Are Carbohydrates an Essential Nutrient? An update to: "Can a Low Carb Diet Help?"
Several months ago I wrote an article titled, "Can a Low Carb Diet Help?". The feedback I received from the type 2 diabetes community inspired me to write a follow-up article.
Carbohydrates and type 2 diabetes
Low carbohydrate diets are a hot topic in the world of diabetes. Low carbohydrate diets have received praise for their potential to help with weight loss, insulin sensitivity, and improve blood glucose control.
The lower limit of dietary carbohydrate compatible with life appears to be ZERO (this is according to Chapter 6 of the book: Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids), provided that adequate amounts of fat and protein are consumed. This means, unlike certain fatty acids (fat) and amino acids (protein), carbohydrates are not an essential nutrient.
What is considered "low carb?"
There is no universal definition for what amount of carbohydrate equals "low carb." Some of the proposed definitions of “low carb” include:
- 50-150 grams/day
- <130 grams/day or less than 26% of total energy intake
- 20-25 % of total energy intake
The recommended dietary allowance (RDA) for carbohydrates was set at 130 grams/day (1 to > 70 years old; not pregnant or lactating) based on the knowledge that the brain requires approximately 110-140 grams of glucose each day.
- The body breaks down most carbohydrates (with the exception of fiber) into glucose, which the body cells use as an energy source.
- Glucose is an essential nutrient for the red bloods cells and is the preferred energy source for the brain, central nervous system, placenta and fetus.
What happens if you follow a low carbohydrate diet?
- When blood glucose level drops (as a result of a low carbohydrate diet) insulin secretion decreases (*unless you have type 1 diabetes or advanced type 2 diabetes and no longer make insulin).
- Low insulin levels result in muscle and liver shifting from using glucose as their primary energy source to using fatty acids as an energy source.
- When on a low carbohydrate diet, glucose can be made from amino acids (from the diet or gluconeogenesis) or from glycerol (derived from fat)
- Initially glucose comes from glycogenolysis. Glycogenolysis is the formation of glucose from stored glucose (glycogen)- in the liver.
- Once glycogen stores start to run low or are depleted gluconeogenesis occurs to maintain blood glucose levels and ensure the brain has a sufficient supply of glucose.
- Gluconeogenesis is the formation of glucose from non-carbohydrate sources, such as amino acids and glycerol.
- The brain learns to adapt to a low carbohydrate diet by partially using keto acids as a fuel source. Keto acids are derived from incomplete break down of fat.
- Using keto acids as a fuel source limits the amount of glucose required by the brain. This in turn reduces gluconeogenesis which is important for conserving muscle mass.
Important: Keto acids are not usually produced until a very low carb diet is followed or a person becomes severely insulin deficient (i.e. type 1 diabetes or advanced type 2 diabetes
Considerations when following a low carb diet
- Before starting a new diet speak with your health care provider. He/she may want to adjust your medication and possibly have you monitor your blood glucose levels more closely.
- Make sure you know where your carbs are coming from (breads/grains, dairy, fruit, starchy vegetables, snack foods, desserts).
- Document your typical carb intake for several days (include both week days and weekend days).
- Do some planning. Planning will help keep you on track and help you cope with difficult situations.
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