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Archive for the ‘Science’ Category

Do vaccines prevent disease?

Monday, January 13th, 2014

Here’s an interesting graph comparing disease prevalence before vaccines and now:
disease pre and post vaccination

This is quite a strong correlation, but how do we know that vaccines caused the diseases to become so rare? Did vaccines causes disease incidence for all these diseases to bottom out, or is it something else, say a coincidence, or maybe all diseases are just disappearing because Americans are healthier today?

So more information is needed. The first thing to consider is that all infectious disease hasn’t gone away. The cold is still as common as ever. Kids still get sore throats and ear aches. There are also the ones I don’t think about or haven’t heard of, like RSV, croup, Fifth disease. And looking at adults, clap, HPV, and gonnorhia are at epidemic levels. So infectious disease is still very common, but the worst diseases have become rare–the ones for which general vaccination is practiced .

Another line of evidence that vaccines are what stomped out the targeted diseases is the timing. They didn’t all disappear at once, not even close. What was observed is that each disease dropped off after widespread vaccination became common.

Here’s a study that looked at incidence for several disease in the US over decades: pdf

If you look at page 4, they summarize incidence over time for 8 diseases. At the top they summarize incidence. The colored section of the graph is detailed regional data. The grey vertical bar shows when widespread vaccination was introduced–a different year for each disease. After the vaccine is introduced, the disease incidence goes way down. Note that for smallpox, it was better vaccines replacing ones started in the 1800’s, so no grey bar is shown.

Here’s a simpler graph of measles from the CDC site:
CDC measles
measles incidence in the US

So it isn’t general health or healthier people with immune systems that prevent disease causing a gradual decline in infectious disease. Instead, the incidence of a specific disease drops when the vaccine is introduced.

Rotavirus

And here’s one of the new vaccines–for rotavirus. Nearly all kids used to get it: “four of five children in the US had symptomatic rotavirus gastroenteritis, one in seven required a clinic or emergency department (ED) visit, one in 70 was hospitalized”. The vaccine was introduced in 2006 and the disease has already become much less common: CDC Surveillance of Rotavirus

clinical lab rotavirus findings
See fig 4 especially.

So what I conclude from these lines of evidence is that the introduction of widespread vaccination for a disease causes it to become much, much less common.

Dinosaur coloration

Thursday, January 9th, 2014

In the last decade or so, dinosaurs have started being depicted as brightly colored. The reason for the trend of brightly colored dinosaurs in movies is that in recent years techniques for identifying pigments from fossils have been developed, using electron microscopy and ion bombardment mass spectrometry.

News report: Ancient Pigments Unearthed: Fossilized skin reveals the colors of three extinct marine reptiles by Ed Yong. The Scientist, January 8, 2014
Original article: (Abstract) Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles. Lindgren et. al., Nature 08 Jan 2014

and news report: Pictures: Dinosaur True Colors Revealed by Feather Find, Chris Sloan, National Geographic Daily News
Original article: Zhang et. al., 2010

Fossil color studies were pioneered by Jakob Vinther at Yale

No doubt movie speculation is running far ahead of the science, but these are the discoveries that unleashed the trend of brightly colored dinosaurs. At this point, it is reasonable to think dinosaurs are as brightly colored as birds or reptiles are today, and in some cases the coloring of specific species is known.

ABI 377 Teardown

Thursday, January 2nd, 2014

I picked up two ABI PRISM 377 DNA sequencers. These are the last generation of slab gel sequencers.
ABI 377

ABI 377

With the front open, you can see the place where the gel gets mounted.

gel door open

The left side opens, and the bottom cover comes off. The laser can be seen at the bottom, and some of the power supplies on the left.

Open cabinet

Here is the laser, a Uniphase Argon laser, 0.5W 2214-40MLA 1998.

laser
laser

The power supply modules are located on the left side. On the top left is the laser power supply. The electrophoresis power supply is on the left in the middle. To the right of it is the power distribution center–plugs for the laser and electrophoresis power supplies, and the blower motor. On the bottom at the left is the blower motor. In the middle at the bottom the top of a mirror module that bounces the laser back to the right at the level of the bottom of the gel. On the right at the bottom, the servo motor that moves the detector unit along the bottom of the gel.

left side

Here’s the laser power supply. The laser is not plugged in.
laser power supply

Close up of the laser power supply, Uniphase 2114B-40MLA 12A:
laser power supply

The power distribution center labels: J41 DC Power Supply Max 4000W J40 Heater and Pump Control

The electrophoresis power supply: Spellman P/N X2094 Rev. E4 Model No PTV5P300X2094
230V 5A, output 0-5kV, 0-60mA.

Here is a closeup of the servo: Telcomm brushless servo motor
servo

On the back side of the machine behind the top panel is this circuit board, the control, data processing, and interface board.

main board

Two interesting chips on the board, a FPGA and a pair of voltage converters.

xilinx
The FPGA is a Xilinx XC3064A

The voltage converter.
voltage converter

On the left of the main board is region with cooling lines:
pump area

The Metabolic Theory of Cancer

Saturday, September 21st, 2013

Notes on “What Is The Origin of Cancer?” by Travis M Christofferson.

The most useful thing about this article is that it reminded me of the 2010 book, “The Emperor of all Maladies”, by Siddhartha Mukherjee.

The article has is divided into a few sections: a description and dismissal of the genetic theory of cancer, a discussion of the Cancer Genome Atlas project and a dismissal of it, and then the metabolic theory of cancer is described and touted.

The article starts by making some assertion about cancer to frame the discussion. “We are not winning the war against cancer; we are no closer to cures than when Nixon declared the war on cancer in 1971 – in fact, we may be further away.” Cancer has proved a difficult disease–there have been some improvements in survival times in some types of cancer, some cures, but the change in overall cancer treatment has been modest. Currently, a number of targeted cancer drugs are being used and making a difference. Let’s call them 2nd generation drugs to differentiate them from the chemotherapy drugs that kill dividing cells indiscriminately. There are also a bunch of new therapies, several different kinds currently in the works, let’s call them 3rd generation treatments.

In 1971, when the big push to cure cancer began, the difficulty wasn’t clear. At that time, not much was known about what caused cancer and how it progressed. Now we have a decent understanding of it, and there are *several* promising approaches that could substantially improve treatment and outcome.

We’ve understood cancer pretty well for some time, since the 90’s. Unfortunately, treatments have been hard to come by. Treatments are technology, and cancer is a hard nut to crack. Cancer is a body’s cells dividing without limit. These cells start ignoring the signals and controls that keep cells dividing only when and where they are needed. A treatment for cancer needs to get these cells to stop dividing or kill them. It is difficult to treat cancer for two reasons: 1) cancer cells are human cells, so treatments that kill cancer cells and bypass normal cells are hard to engineer, and 2) cancer evolves to resist treatments.

The second factor is the real killer. Think of a cancer of as a population of millions of cells, each a bit from the others due to mutations in DNA or other changes. A treatment that kills almost all of them leaves thousands that are resistant to the treatment. They continue growing and picking up more changes. A second, different treatment will have the same effect. While some of these changes make cancer resistant to treatment, others allow it to escape other limits. A growing tumor runs out of space and out of blood. So cells that can invade surrounding tissue or metastasize to a new place in the body are also successfully evolved tumor cells.

Cancer treatments usually run through these cycles: a treatment initially has great success, but then the cancer comes back. Some cancer cells have survived and they grow and divide and the tumor comes back, changed. If a treatment is repeated, it is less effective each time.

So a cancer cell is a cell that has changed to ignore the normal signals to stop dividing, and as a tumor grows cells that have additional changes keep occurring. Whether a change to a cell’s DNA or metabolism starts it dividing, the process will continue and the cancer cells will keep changing to ignore or bypass things the keep them from dividing. So if a diet change robs cancer cells of glucose or metabolic changes signal them to stop dividing, some cancer cells will not stop dividing and the cancer continues.

A number of genes are known to play a role in cancer, mutations in oncogenes or tumor suppressor genes are found in all (or pretty much all) cancers. The role of mutations in causing cancer is the Somatic Mutation Theory of Cancer. Changes to genes that are involved in controlling cell division allow cells to ignore the normal checks on cell growth and division.

When the Cancer Genome Atlas Project began, years of research had already identified the main cancer genes (hundreds of genes). This link summarizes the project (TCGA). The idea is to get a comprehensive look at what genes are changed in different kinds of cancer at different stages of the disease. Not really expected to be revolutionary, instead just round out the genetic picture of cancer.

A number of 2nd generation cancer drugs target these cancer genes. They knock down cancer for a while, and give patients added months of life. Eventually, the cancers pick up mutations in other genes and bypass the drug. So these drugs usually don’t cure cancer. New methods of characterizing cancer are beginning to reach the clinic that allow each patient to get the drug that targets the genes mutated in their cancer, so these drugs are becoming more effective.

I’ve met Bert Vogelstein, he’s an intense guy. He discovered how p53 mutations cause cancers, and the most common colon cancer gene, APC. He played a role in fleshing out the somatic mutation theory of cancer. The theory is holding up well–sequence a tumor’s DNA, and known cancer genes show up with mutations.

Cancers aren’t all the same. Each one is a cell that pciked up mutations and started dividing and then picked up more mutations. There are lots of cancer genes, so different tumors pick up different mutations, in different orders. The different types of cancer arise from different types of cells. For a particular cell type, it is easier to start dividing if certain genes mutate (a gene already turned on in a cell, for example) so certain cancer genes are common in different types of cancer. There is also a lot of flexibility as cells pick up mutations and lots of potential cancer genes, so each cancer is unique. This has been known for a long time in general terms, but new techniques are allowing each cancer to be characterized in detail. Volgelstein’s review in the journal Science describes this.

The metabolic alterations in cancer have been known about for a long time–biologists developed tools to study biochemistry before the method for genetic studies came along. Cancer cell’s great demand for glucose has been known for a long time. Cell growth and division and metabolism are tightly linked, so changes in cancer genes change cell metabolism and vice versa.

Can changing diet, starving a cancer of glucose stop it, cure it, or at least put it on hold permanently? I can only find a few published studies, mostly in mice. It seems like it may be effective in slowing the progression of some types of cancer, at least temporarily. However, ketogenic diets have been known about for a long time, and trying them for cancer seems obvious. So if it worked well for cancer, it seems likely it would be well known by now.

Thomas Seyfried has worked on cell metabolism in cancer for a long time. He has a book out on his work, and wrote a review for the Medscape site.

In the Medscape article, Seyfried calls “impaired cellular energy metabolism is the defining characteristic of nearly all cancers regardless of cellular or tissue origin”. This claim seems way too strong. There are many defining characteristics of cancer–things that differentiate it from normal cells. Each one is a potential line of attack on tumor cells, a target for drugs or other treatments. Hopefully, treatments that target metabolic changes can be developed, in addition to Metformin. They would be as welcome, and as profitable for drug companies as any other cancer drug. Most likely, treatments targeting cancer cell metabolism can be effective and retard cancer progression for months, but populations of cancer cells evolve, and they will most likely evolve to bypass each metabolic restraint.

Christofferson’s article touts the metabolic theory all out of proportion to the evidence for it.
He writes that a ketogenic diet cures cancer. He takes the disgraceful step of pulling out a few cases where cancer was ‘cured’ by this diet. Every one of the hundreds of scam cancer treatments comes packaged with patient testimonial ‘cures’. Christofferson quotes Seyfried as saying “If one was able to patent and package the ketogenic diet as a pill for cancer it would be a blockbuster”, but if you read Seyfried’s article in Medscape, written for doctors, he doesn’t make this claim. Either Christofferson or Seyfried isn’t being honest with us.

App ideas

Thursday, April 18th, 2013

Micro movement sensing

Use the orientation sensor in a cell phone to monitor small regular movements. For example, the movement due to the heart beat. It might be possible to measure breathing movement. It may also be possible to measure anomalous movements–tremors, the sway due to microadjustments involved in standing.

Also, if the heartbeat moves a phone to a noticeable degree, does this make cell phone photos blurrier? If so, add heartbeat detection to the camera app–have pictures be snapped between heartbeats.

Basically, orientation data would be collected, and a frequency analysis done to detect the freq and amplitude of the movements. I don’t know how fast the orientation can be polled. If it is too slow, it may be possible to use intermittent polling at precise times to identify the frequency of movements.

Shadow boxing

A related use would be as a shadow boxing app. This would clearly be better as a wrist strap standalone device, but might work as an app. Hold the phone in a hand (or strap it firmly to the wrist), and follow the movements of the hand/arm, recording punches and the speed of them. The user would indicate the hand being scored in setup, and then as hands are switched, the punching of the two could be compared. Groups of friends could play together to see who can punch the fastest or do the most punches in 30s.

Spectrophotometer

This app would run simultaneously on two phones. One phone would display bands of pure red, blue, and green. A sample would be placed across one half of the bands. The second phone would take a picture of the first phone. Image analysis would compare the brightness of the control and sample covered regions and calculate absorbance in the three channels. Cell phone displays are either OLED or IMOD. There are a range of displays used in phones, so this would never be super accurate without calibration. The OLED displays seem to have fairly narrow spectrum pure colors while the iphones have broader colors.

This could be used either as an exploration tool–test substances and record spectra, or reference data could be used to make guesses at substances.

Or you could use a diffraction gratings and make a real spec.

Titan landing

Sunday, November 13th, 2011

At Windycon, I went to a talk by Christian Ready from the Space Telescope Science Institute on the solar system and saw pictures of the surface of Titan. Wow, I didn’t realize that a probe had made a landing!

Surface of Titan

The surface of Titan as seen by Huygens after its landing on January 14, 2005. (credit: ESA/NASA/JPL/University of Arizona)

Book review: Parasite Rex

Tuesday, March 1st, 2011

Parasite Rex: Inside the Bizarre World of Nature’s Most Dangerous Creatures by Carl Zimmer.

Great book. About parasites. What they are, the recent discovery of how big a role they have in ecosystems, how they live, how they have jumped from animal to animal, and of course, which ones afflict people.

Several chapters describe a range of human parasites in amazing and often frightening detail. From botfly larvae to liver flukes, malaria’s Plasmodium to the nematodes that parasitize humans. There is some discussion of microbial parasites, but most of the book covers metazoan parasites. Zimmer tells the stories of some of these parasites–how they find their way to people, what they do once they arrive in a new host, how they escape detection, and the course of the disease. The story of how several parasites were discovered, how they were identified and followed through their changes of form and host are told. And there are pictures!

Word cloud of Parasite Rex by Carl_Zimmer

Fluoridation

Tuesday, October 26th, 2010

Notes on water fluoridation and the Fluoride Deception video

I’d heard of the great water fluoridation fight but never looked into it. In the 60’s the John Birchers were saying it was a Commie plot to weaken America’s vital fluids or something of the sort. And it was parodied in the movie Dr. Strangelove…

Let’s start by bracketing things. Fluoride in water can’t be highly dangerous or people would have noticed. Not putting fluoride in water is not a risk-free choice–it prevents cavities. Cavities don’t just make your teeth fall out, they also increase risks of bacteria related heart disease, and the occasional person dies of a tooth abscess. So the question is, is there disease caused by fluoridation, and is it worse than the diseases caused by no fluoridation?

OK, let’s look at the video.
5:42 Suggests that the idea of adding fluoride to water supplies was to hide the dangers of for fluoride pollution or avoid responsibility for damage due to fluoride pollution. Doesn’t really make sense so far. Ah, reading in the history, when government regs made industry stop dumping fluoride in air and water, one thing they did with it was process out fluoride for water fluoridation. Doesn’t sound that damning, after all it would have been cheaper to dump it in a landfill.

~7:00-20:00 Fluoride air pollution can be bad. Some of the early fluoride researchers also worked on and perhaps had a part in the worst cover ups regarding industrial pollutants. What I’ve read of the tetraethyl lead story is appalling. The connection with the lead story is tenuous. Fluoridating water wasn’t a gold mine, I don’t see there being much pressure to push fluoridation back when it started.

21:30 The NRC report (below) discusses Waldbott’s results, concludes that some people are sensitive to typical water concentrations of fluoride and that it appears to be fairly rare.

From the NRC report, it doesn’t appear that the safety of water fluoridation was well-established, certainly nowhere near today’s standards, back when it began. It was safe by 1940’s standards, and had a clear benefit. I’ve probably got an extra tooth in my mouth due to it.

25:00 The NRC report discusses the Mullenix study. Calls it inconclusive, calls for more studies.

The video didn’t have much info. Here are the establishment reference sources:

CDC recommendations

Fluoride reduces cavities by 15-40%, depending on the study. The low figure is an estimate of the benefit of water fluoridation in a population that already uses fluoride toothpaste.

2006 National Academy report (the greybeards)

Here’s the meat! Water fluoridation is 1 mg / L, when the level hits 4 mg / L studies start seeing negative health effects. That’s a pretty narrow window between benefit and danger level, the smallest one for an environmental exposure I’ve run into. YMMV, I’m not an environmental toxicologist.

What hasn’t really been studied are neurotoxic effects of low level exposure. A few studies have turned up disturbing results. Check out the summary on page 205.

Interesting take on differences between Europe and US fluoridation, Pizzo et al. 2008

The bit about Europe in the video is misleading. Europe hasn’t avoided fluoride, it’s just mostly not in water, it’s in salt or toothpaste.

Internet rumors that aspartame is deadly

Wednesday, October 20th, 2010

Many internet sources claim aspartame is dangerous to human health. This is an example:

Aspartame has been renamed and is now being marketed as a natural sweetener

Friday, February 12, 2010 by: Ethan Huff, citizen journalist

(NaturalNews) In response to growing awareness about the dangers of artificial sweeteners, what does the manufacturer of one of the world’s most notable artificial sweeteners do? Why, rename it and begin marketing it as natural, of course. This is precisely the strategy of Ajinomoto, maker of aspartame, which hopes to pull the wool over the eyes of the public with its rebranded version of aspartame, called “AminoSweet”.

Yeah, tell it to the slimehead (aka, orange roughy) or to rapeseed (aka, canola).
slimehead
rapeseed

Over 25 years ago, aspartame was first introduced into the European food supply. Today, it is an everyday component of most diet beverages, sugar-free desserts, and chewing gums in countries worldwide. But the tides have been turning as the general public is waking up to the truth about artificial sweeteners like aspartame and the harm they cause to health. The latest aspartame marketing scheme is a desperate effort to indoctrinate the public into accepting the chemical sweetener as natural and safe, despite evidence to the contrary.

Aspartame was an accidental discovery by James Schlatter, a chemist who had been trying to produce an anti-ulcer pharmaceutical drug for G.D. Searle & Company back in 1965. Upon mixing aspartic acid and phenylalanine, two naturally-occurring amino acids, he discovered that the new compound had a sweet taste. The company merely changed its FDA approval application from drug to food additive and, voila, aspartame was born.

G.D. Searle & Company first patented aspartame in 1970. An internal memo released in the same year urged company executives to work on getting the FDA into the “habit of saying yes” and of encouraging a “subconscious spirit of participation” in getting the chemical approved.

Of course they wanted their new product approved. Pet peeve of mine: Unsourced quotes of a fraction of a sentence. Often misleading, or copied from somewhere else, and so on leading back to who knows where.

In 1976, then FDA Commissioner Alexander Schmidt wrote a letter to Sen. Ted Kennedy expressing concern over the “questionable integrity of the basic safety data submitted for aspartame safety”. FDA Chief Counsel Richard Merrill believed that a grand jury should investigate G.D. Searle & Company for lying about the safety of aspartame in its reports and for concealing evidence proving the chemical is unsafe for consumption.

A claim! Let’s google around. Here’s some info:

The History of Aspartame by Ashley Nill

This law article has more details of the aspartame approval process. This section is relevant:

The first obstacle that Searle met came from Dr. John W. Olney, M.D., psychiatrist and Professor of Psychiatry at Washington University of St. Louis, and James S. Turner, author of The Chemical Feast, and co-founder of the Center for Study of Responsive Law.[30] Olney and Turner formally objected to the regulation that authorized the marketing of aspartame as a sweetener in foods.[31] Dr. Olney had performed research in animals regarding the toxic effects on the brain of certain Amino acids, including asparatic acid. Both parties objected to the use of aspartame in foods, especially those consumed by children. They asserted that aspartame might cause brain damage resulting in mental retardation, endocrine dysfunction, or both. Turner and Olney also argued that aspartame could be dangerous to persons with the genetic disorder phenylketonuria (PKU), a disorder that prevents the metabolism of phenylalanine, one of the amino acids in aspartame.[32]

These along with other concerns and allegations necessitated a FDA hearing provided for by 21 U. S. C. 348.[33] Instead of having a full evidentiary hearing, which was customary at the time, the parties waived their right and accepted a hearing before a public board of inquiry instead.[34] This was the first time that the FDA had ever used this type of hearing in place of a full evidentiary hearing. Searle agreed to delay marketing of aspartame temporarily, pending resolution of the safety questions.[35]

Before the board could hold a hearing regarding the safety of aspartame as a food additive in response to Olney and Turner’s allegations, however, Searle’s quest for aspartame approval hit another snag. Preliminary results from an audit of the records of certain animal studies conducted by or for Searle, including studies on aspartame, indicated a need for a comprehensive review of the authenticity of the aspartame research data. Apparently, the audit of Searle’s clinical methods revealed “sloppy” research, including some research that was being done on aspartame.[38] The negative publicity that surrounded Searle’s clinical methods bolstered consumer criticism of aspartame, and further clouded the safety issues that had not yet been addressed. Alexander Schmidt, then FDA commissioner, noted that the FDA audit revealed “different discrepancies of different kinds.”[39] Pursuant to 21 U. S. C. 348(e), FDA formally stayed the regulation authorizing the marketing of aspartame.[40]

G.D. Searle & Company submitted its first petition to the FDA in 1973 and fought for years to gain FDA approval, submitting its own safety studies that many believed were inadequate and deceptive. Despite numerous objections, including one from its own scientists, the company was able to convince the FDA to approve aspartame for commercial use in a few products in 1974, igniting a blaze of controversy.

So, the FDA was cautious. Good to hear they don’t let companies put untested new chemicals in the human food supply. G.D. Searle & Company’s safety studies were sloppy, and this delayed the approval of aspartame until 1981, a delay probably costing the company at least tens of millions in lost profits.

It looks like G.D. Searle & Company did what it could to push and influence the approval process through means fair and foul. The worst case interpretation of the company’s actions is put forward here. It’s initial approval application in 1973 was crap but by the time 1981 rolled around enough other studies had been done for aspartame to squeak by to approval.

Wikipedia usually is a poor source for controversies and alt-med claims but its aspartame controversy article at least shows the shape of the debate.

Despite the myriad of evidence gained over the years showing that aspartame is a dangerous toxin, it has remained on the global market with the exception of a few countries that have banned it. In fact, it continued to gain approval for use in new types of food despite evidence showing that it causes neurological brain damage, cancerous tumors, and endocrine disruption, among other things.

OK, let’s look at evidence of:
“cancerous tumors”: As I wrote before 10:1 no cancer:cancer so far. Either not a carcinogen or a very weak one.

“endocrine disruption”: No evidence. The claim traces back to a hypothesis made by Olney in 1975. Basically large doses of MSG can cause stunting and he suggested the aspartic acid in aspartame would have the same effect. There was never much evidence for this idea, and by the time of this 1988 review article it was known to be false. While MSG can make a person head buzz a bit (it has this effect on me), aspartame doesn’t–so it must have a much weaker effect than MSG.

“neurological brain damage”: No evidence I can find.

This claim was rejected during the FDA approval process. Again from the History of Aspartame article:

The board had its first meetings on January 30, 31 and February 1, 1980.[65] On the first question, whether the ingestion of aspartame poses a risk of contributing to mental retardation, brain damage, or undesirable effects on the neuroendocrine regulatory system, the board found that aspartame did not pose an increased risk of brain or endocrine dysfunction.[66]

The Humphries et al., 2008 article I mentioned in the previous post is the recent source for most of these claims on the internet. But the claims in the review article are all hypotheses and maybes and don’t have any evidence behind them. In fact, aspartame’s neurological effects have been studied extensively since the controversy over its approval thirty years ago and there’s still no evidence it causes any damage to the brain.

What countries have banned aspartame? As far as Wikipedia knows, no countries have banned aspartame, certainly not US/Canada/Europe.

The details of aspartame’s history are lengthy, but the point remains that the carcinogen was illegitimately approved as a food additive through heavy-handed prodding by a powerful corporation with its own interests in mind. Practically all drugs and food additives are approved by the FDA not because science shows they are safe but because companies essentially lobby the FDA with monetary payoffs and complete the agency’s multi-million dollar approval process.

From the Wikipedia article: “In 1987, the U.S. Government Accountability Office concluded that the food additive approval process had been followed properly for aspartame.” As the discussion above notes, it was a bumpy approval, but the FDA did scrutinize it.

FDA review and approval is a barrier, the main barrier, to companies selling dangerous or ineffective products. It was designed to work in the face of corporate opposition and evasion. And it works OK–there are only a few cases where the FDA has approved something later shown to be dangerous, and while it is expensive to do the studies to prove a product safe, the FDA makes approval decisions pretty quickly.

That the FDA is a barrier to selling crap is apparent in how happy the alt-med product companies were to get Congress to exclude them from FDA oversight and how hard they lobby to keep their special status (Dietary Supplement Health and Education Act (DSHEA) of 1994).

Aspartame

Wednesday, October 20th, 2010

The artificial sweetener aspartame is about 200 times sweeter than sugar. It is widely consumed in large quantities–diet sodas contain 140-185mg per 12 oz., so a person drinking a lot of diet soda may consume a gram a day. The FDA recommends 40mg per kg body weight as a safe daily dose–about 2 grams per day for a average sized person.

In the human gut aspartame breaks down into three components: two amino acids, phenylalanine and aspartic acid, and methanol. Phenylalanine and aspartic acid, being amino acids, are a normal part of the human diet. Methanol is absorbed from the gut and converted by the liver to into formaldehyde and formic acid, both nasty but non-specific poisons. In the small amounts formed from aspartame they are thought to not be dangerous. Some foods, some normal body processes, and alcohol consumption produce methanol, though I don’t have figures as to how much.

There has been some controversy over whether aspartame is safe. There have been a few studies showing some cancer risk in animals, three recent mouse studies from Soffritti et. al. being the most convincing. Any cancer risk is thought to come from the methanol. Recent studies in animals seem to running about 10:1 no cancer:cancer. As aspartame has been in food for thirty years, there have been some large human studies, and none of them show increased cancer due to eating aspartame.

Here are American Cancer Society and National Cancer Institute pages assessing aspartame.

The other concern brought up is whether the phenylalanine and aspartic acid that aspartame breaks down into have an effect on the nervous system. In addition to being used for making protein, these amino acids are also feedstock for making catecholamine neurotransmitters. There is some evidence that a large ingestion of these two amino acids alone might throw off normal neurotransmitter levels. It’s not clear what, if any, effect this has on human brains–it clearly has no striking consequence. Any effect is of course relative–aspartame is often consumed with caffeine, a substance that clearly effects brain function. :)

This 2008 review article makes a number of alarmist suggestions but has almost no actual evidence. It’s a very odd article. A large human dose of aspartame is about 1 gram a day. The RDA for protein consumption is 0.8 g / kg day, which contains about 2 grams of phenylalanine and aspartic acid. Not all foods have an even balance of amino acids, so animals must have fair ability to buffer a diet rich in one or another.

Aspartame has been well-studied and is safe. It is still being studied–it may turn out to be a very weak carcinogen, too weak to show up clearly in the studies so far. Or have a subtle effect that screws up the rare person’s brain. Risks are relative–aspartame is certainly much better for a person’s health than the sugar it replaces. On the other hand, you can’t go wrong drinking water.