Fructose

John – I was at your most recent CrossFit Football certification and during the nutrition talk you cautioned us about over-consumption of fruit and more specifically fructose. Can you go into more detail on why I should be weary of fructose ?

Interesting you should ask…I happen to re-working the nutrition portion of the CrossFit Football certification for this weekend in San Francisco…food selection and limiting of fructose is high on my list.

The off-season goal of every football player, and power athlete for that matter, is to get bigger, stronger and faster. We know that increased muscle diameter has direct correlation to getting stronger. In theory, a bigger muscle has the potential to be stronger

With this in mind, how do we create bigger, stronger athletes?

Before everyone blurts out the answer…how does lift heavy weights and eat a significant amount of food sound? Ding, ding, ding, we have a winner.

If you are an athlete trying to gain weight or doing a high volume of training, eating 4000 – 5000 calories is very doable. However, for most people to get consume this amount of food they will have to resort to crap carbs and refined sugars as a means to getting there. Eating a high volume of food is paramount of bigger muscles and the realization that consuming large amounts of sugar has negative and pronounced effects on the body. With high volumes of fructose leading that way to obesity, metabolic derangement, diabetes and cancer.

Eating a high calorie diet where the majority of calories come from sugars, processed foods and gluten is not advisable and, I am totally against it.

A diet of 4000-5000 calories has to be met with significant amounts of meat, fat, and both, green and starchy vegetables. A diet consisting of a minimum of one gram of protein per pound of body weight, fats coming from both saturated and mono-unsaturated and carbs from green veggies and starchy ones like sweet potatoes, yams and turnips. If you are an athlete trying to gain weight or doing a high volume of training, eating 4000 – 5000 calories is very doable. However, for most people to consume this amount of food, they will have to resort to crap carbs and refined sugars as a means to getting there. Eating a high volume of food is paramount for muscle growth and repair. However, consuming large amounts of sugar, especially fructose, has pronounced negative effects on the body. Chronic overconsumption of fructose has been shown to lead the way to obesity, metabolic derangement, diabetes and cancer. Eating a high calorie diet where the majority of calories come from sugars, processed foods and gluten is not advisable and, I am totally against it.

A diet of 4000-5000 calories has to be met with significant amounts of meat, fat, and both, green and starchy vegetables. A diet consisting of a minimum of one gram of protein per pound of body weight, fats in both saturated and mono-unsaturated forms and carbs from green veggies as well as starchy tubers like sweet potatoes, yams and turnips.

Since Chuck Norris received complaints about my usage of his valuable knowledge (you know who you are), I decided to replace it with a TTMJ-approved version of digestion. Last thing you want to do is upset Chuck Norris.

The first major movement occurs when something sweet enters the mouth. The saliva produced contains an enzyme (salivary amylase) that begins to digest the starch from food into smaller molecules. Amylase is an enzyme that breaks starch down into simpler sugars.

Swallowed food is pushed into the esophagus, which connects the throat above with the stomach below. The stomach has three tasks: to store the swallowed food and liquid. Second, mix up the food, liquid, and digestive juice produced by the stomach. Lastly, it empties its contents into the small intestine. Carbs spend the smallest amount of time in the stomach, followed by protein and lastly, fat.

The main hormones controlling digestion are gastrin, secretin, and cholecystokinin (CCK). Gastrin causes the stomach to produce an acid for dissolving and digesting some foods. Secretin causes the pancreas to send out a digestive juice that is rich in bicarbonate, this helps neutralize the acidic stomach. CCK causes the pancreas to produce the enzymes of pancreatic juice, and causes the gallbladder to empty.

Ghrelin is produced in the stomach and upper intestine in the absence of food in the digestive system and stimulates appetite. Free glucose will suppress ghrelin, while fructose has no effect on ghrelin. Peptide YY is produced in the digestive track in response to food and contributes to controlling appetite. The amount of PYY released depends on the macronutrient, protein will stimulate more than fat, and fat will stimulate more than carbs. PYY also regulates food intake, energy and improves leptin sensitivity.

Leptin release is spurred in the stomach in response to the food. Leptin travels to the CNS and signals the body that food has been consumed.

What about fructose?

Fructose can only be metabolized in the liver. The liver can process a decent amount of glucose but it gets full quickly. And while fructose can be used to replenish liver glycogen it does not suppress ghrelin and does not stimulate insulin or leptin secretion. Ghrelin is the hormone that regulates hunger.

So what happens when the liver gets bombarded with fructose and the liver has full glycogen stores?

Once the liver is full of glycogen, the body reacts and starts making fats (palmitic acid) from the fructose and sending them off into the bloodstream as triglycerides.

Excessive amounts of carbohydrates are converted to palmitic acid, a saturated fatty acid; this fatty acid is synthesized into triglycerides and sent into the blood stream. Once palmitic acid hits the blood stream it heads over to the CNS where is does its best to disrupt insulin and leptin signaling.

Everyone is familiar with insulin but what does Leptin do?

Lepin regulates energy intake (appetite) and expenditure. Leptin resistance prevents the brain from detecting its energy reserves or signals of satiety. This results in overeating and changes the body fat mass, which leads to weight gain.

Once liver insulin resistance sets in, the liver becomes a garbage dump releasing glucose into the bloodstream regardless of the levels. The resulting high levels of blood glucose, insulin and triglycerides will stimulate adipocytes (fat cells) to store fat and muscle cells to store glucose as glycogen.

Glucose and fructose become toxic to the cells in high concentrations.  Glucose toxicity contributes to the development of diabetes. Long-term effects of glucose toxicity leave individuals with decreased insulin sensitivity. And diabetes develops when insulin production is inadequate for a given level of insulin sensitivity.

How much fructose can the body handle before we start running in to problems?

From my understanding, we can safely process about 50 grams of fructose before things become problematic. That is a pretty low dose of fructose so use the chart below to gauge how much fructose you can consume. We know that problems with fructose are dose-dependent and time-dependent.

There is a table of fruits and sugars on The Paleo Diet listing quantities of sugars in fruits, sweeteners and candies. You can get an idea of which fruits/sugars/foods are highest in fructose, glucose and sucrose. From this you can start to understand where fructose is found in large amounts. Dried fruit is one of the highest on the list (one of the reason we discontinued the sale of beef jerky and dried fruit packs from Paleo Brands), high fructose corn syrup, mangos, apples, oranges, grapes and the amount of fructose in the juice version of these fruits is staggering.

Now let me preface this with… if you are a 145 lbs athlete who eats 1200 calories a day a day and your workouts consist of distance running, metcon and some weights,  the problems I have outlined are not as pronounced as an athlete consuming 5000 calories a day with processed carbs, sugars and downing PowerAde or Gatorade before, during and after practice.

By the way ditch the sports drinks; they are packed with high fructose corn syrup!

And thank  you Chuck Norris.

John