Connections between nutrition, genetics and disease

Do you think that nutrition needs to get more personalized?
It certainly needs to get more personalized for specific diseases like heart disease and like osteoporosis. Specific diseases that we know have a nutritional connection.

Would this be based on a person’s genetic code?
There are breakthroughs in the last several years in molecular biology which will allow determination of whether or not people are susceptible to particular diseases. Some appear to have a relatively simple genetic relationship such as osteoporosis, while others like heart disease have a very complex genetic relationship. There are markers being discovered that will help ascertain whether or not someone is susceptible.

Once we can determine if this person is susceptible then what would happen with their diet, how can we use that information?
One of the things that it will allow us to do is to test whether diet is really going to have an effect on a particular disease, in people who have a susceptibility. One of the things we do right now is use large populations of people for study. The problem with that is we don’t know who is susceptible and who isn’t so we just take a chance that we’re getting a significant number of susceptible people and then determine whether diet has an effect or not. If you happen to get susceptible people then it looks like diet might have an effect and if you happen not to you don’t see a dietary effect, that’s why there is so much confusion in the reports that come out in the literature. This dietary treatment helps in one report and it doesn’t help in the next report, so by working with those who are susceptible then we have a much better shot at determining specifically whether or not a dietary or drug treatment is effective.

What effect might this have on diseases in the future?
One of the things that we tell people for example is to increase the amount of fiber in their diet with the hope that this might reduce the possibility of colon cancer. If we know who is susceptible for colon cancer, and there are particular markers for particular types of colon cancer, then we can determine whether a high fiber diet helps them or doesn’t help them. If it does we can target them for a high fiber diet and not try to get the entire population to eat more fiber.

Do you think this might actually be able to prevent diseases, if people eat the right kind of foods based on their genetic code earlier in life?
This kind of information will help us to be able to determine whether or not eating a particular kind of food is going to be helpful. Right now recommendations are based on statistical probability, not genetics. If we can base them on genetics and work with a susceptible group of people specifically, then we have a much better shot at determining whether any dietary choices are helpful or not.

Explain how this kind of diet might work. Let’s take osteoporosis for example, researchers have suspected a genetic link to the disease right?
There has been a suspicion for many years of a genetic link. One of the genetic links has been discovered in the last few years that a defective gene affects Vitamin D absorption from our diet. In order for Vitamin D to get into the body like anything else it has to cross from the gastrointestinal tract into the blood stream. There is a particular protein required for Vitamin D to get across into the blood stream. People who do not have that protein or not enough of it get more osteoporosis. If you know who those people are you can give them higher levels of Vitamin D and therefore increase calcium absorption and increase calcium utilization. The problem is that you can’t give everybody that level of Vitamin D because Vitamin D is toxic.

If someone has osteoporosis and if you’re able to increase their absorption of calcium through Vitamin D, if they did this early in life could that possibly prevent them from getting the disease later in life?
That’s what one would expect, yes. That if you could get enough calcium absorbed and deposited in the bones early in life then you could prevent osteoporosis later in life.

That would be a really big breakthrough.
Yes, there are potentially several of those kinds of breakthroughs that are coming down the road. Maybe in the next few years, maybe in the next decade but they are certainly coming.

What other kinds of diseases, aside from osteoporosis?
Heart disease, or stroke caused by high blood pressure. There’s been some interesting information coming out on high blood pressure. Muscular dystrophy and cystic fibrosis have been studied extensively and so have numerous other diseases that affect humans.

When do you think we could be looking at diet based on genetic codes, how many years down the road?
It will vary depending on which particular disease we’re talking about. We expect that the osteoporosis breakthrough will happen in the next few years because it seems to be a relatively simple genetic relationship. On the other hand cancer, that might take a long time because you can either inherit a defective gene that causes cancer or the defective gene can be made through mutation during your life. So that’s going to take much longer.

When researchers get a handle on this what effect do you think it will have on the diseases that the population gets? Do you think you will get a sharp reduction?
Hopefully, it really depends on whether or not you can make dietary or drug changes that affects the progress of that disease. Some cases I think we can, and some cases it may simply not be possible. It may be just part of human existence.

If you could give me in a nutshell why do we need to change the way we tell people what’s good for them to eat, why do we need to get more specific and base it on this genetic code?
Right now we make general population wide recommendations. For example, we’ve recommended that there be about twelve hundred milligrams per day of calcium intake. This is particularly important during the teenage years up through the age of thirty years old. The compliance with that recommendation has been depressingly little. If we knew which particular people were susceptible and which particular people needed the dietary treatment, then I think if we could get those people to comply and leave the rest of the world alone in terms of how much calcium they consume, or at least in terms of needing to consume large amounts of calcium.

We’re doing a one size fits all diet plan and that’s not really working?
We are making general recommendations for the whole population and in a lot of cases it’s not working. People are not doing what those recommendations would suggest that they do. One of the problems in the last eight or ten years has been a wide spread body weight increase. Well one of the recommendations is that you limit caloric intake. People are not doing it and they’re gaining weight. If we knew who was susceptible to particular diseases then I think we have a better shot at getting them to change their particular diet or drug treatment in order to prevent or at least ameliorate the consequence of that disease.

You’ve done informal research in your classes where you ask people if they comply with different guidelines, dietary, what’s the response when you ask the students that?
One of the things I ask students is to give me a list of their top five favorite foods. Usually pizza tops the list but nowhere on the top five do you find fruits and vegetables for college age students. If you ask them, how many of you drink three glasses of milk a day. Only a very small percentage drink that much milk each day. They are probably not getting sufficient calcium, or at least the calcium amount that’s recommended.