Sunday, August 9, 2009

Diet Drinks, Ups and Downs


Diet drinks are one of the mainstays of the low-carb community. Diet Coke, Diet Pepsi, Diet Rite and many more provide fairly palatable carb-free alternatives to sugar-laden soda pop.

Some low-carbers drink all sorts of diet drinks and claim they have no problems with them. Others state that diet drinks cause them to gain weight or cause them to stall in their weight-loss programs, almost as if they were drinking the full-sugar equivalents. One of the ways to look at this phenomenon is to see if diet drinks cause the release of insulin.

One possibility is that the sweet taste of the diet drinks causes a cephalic or first-phase insulin response. Two 1995 studies by Teff, Devine and Engelman had normal-weight men sip and spit solutions that contained either water, aspartame, saccharin, or sucrose. Blood was drawn before and at two-minute intervals after the solutions were tasted. They found no significant increase in plasma insulin, even though the men had tasted the sweetened solutions for as long as three minutes.

Another possibility is that the presence of a sweet taste in the gut causes the release of peptides, and these in turn increase the secretion of insulin as part of a second-phase insulin response. It has recently been found that there is a TR2+T1R3 sweet taste receptor in the intestinal endocrine cells of the gut. In 2007, Margolskee et al. demonstrated that sucralose (brand name, Splenda) could activate this receptor in dishes of intestinal endocrine cells and cause the release of two incretin hormones, GLP-1 and GIP. In a whole organism, the incretin hormones would be expected to promote the release of insulin.

In 2009, Jin Ma et al. tested this hypothesis by infusing 500 ml of various solutions into the stomachs of seven healthy humans. (Putting a solution directly into the stomach bypassed any possible cephalic insulin response.) The first solution contained 50 grams of sucrose in water. The remaining solutions were: normal saline, 80 mg of sucralose in normal saline, and 800 mg of sucralose in normal saline. Of the four solutions, only the sucrose solution caused an increase in blood glucose. And contrary to the findings expected from the intestinal endrocrine cell study, only the sucrose caused an increase in GLP-1, GIP and insulin. The saline and sucralose solutions had no effect. Fujita et al. saw similar results when diabetic Zucker rats were given gastric boluses of solutions of glucose, sucralose, saccharin, acesulfame potassium, and stevia. Only the glucose solution affected the blood glucose, and only the glucose solution
increased the plasma GLP-1 and GIP levels. The artifically-sweetened solutions had no effect.

To drink or not to drink? A recent review of the literature in the American Journal of Clinical Nutrition noted that the use of nonnutritive sweeteners has increased along with the increase in Body Mass Index (BMI) in the United States. However, the authors found that if this is a cause-and-effect relationship, most of the mechanisms by which it is postulated to occur cannot be supported by current evidence. As we can see from the studies cited above, it appears that increased first-phase or second-phase insulin secretion is probably not a good explanation for any gain in weight as a result of diet drinks. As always, research is ongoing, but for now it looks as if diet drinks can be consumed without undue worry about their effect on insulin secretion and an insulin-associated gain in weight.

25 comments:

Nancy said...

for me either one is ok, but aspartame makes me ill and makes my younger daughter positively crazed. So maybe we're just sensitive. I hear bad things about Splenda too, so maybe stevia is the only one truly ok for us, but so far I've only found one soda with stevia in it, Zevia, and I havent tried it yet. (but soon!)

Chris said...

maybe.....

If you are interested in eating for health though I think you would still keep away from these cocktails.

anne h said...

You are like, my hero!
Excellent post, as always.

Stargazey said...

Nancy, aspartame makes me sick, too, so I know what you mean. I've heard scare stories about Splenda, but so far no more than that. Stevia seems to be more natural, but natural things (e.g., potatoes and wheat) can contain potentially harmful chemicals. I can't guarantee any of the non-nutritive sweeteners to be safe--all I can say is that they don't appear to provoke an insulin response.

Chris, :-) Yes, I'm eating for health, but sometimes the evil Stargazey takes over and heads for the diet pop. What can I say?

Thanks, Anne H!

whatsonthemenu said...

Thanks for the unbiased review of scientific research. There appears to be no metabolic cause-effect between increased consumption of non-caloric sweeteners and weight gain, so perhaps the most plausible explanation is theory that people compensate or reward themselves by eating more or eating fattening, low-nutrient foods like chips or cookies. I used to do that - after eating a healthy meal of chicken or salmon and veggies like broccoli and chard, I'd treat myself to dark chocolate or an occasional brownie. After I restricted my treats to once a week, I lost the ten pounds I had gained and have kept it off.

Chris said...

Ok.

however, if it is once in a while why not just have something naturally sweet without the artificial sweeteners?

A weekly coke will not do any harm, but the danger with artificial ones is that people think it harmless and suddenly they are gulping down huge daily volumes of weird chemicals....but it is ok because it is sugar free.

Stargazey said...

...why not just have something naturally sweet without the artificial sweeteners?

Because I'm scared to death of fructose. It makes fatty deposits in the liver and it glycosylates everything in sight.

I hear you about the chemicals, Chris. But I spent my formative years in labs with benzene, acrylamide and all manner of radioactive isotopes. After that, a little Splenda doesn't seem so scary, especially since I can't find any scientific studies that link it to health issues. But if you've got references on it, I'll be glad to read them.

Chris said...

Fair enough - and I was not trying to be awkward or critical - this is just about the best low carb blog there is and I really appreciate it.

I have no references just irrational prejudices in favour of real food, stuff that used to be alive.

I do take your points - fructose does seem increasingly scary.

Stargazey said...

No worries, Chris. I know you are a very kind person, and I appreciate your analytical insights.

Dexter said...

For just how scary fructose and high fructose corn syrup can be, look at this lecture by a MD at Univ of Ca. SF.
http://tinyurl.com/m5oqtj
If one must drink a beverage other than water, I guess diet something is better than the sugar laden product.

Sue said...

"Diet drinks are one of the mainstays of the low-carb community."

I don't think thats an accurate statement.

Stargazey said...

Sue, I don't have any statistics to back up my contention that diet drinks are commonly used in the low-carb community. It's more of an impression I've had from reading low-carb boards.

If you search for "Diet Coke" over at Low Carb Friends, you'll find 300 references for it since July 8, 2009. If you search for "Splenda" you'll find 300 references since August 2, 2009. Low-carbers may not like to admit it, but many of them appear to be using nonnutritive sweeteners.

Sue said...

I think low-carbers may start out consuming diet sodas and then scale back. Others use them daily.

Have you considered how the brain reacts to artificial sweeteners?
Interesting post with paper attached (rat study):
http://scienceblogs.com/cortex/2009/02/diet_soda.php

Nancy said...

well I've been following this thread and Chris, and I have to disagree that a weekly coke would do no harm. A weekly coke would do harm to me. I cant drink sugary drinks at all, they send me into a hypoglycemic attack very quickly. Within 2 hours I am dizzy, shaking, vomiting and possibly passing out from low blood sugar. I've never had that happen with a drink sweetened with splenda. Not to say splenda is perfect but as a once a week drink, its tops for me. The only way for me to avoid hypoglycemic attacks is to avoid sugar and especially sugary drinks.

Stargazey said...

Thanks, Sue. Here's the article in PDF format: Sucrose activates human taste pathways differently from
artificial sweetener
.

It's an interesting idea and goes along with what Whatsonthemenu discussed.

Stargazey said...

Dexter, I just finished listening to the lecture on fructose by Robert H. Lustig, M.D. Thanks for the URL!

Dr. Lustig presents lots of good biochemistry when he deals with the metabolism of fructose and its associated health risks.

On the other hand, if anybody makes it through the whole 90 minutes, please note that he has great enthusiasm but not much evidence for his mantra that "glucose is the energy of life," that lots of fiber is good for you, and that exercise helps you lose weight. Gary Taubes presents study results that argue against each of those ideas in "Good Calories Bad Calories." The guidelines for eating complex carbohydrates, getting lots of fiber and exercising for weight loss are popular in the medical community, but none of these recommendations has definitive support in the scientific literature.

Amber said...

Stargazey, did you find anything about the effect on bone density in women that was written about last year? There were a few items about it, but it never said why it happened (with women or only coke) and noone seemed to follow it up. I was surprised as women have babies and surely if it effects bone density in women it could be a problem during pregnancy?

Isn't it in peoples nature to try and find a 'healthy' alternative to things? They did low fat, now low carb (products). It seems that we seem to only focus on what we cannot have, not what we can. It was so much easier when there was less choice!

Stargazey said...

Amber, do you have a reference for the report of loss of bone density? I missed it.

Amber said...

erm... I remember some of us chatting about it on JM's menu blog, but I forget when.

Stargazey said...

Here's an article from 2006: Colas, but not other carbonated beverages, are associated with low
bone mineral density in older women: The Framingham Osteoporosis Study.


The correlation between cola consumption and low bone mineral density was found for women but not men. It was found both for sugared and for diet colas. It was stronger in colas that contained caffeine. It was noted that for the women in the study, an increased intake of cola was not associated with a significantly lower intake of milk.

The authors speculate that the decrease in bone mineral density could be caused by phosphoric acid, which is found in colas but not in most other soft drinks. By definition, colas are made with cola extract, which contains catechins, theobromine, tannins and numerous other undefined plant products. It is conceivable that one of these could cause the loss in bone mineral density.

While the possible contribution of cola drinks to osteoporosis is potentially significant from a public health standpoint, the list of subsequent articles that cited this article shows that only a few investigators appear to be pursuing this type of study.

Amber said...

I guess there is no money in telling people not to drink something.

Chris said...

did you see this?

http://www.drbriffa.com/blog/2009/09/04/the-myriad-of-reasons-why-artificial-sweetners-may-not-deliver-on-their-weight-loss-promise/

Stargazey said...

No, I haven't, Chris. I'm covered up with real-world responsibilities today, but I'll look at it tonight. :-)

Stargazey said...

I did look at it, Chris. The most interesting reference was Cephalic phase insulin release in healthy humans after taste stimulation? From the abstract, that paper directly contradicts the findings of Teff et al. that saccharine did NOT stimulate a cephalic-phase insulin response. I don't have access to the complete paper--perhaps they address the issue in their Discussion section.

As far as the other studies, they may well be true. I was only looking at insulin response, just to keep the discussion contained. It would be interesting to compare weight loss in people who use artificial sweeteners versus those who avoid sweeteners altogether. Are you aware of any such studies?

Chris said...

Sorry - I'm not aware of any.