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Mediterranean vs. Keto Diet? Here’s The Scientific Lowdown on Carbohydrates

June 06, 2019

Mary Noon

Mary Noon

With high-carb, low-carb, no-carb, the diet landscape is confusing and everyone has a different take on how or if carbohydrate foods fit onto our daily plates.

The top-rated Mediterranean Diet promotes healthy carbs and the keto diet calls them toxic. Let’s look at carbohydrates through the lens of the science of nutrition.

Carbohydrate is a macronutrient supplying our body with energy or calories and serving as the preferred fuel for the brain. Carbohydrate foods (carbs) can be divided into three categories: starches, sugars and fiber.

Many foods are made up of these three components:


What starch foods do you think of? Potatoes, corn, rice, bread and pasta? These are starches from grains or starchy vegetables. Some starches are healthy and others are not.

It is better to eat whole grains (brown rice, quinoa, bulgur, whole wheat, millet, oatmeal and buckwheat) that are richer in nutrients than their highly processed, refined counterparts (white rice mixes, couscous, white pasta, white bread and sweetened rice cereal).

People eating whole grains as more than half of their daily starch servings (three to five) benefit from a lower risk of heart disease, obesity, diabetes and cancer. On Nutrition Facts labels, in the product’s ingredients list, look for the word “whole” like whole wheat flour in breads or whole oats in cereal. Remember, ingredients are arranged in descending order. Buckwheat, bulgur and quinoa are already whole grains.

Another rule of thumb: The fewer ingredients, the better. Just think how many steps it takes to get a product to you from its natural source. The product is more apt to be made from whole foods.

Starchy vegetables are a great option. Sweet potatoes, red potatoes, legumes, peas, corn and winter squashes are not processed. They’re  whole foods that supply us with valuable nutrients like vitamins, minerals, antioxidants and fiber. Instead of choosing white rice for dinner, try corn on the cob or a sweet potato for extra Vitamin A, fiber and potassium. Less- or non-starchy vegetables like broccoli, cauliflower, asparagus, green beans, peppers, onions, lettuce and tomatoes also contain carbohydrate but at a very low level.


Sugar might make us think of pies, cakes, cookies, soda and candy, all of which are carbohydrate foods we know are not nutritious.

The U.S. Dietary Guidelines for 2015-20 suggest only 10 percent of our calories should come from these carbohydrates, known as “added sugars.” This includes, but is not limited to: sugar, high fructose corn syrup, corn syrup, honey, fruit juice concentrate and evaporated cane juice. So, if you have a 2,000-calorie diet, no more than 200 calories or 50 grams of sugar should come from these types of foods.

The American Heart Association further recommends 150 daily calories for men and 100 for women from added sugars, which equals 38 grams (9 teaspoons) and 25 grams (6 teaspoons) of sugar, respectively. So when reading a Nutrition Facts label, look for “added sugar” for the serving size and see how it fits your daily limit. Some labels may still list sugar, which includes natural and added sugars. By January 2020, this will change on all food labels to sugar (natural) and added sugar.

In looking at a typical label on a 20-ounce soda, added sugar is 65 grams — is 130 percent and over the limit. Added sugar is high fructose corn syrup in this instance. Think about these swaps to reduce added sugar and increase the nutrient content of your diet.

  • Then: sweetened rice cereal. Now: whole-grain oat cereal with berries.
  • Then: sweetened ice tea. Now: brewed orange herbal tea with fresh mint.
  • Then: chocolate-covered ice cream bar. Now: frozen whole-fruit bar.
  • Then: candy bar. Now: fresh berries and a few dark chocolate squares.
  • Then: sweetened peanut butter and jelly on white bread. Now: almond butter with sliced bananas on whole wheat

Sugar also occurs naturally in fruits and milk, but as fruits and milk have a higher nutrient profile they are better carbohydrate choices. Vitamins like Vitamin D are found in milk products and all fruits are rich in antioxidants that ward off aging cells. Fruits, like all plants, have the added benefit of fiber which helps foster a healthy gut microbiome. These carbohydrates supply quick energy and get the green light for everyone.

Carbohydrate content from natural sugar found in fruit and milk will not be included in future Nutrition Facts labels under added sugar but as sugar. Take a look at the new food label here.


Fiber is a carbohydrate only found in plants, so whole grains, fruits and vegetables contain fiber. Fiber, which is not completely digestible by humans, is associated with good bowel health, beneficial gut bacteria and lower caloric intake because eating it makes you feel full faster than low-fiber foods. Fiber slows digestion, releasing nutrients slower and helping with blood glucose control.

Adults need 25 to 38 grams fiber daily, which is nearly impossible on a very low carbohydrate or keto diet. Fiber information is listed on Nutrition Facts labels here.

Next time you’re grocery shopping, try some of these foods swaps:

  • Fresh apples instead of applesauce.
  • Old-fashioned whole oats instead of instant oatmeal.
  • Fresh sweet potatoes versus canned (and eat the skin).
  • Whole wheat or quinoa pasta versus white.
  • Ready-to-pop popcorn kernals versus potato chips.

When it comes to carbohydrate, the question that invariably comes up is how much does one need to be healthy? There is no one answer because the carbohydrate content of one’s diet varies by age, activity level, gender and other factors. Most registered dietitians will say 100 to 120 grams minimum daily, which is a “low carb” for a healthy young woman.

Popular diets with 0 to 20 grams of carbohydrate are known as ketogenic or “keto” because the body uses fat for calories, which causes an accumulation of ketones in the body. You can see how healthy carbohydrate foods  — whole grains, fruits, milk and vegetables — would be severely underrepresented on such a restrictive, difficult-to-follow diet.

A registered dietitian can help devise a diet uniquely suited for you.

Want even more information and personalized advice? Make an appointment with a registered dietitian. Call us at Hartford Hospital (860.972.2604) and we can tell you how. For information on nutritional support at Hartford HealthCare, click here.

Looking for information on surgical weight loss? Visit WhatWillYouGain.org to find a FREE community education class near you!