Foods set switches for better health

Everyone reacts differently to foods, but the reasons for this have become clearer only recently.
Some of the answers are coming from the new field of nutrigenomics, now the focus of a nationwide research program in New Zealand. The term is a truncation of nutritional genomics.

"It's the interaction between your food and your genetic make-up," said Matthew Barnett, who has been working in the field since 2004. "Different foods can affect different people in different ways, and that's because they have slight variations in their genes." Coffee is an obvious example. While some people can drink several cups a day with only minor effects, a single cup will keep others awake all night. It comes down to how fast your body breaks down caffeine and your genetic make-up plays a large part in that. "If you don't metabolise it quickly it floats around in your bloodstream for longer, whereas some people metabolise it extremely quickly and within an hour they're ready for their next cup." Dr Barnett is a research scientist in AgResearch's food, metabolism and microbiology section.

The nutrigenomics program is investigating whether whole foods can be targeted to population groups.
"We might genotype someone and say, on the basis of your genetic variation maybe you should eat blueberries, or drink green tea or something like that. But also, can we add something to a food? We may be able to make a milk-based shake that has desirable ingredients. Enhancing sports performance is another possibility."

But genes are only the beginning of the story. Although there are hundreds of different cell types in the human body, they all carry the same genes. But in each cell only a subset of the genes is turned on the genes all have switches which can be set by other chemical substances within the cell. The study of how some of these switches can be modified to change gene expression without changing the underlying DNA sequence is known as epigenetics. "If you look at development, you don't want certain genes turned on in certain organs. Your eye is quite different from your kidney and so you never want some genes turned on in your eye. There are systems that make those genes unable to be turned on there. And that could be an epigenetic change."

There are many ways in which genes can be switched on and off. One common way is to attach a small molecular subunit called a methyl group next to the gene. This acts as a marker which tells the cell's DNA-reading mechanisms to ignore the gene or, in a few cases, to transcribe it into a protein. What's exciting about these epigenetic switches is that, unlike the genes themselves, they can be altered, and this is what Dr Barnett's work is now focusing on.

"We're trying to find out how food interacts with the epigenetic machinery. Because with epigenetics there's no change to the genetic sequence, there's the potential for it to be reversed. So an epigenetic change that might cause you to be more at risk of diabetes might be reversible, and it's possible that a food can do that because there are certain foods that act through the mechanisms of the epigenetic machinery."

Folate (vitamin B9) is one example. This plays an important role in methyl metabolism and a shortage of folate at a key stage of development may mean that methyl groups are not attached to the correct genetic switches. "So what we're trying to understand is when does that happen and how does it happen?"

Some of these epigenetic changes can be inherited. The children of mothers who have grown up in a nutrient-poor environment, for example, may have genetic switches set to make the most of any available food. If those children grow up in a nutrient-rich environment they may be prone to obesity.

The disease model Dr Barnett is working on is crohn's disease, an inflammatory bowel disease believed to have a strong genetic component. The work is centered around varieties of mice which have symptoms similar to the human disease and studying the genetic make-up and food preferences of human crohn's sufferers. Foods which are identified as either helpful or aggravating are tested on cells containing a genetic variant commonly associated with the disease, to see whether they switch the gene's activity on or off. "If a food component is harmful, one explanation might be that the gene isn't metabolising that food and it's causing an inflammatory reaction, but if the food is beneficial it may be turning on an epigenetic switch, which is allowing people to deal with their condition more easily.
"Essentially we're trying to see whether the foods `fix' the gene to make it function as it would in a person who doesn't have crohn's disease."

The data so far are preliminary, but there are indications that some fruits seem to be helpful. Nutrigenomics is about making people as well as they can be, as naturally as possible through food and nutrients. "Ultimately it's less about disease and more about health, but it's easier to diagnose a disease than to diagnose a degree of healthiness. Essentially our long-term goal is to learn how foods might reverse or prevent certain conditions, and how to either change a food or select the right food for a given person.

Steve - this is what we have been talking about for the last several years. How these researchers differ from the rest are that instead of looking to create chemicals to block or cut epigenetic messages, they are looking to harmonize or calm the messages. This is exactly what we try to do in our practice.