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Frequently Asked Questions

Do you want to know more about us? Do you need more information on the Blood Type Diet? Find your answers here:

Blood Type Related Questions: Blood Type O
  The following section is an extract from Dr. D'Adamo's website ( Please visit his site if you wish to clarify any of the answers provided.  
MENU:    All Blood Types   |    Type A   |    Type AB   |    Type B   |    Type O


I have been following your diet for Type O for just about a month and it has improved my acid reflux condition immensely. However I suffer from a condition called Polycystic Ovarian Syndrome. I had been having extremely irregular and heavy periods. I was diagnosed and put on the pill Dianette. Recent saying that the pill was quite dangerous for Type O. Do you think that your diet could regulate my erring hormone levels and so I could come off the pill without risk of cancer?

The basic answer to your question is that if you don't suffer or have a history of blood clotting disorders, birth control pills can be used even by type O women, especially the new, low estrogen types. Having answered that, what else can we add to the mix which might be of value?

Follow the O diet, especially the lectin avoidance foods, such as wheat and corn. Polycystic ovarian syndrome is characterized by insulin resistance, and insulin resistance is largely the effect of consuming large amounts of food lectins improper for your blood type. Insulin resistance a common phenomena in women with poly cystic ovaries, is often a cause of heart disease, obesity and other hormonal problems later on in life. Find a good "food-derived" carotene (sometimes called "carotenoid") preparation. By this I mean a carotene supplement not just composed of beta carotene, but rather beta carotene and its cousins, gamma carotene, lycopene and lutein. Lutein especially, has been shown to decrease the amount of cystic formation on the ovary by its anti-oxidant abilities.

The female ovary is a very metabolically active organ, and the follicles must cut their way out when a woman ovulates, by secreting an enzyme to bore a hole to the exterior. Normally there is quite a bit of lutein in the ovarian tissue to snuff out the inflamation that results. If not, the tissue becomes cystic.

It is interesting to note that lutein is the yellow pigment in plants (lutea is Latin for "yellow"). Many tissues which are metabolically unstable, such as the retina of the eye ("macula lutea") and the ovulatory product ("corpus luteum") are yellow from the deposition of lutein. Unhealthy ovaries tend to be whitish colored at autopsy because of an inability to deposit lutein or an inadequate amount in the diet. Unlike beta carotene, which is often synthetic and only pure beta carotene, the "food derived carotenes" have a broad mixture of carotenoids, and are closer to what is found in a healthy diet.


Blood type O more prone to ulcer?
This is a connundrum seen repeatedly in clinical medicine, where a simple notion of pathology is confounded by polymorphic differences such as ABO blood type. In this study the evidence cearly shows that the most common mediators of inflammation, immune response hormones such as Interleukin and Tumor Necrosis Factor, are elevated in type O individuals with H. pylori ulcers over the other ABO blood groups. Thus, a symptom (stomach ulcers) which can have multiple causes (bacteria, hyperacidity) has individual variations in severity and other characteristics which can be predicted by ABO blood type. Until these characteristics are more widely recognized and factored into clinical considerations, modern medicine will remain behind the other 'pure' sciences, such as physics and chemistry.

I've been reading your material on stinging nettle. I'm familiar with its use in allergy, but was surprised to see so many other possible health effects. I'm interested in possibly using the herb in my GP practice. Any additional info?

Urica dioica rhizome (root) is a well-accepted remedy in Europe for prostatic enlargement. It has even been compared to the drug Proscar and found to be more effective, with less side effects. Lignans ((+)-neoolivil, (-)-secoisolariciresinol, dehydrodiconiferyl alcohol, isolariciresinol, pinoresinol, and 3,4-divanillyltetrahydrofuran) from the roots of Urtica dioica and their metabolites bind to human sex hormone binding globulin (SHBG).

The net effect of this anti SHBG activity is a positive influence on testosterone metabolism. Testosterone is also metabolized by enzymes called aromatase and 5-alpha-reductase. Prostate enlargement is characterized by elevated testosterone levels (specifically elevated levels of the enzymes involved in testosterone metabolism), and stinging nettle is thought to lower the activity of one or both of these enzymes.

This probably plays a key role in the traditional use of the plant to control prostatic enlargement. Stinging nettle (both the leaf and root) also appears to prevent the over stimulation of proinflammatory cytokines like tumor necrosis factor-alpha and interleukin-1 beta. Cytokines can be thought of in simple terms as immune system messengers.

And while a discussion of these proinflammatory cytokines and immune system balance is beyond the scope of this column, cytokine balance is a growing area of interest in medicine. In fact, virtually all immune disorders (from HIV, to cancer, to autoimmune diseases), allergic conditions (like asthma and allergies) and even obesity/insulin resistance have characteristic imbalances in cytokine levels as part of the functional derangement occurring at a metabolic level.

Urtica dioica has a lectin with many unique characteristics. Urtica dioica agglutinin (UDA), a V beta 8.3-specific superantigen, prevents the development of the systemic lupus erythematosus-like pathology in mice. Stinging nettle lectin is actually a "super lectin" called UDA superantigen (UDA for short).

For those interested, UDA appears to be an N-acetylglucosamine specific lectin. Evidence indicates that this super lectin can inhibit a range of viruses including those responsible for HIV, colds, and influenza.

For prostate and immune health, Urtica dioica, the humble nettle plant, is hard to beat.


Does any one blood type have a history of longevity superior to the others?

This question has not been looked at with any degree of exactitude, but two studies did show a slight increase in life span for those individuals who were type O (over type A). Whether this is the result of any genetic link or simply the result of the fact that the modern hi-fat diet, hi-stress lifestyle is inherently more poisonous to type A over type O has not been determined. In any case, the studies are on small numbers of people and have not been replicated. One older study looking at different rates of longevity between different nationalities saw the rate as being influenced by the percentage of type A in the population.

They stated that : "Innumerable influences of various types can cause diseases, primarily the high incidence of certain tumors in old age, climatic influences, overeating and malnutrition, and furthermore abuse of coffee, tea, tobacco and alcohol, medicines and insufficient movement. It can be assumed that wherever blood group A is prevailing the genes of blood group A constitute a factor. The impact of the blood group genes varies as a function of the underlying disease, the effectiveness of the exogenic factors and the general constitution of the individual patient."

Another study of Italian dentists showed a higher incidence of type O among those who lived beyond 75. Remember that these are populations that have done no interventions such as diet or lifestyle modification. By following ER4YT, most type A's can be expected to better the odds considerably.


In your book you mentioned helping a person with hypertension by (1) having the individual follow the blood type diet and (2) recommending certain botanicals. I would like to know about these botanicals and any other recommendations on the topic of hypertension.

Renewed interest in the neurotransmitter nitric oxide has researchers looking at its precursor, L-arginine, for treating certain kinds of heart disease. Once thought to be only a dangerous environmental pollutant and a poison, it is now known that nitric oxide is made in the body and plays numerous roles including brain activity regulation and circulation control.

Using nitric oxide for vasodilation, the widening of blood vessels, has been a common practice for a long time but has only recently been understood. In World War I, doctors noticed that workers in ammunition factories who were packing shells with nitroglycerin had very low blood pressures. The observation eventually led to the development of a nitroglycerin pill for the rapid relief of angina--that is, exercise-induced chest pain caused by oxygen deficiency in the heart.

In 1987 nitric oxide was determined to be the relaxant factor released by endothelial cells, explaining how nitroglycerin tablets help angina sufferers. Nitric oxide controls blood pressure and prevents formation of blood clots by signaling the muscles that control relaxation and expansion of blood vessels. There is some evidence that the night time urination many people find so disturbing to their sleep may be the result of nocturnal variations in blood pressure that are the result of the fluctuations in nitric oxide activity.

When arteries become clogged, they produce less nitric oxide than normal. Treatment with nitroglycerin can increase nitric oxide, widening blood vessels and increasing blood flow. Nitric oxide also interacts with blood platelets to decrease platelet aggregation, thus lowering the risk of blood clots.

Healthy cardiovascular function can be enhanced by nutritional supplementation such as NAPS Nitricycle (proper modulation of nitric oxide function) and Hawthorn Plus (anti-oxidant support). Quercetin is a very common flavonoid widely distributed in many plants. The flavonoid intake has been linked to the prevention of some human diseases including cancer. Quercetin inhibits heat shock protein expression and in this way triggers apoptosis of tumor cells. The present study was designed to investigate whether quercetin exerts cytotoxic activity against human colon adenocarcinoma cells.

The studies have shown that quercetin alone and in combination with the heat shock can induce apoptosis and necrosis in vitro in human colon adenocarcinoma cells (LS 180).


Is there a reproductive compatibility or incompatibility regarding the blood groups?
Studies have shown a significant excess (87%) of ABO incompatible couples in 102 persistently sterile marriages. The same researchers also found that in 7 couples with markedly delayed fertility, the 9 children that did result were all blood type O, and hence would have been compatible with the mother. The authors suggested that the infertility was due to the presence of antibodies in the secretions of the mother's genital tract, or incompatible sperm from the father. Several older studies have shown childlessness more frequent among blood type A and B women than among AB or O, while a 1965 study showed an increased proportion of type O children in families with more than one child. All these studies consistently showed that if the father possesses an A antigen which the mother does not, there is a marked selection against the survival of the A offspring.

There is a marked tendency of blood type O babies of blood type O mothers to be male as opposed to blood type A babies of type A mothers, who tend to be female. Blood type B and type O offspring have a greater chance of being male if their mother is the same blood type as their offspring. While other studies showed that blood type AB offspring tended to be female more often than expected (as in blood type A) which led the investigators to conclude that the presence of the A antigen may have some effect in skewing sex ratios in favor of higher percentages of female offspring.

A recent study compared 589 ABO compatible (that is, the husband and wife had blood types which could be exchanged) against 432 ABO incompatible mating couples. The mean number of living children presents a significant difference. In the incompatible couples, there was 21% deficiency of blood type A children and 16% deficiency of blood type B children when compared to couples which were ABO compatible.

This has led some researchers to theorize that ABO incompatibility results in 'cervical hostility' between the man's blood type antigen on the sperm, and the woman's opposing antibodies in her cervical mucus.


What's the link between blood type O with asthma?

A positive association has recently been reported in adult subjects between O/nonSecretor phenotype and asthma. To confirm this association, this study investigated the joint ABO/Secretor phenotype in a cohort of 165 asthmatic children. Three-hundred and sixty-two consecutive newborn infants from the same population were also studied as controls. The proportion of O/nonSecretor in asthmatic children was higher than in controls, thus confirming the association found in adults.

The association was more marked in males than in females. In males, the pattern of association between the joint ABO/Secretor phenotype and asthma is dependent on the age at on-set of symptoms. Since the oligosaccharide composition of cell membrane and mucosal secretions is controlled by the cooperative interaction of ABO and Secretor genes, and since such composition influences the adhesion of infectious agents, the age pattern could reflect a more general interaction between developmental maturation and oligosaccharide structure concerning their effects on susceptibility to viral and bacterial agents.

Studies support my own observations that asthmatics (especially childhood asthmatics) have a higher incidence and severity of asthma. Probably the best long-term strategy is the O-non secretor diet, with its low-lectin elements.


My wife has been diagnosed with kidney failure (around 13% functional according to tests) and I wanted to know if your diet program would be of any help to her condition. She does not desire a kidney transplant or dialysis.

Dietary lectins have been shown to increase antibodies against the kidney glomerulus (the filtration device used to detoxify the blood). Thus following the Blood Type Diet can help prevent this since it does minimize exposure to foods which may contain lectins capable of doing this. Another interesting idea is to use certain types of dietary fibers to help eliminate certain poisons that can build up in a person with compromised kidney function. Larch arabinogalactan (ARA6) has been studied with regard to this.

The researchers tested the hypothesis that dietary fiber, by inhibiting colonic bacterial ammonia generation and increasing fecal nitrogen excretion, might decrease hepatic urea synthesis and thereby reduce plasma urea in patients with chronic renal failure. Larch arabinogalactan decreased mean plasma urea in uremic subjects by 11% over 6-8 weeks. They concluded that "The reduction in plasma urea caused by dietary fiber is likely to be due to inhibition of colonic bacterial production of ammonia; such therapy could conceivably alleviate some of the symptoms of uremia and postpone dialysis in patients with endstage renal disease."


I have found your observations/ recommendations for my blood type (O) to be very accurate. After a lifetime of unsuccessful treatment for depression and anxiety, I have just been diagnosed as bipolar II, proving yet another of your theories. Any ideas?
There is some evidence that type O blood is associated with higher a higher incidence of bi-polar problems, sometimes also referred to a 'manic depressive disease.' This may be related to a genetic linkage between the allele for type O blood on the ABO chromosome, and the proper functioning of a gene which controls dopamine synthesis, called DBH. DBH controls the proper conversion of the amino acid tyrosine into dopamine, catecholamines or thyroid hormone. Because of this it appears that type O's may not be as efficient as the other blood types in processing catecholamines (the most famous catecholamine being adrenaline). Thus, they can oscillate between high and low levels of catecholamines, consequently also having high and low levels of dopamine. Best strategies for using blood type to help manage bi-polar illness:
1. The type O diet (low wheat, higher protein) is very beneficial for enhancing catecholamine metabolism. many O's will use wheat to manipulate their dopamine levels. Better to use protein instead.
2. Aerobic exercise increases the efficiency of the body's handling of both dopamine and adrenaline.
3. Catechol (from North American Pharmacal)

My sister and I are both O type, and she is diabetic. We are wondering if whey protein in morning shakes are a good idea for us. Any advice?
I would not recommend whey products for type O, and especially type O diabetics, since diabetics have shown tendencies towards elevated antibodies to milk proteins. What I would recommend would include: (1) Fenugreek seeds: 1-2 tsp daily. These can help regulate blood sugars; (2) One handful of standard domestic mushrooms daily. Mushroom can increase insulin-like activity in the body (this is not usable by O secretors, who may instead want to opt for fava beans.); (3) The bioflavanoid quercetin. Quercetin has shown an ability to block the enzyme aldose reductase, which is responsible for many of the late stage developments, such as neuropathy and eye damage.

I have type O blood and was on a diet very close to the type O diet for many years, with cholesterol of 126. Then I had a heart attack and my physicians put me on a vegan (type A) diet, on which I have lost 60 pounds, but my cholesterol went up to 244. I'm concerned about the amount of saturated fat on a type O diet.
Not a problem (as you can tell) if you are using lean, organic meats and exercising. By the way, an increase in cholesterol in type O vegans is not uncommon, probably a response of excess insulin production (because, as my colleague Greg Kelly says, "Most vege-tarians are in reality starch-etarians."). Hyperinsulinemia has twice the risk factor for heart disease as elevated cholesterol and would be much more of a threat to you.

My son has Crohns Disease, and is taking Pentasa (Mesalamine). He is blood type O. We got the multi vitamin for type O and he did very well. My question is this. The Pentasa is very hard on him and the doctor told him it was making him lose his hair. Is there something else he should be taking in your line of products?
Pentasa tends to interfere with PABA and folic acid metabolism, which can predispose to increased activity of yeast on the scalp. This can result in destruction of the hair follicle and loss of hair. Your son can make a very effective hair rinse out of oil of rosemary, glycerine and oil of bergamot. To eight ounces of distilled water, add 15 drops oil of bergamot, 1 tblsp glycerine and 10 drops oil of rosemary. Have you son apply this to the scalp before bed, accompanied with vigorous scalp massage. To this procedure I would also add taking the B vitamins biotin (8mg daily) and folic acid (2-3 mg daily).

I have been on the O diet before and loved it. Want to start again and can't seem to get through the first 3-5 days that it takes for me to get over the obsessive cravings, especially to wheat. Any suggestions for supplements, etc. to "jump start"?
A lot of type O's report having rough times adjusting to the loss of wheat in the diet, especially in the first few weeks. I've found that the use of the amino acid glutamine can help offset these feelings until the O diet begins to help upregulate dopamine levels. In the brain, glutamine is converted to glutamic acid, the only alternate source of glucose available to the brain. It provides a ready source of brain fuel for hypoglycemics and helps stave off sugar cravings and hypoglycemic symptoms that develop when blood-sugar levels drop too low. In the brain, glutamine is a substrate for the production of both excitatory and inhibitory neurotransmitters (glutamate and gamma-aminobutyric acid, popularly known as GABA). Glutamine is also an important source of energy for the nervous system. If the brain is not receiving enough glucose, it compensates by increasing glutamine metabolism for energy-hence the popular perception of glutamine as "brain food" and its use as a pick-me-up. Glutamine users often report more energy, less fatigue and better mood.
Glutamine is plentiful in both animal and plant protein. Heavy stress, such as strenuous exercise, infectious disease, surgery, burn injury or other acute trauma leads to glutamine depletion with consequent immune dysfunction, intestinal problems and muscle wasting. Consequently, it has been proposed that glutamine should be classified as a "conditionally essential amino acid." Typically, a useful dose is 500-750mg in powder or capsules between meals for a week or two. By the way, glutamine (unlike most amino acids) is rather pleasant tasting, with a slightly sweetish flavor.

I am a 43 year old 'O' who has noticed a great improvement of my arthritis (sacroillitis) in one week following your diet. For the past few months, I have been trying homeopathic medicine for the arthritis: glucosamine sulfate and GDU (protolytic enzymes). Could my improvement be due to a combination of the medicine and your diet?
Although research documenting the positive effects of GLUCOSAMINE sulphate in treating arthritis are now beginning to appear with regularity, it is still far from a perfect therapy. In my own practice, I've found that about 60% of the arthritic patients get some form of symptomatic relief, though in most instances I have not seen much actual improvement in the joints themselves. One aspect of glucosamine's recognized actions goes largely unnoticed, but is important with regard to the blood type diet theory. There is strong evidence, that glucosamine binds many food lectins, including WGA or wheat germ agglutinin. One of several well-designed studies documenting this also showed definite systemic uptake of wheat lectin, where it deposited on the walls of the blood vessels and lymph nodes.
Interestingly, the percentage goes DOWN in individuals who take CHONDROITIN sulphate in addition to glucosamine, as part of a regimen advocated in the bestseller "The Arthritis Cure." How could this be? One simple explanation is that chondroitin sulphate is actually comprised of long linked chains of the sugar acetylated galactosamine. You might remember that galactosamine is also the blood type A antigen. Thus, upon hydrolysis (acid breakdown) in the stomach, chondroitin becomes free A-antigen. This would not be to much of a problem in type A or AB, who recognize A antigen as "self," but could be a major problem in types O and B, who recognize A antigen as "non-self." In essence, taking chondroitin sulphate if you are either O or B is the chemical equivalent of giving yourself a bad blood transfusion.
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