Aspartame Research - an in-depth review of the most popular sweetener

Q: Does aspartame influence appetite/hunger or the feeling of fullness?

In the majority of cases, aspartame has no effect on appetite/hunger or perceived fullness. Individual effects do seem possible in either direction, but aspartame seems to actually be more likely to suppress hunger, performing similar to water.

Q: Compared to regular sugar, does aspartame influence the total amount of calories consumed?

Substituting regular sugar for aspartame will almost always result in the reduction of total caloric intake. Aspartame seems well suited for the task of limiting weight gain and promoting fat loss through caloric restriction.

Q: Does aspartame intake stimulate insulin release?

In the majority of cases, aspartame has negligible effect on insulin release. However, individual responses are possible and there might be a connection with perceived sweetness and the following blood sugar changes which can influence insulin levels.

Q: Does aspartame elevate blood sugar levels?

In most cases aspartame will not have a noticeable effect on blood sugar. However, depending on the perceived sweetness of the food or drink consumed, there may be a rare individual reaction in any direction

Q: Does aspartame promote obesity?

Aspartame is strongly correlated with weight loss, not weight gain. Because of the negligible caloric content of aspartame, there is no way for aspartame to directly promote obesity. Very rare individual responses to hunger and appetite are possible, but unlikely.

Q: Does aspartame cause headaches?

Out of all the negative side-effects claimed to be caused by aspartame, headaches seem to be the most common. After analyzing the current scientific literature, I can say with some certainty that there is a definite connection between aspartame consumption and headaches. However, the connection seems to be limited to individuals who have a prior history with headaches and migraines. Most confirmed cases of increased headache frequency or severity seem to all be connected to individuals with increased susceptibility to headaches in general. Clinical trials done on healthy individuals with no history of headaches or migraines result in no noticeable issues even with extreme doses of aspartame. It may be wise to avoid aspartame if you have history with headaches or migraines.

Number of References

Words written

LAST UPDATED - MARCH 2020

March 2020 – Added References #90, #91, #92, #93, #94, #95; #96.

Some possible connections to depression in study #90.
Zero symptoms from study #91 comparing self-diagnosed “aspartame sensitive” individuals with a healthy control group.
In #92, over 100,000 people were studied for cancer risk concerning aspartame sweetened beverages. No elevated risk for cancers was detected.
#93 studied the effects of various beverages (caffeinated soft drinks, non-caffeinated sodas, aspartame sweetened sodas, and natural juices) for risk of early menarche. Possible correlations exist for both caffeine and aspartame for a small increased risk of early menarche, however the study had many limitations.
#94 looked at insulin responses and feelings of hunger or fullness. Aspartame had no effect.
#95 checked whether or not aspartame affects gut microbiota. It does not.
#96 was a study comparing sugary drinks and measuring their effect on total calories consumed in ad libitum (no restrictions), with a 0 calorie aspartame drink as a control. Sugary drinks resulted in people consuming more calories through-out the day compared to aspartame.

Artificial sweeteners have been around for quite some time, aiming to combat the obesity epidemic by providing low-calorie alternatives for sweetening our foods and beverages. Yet, despite the green light given by the governments and the food industry, many consumers are still concerned about the safety of these substances.

One of the oldest and most popular artificial sweeteners is Aspartame. It also happens to be the most thoroughly researched.

Despite being heavily researched and having its use supported by more than 90 governments around the world (86; 87), Aspartame has taken central stage in many health campaigns that are rallying against the use of artificial sweeteners. Countless privately owned websites, consumer reports and even medical professionals regularly accuse Aspartame of being poisonous and toxic to human health in a myriad of ways.

I have decided to write this unbiased and objective article to definitively answer the question, based on our current scientific understanding, if Aspartame is safe for general consumption or not. My goal is to review the evidence that is publicly accessible and make reasonable, logical conclusions based on that evidence.

Let’s start of with the basics. What exactly is Aspartame?

Aspartame is a man made compound that is produced and marketed as an artificial sweetener. For that task it is indeed well suited, as it is roughly 200 times sweeter than sugar. What that means, is that you only need a fraction of the substance, compared to regular sugar, to get the same level of sweetness. That in turn means that the caloric content required to achieve that sweetness is extremely low, basically non-existent. A single teaspoon full of aspartame is equal to roughly 2.2lb (~1kg) of regular sugar. Because of these qualities, it is a popular food additive in diet-products like diet Coke.

On closer inspection, we can see that aspartame is a methyl ester of the dipeptide of the natural amino acids L-aspartic acid and L-phenylalanine. Sounds complicated, but amino acids are basically just building blocks for proteins that perform countless vital tasks within our body. Because we cannot synthesize every amino acid required to build these proteins ourselves, we need to consume protein from regular food. The two amino acids that make up aspartame are also found in nearly all food sources we consume every day and in far greater concentrations.

These two amino acids are completely natural substances that are part of every healthy diet and are no cause for worry. The only exception is a very rare medical condition called phenylketonuria (PKU), in which case the consumption of phenylalanine can lead to death or mental retardation. In the case of such an illness, the consumption of phenylalanine – which is a component in aspartame, but also found in foods like meat, eggs and milk, – is prohibited. However, this disease is nearly always diagnosed immediately at birth and the people suffering from the ailment are taught to pay attention to their food sources at an early age. For this reason, products containing aspartame have a warning label, advising PKU patients of the phenylalanine content. It is not a concern for healthy individuals. (87)

In normal and PKU heterozygotes, aspartame intakes up to the ADI of 40 mg/kg bw/day, in addition to dietary phenylalanine, would not lead to peak plasma phenylalanine concentrations above the current clinical guideline for the prevention of adverse effects in fetuses. The Panel concluded that aspartame was not of safety concern at the current aspartame exposure estimates or at the ADI of 40 mg/kg bw/day. (87)

Separately, these ingredients are quite common and safe, just a couple of basic components found in foods that have protein. In aspartame however, they are fused together using special chemical processes. But when aspartame is exposed to highly acidic or alkaline environments (similar to our digestive system), it is rapidly broken down to it’s basic components again. We get the two common amino acids we talked about and as an addition, through the hydrolysis of the Methyl Ester, we also get Methanol. Methanol is also known as wood alcohol or wood spirit. You may be aware that this form of alcohol can be extremely toxic and very dangerous when consumed. Large doses can result in blindness and even death.

Because of this fact, it makes sense to discuss Methanol first. As the methanol content is used in various media outlets as the main argument against the safety of aspartame. Let’s see if there’s any truth to this concern.

Roughly 10% of the aspartame we ingest ends up as methanol in our body.

This is very much true. Now, you might be thinking that this is all the proof you need to avoid aspartame… but hold your horses. There is actually very little reason for concern. First off, you have to be aware that methanol is found in many places in nature and most of us get some level of exposure to it every single day. That’s right. We consume a small amount of methanol through fruits and vegetables and their juices. There is some methanol in various alcoholic products and we inhale some methanol particles through tobacco smoke and automobile exhaust gases. (10; 11, 12)

The fact is, that methanol is almost everywhere and it’s just about impossible to avoid it. So we shouldn’t be alarmed simply because of its presence. It is the dose and the context that is important. So let’s put a hold of freaking out and analyze what actually happens once we consume methanol. Lets find out what exactly causes the health issues and if aspartame can be dangerous.

Methanol Breakdown

During digestion, methanol is broken down into two substances. Formaldehyde and formic acid. Both of these substances can be potentially toxic and are responsible for methanol having the reputation of being dangerous. Both of these are also often used as arguments against aspartame safety in anti-aspartame campaigns. However, once again I must emphasize that dose and context is paramount. And I’ll explain why.

Let’s start with formaldehyde.

Many of you probably know of this stuff as the substance used in embalming fluid as-well as from its other industrial uses. That definitely sounds like a nasty to thing to have in our foods or drinks, right? It can definitely seem that way, however, the truth is that there is a massive difference in the quantities used by the various industries compared to the exposure we get through methanol breakdown from food sources. The fact is, that formaldehyde is actually something that we, the whole of humanity, have been in contact with for thousands and thousands of years. Formaldehyde is found just about everywhere in nature just like methanol. It is made in the upper atmosphere or in fires and it has seeped into the very soil. We consume small doses of formaldehyde every day through foods like meat, fish, fruits and vegetables and basically through just about everything else that we get from nature.

Through-out the majority of our lives, we have been exposed to small doses of formaldehyde on a daily basis. (1; 2; 3; 4; 5)

But does that mean we’re constantly being harmed by formaldehyde toxicity? Not quite. Luckily, small doses of formaldehyde don’t really pose any health risks for our body. Why? Because the fact is, our body already contains formaldehyde by default, and it has a normal part to play in our metabolism. In fact, our body can produce its own formaldehyde through various amino-acid related processes, and does so constantly. And, like I mentioned earlier, we regularly get some through our food and other environmental exposures. Furthermore, formaldehyde actually plays a part in the production of amino acids and is even involved in the creation of DNA Particles. (1; 2)

Our blood has a formaldehyde concentration of about 2.5mg/L and based on research done on our metabolism, we know that our liver processes around 22mg of formaldehyde per minute to be released as carbon dioxide. Combining this with the other possible uses for it in the body, it is reasonable to conclude that the total amount processed by our body can be as high as 50 000mg per day. (2)

What that means is that formaldehyde, as „nasty“ as it may appear at first glance – is not always the bad guy. We are regularly exposed to it, our body can actually produce its own and our metabolism is used to processing large quantities every day.

Though, just to be clear, we don’t actually have to consume formaldehyde and certainly nobody would advise you to even try. It is still a potential toxin.

However, like always, dose and context is important. It is important to pay attention to as to where our body obtains it from and in what quantities. The biggest source of danger is various industrial exposures, where people can come in contact with large quantities of the raw substance. For example, formaldehyde in gas form is likely to irritate our eyes and respiratory system (though long term health risks may be low, 88), while liquid solutions can irritate the skin. Drinking some can be outright deadly.

All that however, is not exactly relevant to aspartame intake.

So let’s tone it down a bit. How dangerous are the quantities of formaldehyde we can ingest through aspartame?

Well… let’s look at a few examples.

1 litre of Coca-Cola Zero contains about 225mg of aspartame, while Coca-Cola Light contains roughly twice as much at 500mg/L. Because we know that only 10% is released as methanol, the numbers we are concerned with are 22.5mg and 50mg. That is roughly the amount of formaldehyde we could ingest from one liter (33 oz) of diet Cola.

Considering that our liver alone can process that much in a minute or two and our body is regularly processing up to 50 000mg a day, it is very hard to see any danger in aspartame related formaldehyde intake.

While it’s true that some products can contain more aspartame, it is not by much. There is a realistic limit as to how sweet you can make something and keep it edible or drinkable. Certainly nobody would be able to put dangerous levels of raw aspartame in any commercially distributed product, because nobody could tolerate the taste. And that is even if the government didn’t test for it, which they do.

To conclude – Formaldehyde is not the source of all evil, at least certainly not in the way we get it from aspartame. It’s a by-product of methanol metabolism that isn’t even a concentrated dose. The way we obtain it from aspartame means that it is metabolized over a longer period of time that doesn’t even come close to the amounts our body is quite used to processing every day anyway. It is literally a drop of formaldehyde in a river of formaldehyde that is coursing through our veins 24/7.

We discussed formaldehyde, let’s now discuss Formic Acid.

Formic acid is the next step in methanol metabolism. The formaldehyde that is not used for other purposes, will be metabolized into Formic Acid, which is really the main cause for the symptoms of methanol toxicity.

But, once again, I must emphasize that dose and context must be taken into account. The substance itself is not an uncommon presence in our system. After our body creates formic acid, it is then further used in various amino acid related processes and then excreted in urine or metabolized into carbon dioxide and water, the former of which we simply exhale. So, as you can see, our body has quite a few methods to safely dispose of this substance.(1; 2; 3; 4; 5)

This isn’t actually all that surprising. The following may be new information to some of you, but the term “formic” actually comes from the Latin name for the common ant (formica) and formic acid is found in ant venom. Small quantities, especially in low concentrations, are quite harmless. Formic acid is actually used as a food additive in various products and even used as an anti-bacterial substance. (6; 7; 8)

The real cause for concern is when a large dose of methanol is consumed in a very short time period. That causes the methanol to get broken down into large quantities of formaldehyde, which in turn gets metabolized into a large amount of formic acid. Because it can take some time for our body to safely metabolize formic acid, excessive build-up can cause medical issues, like blindness and even death. (2; 9) Most commonly this happens with home made illegal alcohol production and sales, where individuals who make the alcohol attempt to cut costs by buying less expensive methanol, rather than ethanol which is safer. People either aren’t aware of methanol toxicity or they are knowingly poisoning people.

As such, it is quite possible to consume enough methanol that would result in toxic doses of formic acid. It’s not common, but it has happened.

But can we get enough methanol from aspartame to cause formic acid toxicity?

There is no evidence to suggest that the amount of formic acid obtained from the breakdown of aspartame can result in any health issues in the human body. In fact the amount of aspartame consumed from a whole large bottle of Diet Soda isn’t even enough to cause a change in the formic acid content of our blood.

But let’s look at methanol in general again. What does the evidence say?

We already know that about 10% of aspartame ends up as methanol. And we know that the resulting doses of formaldehyde and formic acid shouldn’t be an issue from the amounts of methanol we get from commercial aspartame products. But how much methanol would we really have to consume for it to be dangerous?

This is not the easiest question to answer because it can depend on numerous factors like the individuals age, weight, medical status and individual metabolism specifics. However, in general, we can estimate that about 0.3-1 grams per kg of body weight can be considered a lethal dose. (that’s about 30-100 grams for a 100 kilogram man or roughly 1-3 oz for a 220lb man) (11)

However, negative effects to health can start much lower. Research shows that vision can be noticeably effected by as little as 8 grams of methanol. But let’s go even further than that and create a small buffer for safety’s sake. Let’s say that 4 grams can become a noticeable issue. Now, let’s do some math and see if it’s possible to get dangerous doses of methanol from aspartame consumption.

Previously we talked about Coke Light and Zero. Again, let’s be on the safe side and say that 500mg of aspartame per 1 liter (33oz) of liquid is an average dose. That results in about 50mg of methanol per liter.

If the dangerous dose of methanol is set at 4 grams, then it would take 4000 mg (4 grams = 4000 milligrams) / 50 mg = 80 liters or 2640 oz / 20.6 gallons of diet Coke, consumed in a fairly short time frame, like a single day, to cause noticeable health issues.

Unless your daily diet involves drinking an entire pallet’s worth of Diet Soda, methanol from aspartame products isn’t going to be an issue.

Let that sink in. You would have to consume 80 liters or 20.6 gallons of aspartame filled soft drinks in a single day, to reach dangerous levels. That is not even remotely possible. Even if you tried, you would die from excessive liquid intake far before getting anywhere near dangerous methanol levels. Even if we considered the possibility of some methanol saturation in the body building up over time (we know that our body processes quite a bit of it every day), there would be no way to reach dangerous levels.

As additional evidence, consider this: 1 liter of fruit juice contains roughly 140mg of methanol and eating 1kg of apples (a couple of big apples) can provide us with as much as 500mg. That is a lot more than is found in any aspartame filled drink or food anyone is likely to ever consume in a day. (10; 12)

Any way you look at it, there just isn’t any way to consume dangerous doses of methanol (nor formaldehyde or formic acid that we metabolize from it) from aspartame filled commercial products. The only way to obtain a toxic dose would be to ingest raw aspartame powder, which, as we remember, is 200 times sweeter than sugar. It’s practically inconceivable that anyone could do that even by accident.

There is no scientific reason to disagree with the statement of the Food and Agriculture Organization of the United Nations, the World Health Organization, the EU Scientific Committee for Food, the Panel on Food Additives and Nutrient Sources added to Food, and the European Food Safety Authority:

Aspartame (E 951) is a sweetener authorized as a food additive in the EU that was previously evaluated by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), the EU Scientific Committee for Food (SCF) and the European Food Safety Authority (EFSA). Both JECFA and SCF established an Acceptable Daily Intake (ADI) of 40 mg/kg body weight (bw)/day.

Following a request from the European Commission, the Panel on Food Additives and Nutrient Sources added to Food (ANS) of the European Food Safety Authority (EFSA) was asked to deliver a scientific opinion on the re-evaluation of aspartame (E 951) as a food additive.

Overall, the Panel concluded from the present assessment of aspartame that there were no safety concerns at the current ADI of 40 mg/kg bw/day. Therefore, there was no reason to revise the ADI for aspartame.

I think it’s time to take this review of Aspartame in a different direction altogether. Let us stop trying to figure out the specific method of aspartame toxicity, if there even is one, and let’s just look at the research. More specifically, let’s look at the research done on humans.

It’s time to find out if there is any tangible real world evidence that would suggest aspartame causes health issues in the wider population. Regardless if we know why the issues exist, let us find out if there even are any issues in the first place.

If aspartame is as dangerous as many people report and campaign it to be, surely there must be plenty of evidence about it, right?

Aspartame has been in use for more than 30 years and has found its way into numerous commercial food and drink products. Because of its popularity and availability, it has been researched extensively in order to assure the governments, the food industry and the consumers, that it is safe to use. Unfortunately, a large deal of the research has been done on animals and has little value.

Animals do not have the exact same metabolism as humans do nor do they live in the exact same environment or have similar lifestyle aspects. All these factors can considerably alter the effects of any diet or any specific nutrient. What is dangerous to a rat or a mouse in a cage, is not always so for a human and vice-versa. While animal research is a stepping stone for establishing hypothesis’s and moving towards human trials, it is of little value in determining actual realistic dangers or safety for humans. Unless you are a rat or have a pet rat you care for, I suggest not putting stock in rat studies.

Due to this fact, I will not speculate on animal research but rather look only at human trials which are infinitely more valuable.(something that most anti-aspartame campaigners rarely do)

I have categorized the research I have reviewed into separate categories based on health concern symptoms or other topics.

1) Does aspartame influence appetite/hunger or the feeling of fullness?

No (18 studies; 13; 14; 15; 16; 17; 18; 19; 22, 23; 24; 25; 26; 29; 30; 33; 58; 59; 94)
Reference #14
Yes – reduces appetite/hunger (20; 57; 89)
Maybe – reduces appetite/hunger (1 study; 34**)
Maybe – increases appetite/hunger (2 studies; 28*; 34**)

*Aspartame in capsule form had no effect on appetite. Aspartame used in sweetened carbonated drinks slightly increased appetite.

**In this research, reactions to aspartame were conflicting. Some people reported experiencing increased hunger while others didn’t. It seemed to be related to their individual blood sugar reactions to aspartame intake.

My personal conclusion: in the majority of cases, aspartame has no effect on appetite/hunger or perceived fullness. Individual effects do seem possible in either direction, but aspartame seems to actually be more likely to suppress hunger, performing similar to water.

2) Compared to regular sugar, does aspartame influence the total amount of calories consumed?

Yes, lowers total caloric intake (14 studies; 13; 14; 16; 18; 21; 24*; 25; 27; 30; 56; 57; 58; 59; 89; 96)
Reference #14
Yes, increases the total amount of calories consumed (2 studies; 22**; 23)
No (1 study; 26; )
Maybe (3 studies; 33***; 38****; 60*****)

*Aspartame was not compared to equal sweetness, but caloric intake was reduced afterwards.

**Post-exercise ad-libitum caloric intake increased, however total daily intake was not measured.

***Unfortunately only the abstract was available. Total daily caloric intake was said to be equal between test groups, yet the aspartame containing meal was said to be 200kcal smaller and the energy compensation from later meals was not significant.

****Equal weight loss was measured in both groups during the diet. The period following the dieting protocol saw the aspartame group regain less weight compared to the control group.

*****Aspartame seemed to have no effect on men, but the female test group lost more weight compared to the control.

My conclusions: substituting regular sugar for aspartame will almost always result in the reduction of total caloric intake. Aspartame seems well suited for the task of limiting weight gain and promoting fat loss through caloric restriction.

3) Does aspartame intake stimulate insulin release?

No (6 studies; 13; 17; 31; 32; 40; 94)
Reference #17
Yes (1 study; 16)

My conclusions: in the majority of cases, aspartame has negligible effect on insulin release. However, individual responses are possible and there might be a connection with perceived sweetness and the following blood sugar changes which can influence insulin levels.

4) Does aspartame elevate blood sugar levels?

Yes (-)
No (5 studies; 13; 29; 31; 32; 35)
Maybe (1 study; 34*)

*The reaction to aspartame intake was somewhat confusing in this study. While some subjects experienced a decrease in blood sugar levels, others experienced an increase and some had no reaction at all. It’s possible that the perceived level of sweetness causes individual reactions.

My conclusions: in most cases aspartame will not have a noticeable effect on blood sugar. However, depending on the perceived sweetness of the food or drink consumed, there may be a rare individual reaction in any direction.

5) Does aspartame promote obesity?

No (8 studies; 19; 25; 33; 36; 37; 60; 89; 96)
Reference #36
Yes(-)
Maybe (1 study; 23)

My conclusions: aspartame is strongly correlated with weight loss, not weight gain. Because of the negligible caloric content of aspartame, there is no way for aspartame to directly promote obesity. Very rare individual responses to hunger and appetite are possible, but unlikely. Also see topic #2.

6) Does aspartame cause headaches?

No (6 studies 19; 29; 38; 40; 90; 91)
Yes (-)
Maybe (5 studies; 39; 68*; 74**; 75***; 76)

*This study was done on migraineurs (individuals suffering from regular migraines) and some test subjects did experience an increase in headache frequency with aspartame consumption.

**Two patients who were prescribed headache medicine containing aspartame, experienced an increase in headache severity. However, due to the fact that the medicine itself had a potential side-effect on causing headaches on some individuals, it is not possible to make a definitive connection between aspartame and headaches.

***Various research done in the past has shown that migraineurs taking placebo drugs often experience an increase in headaches. This one man trial was done to assess the potential headache promoting effects of the capsules that contained the placebo. The research did seem to indicate that the capsules themselves could have an effect on headache frequency and not necessarily the capsules content.

My conclusions: out of all the negative side-effects claimed to be caused by aspartame, headaches seem to be the most common. After analyzing the current scientific literature, I can say with some certainty that there is a definite connection between aspartame consumption and headaches. However, the connection seems to be limited to individuals who have a prior history with headaches and migraines. Most confirmed cases of increased headache frequency or severity seem to all be connected to individuals with increased susceptibility to headaches in general. Clinical trials done on healthy individuals with no history of headaches or migraines result in no noticeable issues even with extreme doses of aspartame.

It may be wise to avoid aspartame if you have history with headaches or migraines.

It is also worth noting that headaches are by far one of the most common health complaints out there. Roughly 90% of all people experience headaches every year and as many as 12-18% report having migraines. Because of this fact, any conclusions on this topic must be taken with a grain of salt. There are countless causes for headaches ranging from acute and chronic stress, emotional issues, trauma, disease and more. Isolating a single culprit is essentially impossible. Furthermore, testing for headaches is extremely complicated as medical professionals rely almost completely on the feedback given by the patients, making it difficult to validate the specifics of the issue.

In one clinical trial the placebo group actually reported a higher incidence of headaches than the aspartame group. And that was despite all the test subjects having described themselves as extremely sensitive to aspartame. (40) In my opinion this is a very clear demonstration of a negative bias towards aspartame on a psychological level that can express itself on a physiological level. People are literally thinking themselves sick.

7) Does aspartame cause cancer?

No (7 studies; 31; 65; 66; 67; 71; 72; 92)
Yes (-)
Maybe(1 study; 73*)

*Results of this study were somewhat peculiar. As a whole, there was no increased risk for non-Hodkins lymphoma or myeloma detected. However, some increased risk was found in the male test subjects who consumed aspartame sweetened diet drinks, but not in women. Increased risk for cancer was also found in the male subjects who consumed regular soft drinks. But, yet again, not in women. When testing for leukemia risks, no increases were found in any separate test groups, no matter the beverage. However, when the results of all test groups were pooled, some increase of leukemia risk was found in the aspartame group.

Researchers admitted the possibility of coincidence due to the confusing results of the study.

My conclusions: I see no definitive proof in the current scientific literature that aspartame consumption increases the risk of cancer. However, due to the long-term nature of the ailments, and the myriad of confounding factors present, there is simply not enough research currently available to rule out every possibility.

8) Does aspartame have a negative effect on tooth enamel?

No (2 studies; 42; 43)
Yes (-)
Maybe (-)

My conclusions: there is no data to suggest that aspartame flavored beverages damage tooth enamel.

9) Does aspartame cause fatigue?

No (2 studies; 38; 91)
Yes (-)
Maybe(1 study; 84)

My conclusions: The information is severely lacking in this area, but there are references to a case study where two individuals were reported to have developed fibromyalgia, which lead to fatigue and chronic pain. After ceasing daily aspartame intake however, the symptoms slowly receded.

After having gone through dozens of studies that make no mention of any fatigue symptoms, it is my conclusion that this is not a common complaint. The only study I found, reports fatigue symptoms no more often than regular sugar or placebo.

10) Does aspartame cause acne?

No (2 studies; 38; 91)
Yes (-)
Maybe(-)

My conclusions: There really isn’t much to say. I found no specific studies relating to acne and it is not mentioned as a symptom in any of the research. Aspartame seems to have no connection to acne.

11) Does aspartame cause nausea?

No (2 studies; 38; 91)
Yes (-)
Maybe(-)

My conclusions: There is no evidence to suggest that aspartame consumption can cause nausea.

12) Does aspartame use influence neurological/cognitive function and behavior?

No (16 studies; 29; 38; 40; 44; 45; 46; 47; 48; 49; 51; 54; 55; 63; 64; 67; 91)
Yes (-)
Maybe (4 studies; 39; 52*; 53**; 90)

*Individuals with a history of depression may experience an increase in severity following the consumption of large doses of aspartame.

**EEG spike discharge time was increased in children suffering from epilepsy.

My conclusions: Similar to the research concerning headaches, there is no data to suggest that aspartame poses any danger to healthy individuals. The overwhelming majority of the research validates aspartame safety. However, those who are already suffering from certain neurological ailments may find that aspartame consumption can exacerbate their symptoms.

There is no reason fear that aspartame has negative effects on the brain function of healthy individuals.

13) Can aspartame cause seizures?

No (4 studies; 44; 50; 67; 91 )
Yes (-)
Maybe (2 studies; 53*; 70**)

*Increase in seizure time in epileptic children

**A single case study concerning an individual who developed seizures and hyponatremia following excessive consumption of diet drinks. It is impossible to say if the seizures were caused by aspartame, caffeine or if they were simply the side-effect of hyponatremia in general.

My conclusions: Research on this symptom is very limited but there is no reason to suspect that aspartame plays any direct role in causing seizures in the wider population. Some correlations exist between aspartame intake and exacerbation of existing seizure symptoms, but even there the evidence is conflicting.

14) Does aspartame cause allergic reactions?

No (3 studies; 61; 62; 91)
Yes (-)
Maybe(-)

My conclusions: There is no evidence to suggest that aspartame causes allergic reactions. In test subjects who claimed sensitivity to aspartame, no connection was found in blinded clinical trials compared to placebo. It is possible that a negative bias towards aspartame results in scapegoating it to explain non-related ailments.

15) Can aspartame cause depression or mood swings?

No (1 study: 91)
Yes (-)
Maybe (2 studies; 52*; 90**)

*Depression symptoms were increased in test subjects who had a prior history of depression.

**Researchers admitted faults in study design concerning washout periods and a low and homogeneous sample size.

My conclusions: There is some reason to conclude that aspartame is related to depression and mood swings. However, this relation is not completely clear. Similar to headaches and various neurological issues, aspartame may exacerbate already existing symptoms. The threat of aspartame being the root cause of developing these issues seems to be low.

16) Is aspartame intake dangerous during pregnancy?

No (-)
Yes (-)
Maybe (1 study; 69)

My conclusions: There isn’t a whole lot to be found on this topic. No clinical trials, which isn’t really surprising considering that it’s highly unlikely for any mother to want to experiment with their pregnancy. Not to mention that ethical committees probably wouldn’t sanction such experiments anyway.

I did come across a research paper that examined the possible situation of heterozygous mothers carrying the alleel for phenylketonuria. In such incidences it is possible that a high enough aspartame intake could negatively affect the fetus. However, because of the rarity of such conditions, it isn’t applicable to the general population.

17) Does aspartame affect gut microbiota?

No (1 study: 95)
Yes (-)
Maybe (-)

My conclusions: There is no data to indicate aspartame has any effect on gut microbiota. Aspartame is very rapidly digested and none of the resulting particles reach the large intestine.

At this point I’ll end the analysis of the most commonly researched symptoms and topics relating to aspartame safety. Keep in mind that I only looked at human trials as they are by far the most relevant. As a finishing touch I will add a few more interesting findings that didn’t fit into any specific symptoms or topics.

Aspartame consumption seems to have a beneficial effect for patients suffering from sickle cell anemia and may be able to reduce the amount of faulty red blood cells. (80)
Aspartame does not seem to negatively affect people suffering from Parkinson’s disease. (81)
Aspartame seems safe for diabetics suffering from renal failure. (82)
Aspartame appears to be safe for diabetics. (83)
Aspartame may be linked to an earlier onset of menarche. (93)

Final Conclusions:

Aspartame is a substance that has been researched very thoroughly, even though actual clinical trials on humans are still limited in many cases. For some claims or symptoms, it is not yet possible to make a definitive argument for safety or danger. However, the vast majority of research has been either neutral, finding little effect on anything – or even positive, finding benefits to weight management and weight loss. Nearly all of the research that has discovered negative effects, is questionable – often finding nothing but correlations in specific subgroups of people.

My personal opinion is this:

The many dangers attributed to aspartame intake have been grossly blown out of proportion, misunderstood or simply flat out fictional. It seems that the majority of negativity towards aspartame originates from a few conspiracy websites run by a small number of people and then propagated by the gullible and frightful public. (85) Factual, scientific evidence needed to support most of these claims against the safety of aspartame simply do not exist. Most anti-aspartame campaigns cite ridiculous rat-studies to support their arguments. Studies that use incredibly extreme doses of raw aspartame, often injecting it directly into the brains or the blood stream, causing side-effects that simply would not happen through oral consumption of the sweetener.

The fact is, that aspartame has a very practical use as a weight loss or management aid, that can help combat obesity. That in turn results in improved health markers.

Potential health risks have been examined and dismissed by numerous scientific research projects. With the exception of the risk to those with phenylketonuria, aspartame is considered to be a safe food additive by governments, worldwide, and major health and food safety organizations. FDA officials describe aspartame as “one of the most thoroughly tested and studied food additives the agency has ever approved” and its safety as “clear cut”. The weight of existing scientific evidence indicates that aspartame is safe as a non-nutritive sweetener. (85)

I am not alone in this opinion:

Aside from the various scientists, governments and food industry officials I have already cited, some of the best and most well respected nutrition experts also agree. On the questions of “Is aspartame safe?”,

Martin Berkhan from leangains.com wrote the following:

…the consenus is that aspartame is very safe for human consumption, and I have nothing against it.
Also, I should note that the rodent studies used such extreme dosages that it would be impossible for any human to ingest that amount save from walking around with an IV-drip of pure aspartame 24/7.

Lyle McDonald from bodyrecomposition.com wrote this:

In predisposed rats fed absolutely horse doses of the stuff (the amounts given in these situations are so far beyond what any human could conceivably consume), there may be an issue and this is where the scaremongering about the compound comes from. But consider that aspartame is simply a combination of the amino acids phenylalanine and aspartic acid, both found in dietary protein. Most of the fear comes out of an oddity whereby there can be a conversion of one of the amino acids to methanol. But that occurs with compounds found in fruit as well. Honestly, I consider most of the fear mongering about the stuff to be out in left field, some people just need for something to be ‘the enemy’. And they choose aspartame. But unless you’re getting the equivalent of like 200 cans of soda per day (or whatever the insane rat dose works out to), it’s just not an issue.

James Krieger from weightology.net wrote:

The whole “Aspartame is poison” thing is ridiculous…
I’ve seen… “documentaries” (*about aspartame) before, as well as reading the book “Sweet Deception”. These documentaries and books are filled with half-truths, distortions, and flat out fabrications

Alan Aragon from alanaragon.com writes:

Its “badness” depends on the dose.
FDA’s estimate of acceptable daily intake for aspartame is limited to 18-19 twelve-ounce cans per day. If you’re really worried about it, stop at your 12th can.

Armi Legge, Editor-in-chief at legionathletics.com had this to say:

Studies have repeatedly shown that you’d have to consume ridiculous amounts of aspartame to even get close to a potentially harmful level. Or, about three, two-liter bottles of diet soda. But, those recommendations already have a large safety margin built in, which means the amount you’d have to drink to actually cause harm is likely much, much higher. Aspartame is one of the most widely tested calorie-free sweeteners on the planet, and so far it’s been shown to be safe.

With all that said, aspartame is not without potential side-effects. However, the same can be said for every drug, supplement or even any food source on the planet. Roughly 1% of the population is allergic to nuts for example, far, far beyond the number of people likely to be affected negatively by aspartame. Yet I see no world-wide health campaigns against the consumption of nuts.

It seems to me, that aspartame is a victim of negative bias, largely because of its origin. It is a man made substance that causes people to fear it as something unnatural and dangerous. To everyone who feels this way, I would like to remind you that countless forms of medicines are man made and utterly unnatural, yet still save countless lives every day. Furthermore, keep in mind that some of the most dangerous diseases and ailments ever recorded, have come from nature and have existed far before the time of man. The fact is, that nature is filled with things out to kill us, it isn’t all rainbows and butterflies.

Do not judge something simply based on its origin or rumors and hearsay. Be objective, reasonable and use logic to validate opinions and claims.

– Aspartame-Research Team