blood sugars can vary from person to person. Some people notice an effect; others, nothing. If you’re lucky enough to wear a CGM, you might pay attention to how your morning coffee (or, perhaps, your tea or diet cola) affect your glucose. If you notice a substantial spike in your blood sugar (ruling out other factors), you then have some options:

  • Limit your caffeine intake. For example, keep your coffee consumption to no more than, say, three cups each day. And rather than guzzle diet cola, switch to caffeine-free beverages, such as seltzer water.
  • Switch to decaf versions of coffee, tea, and soda. Skip the caffeine-infused energy drinks, too.
  • Go for a walk after drinking anything with caffeine. Being more active may help blunt the rise in blood sugar.

Which foods have the greatest or smallest effects on your blood sugar? Tell us by adding a comment below.