Summary
Highlights
Dr. McDougall attributes bad breath (halitosis) largely to animal protein due to its high methionine and cysteine content, which are sulfur-containing amino acids. He states that 'if you eat it, you ooze it,' meaning one's smell reflects their diet. The mouth is seen as a mirror of overall health.
Animal protein's sulfur-containing amino acids contribute to a low-grade metabolic acidosis, converting to sulfuric acid and leading to calcium excretion from bones. This can cause osteoporosis, not just in the spine, but also in the jawbones, increasing tooth loss. The speaker notes a correlation between poor dental health (and bilateral cataract surgery) and dementia in his patients, suggesting oral health issues could be early warning signs.
Bacteria in the mouth and gut break down animal proteins, releasing gaseous sulfur compounds like dihydrogen sulfide (H2S) and methyl mercaptan, which smell like rotten eggs. These gases enter the bloodstream, then the lungs, causing sulfur to be exhaled, making bad breath immune to brushing or mouthwash.
Using fluoride toothpaste or mouthwash can kill beneficial bacteria on the tongue. These bacteria are crucial for converting nitrates from greens into nitrites, which then become nitric oxide (NO) in the stomach. Nitric oxide promotes vasodilation and keeps arteries open. Eliminating these bacteria can increase the risk of hypertension and atherosclerosis.
McDougall suggests that bad breath can be fixed by diet alone. Studies showed a 50% reduction in exhaled sulfur after just 7 days on the McDougall diet, a low-fat, oil-free vegan diet. Animal protein contains about five times more methionine than plant proteins, exacerbating the sulfur burden and its effects on bone health.
The speaker disagrees with some of McDougall's advice, such as visiting a dental hygienist every 3-6 months, preferring his own dental care routine. He also points out that McDougall's recommendation for chlorine dioxide mouthwash is outdated, as the importance of the nitric oxide pathway (via tongue bacteria) was unknown when the book was written.