How Much Whole Grains Should You Eat on a Low-Carb Diet

grain foods
Jeffrey Coolidge/Stone/Getty Images

Eating grains on a low-carb diet may seem like cheating, but that's not the case if you adhere to the guidelines of your specific diet. How much grain-based food a person should eat depends heavily on the person in question. That's why asking different people usually nets different advice to the same question. Grain-based foods include cereals, rice, barley, quinoa, etc, and anything used in the baking process that's derived from grains such as wheat flour, corn meal, bread, crackers, cakes and the like.

When it Comes to Grains, to Each His/Her Own

People vary greatly in how much carbohydrate they can tolerate. People who are following a truly low-carb way of eating for their weight or health should minimize the starchy foods they eat from all sources, not just grains. This article is for people who wish to make smaller changes in their diets and want some guidance about ways to do this.

Check Your Food Diary for Your Grain Intake

The first step is simply to pay attention to the amount of grain-based food you are currently eating. Most people are eating more than the generally recommended amounts of starchy foods, mainly because serving sizes are often larger than recommended. For example, what used to be considered "a slice of bread" now looks small, as the loaf pans have grown larger over the years. Similarly, people rarely eat only the half-cup of rice or oatmeal that is considered one serving.

How Much Grain to Eat for All?

According to the 2015 Dietary Guidelines for Americans, a 35-year-old woman is recommended to eat six ounce-equivalents of grains per day, at least three of which should be whole grains.

How much is an “ounce equivalent" of a grain-based food? Here are some examples:

  • 1 regular-sized piece of bread (now sometimes labeled "small")
  • ½ cup rice or pasta (get out a measuring cup and look at how much this really is)
  • ½ cup cooked oatmeal
  • ½ of a biscuit
  • ¼ of a large bagel
  • ⅓ of a large muffin

This table shows more grain serving sizes plus ounce equivalents (click on the blue plus marks).

This means that the 35-year-old woman could eat a half-cup of oatmeal, a sandwich on regular-sized 100% whole grain bread, and a cup of pasta (or a slice of pizza) over the course of the day, and have a serving left over for a snack of a few crackers or some popcorn. If you are tending to eat more than this, cutting back to this point is a great start, and could yield good results. Also, remember that foods such as cakes, cookies, and other sweet foods made with flour count as grain servings, in addition to the added sugars, which also should be limited.

Eat Your Grains Whole as Much as Possible 

In this case, I mean grains that are truly "whole" - that is, not ground up into flour or processed into flakes. The more ground up and/or processed the grain, the more it acts like a refined grain or just plain sugar in the body. Read more about the blood sugar impact of starches.

Why Are We Eating so Much Grain-Based Food?

Part of the problem I think we are running into is that people have been taught that carbohydrates are good and fats are bad.

With the introduction of the U.S. Department of Agriculture Food Pyramid about 30 years ago, consumption of wheat began to rise. Since grain foods were at the base of that pyramid, they almost have been thought of as "free foods" by many people. Also, grains are often thought of as being synonymous with "healthy." ("Hungry between meals? Have a large bagel with a low-fat spread.") Now we are seeing that this approach has had negative consequences for many people since starches break down very quickly into sugars in our bodies.

Incidentally, it turns out that those "healthy grains" are not very nutrient-dense at all, as starch is mostly empty calories unless the product is fortified with extra vitamins.

The germ and bran (which are stripped away to make "white" or refined versions of the grain) are where the fiber and nutrients mostly can be found. However, grains are easily stored and transported, and people have come to rely on them as an inexpensive calorie source as well as an easy fast food.

What Should We Eat Instead?

The crucial question becomes, "what should we eat instead?" The answer is to include more non-starchy vegetables, some fruit, and foods higher in proteins and fats. In the example of the large bagel, which is four-grain servings, a good substitute would be a few whole-grain crackers with peanut butter, or some nuts, or vegetables with dip. More Examples: Low-Carb Snack List

After a one- to two-week adjustment period, evaluate how cutting back on high-carb foods has affected you. If decreasing sugars and starches have had a good effect (for example, on your blood pressure, blood sugar, or just how you feel), you may want to experiment further to find out what works best for you.


USDA. "Choose My Plate" Website, based on the 2015-2020 Dietary Guidelines for Americans.

USDA Economic Research Service. "Wheat's Role in the U.S. Diet Has Changed Over the Decades". 2009.

Continue Reading