Carbohydrate Cravings, Serotonin and Satiety

Introduction by: Jessica Apple

Diabetes and depression often go hand-in-hand, and recently I spoke to my doctor about my own case of the blues.  “Your diet may have something to do with it,” he said.

“What?” I asked.  I had no idea what he was talking about.  I eat a very low-carb diet, which helps me keep my blood sugar levels in the normal range almost all of the time.  And there is nothing depressing about normal blood sugar levels.  “I don’t understand what you  mean,” I said to my doctor.

“The Atkins diet is associated with depression,” he said.  “Maybe you should eat more carbohydrate and cover it with insulin.”

I’m not on the Atkins diet, but I do limit my carbohydrate intake to 30-50 grams a day, depending on how much I exercise.  And since I can’t stand the idea of out-of-control blood sugar levels, I blew off my doctor’s suggestion about increasing my carbohydrate intake.  I was, however, curious about the link between a low-carb diet and depression and when I began to look into it, I came across the work of Judith Wurtman, co-author with Nina Marquis, M.D , of The Serotonin Power Diet.  Judith’s research has focused on the relationship between a person’s emotional state, carbohydrate craving and brain serotonin. With her husband, Richard, she demonstrated that overeating is often related to the need to decrease stress. They showed that when carbohydrate-rich foods are eaten, the resulting  production of brain serotonin improved emotional stability.

To find out more, I contacted Judith and asked her about her work.  And what, I asked specifically, can someone who has diabetes (and can’t consume a lot of carbohydrates) do?  Here is an essay she wrote for ASweetLife.

Carbohydrate Cravings, Serotonin and Satiety

By: Judith Wurtman

In the 1970s John Blundell and researchers at the University of Leeds discovered that satisfaction or satiety after eating comes not from filling or stuffing the stomach but from making a chemical in the brain called serotonin.[1] And when serotonin is not made, the eater feels a vague dissatisfaction with the meal just consumed. Fullness is present but not satiety.

Blundell’s research found that if lab animals were treated with a drug that increased serotonin activity, rats would stop eating sooner  than their untreated cage mates  even if there was still food in their food bowls.  The researchers dubbed serotonin the satiety chemical or neurotransmitter  and  confirmed its role in halting food intake. It can turn off eating as completely as drinking water turns off thirst. When serotonin is active, all interest in eating vanishes.

Serotonin is unlike other neurotransmitters in the brain because its synthesis depends on whether or not carbohydrates are eaten.  If you choose to eat or not eat a potato or rice, you will be affecting the fate of this chemical.  Avoid carbohydrates and no serotonin is made; eat them and the synthesis begins immediately.

There is nothing in a potato or pasta per se  that goes into the manufacture of  serotonin.  However when any non-fructose carbohydrate is digested, the  resulting release of  insulin allows an amino acid, tryptophan, to enter the brain.  Serotonin is made from tryptophan and dependent on insulin to get it into the brain.

Eating protein prevents tryptophan from entering the brain because the digestion of protein causes the  blood to  fill up with other amino acids that prevent  tryptophan from entering the brain.

The dependence of serotonin synthesis on carbohydrate consumption and insulin poses a problem for diabetics. Carbohydrate has to be eaten alone or with very little protein for serotonin to be made. Meals that contain more protein than carbohydrate will prevent this and leave the diabetic eater feeling vaguely dissatisfied. The stomach may be full but that comfortable feeling that comes from being satiated may be missing.

Not being able to make serotonin because of the limitations of carbohydrate consumption can also have an effect on mood. This was a discovery that I made and published along with my husband and in subsequent studies with Harris Lieberman, Ph.D and Bonnie Spring, Ph.D.  We discovered that many people experience a deterioration in their moods late in the afternoon along with a craving for something starchy or sweet.  We studied their moods after  eating carbohydrate and found that small amounts (about 30 grams) improved their moods, increased their concentration and made them feel more energetic.

Craving for carbohydrates in association with a deteriorating mood is not limited to afternoon carbohydrate cravers, however. Women with premenstrual syndrome (PMS) , people experiencing the winter blues or Seasonal Affective Disorder and even ex-smokers  find themselves eating carbohydrates when experiencing  depression, anxiety, anger, exhaustion and the inability to be attentive or focus . Eating carbohydrate seemed to relieve these moods presumably by increasing serotonin.  Avoiding carbohydrate may make it harder to endure the changes in mood of PMS, for example, or put people into a permanent grumpy state. When the Atkins diet was popular, people were said to develop an Atkins attitude that was somewhat similar to PMS.

Recently I’ve discovered that increasing serotonin by eating carbohydrates at specific times of the day is effective in helping people lose weight.  The ‘spoil the appetite’ effect of a small amount of carbohydrate before the meal makes it easier for the dieter to be satisfied with diet size portions.  People whose weight gain was caused by antidepressants or mood stabilizers have an even greater problem losing weight because somehow their medications are increasing their appetites and taking away the feeling of contentment after they eat.   At a weight loss clinic I developed and ran at a Harvard psychiatric hospital, we developed a food plan that included a carbohydrate snack prior to lunch and again in the late afternoon. The increase in serotonin seemed to turn off the cravings and need to eat generated by the medications.

It should be possible to develop a food plan for diabetics that permits carbohydrates to be eaten and serotonin to be made. Low glycemic carbohydrates such as lentils, beans, whole grains,  and high fiber foods may be the optimal source of carbohydrates. Even though some of these foods such as beans contain protein, the amount is too small to interfere with the ability of tryptophan to get into the brain.  We did have a few type 2 diabetics among our weight loss  clients and worked with an MIT research dietician to develop a food plan that was compatible with their needs.

Eating enough carbohydrate to produce serotonin during the dark days of winter will make the wait until spring more bearable . Having a carbohydrate snack during the afternoon doldrums will increase your ability to tolerate a difficult workload or difficult teenagers. And if faced with a meal of vegetables and chicken slivers, eating a roll or whole grain crackers or cup of bean soup before starting the main course will make you actually feel satisfied when the last piece of lettuce is eaten.

[1] Wurtman, J and Wurtman R  Life Sciences, Vol 24, 845-904, l979  Wurtman J, Moses P and Wurtman R, J Nutr 113: 70-78 l983.

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