Blood testing and food intolerance – Tom Greenfield and Roger James

Tom Greenfield, a naturopath, used to wonder why some people did well on a particular diet and not others. The traditional nature cure philosophy is that there is a healthy diet which should suit everyone, but he found the actual results of this were variable. Logically, that would seem to have something to do with our diverse genetic make-up.

For Tom the key to this puzzle lies in the work of Dr. Peter D’Adamo, an American naturopathic physician who found that the ideal diet for any individual could be worked out from information provided by a blood test.

Tom is one of a small group of nature cure practitioners who now uses these blood tests in his practice. He finds that ‘The blood grouping system appears to be effective relatively quickly for people who have quite depleted vitality, which could take a long time to build up with the ‘conventional’ nature-cure approach in today’s toxic world. It can improve health simply through dietary change rather than relying too much on supplements, although supplements do have their place.’ The blood grouping system is based on the following principles.

1. Everyone belongs to a specific blood group, A, O, AB etc for reasons based on natural selection.

2. Substances which can stimulate a response from the immune system are known as antigens. Blood group antigens are carbohydrate (sugar-like) molecules that coat the surface of red blood cells. Some people are able to deposit (or ‘secrete’) antigens from their blood into their body fluids – their saliva, mucous, digestive juices etc. These people are known as ‘secretors’ and you can be a ‘secretor’ or a ‘non secretor’ regardless of your group.

3. Lectins are proteins that are capable of ‘sticking to’ to the surface of cells, and are present in many foods. Wheat lectin (called wheat germ agglutinin or WGA) has a similar chemical structure to the hormone insulin. So WGA can attach itself to receptors on body cell surfaces which were designed for insulin thus taking up the space that insulin would normally take. However the WGA cannot process carbohydrates and sugars in the way that insulin does.

4. The antigens in the blood of ‘secretors’ and blood groups A & AB fit well with the profile of WGA (the protein, or lectin, in wheat) and so are able to bind or stick to the lectin and to ‘re-direct’ it into the body fluids before it gets a chance to displace the insulin from the cells to which the insulin is meant to bind.

5. Blood Group O people and ‘non secretors’ are not able to dispose of the potentially insulin displacing lectins in this way. As a result these people may end up with excess insulin in their blood. This has been displaced from its receptors on the cell surfaces by the WGA and so has been unable to perform its proper carbohydrate processing task. This condition in which the body is failing to react to insulin (because the insulin is unable to ‘bind’ correctly to cells) is known as ‘insulin resistance’ and is a significant factor in the condition known as Syndrome X (see a future issue of Foods Matter.) This excess of insulin can have disease implications such as excess cholesterol, blood lipid disorders, and type II (late onset) diabetes.

6. WGA and other lectins can also cause actual damage to the lining of the intestinal wall in non-secretors by binding to intestinal cell surfaces, eventually leading to a ‘leaky gut’ and the consequent leak of proteins into the blood stream and ‘random’ food sensitivities.

7. Fucose is the carbohydrate molecule that defines blood group O. Fucose can bind with WGA in the intestines. It can also bind with Helicobacter pylori (the bacteria which causes most stomach ulcers) and Candida albicans, making those of blood group O statistically more prone to wheat intolerance, stomach ulcer and candidiasis.

8. Non secretors are also unable to process another carbohydrate (Lewis a) which is very similar to Fucose. This means that, like Blood Group Os, they are statistically more prone to wheat intolerance, stomach ulcer and candidiasis.

It is not surprising therefore that Blood Group O people and ‘non secretors’ do better on a low wheat /low carbohydrate diet. As it happens, regardless of blood group, wheat can be suspect. ‘It has been found that around half of all people complaining of digestive problems have antibodies to gliadin, a wheat protein, in their blood. Could this be as a result of the fact that wheat has been subjected to selective crossbreeding for generations in order to produce plants of the highest protein levels which will help to fatten cattle and to make good bread?’

Blood Group Case Study
As Tom often sees people living some distance away he may ask the client to send him a blood sample, using a kit he supplies, so that he has the test results when he sees them. One visit is therefore often enough. Tom is also a cranio sacral therapist (see FM Dec. 03), so some of his clients come to him initially for physical problems.

Debbie is a professional woman in her early thirties who had had a road accident 18 months previously, but her symptoms had worsened after treatment of an infection with antibiotics. Her energy level had dropped significantly. Tom did cranial work to try to resolve her condition. She also told him that her diet was dairy and sugar free already, and she did not consume fruit or alcohol. Her diet seemed healthy. She had sugar-free muesli in the morning, rice and salad at lunchtime and a cooked meal in the evening.
After a test which showed her to be a blood group O non-secretor, the oldest known blood group in evolutionary terms, he took her right off grains and recommended a supplement which replaces intestinal secretions in non-secretors, and balances the mucous membranes. He suggested that she needed a ‘stone-age’ diet, i.e. with no cultivated grains.
When Tom last saw Debbie things had started to clear up but not before there had been an initial worsening of her nasal and sinus congestion. This is not unusual as the body starts to detoxify itself when eating the correct foods.

Tom Greenfield practises in Canterbury and can be contacted on 01227 761000 or check in at

Tom’s wife, Ingrid, runs Artisan Bread which uses blood group labels on the packaging to indicate whether the bread is compatible for various blood groups. They met when she asked him for advice about the company’s products and were married some years later.

Peter D’Adamo’s website is and gives the names of practitioners using the blood group diet including those in the UK.

‘Eat Right 4 Blood Type O’ £4.99 Penguin Books 2003 ISBN 0141014784
These are simply lists of which foods are good or bad for your particular blood group.
‘Eat Right 4 Your Type’ - designed as a weight loss book this is quite basic, and does not go into secretor status (very important for people with food intolerance).
‘Live Right 4 Your Type’ is more up to date and contains details of the significance of secretor and non-secretor status. Penguin Books 2002 ISBN: 0140297855 £6.99.


First published in 2004

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