Don’t Eat Fruit Bats, and Avoid Algae Blooms!

The people with the world’s highest risk of Lou Gehrig’s disease were the Chamorro people, who were the native people of Guam. These people also had a high risk of Alzheimer-like dementia and disorders like parkinsonism. The problem didn’t seem to be genetic or contagious, and the diseases became less common when the population became more Americanized after World War II. These facts suggested that the problem resulted from something that the people had been eating.

The prime suspect in this case is a neurotoxin called BMAA (beta-methylamino-L-alanine). It’s similar to the amino acid alanine that your body uses in making protein. When BMAA was given to rhesus macaques, the resulting damage to the nervous system was similar to what was happening to the afflicted people on Guam.

The BMAA originally came from cyanobacteria. The cyanobacteria are true bacteria, although they are sometimes called blue-green algae. The cycad plant, which was an important food source for the Chamorro people, has a partnership (symbiotic relationship) with cyanobacteria of the genus Nostoc. The cycads give some sugar to the Nostoc living on their roots. In return, the Nostoc convert some of the nitrogen from the atmosphere into ammonia, which the cycad can use as fertilizer.

Unfortunately, the Nostoc also make some BMAA, which is also absorbed by the cycad. The Chamorro people then were exposed to BMAA when they ate seeds from the cycad plant. They got an even bigger dose of BMAA when they ate fruit bats, because the BMAA had become concentrated in the bats’ bodies. This process of concentration is called bioaccumulation.

There are two take-home lessons from this story. The first is that we may need to be careful about human exposure to cyanobacteria. All types of cyanobacteria but only cyanobacteria produce BMAA. Human beings could be exposed to BMAA as a result of the toxic algae blooms that are becoming increasingly common because of fertilizer runoff. People could become exposed to BMAA by drinking or swimming in contaminated water, such as the water in ponds and reservoirs. They could also be exposed to BMAA through cyanobacteria in foods or supplements made from algae.

The second lesson is that BMAA, like many other toxins, becomes more concentrated as you move up the food chain. Fruit bats contained more BMAA than the cycad seeds did. Other toxins, such as dioxin and mercury, also concentrate as you go up the food chain. It’s another reason why it’s better for us to eat plants, not animals.

Photo by Tambako the Jaguar

21 thoughts on “Don’t Eat Fruit Bats, and Avoid Algae Blooms!”

  1. Hi, I'm a little disturbed by the way you portray a medical experiment involving the intentional poisoning of monkeys in a positive light. You often do cite cruel animal studies as being educational. Obviously, that was not the only way to learn about BMAA (and it is questionable to assume the same result in humans), and it was obviously a horrible experience for the macaques. Can you write an article explaining your views on animal testing?


  2. Hi Fraggle.
    I think it would be a tragic mistake to ignore the results of any scientifically valid study, regardless of whether one approved of how or why it was done. I often write about the lessons we've learned from the consequences of wars or famines. That doesn't mean I approve of wars or famines.

  3. I really love your site.

    I have been a vegetarian since 1979. Recently, I have made the step towards raw vegan.

    I love fruit. However, I have a few reservations and am wondering if you could kindly help clear up these nagging doubts, or direct me to where I could get some answers, please?

    Dr Robert Lustig who appears to be an eminent academic and author raises the issue of cholesterol and other health issues w.r.t. fructose, saying that it is not high fat diets that are dangerous, but diets high in fructose. His book is entitled Sugar: The Bitter Truth.
    Of course, fruit has fructose, and the amount of fibre they contain wouldn't alter that, except to affect the rate of absorption. There is also the aspect that fructose is metabolised differently to sugar, that is, that it is metabolised in the liver, which could lead to liver issues when consumed abundantly, as I suppose would be the case in a diet predominantly of fruit.

    The other issue is that of carbohydrates. Certain research points to high carbohydrate diets affecting cholesterol levels, in particular LDL and triglycerides. A book in this connection is Gary Taubes’ Good Calories, Bad Calories.

    Then of course, there is the glycemic index and glycemic load slant to the argument.

    By eating a lot of fruit, even if the fruit selected is low glycemic, having large quantities in one's diet would nonetheless ensure that there is a sharp spike in the insulin level by virtue of the glycemic load. In other words, the sheer quantity will cause a spike in insulin, which is not only bad for maintaining one's weight, or losing body fat, but high insulin damages cells, and can lead to insulin resistence.

    Please could you help?



  4. Hi Chris:

    Why are you worried about these things? Are you sick or overweight now? If so, I strongly recommend that you ask a registered dietitian for dietary advice.

    I can't give you personal advice, but I can explain some relevant data. When Chris Voigt ate practically nothing but potatoes for 60 days, he lost 21 pounds and ended up with dramatically lower cholesterol and fasting blood sugar levels.
    I think it's nuts to eat only one food for an extended period, but his publicity stunt debunks the theory that high glycemic load foods necessarily make you fat, give you high cholesterol, or make you diabetic.

    The fructose in fruit is so dilute that most people would have to be forcibly fed to get enough fructose from fruit to have serious health problems. On the other hand, you could easily end up with trouble from eating too much honey or agave syrup or table sugar or high-fructose corn syrup, especially if you are adding those things to a fatty, high-cholesterol diet.

    For completeness, I should mention that some people have particular problems with fructose. There's a rare hereditary disease called fructosemia or hereditary fructose intolerance.

    There's also an unrelated condition called fructose malabsorption that's fairly common in people of central European ancestry.

  5. After the Nazis invaded Norway and stole the Norwegian people's farm animals during WWII, the incidence of new cases of multiple sclerosis in Norway dropped precipitously. Existing cases tended to stop progressing. That was just one piece of evidence suggesting that eating a fatty diet based on animal-source foods is a necessary cause of multiple sclerosis. If you correct the diet, the multiple sclerosis stops progressing.

  6. I am reading your book _Not Trivial_ and wanted to see what you thought about Dr. Lustig. I've watched 3 of his videos recently. His big concern is that in processed foods when Dr's warned about fat, in order to reduce fat and to make food still taste good, food makers started adding a lot of fructose to foods. He didn't seem to me very concerned about fresh fruit. He was very convincing. I am inclined to think a balanced diet is best, but what that is is debatable. I try to eat rice, mixed vegetables, and fresh fruit regularly. I also eat a little meat occasionally. I have been unable to altogether resist chocolate. I have type 2 diabetes but it is well controlled. I also wonder about aspartame, which I have read bad things about. I have avoided it altogether for several years (in fact all pop).

  7. Processed foods are generally devoid of fiber, which is a good reason to avoid them. I think that "balance" and "moderation" are dangerous concepts in nutrition. As Caldwell Esselstyn pointed out, "When it comes to lowering cholesterol, moderation kills." People use the word "balance" to imply that you should continue to eat foods that come from animals. If you have type 2 diabetes, you might want to consider going to either Dr. McDougall's program or the Rice Diet program. They can teach you how to become undiabetic.

  8. Nixon was motivated for political reasons (1972) to encourage high fructose corn syrup.
    Dr. Robert Lustig's 90 minute video on fructose.

    He says the fructose in fresh fruit is not a problem because of the higher fiber.
    He seems to think the biggest problem is soft drinks, but does not talk at all about aspartame.

    I have also read:
    Sweetly Seduced – by NJ Rickman
    Suicide by Sugar – by Nancy Appleton, PhD and G. N. Jacobs

    Also on Aspartame.
    Regan was involved: (his appointee to FDA overturned FDA decision, and later moved to company making aspartame)

    So was Rumsfeld: (He was president of company making aspartame)

    I have also read:
    ASPARTAME (NutraSweet*) Is It Safe? By H. J. Roberts, M.D.

    Of course, the involvement of Nixon, Regan and Rumsfeld does not prove the dangers, but does supply motive to suppress the truth.

  9. There's a bit of a misunderstanding about sugar and fat. The excess sugar that people are getting from processed foods such as soft drinks generally does not turn into fat. Instead, the body burns that available sugar right away and then stores the surplus fatty acids from the food as fat. Although the human body can convert sugar to fat, that conversion doesn't generally happen to any significant degree until the amount of sugar that the person is eating is greater than the total energy expenditure.

    There's a huge amount of antisugar nonsense being spread by the popular media. One popular theory is that excess sugar consumption causes diabetes by causing the pancreas to wear out. Lustig believes that fructose causes hypertension. Yet when Walter Kempner taught his patients with malignant hypertension to eat a diet consisting of rice, fruit, and sugar, their blood pressure came down, they lost weight, and their insulin sensitivity improved. If Lustig's theory that fructose causes hypertension were correct, then their blood pressure would have gone up, not down, wouldn't it?

    As for aspartame, do we have any evidence that any particular health problems suddenly became more common after the introduction of aspartame?

  10. According to Dr. Lustig, (he gives a detailed biochemistry lesson in the 80 minute video U gave a link to) we can only digest glucose directly for energy. What we call table sugar or sucrose is about 1/2 glucose and 1/2 fructose and the same is true of high fructose corn syrup. (they are actually larger molecules which break down quickly into these.) From what I have been able to learn, starches as rice and potatoes break down close to 100% glucose. The fructose must be processed by the liver, and causes problems like alcohol. Also one would have to know what Walter Kempner's patients diets were before his test and/or compare to other specific diets.

    Also on aspartame:

    Also, my personal notes are at:

  11. I've read more on your blog, and you and Dr. Lustig do not really seem that far apart. Some of the facts I cited above I got from Dr. Lustig, but are also on your blog. As for aspartame, as a practical matter, I cannot see how it can have any benefit. Tho only one would be to eliminate sugar, but I have stopped all soda pop, and try to avoid too much sugar in other sources,
    although I do not do as well as I would like.

  12. Kempner's patients were eating the standard fatty American diet back in the days before there were any drugs for lowering blood pressure. His diet wasn't a "test diet." It was the standard diet that he recommended to all his patients over the course of many years. Sadly, the Rice Diet program just closed its doors this month, after 70 years of helping people lose weight and recover their health.

  13. The main difference between you and Dr. Lustig is that he finds the main dietary problem to be fructose and you find it to be fat. However the main fructose he wants to avoid is from processed foods, which you also say to avoid. He thinks, at least in some cases, body fat results from too much fructose. My experience is that as I eat a moderate amount of sugar, my glucose level stays OK. Also I I have had my triglycerides and cholesterol well under control. Twenty years ago I had a terrible diet. I just didn't know how to eat. I got way too much of booth sugar and fat. My experience is that after one goes past some threshold (hard to determine) your body loses the ability to handle either of these.

  14. Thanks very much for that link. I am still inclined to believe one can consume too much sugar (partly from my personal diet & glucose records) – at least if you are diabetic. The thing that seems to help my diabetes most, besides medicine, is controlling my weight..

  15. Type 2 diabetes is the body's attempt to prevent further weight gain on a fattening diet. If you add extra calories of any kind to an already fattening diet, such as by drinking sugary sodas, you will make the problem worse. Keep in mind that the high blood sugar levels are merely an effect of type 2 diabetes, albeit an effect that can lead to complications. The goal in managing type 2 diabetes should be to restore normal sensitivity to insulin, not just to control the blood sugar levels. The commonly used dietary and medical approaches to managing type 2 diabetes merely focus on controlling the blood sugar, not on restoring normal sensitivity to insulin. By urging people to go on low-carb diets, doctors are keeping their patients' blood sugar more or less under control but keeping them diabetic.

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