Dr. Tom Greenfield

Dear Dr. Greenfield,

I have decided to try the blood type diet (A). I am aware that Dr. D'Adamo suggests avoiding smoked meat and seafood. I am assuming this is due to the nitrate/nitrite added to the food. However, I shop at Whole Foods Market and they smoke their seafood in house, naturally, without any preservatives. Would this be okay to eat on the blood type diet?

Thank you,

Jennifer

Smoking is a way of preserving foods using smoke typically from hardwood burnt at low temperatures: Certain compounds given off by burning wood have a preservative or antimicrobial effect on the food, and add flavour. Other compounds, such as polycyclic aromatic hydrocarbons (PAHs) may have a detrimental effect on human health at levels found in cooked foods, they are certainly a risk for workers occupationally exposed to PAHs, and also for cigarette smokers. Certain PAHs may become more toxic when metabolised, and metabolism can be dependent on individual polymorphisms. For example, cytochrome P450 1A1 (CYP1A1) is the primary cytochrome P-450 isoenzyme that biologically activates benzopyrene, a tetracyclic hydrocarbon present in smoked food, and the main carcinogen in cigarette smoke. Charbroiled and smoked meats and fish contain more PAHs than uncooked products, with up to 2.0 µg/kg of benzopyrene detected in smoked fish.[1]

Some people may be more at risk from eating smoked foods or other exposure to PAHs: Genetic polymorphisms in CYP1A1 inducibility has been implicated as a factor for susceptibility to lung and laryngeal cancer. CYP1A1 may be induced by other substances. The mechanism by which PAH causes cancer is thought to be via the binding of metabolites to DNA. Infants may be at risk for exposure to PAHs: Animal studies have shown that PAHs and metabolites cross the placenta; Because PAHs are excreted in breast milk, nursing infants of exposed mothers can be exposed through breastfeeding. Polymorphisms causing glutathione transferase deficiencies (GSTM1) may result in elevated breast cancer risk from PAHs.[2] Other risk factors may include blood group, with type A individuals having a greater risk of certain types of cancer, although this can be masked by other genetic factors overriding the blood group phenotype.[3]

Sodium nitrite (E250) is a preservative added to meats, which can form carcinogenic nitrosamines when exposed to high temperatures. Nitrosamine formation can be inhibited by the addition of vitamin C.[4]

The Blood Type Diet™ is based on naturopathic principles, and as such advocates avoiding or minimising consumption of foods that may enhance disease risk either for the individual or for the population in general.

References:
1. Grimmer G. 1968. "Carcinogenic hydrocarbons in the human environment". Dtsch Apoth Ztg 108:529.
2. van der Hel OL, Peeters PH, Hein DW, Doll MA, Grobbee DE, et al. "NAT2 slow acetylation and GSTM1 null genotypes may increase postmenopausal breast cancer risk in long-term smoking women." Pharmacogenetics. 2003 Jul;13(7):399-407. Pubmed.
3. Anderson DE, Haas C. "Blood type A and familial breast cancer." Cancer. 1984 Nov 1;54(9):1845-9. PubMed.
4. Mackerness CW, Leach SA, Thompson MH, Hill MJ. "The inhibition of bacterially mediated N-nitrosation by vitamin C: relevance to the inhibition of endogenous N-nitrosation in the achlorhydric stomach." Carcinogenesis 1989; 10(2) 397-399. PubMed.