Why We All Need Personalised Diets
We are all familiar with the saying “One man’s food is another man’s poison” yet it is only now with the advent of nutrigenomics and microbiome research that it is becoming apparent why.
Poisons are not restricted to lectins in grains and legumes or to common food intolerances such as to gluten, casein (dairy), soy, corn and egg protein. Popular food items that are generally considered “heathy” may have deleterious effects in some people and recent nutrigenomics and microbiome research has shed a lot of light in this area.
We know now that our genes and the proteins they produce (enzymes, transporters, receptors, hormones etc.) interact with components of the food we eat to influence our health and nutritional status. Genetic differences can tremendously affect how we respond to what we eat, giving each of us our own specific nutritional needs and the need for a personalised diet. Sometimes this can be a matter of life and death. To give just a few examples:
Should You Say No to Your Second Cup of Coffee?
Well, it depends on its caffeine content and your genetics.
While coffee is one of the beverages that has been most widely studied in epidemiological studies with respect to its health benefits, being praised for its high polyphenol content which accounts for the highest intake of antioxidants in our diet (1), some of us don’t respond very well to the caffeine in it.
Research has shown that depending on our genetics, caffeine can have a significant impact on heart health and it can either be protective or detrimental for an individual. The effect of coffee on cardiovascular disease depends on a variation in a gene called CYP1A2 which produces an enzyme responsible for breaking down coffee in the body, thus affecting the rate at which caffeine is broken down (2, 3). For those with the GG variant, moderate coffee consumption lowers the risk of heart disease but people who possess the GA or AA variant break down caffeine more slowly and are at greater risk of high blood pressure and myocardial infarction when caffeine intake is high. These people should better stay below 200mg daily which is the equivalent of two small cups. But there are other healthy foods and beverages that contain caffeine such as black tea, green tea and dark chocolate. It all adds up…
When to Stay Away From Iron-Rich Foods
The spinach-obsessed cartoon character Popeye the Sailor did us a great service by highlighting the importance of iron-rich foods in the diet, iron being a metal that helps carry oxygen around the body which is vital for sustaining life. However, the beloved Popeye must have had genetics that put him at risk of low iron status. Some people on the other hand may be absorbing too much iron from their diet and too much iron is extremely harmful. These are people with certain variants in the SLC17A1 and HFE genes that regulate iron uptake in the small intestine (4,5). Ironically, these genetic variants offered us an evolutionary advantage in the past when iron was scarce but with our high meat diets nowadays, iron overload is becoming more and more of a problem and may lead to a condition called hereditary hemochromatosis.
The extra iron builds up in various organs and over time; this internal rusting can contribute to liver diseases, arthritis, cancer, heart disease and diabetes. These people need to regularly monitor blood markers of iron status (ferritin, hepcidin, transferrin saturation) and would greatly benefit from a low-iron, high-antioxidant diet. Moreover, the extra iron can predispose you to fungal and bacterial infections. In the words of Sharon Moalem, MD, PhD: “The more iron you have, the tastier a meal you would make in the eyes of pathogenic microbes” (6). This might sound counterintuitive but the fight for life is in essence the fight over resources like iron and the better your body is at managing its iron stores, the better it is at fighting infections.
When Yoghurt, Kefir, Sauerkraut and Bone Broth are Bad For You
Including fermented foods in our diet is part of “general health advice” and rightly so. However, some of us may benefit from eliminating these, at least for a while. Here’s why.
An increasing number of people are suffering from “histamine intolerance” or overload due to a combination of genetic variation in DAO and HNMT (7), microbiome composition and other triggers (overuse of antibiotics, antidepressants, NSAIDs) which means that their histamine degradation is impaired. As histamine is inflammatory, this build-up can cause headaches, nasal congestion, fatigue, abdominal cramps, diarrhoea, dysmenorrhea, skin flushing, hives, vertigo and can leave people feeling flushed, itchy and miserable.
What is maybe less well-known is that poor gut health is another key driver in the production of excess histamine, with an overgrowth of certain bacteria, such as Escherichia coli and Salmonella typhimurium being responsible for increased histamine production (8).
Thus, if you’re suffering from histamine intolerance, including otherwise healthy fermented foods in your diet would be like adding fuel to the fire. Many of the foods that are high in histamine are often fermented, such as yoghurt, sauerkraut, kimchi, kombucha, kefir and pickles. But the list doesn’t stop here: cheese and wine are other high-histamine foods as well as shellfish, nuts, chocolate, citrus fruits, tomatoes, black and green tea, spinach, collagen, and the very popular bone broth. What this all means is that for some of us, a gut restoration strategy would initially eliminate probiotic foods, a counterintuitive move since we all have come to equate probiotics with good health but obviously there are exceptions to the rule and this is no minor one.
(1) Pérez-Jiménez J, Fezeu L, Touvier M, et al. (2011) Dietary intake of 337 polyphenols in French adults. Am J Clin Nutr 93, 1220–1228.
(2) Cornelis et al. Coffee, CYP1A2 genotype, and risk of myocardial infarction. Journal of the American Medical Association. 2006;295:1135-41.
(3) Palatini P et al. CYP1A2 genotype modifies the association between coffee intake and the risk of hypertension. Journal of Hypertension. 2009;27:1594-1601
(4) Allen KJ et al. Iron-Overload- related disease in HFE hereditary hemochromatosis. New England Journal of Medicine. 2008; 358:221-30
(5) Pichler I et al. Identification of a common variant in the TFR2 gene implicated in the physiological regulation of serum iron levels. Human Molecular Genetics. 2011;15:1232-40
(6) Sharon Moalem, MD, PhD (2016) The DNA Restart, Rodale Wellness, p. 23
(7) Jones BL, Sherwin CM, Liu X, Dai H, Vyhlidal CA. Genetic Variation in the Histamine Production, Response, and Degradation Pathway Is Associated with Histamine Pharmacodynamic Response in Children with Asthma. Front Pharmacol. 2017;7:524. Published 2017 Jan 4. doi:10.3389/fphar.2016.00524
(8) Pugin B, Barcik W, Westermann P, et al. A wide diversity of bacteria from the human gut produces and degrades biogenic amines. Microb Ecol Health Dis. 2017;28(1):1353881. Published 2017 Jan 1. doi:10.1080/16512235.2017.1353881