Is Splenda safe? by Dana Carpender

I wrote this article a decade ago, but it only needed minor updating for re-release:

Q: Is it true that Splenda is more dangerous than they’re letting on?

I recently got an email from reader Karen Kosel asking exactly that; she followed up by posting me a website that said some really unpleasant things about Splenda – to be specific, that it may cause shrinkage of the thymus gland, which is part of the immune system, and may also cause enlarged liver and kidneys. For balance, they also concluded that sucralose (the chemical that makes Splenda sweet) was probably “not as toxic as aspartame”.

Uh-oh. I was not aware of any of this, and it sure wasn’t makin’ me happy. I started looking for more information. Found it! Actually found the text of the FDA’s documents regarding the approval of sucralose. Here – in nice, dense, scientific gobbledygook – is what it has to say about sucralose and the immune system (You may want to skim this if you’re prone to nodding off in front of the computer, but I’ll summarize after…)

Immunotoxicity study in rats. As reported by McNeil and as noted in the agency’s review of the sucralose data, thymus, spleen, and hematological changes were observed in rats at the high-dose levels in some of the short-term and long-term sucralose feeding studies. For example, when rats were fed sucralose in a 4- to 8-week range-finding study (E031) the following effects were noted: Decreased thymus and spleen weights, lymphocytopenia, and cortical hypoplasia of the spleen and thymus. In the two-generation reproductive toxicity study (E056), decreased thymus weights were noted in the F0 and F1 generations of the high-dose sucralose (3 percent in the
diet) group. McNeil stated that the above effects were secondary to the palatability-related reduction in food consumption in treated rats. In an effort to provide more specific and detailed assessment of the immunotoxic potential of sucralose, the petitioner conducted a 28- day oral immunotoxicity study (El62) of sucralose in rats. In this study, groups of male and female Sprague- Dawley rats (13 per sex per group) were administered sucralose by gavage at dose levels of 750, 1,500, and 3,000 mg/kg bw/d for 28 days. Additional groups (13 per sex per group) of rats formed a gavage control group, an ad libitum diet control group, a dietary sucralose (3,000 mg/kg bw/d) group, and a diet restricted (90 percent of ad libitum control) group.

Immunotoxicological parameters examined in this study were: Thymus and spleen weights at study termination; standard histopathology evaluation of the spleen, thymus, bone marrow, and lymph nodes; and total and differential white blood cell counts. The study also examined the following specific immunologic parameters: Bone marrow cellularity, immunoglobulin subtypes, splenic lymphocyte subsets, and splenic natural killer cell activity.

Significant decreases were observed in the mean thymus weight of the males in the high dose (3,000 mg/kg bw/d) gavage group. Thymus weight was not significantly affected by sucralose when administered to rats by gavage at either 1,500 or 750 mg/kg bw/d; nor was it affected in the sucralose-fed group or the diet restricted group. No morphological changes in thymus or any other lymphoid tissues were observed in any of the sucralose treated groups.

In the mid-dose (1,500 mg/kg bw/d) sucralose-gavaged male rats, there appeared to be a trend toward decreasing white blood cell and lymphocyte counts with increasing dose levels of sucralose, but the trend did not reach statistical significance. No significant differences were seen in other immunologic parameters in the sucralose gavage groups relative to the control gavage group. However, because of the large variation seen in the data from the gavaged animals at the mid-dose, the agency finds that the study is inconclusive regarding treatment-related effects for these parameters at the mid-dose.

The agency concludes that the highest dose (3,000 mg/kg bw/d) tested in the gavage groups showed an effect based on the significant changes in thymus weight. Because of the difficulty in interpreting data from the mid-dose animals, the agency has determined that the low dose, 750 mg/kg bw/d, is the no-observed-effect level for the immunological endpoints examined in this study (Ref. 37).

Whew. Eyes glazed over yet? Here’s what appears to me to be the point of the preceding: Yes, sucralose (Splenda) does appear to have an effect on the thymus gland, in rats at any rate, when fed in whopping big doses. There also appears to be a small reduction in white blood cell count – also important for immune function, of course – when fed in somewhat smaller but still effectively huge doses. In low doses, the problems do not appear to occur.

Regarding increased kidney weight, the report said that this effect occurred in the highest dose group, but was not accompanied by any pathological changes in the tissue itself, nor by any changes in electrolytes in the blood plasma, which you would expect to see with kidney damage. The increase in kidney weight didn’t happen with the lower dosage groups.

This may remind you of the tests on saccharine and cyclamates, both of which involved feeding rats something like the human equivalent of 600 cans of diet soda a day for 10 years, or something equally ridiculous, and then claiming that the substance was dangerous because health problems arose at that dose. Let us never forget the first rule of toxicology: Dose is everything.

How big a dose of sucralose are we talking about? Well, the rats on the high dosage were fed 3 grams a day of straight sucralose – not, I want to emphasize, 3 grams of Splenda, in which the sucralose is mixed malto-dextrin to bulk it up – per each kilogram of body weight, every day. A kilogram is 2.2 lbs. So a 150 lb. human being weighs just over 68 kilos. How much Splenda would that 68 kilo person have to eat to get 3 g of sucralose per kilo of body weight? My package of Splenda tablets says that one tablet contains 5.8 mg. of sucralose, and that one tablet equals one teaspoon of sugar in sweetness. From this I gather that one teaspoon of granular Splenda has about 5.8 mg. of sucralose as well.

Okay, math time: 68 x 3 = 204 g. of sucralose per day. 204 grams of sucralose = 204,000 mg. Dividing that by the 5.8 mg of sucralose in a teaspoonful of Splenda, I get 35,172 teaspoonfuls per day of Splenda to reach the dosage that was being given to the rats in the high dosage group. The middle dosage group was getting half that dosage, or the human equivalent of 17,586 teaspoonfuls of Splenda per day. And the low dosage group – the group which showed no thymus gland shrinkage or changes in white cell count – were getting half of that, or 8,793 teaspoons of Splenda a day for an equivalent dose in a 150 lb. human being.

Anyone out there eating 8,793 teaspoons of Splenda a day? Anyone care to guess at the health effects if you fed rats an equivalent dose of sugar? (By the way, I just worked it out: The average American eats 152 lbs of sugar per year. That works out to about 45 teaspoonsfuls a day. Does anyone really think that we’re going to eat that much more artificial sweetener than we did sugar? And why don’t they do these experiments on sugar, anyway?)

I haven’t read the entire FDA document yet; it’s long, and as you’ve seen, it’s not exactly a quick read. However, from what I’ve seen, I find myself reaching the same conclusions about Splenda that I’ve had about artificial sweeteners all along: They may not be 100% safe, but then, nothing is. Used with a modicum of sense and moderation, they’re safer than sugar by a wide margin. I don’t advocate the consumption of huge amounts of artificial sweetener, nor of artificially sweetened foods – for instance, I don’t drink diet pop or Crystal Lite, myself, nor do I have artificially sweetened desserts every day. But if having the Splenda-sweetened cookie or pie or smoothie keeps me happy and satisfied with my lifetime commitment to a low carb diet, then I think it’s a boon to my health, not a detriment. Ditto the use of a couple of teaspoons of Splenda here and there in a salad dressing, sauce, or other creative low carb recipe.

If you’re still concerned, here’s a few possible strategies:

  • Cut back on use of sweeteners over all. Not everything has to taste sweet to taste good. In particular, the American notion that every beverage must be sweet is a very destructive one.
  • Use a variety of sweeteners – saccharine has been cleared of the cancer warning it carried all these years, so you could use, say, Sweet ‘n’ Low in things like coffee and iced tea, and save Splenda for places where it really improves things, like sugar-free desserts. This lowers your dose of any one substance.
  • You could use stevia. I find stevia to be a bit difficult to use, with a bit of an aftertaste or undertaste, especially if used in strong concentration. Still, for things where only a touch of sweetness is needed, it can be useful.
  • Try the new stevia/erythritol blends, like Truvia. You could also use straight erythritol, though I find its cooling effect disconcerting in some applications. Xylitol is another sweetener whose popularity is increasing; it has the same cooling effect as erythritol. It’s also profoundly toxic to dogs, so I won’t have it in the house, but if you don’t have dogs it’s worth a try.
  • If I were pregnant, I would probably limit my used of artificial sweeteners, even though they are tested for bad effects on a fetus. You can’t be too careful when there’s no second chance. On the other hand, I sure wouldn’t start using sugar instead. The most common time for women to become diabetic is during pregnancy, and it’s very dangerous for both mother and child.
  • If you’re making a dessert using low sugar fruits such as strawberries, pie cherries, or cranberries, you can cut the amount of sweetener of any kind that you’ll need by adding a little baking soda. This will neutralize some of the acid, making the fruit less tart. It will also make your concoction foam, big time, so make sure it’s in a big enough pan! Start with a 1/4 – 1/2 teaspoon, and taste as you go.

Still, all told, I’m not panicking about Splenda, or artificial sweeteners in general. I’d recommend that you not panic either!

Find Splenda @

© 2010 by Dana Carpender. Used by kind permission of our sweet editor. What do you think? Please send Dana your comments to Dana Carpender.

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