The toxic effects of … sugar

UCSF Lecture on Sugar & Obesity Goes Viral as Experts Confront Health Crisis

March 10, 2010 UCSF news release (University of California San Francisco)

Background

Metabolic syndrome (from National Library of Medicine) – a group of conditions that put you at risk for heart disease and diabetes. These conditions are

• High blood pressure
• High blood sugar levels
• High levels of triglycerides, a type of fat, in your blood
• Low levels of HDL, the good cholesterol, in your blood
• Too much fat around your waist

See also Metabolic Syndrome from the Nemours Foundation.

Connection between sugar and the metabolic syndrome

The news release includes a presentation by Dr. Robert H. Lustig, UCSF, on “Sugar: The Bitter Truth” (approx. 1h, 30min.)

Dr. Lustig explores the damage caused by sugary foods. He argues that fructose (too much) and fiber (not enough) appear to be cornerstones of the obesity epidemic through their effects on insulin. Series: UCSF Mini Medical School for the Public [7/2009].  (In case you don’t have an hour and a half to spare, I found a basic version of Lustig’s presentation on the NIEHS website.  Also includes a QuickTime version of the presentation Lustig gave at that workshop.)

I’m still convinced that environmental chemicals could be contributing to occurrence of metabolic syndrome, but Dr. Lustig’s presentation was eye-opening.  I don’t understand all the biochemistry, but he makes what I think is a convincing argument that fructose, whether from high fructose corn syrup (HFCS) or from refined sugar (sugar = fructose + glucose), is responsible for the development of metabolic syndrome.

The basic reason is not because we’re taking in too many calories, but that fructose is metabolized differently than glucose is.

Lustig goes through the history of sugar in drinks and food and the production of HFCS before diving into biochemistry.  He compares the metabolism of glucose, ethanol, and fructose, covering all the metabolic pathways for each.

All of the cells in the body can metabolize glucose, some ethanol is absorbed bv the gastrointestinal tract, then metabolized by the brain and liver.

Fructose is primarily metabolized by the liver.  I won’t go into the details here, but fructose increases the level of triglycerides, messes with the insulin and leptin processes, makes the pancreas work harder, and has other negative effects on your body.

Dr. Lustig makes a very convincing argument that overconsumption of fructose has causes metabolic syndrome and had led to the obesity epidemic.

Some people argue that it’s Americans’ eating habits and lack of exercise that have caused the obesity epidemic.  Lustig asks, if that’s true, how do you explain the epidemic of obese six-month-olds? (Lustig looks at the amount of sugar contained in many formulas.)

Lustig also notes that the role of exercise isn’t really to burn calories, but to keep our bodies’ metabolic processes running smoothly and discusses the important role of fiber in fructose metabolism.

From the NIEHS website (a basic version of Lustig’s presentation)

(presented at a workshop on “Children’s Environmental Health Research: Past, Present & Future,” Jan. 2007) – this workshop had sessions focusing on lead and neurotoxicity, asthma, metabolic disorders, and ADHD)

Summary

Fructose (sucrose or HFCS) consumption has increased in the past 30 years, coinciding with the obesity epidemic

• Fructose is everywhere
• Fructose is not glucose

• Hepatic fructose metabolism leads to all the manifestations of the Metabolic Syndrome:

• • • hypertension
    • de novo lipogenesis, dyslipidemia, and hepatic steatosis
    • inflammation
    • hepatic insulin resistance
    • obesity
    • CNS leptin resistance, promoting continuous consumption

• Fructose ingestion interferes with obesity intervention
• Fructose is a chronic toxin (it’s metabolized like ethanol)

Links (from UCSF)

UCSF Center for Obesity Assessment, Study & Treatment (COAST)

WATCH Clinic
UCSF Children’s Hospital

Adult Weight Management Program
UCSF Medical Center

New Center to Focus on Effects of Stress, Socioeconomic Status on Obesity
UCSF Today, August 11, 2009

Sugar is a Poison, Says UCSF Obesity Expert
Science Café, June 25, 2009

The Biology of Fat (or Why Literally Running Away from Stress Is a Good Idea)
Science Café, July 6, 2007

Note: A much briefer (and less rigorous) discussion of the harmful effects of HFCS can be found at High-Fructose Corn Syrup Truth, Still Not Sexy, HFCS.