February 2021




    Should Americans get half their calories from carbohydrates?  As the U.S. government revises its dietary guidelines, two opposing camps are fighting it out.

    A food fight over carbohydrates is shaping up for control of Americans’ plates.  Years after low-carb eating gained attention with the Atkins diet, the low-carb movement is trying to gain wider mainstream acceptance and a nod of government endorsement.  The latest battleground is the U.S. government’s dietary guidelines, which are being revised for the first time in 5 years.  Low-carb advocates believe the current guidelines, which recommend Americans get half their calories from carbohydrates, are partly to blame for America’s high rates of obesity and type 2 diabetes.  Lining up against them are supporters of plant-based diets, among others, who argue that low-carb diets often include too much saturated fat from meat and dairy products and neglect important sources of nutrients like vegetables, fruits and whole grains.  During heated public hearings over the past 18 months, low-carb advocates pushed to include a low-carb diet option in the new dietary guidelines, which the government was expected to finalize last December (they didn’t).  A federal advisory committee rejected that idea, saying evidence supporting that approach wasn’t conclusive.  Now low-carb advocates have regrouped and are pushing the government to include a disclaimer with the final guidelines saying they are “only for healthy Americans”, making them irrelevant for the majority of the country’s citizens who are overweight and have diabetes or pre-diabetes.  For many such people, low-carb advocates say it’s unhealthy to follow the current guidelines and better to follow a low-carb approach.   About half the country has either diabetes or prediabetes, 40% are obese and if you include overweight Americans the number reaches about 70%.  The people who are well, they really don’t need the government’s advice.  (No one needs the government’s advice about how to eat healthfully.)

    Seven percent of Americans report eating a low-carb diet this past year, up from 5% in 2018.  Advocates argue that the approach should be more widespread and were vocal enough at the hearings to get the committee to review their case.   They further state that reducing carbohydrates can help prevent or even reverse type 2 diabetes, help people lose weight, and reduce the risk of heart disease.  While all foods can raise blood sugar, carbohydrates are the most readily available source of glucose, or sugar in the blood.  The body produces insulin to regulate blood glucose levels.   While advocates cite research regarding blood sugar spikes and insulin levels, they fail to point out that the types of foods that cause this response are concentrated carbohydrates like sweets, cereals, desserts and soda, not vegetables, fruits and whole grains.  These concentrated carbohydrates lack fiber, and do in fact contribute to risk for diabetes, heart disease, elevated LDL and triglycerides and blood pressure.  But it’s impossible and rather simplistic to lump all carbohydrate foods in to one category.  Rather, the focus needs to be on eliminating foods that are highly processed and refined.  When foods are processed, their nutrient content is diminished, and their fiber content destroyed.  These are the true factors in the disease processes currently ailing Americans.  While advocates further argue that low-carb diets reduce appetite, this lack of interest in eating is caused by a metabolic process called ketosis, which can be dangerous and cause not only metabolic acidosis but also exacerbate kidney disease.   And very low-carbohydrate diets (no more that 25% of calories) are constipating, which is not only uncomfortable, it’s downright dangerous.

    While it’s true that low-carb diets are often higher in fat, it’s not the type of fat that is most healthy.  The goal is to focus on plant-based fats found in nuts, seeds, olives and avocados.   These types of fats, along with vegetables, fruits and whole grains and beans, slow the rate at which glucose from food enters the blood.  These foods are nutrient dense and contain fiber as well as the nutrients beneficial for weight reduction, managing blood glucose and cholesterol, and improving autoimmunity.   Americans already consume too few carbohydrates in their healthful form.  Again, the demonization of healthy carbohydrates is because of our inability (or unwillingness) to separate unhealthy foods from healthy ones.  It’s also important to note that it’s not clear whether benefits come from reducing carbohydrates or simply from reducing overall calories. 

    For now, focus on a wide variety of plant-based foods, lean protein and healthful plant-based fats.  This is your best bet for good nutrition.

    Sumathi Reddi with edits by Dr. Jan Evans