Natural sugar?

Author: 

Micaela Karlsen, MSPH

Question: 

I have been eating a whole food plant based diet (no added oil, sugar or salt) since March, 2013, and I have never felt better!  In one month, my total cholesterol dropped 20 points and since I changed my diet, I've lost a little over twenty pounds.

However, my one nagging question is sugar.  There is a great deal of information out there about how much added, processed sugars one should be eating per day, but I've yet to find any information on how much natural sugar should be included in one's diet per day.  Any thoughts on this you might be able to provide would be most helpful.

I am curious if I am eating too much natural sugars - I am definitely eating more fruit than I did before I went plant based - and I'm finding that some of the sweeter vegetables can really add up on the sugar scale with the food tracker I'm using.  My weight loss stopped about a month ago despite low calories and low fat, so I'm curious if this might have some baring.

Answer: 

What great adherence you are practicing to the diet, and what great results you are getting with your cholesterol and weight!

The question of sugar can be complicated, because most people are familiar with the dangers of refined and processed carbohydrates. "Sugar" has become a bad word, and there is much justification for this, as the sugars that most people are eating in their usual diets are refined sugars, meaning the carbohydrates found in whole foods have been extracted, stripped from the fiber and other components present in intact food, sometimes broken down further into simple sugars, and concentrated. Concentrated, refined carbohydrates take the form of table sugar, brown sugar, concentrated fructose or dextrose, high-fructose corn syrup, agave syrup, maple syrup, and many others.

Let's clear up some of the terminology:

A simple sugar, or simple carbohydrate, is composed of 1-2 sugar molecules (monosaccharide or dissaccharide).

  • Fructose (found in fruit), lactose (found in milk), and sucrose (white sugar) are examples of simple sugars.
  • Simple sugars are found naturally in fruits, dairy, and some vegetables, and unnaturally in refined carbohydrate products, candy, or syrups.
  • Glucose is the most abundant monosaccharide and is what is referred to when blood sugar is measured.

A complex carbohydrate is a long-chain carbohydrate, composed of 3 or more sugar molecules (polysaccharide).

  • Cellulose, starch, and glycogen are examples of three polysaccharides prevalent in nature.
  • Cellulose is found in the walls of most plants, and much of the insoluble fiber in our diet is cellulose - humans do not possess the enzyme to digest it.
  • Starch is found in the seeds and roots plants, such as corn, rice, wheat, potatoes, squash, and quinoa - starch is water soluble, and humans do posses the necessary amylase enzymes to digest it.
  • Glycogen is the major form of polysacchrides that are stored in animals for energy, primarily in the liver and muscle.

While consumption of added sugar is associated with adiposity in humans, there is no body of evidence yet suggesting people need to limit fruit consumption.

As far as the quantity of sugar or carbohydrate someone is consuming, because we need no more than 10-15% fat and 10% protein, a diet composed of 75-80% carbohydrate is extremely healthy. The word "natural" is tricky - it can mean different things to different people, but if we are talking about sugar as it exists in whole food, then we need the majority of our calories to come from "natural sugar". "Natural sugar" is the primary source of energy for the body, and in fact the brain can only burn sugar as fuel (as opposed to other parts which can make use of fat or protein if carbohydrate is not available). Remember that syrup, even maple syrup and honey, are still concentrated sugars that are best thought of as "added sweeteners" and are best used sparingly.

All whole plant foods - vegetables, fruit, grains, and legumes (with the exception of nuts, seeds, and fatty fruit) are very high in "natural sugar", because the majority of calories comes both carbohydrate, both simple and complex.

Many people who switch to a whole food, plant-based diet eventually do find that they need to incorporate some kind of exercise program into their lifestyle to achieve their optimal weight, even if there is an initial and effortless weight loss following a dietary change without exercise.

It is still possible to overeat on a plant-based diet if:

  • you eat without being hungry
  • you eat until you feel stuffed instead of full
  • you eat oil or a lot of flour 
  • you drink fruit juice

Staying active (the USDA guidelines for physical fitness suggest adults should be spending 2.5-5 hrs per week in total aerobic activity, with 2 days per week of muscle building activity) and eating only whole foods (no juice, limit the flour, no oil, no added sweeteners) offer the best chance for achieving a healthy weight.

Given this information, if you suspect that you could benefit from changes, the best course of action is to conduct an experiment. Perhaps after reading this you hypothesize that if you change your dietary pattern a little bit and start doing vigorous walking 3x per week for 1 hr, you may start to reach your ideal weight again. Perhaps you will try this and see some result, and perhaps you may plateau again. At that point, you may want to consider what else you can try - adding the 2 days of recommended muscle building activity may required. (Though remember it is recommended for all adults anyway).