Studies of identical twins have established that genetics contributes about 30% of disease whilst environmental factors account for the remaining 70%. Environmental factors include toxins, infectious agents, physical trauma, sleep patterns, stress, exercise and diet. Of these diet is by far the biggest environmental factor affecting general health and is also one of the most easily modified. And whilst we manage to avoid traumatic injury and infectious disease through most of our lives no one avoids eating for long.

One of the biggest breakthrough’s in the last two decades has been an understanding of epigenetics – the study of how environmental factors can switch genes on and off. Some of these changes are passed on to offspring, meaning that your parent’s diet influences your health and even the health of your children – which is one of the reasons I ask new patients about their family’s health and diet.

The ability of diet to modify health at the gene expression level is illustrated in the following experiment. Mother lab mice were fed a toxin, bisphenol-A (BPA) which is found in polycarbonate plastics. This induced epigenetic changes in the offspring, making them obese and tending to have a yellow fur colour. This alone is a good example of how environmental factors (toxins) can effect health. What is really interesting is that when the experiment was repeated, but the mother’s diet was supplemented with methyl rich foods (e.g. high in choline, folate & B12) the offspring were more likely to be normal coloured and healthy. In other words the diet was able to undo the damage caused by the BPA toxin.

Quite simple shifts in diet, even in healthy people, can lead to thousands of genes being switched on and off. This new gene expression can alter the risk of disease or the course of an existing condition. For example, scientists at the Norwegian University of Science and Technology found that when carbohydrates exceed 40% of the energy in a diet (i.e. more than 200g of carbs per day) genes promoting metabolic inflammation are activated. The researchers point out that:

“Genes that are involved in type 2 diabetes, cardiovascular disease, Alzheimer’s disease and some forms of cancer respond to diet, and are up-regulated, or activated, by a carbohydrate-rich diet,”

Studies like these make it clear that diet is pivotal in health management – something that most doctors  and their patients have yet to appreciate. My job is to stay up to date with the science so that I can provide targeted, evidence based dietary advice for my patients to help them get on top of their health.

The science on nutrition and health is advancing with enormous speed. Keeping up with it all takes a considerable amount of time and energy. I read hundreds of scientific papers each year as well as attending dozens of live and online seminars. One of the reasons I write a nutrition blog is to help me assimilate and link up some of the new information.

There are many popular diets that appear in the newspapers and get celebrity endorsements such as the Paleo, Zone, South Beach or DASH diets. These are often promoted in the media as weight-loss or ‘healthy’ diets and are often over-hyped one month only to be knocked down the next, leaving the public bewildered and sceptical. In my work as a clinician such a superficial understanding has no place and I certainly do not promote any one diet as a the Ideal. People are far too individual for that.

However, what few people realise it that behind the headlines some of these diets or aspects of them, have profound disease altering properties. Here are a few examples:

Despite having their own names these diets are not used in isolation and often a combination of several diets will be necessary. For example a gluten-free diet consisting of gluten-free bread, cakes and biscuits, will have a very different effect to a gluten-free Mediterranean diet based around fresh ingredients.

As well as the named diets above I use foods with specific actions in the following:

• Increasing or decreasing intestinal fermentation (e.g. FODMAP, probiotic, prebiotic)
• Altering gut permeability
• Reducing histamine levels
• Increasing antioxidant status
• Increasing liver or gall bladder function
• Altering methylation pathways and gene expression (epigenetics)
• Addressing specific mineral or vitamin imbalances

My dietary recommendations will depend on the individual condition, symptoms and background, and can be informed by lab tests (e.g. genetic testing, organic acid test and food reactivity tests). In some cases lab testing is crucial if dietary changes are to be effective. In some situations nutritional supplements and herbal medicines have a clear role alongside diet.

The term ‘doctor’ originally meant ‘teacher’, and in making dietary recommendations for my patients I spend considerable time explaining the reasons behind the changes. Knowledge, as they say, is power. Empowering patients is what it is all about and is why I run workshops and talks.