Do dietary lectins cause disease?

I’m lifting this wholesale from the NCBI site because it’s one of the more reliable articles on lectins and as it dates back to 1999, it seems to be mostly off the radar. My emphasis added.

In 1988 a hospital launched a “healthy eating day” in its staff canteen at lunchtime. One dish contained red kidney beans, and 31 portions were served. At 3 pm one of the customers, a surgical registrar, vomited in theatre. Over the next four hours 10 more customers suffered profuse vomiting, some with diarrhoea. All had recovered by next day. No pathogens were isolated from the food, but the beans contained an abnormally high concentration of the lectin phytohaemagglutinin. Lectins are carbohydrate binding proteins present in most plants, especially seeds and tubers like cereals, potatoes, and beans. Until recently their main use was as histology and blood transfusion reagents, but in the past two decades we have realised that many lectins are (a) toxic, inflammatory, or both; (b) resistant to cooking and digestive enzymes; and (c) present in much of our food. It is thus no surprise that they sometimes cause “food poisoning.” But the really disturbing finding came with the discovery in 1989 that some food lectins get past the gut wall and deposit themselves in distant organs. So do they cause real life diseases?This is no academic question because diet is one part of the environment that is manipulable and because lectins have excellent antidotes, at least in vitro. Because of their precise carbohydrate specificities, lectins can be blocked by simple sugars and oligosaccharides. Wheat lectin, for example, is blocked by the sugar N-acetyl glucosamine and its polymers. These natural compounds are potentially exploitable as drugs should lectin induced diseases be identified.

Wheat gliadin, which causes coeliac disease, contains a lectin like substance that binds to human intestinal mucosa, and this has been debated as the “coeliac disease toxin” for over 20 years. But coeliac disease is already managed by gluten avoidance, so nothing would change were the lectin hypothesis proved. On the other hand, wheat lectin also binds to glomerular capillary walls, mesangial cells, and tubules of human kidney and (in rodents) binds IgA and induces IgA mesangial deposits. This suggests that in humans IgA nephropathy might be caused or aggravated by wheat lectin; indeed a trial of gluten avoidance in children with this disease reported reduced proteinuria and immune complex levels.

Of particular interest is the implication for autoimmune diseases. Lectins stimulate class II HLA antigens on cells that do not normally display them, such as pancreatic islet and thyroid cells. The islet cell determinant to which cytotoxic autoantibodies bind in insulin dependent diabetes mellitus is the disaccharide N-acetyl lactosamine, which must bind tomato lectin if present and probably also the lectins of wheat, potato, and peanuts. This would result in islet cells expressing both class II HLA antigens and foreign antigen together—a sitting duck for autoimmune attack. Certain foods (wheat, soya) are indeed diabetogenic in genetically susceptible mice. Insulin dependent diabetes therefore is another potential lectin disease and could possibly be prevented by prophylactic oligosaccharides.

Another suspect lectin disease is rheumatoid arthritis. The normal human IgG molecule possesses carbohydrate side chains, which terminate with galactose. In rheumatoid arthritis much of the galactose is missing, so that the subterminal sugar—N-acetyl glucosamine—is exposed instead. These deficient IgG molecules feature strongly in the circulating immune complexes that cause fever and symptoms. In diet responsive rheumatoid arthritis one of the commonest trigger foods is wheat, and wheat lectin is specific for N-acetyl glucosamine—the sugar that is normally hidden but exposed in rheumatoid arthritis. This suggests that N-acetyl glucosamine oligomers such as chitotetraose (derived from the chitin that forms crustacean shells) might be an effective treatment for diet associated rheumatoid arthritis. Interestingly, the health food trade has already siezed on N-acetyl glucosamine as an antiarthritic supplement.

Among the effects observed in the small intestine of lectin fed rodents is stripping away of the mucous coat to expose naked mucosa and overgrowth of the mucosa by abnormal bacteria and protozoa. Lectins also cause discharge of histamine from gastric mast cells, which stimulates acid secretion. So the three main pathogenic factors for peptic ulcer—acid stimulation, failure of the mucous defence layer, and abnormal bacterial proliferation (Helicobacter pylori) are all theoretically linked to lectins. If true, blocking these effects by oligosaccharides would represent an attractive and more physiological treatment for peptic ulcer than suppressing stomach acid. The mucus stripping effect of lectins also offers an explanation for the anecdotal finding of many allergists that a “stone age diet,” which eliminates most starchy foods and therefore most lectins, protects against common upper respiratory viral infections: without lectins in the throat the nasopharyngeal mucus lining would be more effective as a barrier to viruses.

But if we all eat lectins, why don’t we all get insulin dependent diabetes, rheumatoid arthritis, IgA nephropathy, and peptic ulcers? Partly because of biological variation in the glycoconjugates that coat our cells and partly because these are protected behind a fine screen of sialic acid molecules, attached to the glycoprotein tips. We should be safe. But the sialic acid molecules can be stripped off by the enzyme neuraminidase, present in several micro-organisms such as influenzaviruses and streptococci. This may explain why diabetes and rheumatoid arthritis tend to occur as sequelae of infections. This facilitation of lectins by micro-organisms throws a new light on post-infectious diseases and makes the folklore cure of fasting during a fever seem sensible.

Alternative medicine popularisers are already publishing articles about dietary lectins, often with more enthusiasm than caution, so patients are starting to ask about them and doctors need to be armed with facts. The same comment applies to entrepreneurs at the opposite end of the commercial spectrum. Many lectins are powerful allergens, and prohevein, the principal allergen of rubber latex, is one. It has been engineered into transgenic tomatoes for its fungistatic properties, so we can expect an outbreak of tomato allergy in the near future among latex sensitive individuals. Dr Arpad Pusztai lost his job for publicising concerns of this type (20 February, p 483).


Vitamin D Home Test

As a follower of  Dr. William Davis’ Heart Scan blog, I am a convert to the Vitamin D message.

For eight months now I’ve been supplementing with  6000-8000 IU of D3 on a daily basis. In the absence of any initial test of blood levels, my self-prescription was a complete shot in the dark based loosely on posts I’d read on his and others’ blogs.

A Trip to the GP

Finally, a few weeks back, I decided it was time to find out how the supplementation was going. So I asked my GP if he could do the Vitamin D (25-OH) blood test. His immediate response was, “Why do you need that? Just go outside in the sun.” I explained that, being over 40, I was concerned my ability to make my own Vit D was impaired hence the supplements and follow up test. This irritated him even more at which point I was told he was “too busy to discuss this now” and “go talk to the receptionist.”

To make a long story short, the lab they work with does not do this test. I suppose this story is irrelevant other than to warn you that your “weird” views on Vitamin D may be met with derision.


Saved again by the internets!

Fortunately, I had already learned that I could order a home test over the net. They even do the tests internationally! The cost for those outside the US is US$90 including shipping.

So I placed the order and it arrived promptly by courier a few days later.

Basically you need to prick your finger and put a few drops of blood on a paper tablet then return it through the post to the lab.

It’s almost a no-brainer however I would definitely recommend that before you prick your finger, you should swing your arm around a few times to ensure that you get enough flow to fill the card. Swinging your arm after you prick your finger results in a scene out of CSI.

I suppose the swinging bit may not be necessary in all cases but my initial pricking effort produced only one drop of blood. But I digress…

With the test complete including only minor spillage on the test card (excluding aforementioned spatter on walls, ceiling and floor), I sent it back through the regular post… And about two weeks later my results arrived by mail.



Verdict? My 25-OH score was 73 ng/ml – pretty good. This is very close to optimum (the ranges doctors work to vary but for the proponents of Vitamin D it’s typically in the 50-70ng/ml range).

However, my results came with this warning:

Your blood vitamin D level is with the reference range (32-100ng/ml), but slightly above the range most experts consider as optimal for health (50-70 ng/ml). Excessive levels of Vitamin D over a prolonged period of time can be unhealthy.

I suppose they have to say that to cover themselves but frankly I was hoping they were going to tell me what a star I am.

It’s also worth noting that the quote, repeated verbatim, shows some wavering over whether or not to capitalize “Vitamin D.” As I was looking for guidance on that point I’m still lost.


The Test Kit Contents


My Bloody Results


PS: I’m going to drop my daily dose of D3 to 2000IU.

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Vitamin D – Another victim of modern life

If you haven’t already done so, be sure to read The Vitamin D Newsletter reprinted over at The Heart Scan Blog.

Some highlights.


Lack of vitamin D correlated with numerous cancers

Dr. William Grant reported that 15 cancers (colon, esophageal, gallbladder, gastric, pancreatic, rectal, small intestinal, bladder, kidney, prostate, breast, endometrial, ovarian, Hodgkin’s lymphoma, and non-Hodgkin’s lymphoma) are associated with lower UVB light. He concluded that 257,000 cancer deaths in 2007 in the USA were accounted for by inadequate vitamin D levels.

Professor Robert Heaney and Joanne Lappe’s randomized controlled trial [showed] that increasing baseline levels from 29 to 38 ng/ml reduced the risk of getting cancer by around 70%.


Type-1 Diabetes correlated to latitude and UV light

Cedric Garland began by showing the incidence of type-1 diabetes and multiple sclerosis by latitude. I had no idea that the latitudinal data was so strong for type 1 diabetes in children. This disease is almost nonexistent around the equator.


Ideally we need blood 25(OH)D levels of about 50 ng/ml

Hollis and Binkley’s crucial discovery was that the body doesn’t start storing the parent compound, cholecalciferol, until 25(OH)D levels reach about 50 ng/ml. They showed, using basic steroid pharmacology, that 50 ng/ml should be considered the lower limit of adequate 25(OH)D levels.


D is key in DNA

[Robert Heaney] covered calcium absorption, osteoporosis, risk of falling, muscle function, death and disability of the aged, TB, influenza, cardiovascular disease, hypertension, diabetes, cancer, multiple sclerosis, and gum disease. How can one vitamin be involved in so many diseases? Simple said Dr. Heaney, “vitamin D is the key that unlocks the DNA library.”


In modern times, pregnant women need high levels of supplementation to maintain healthy levels for herself and her baby

… when pregnant women keep their levels where we think prehistoric human levels were, about 50 ng/ml, breast milk becomes a rich source of vitamin D. First [doctors Carol Wagner and Bruce Hollis] gave 2,000 IU per day, then 4,000 IU per day and finally 6400 IU of D3 per day to lactating women. Only at 6400 of D3/day did the women maintain both their own 25(OH)D levels and the levels of their breast feeding babies above 50 ng/ml. On 6400 IU/day, the vitamin D activity of the breast milk went from about 80 to 800 IU/L. Quite a discovery, and another reason for all of us to keep our levels above 50 ng/ml.


Most of us could use about 2000 IU per day, but some of us need more…

Then Professor Heaney addressed a public health question. How much would we have to give all Americans to get 98% of people above 32 ng/ml without causing toxicity in anybody? The answer: 2,000 IU per day. Of course 32 ng/ml is not adequate but it would be a great first step. Furthermore, of the people left out, a high percentage would be African Americans. In fact, Dr. Talwar recently reported that 40% of African American women fail to achieve a level of 30 ng/ml even after taking 2,000 IU/day for a year.

Note: Natural sources of Vitamin D include many cold water oily fish.

The easiest way to get your vitamin D is to follow grandma’s advice: take Cod Liver Oil.