Do My Genes Rule My Health?

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Q My parents are overweight, my father has high cholesterol and two of my grandparents had diabetes. How much good does it do to change my lifestyle if these problems run in my family?

A It's true that many health problems do seem to affect generation after generation. But that doesn't mean the condition is genetic—and it certainly doesn't mean it's inevitable. The fact is, we don't give our children only DNA. We also give them recipes for living. We pass along tastes for certain foods and ways of eating that can have a major effect on health. Often, what appears to be a genetic trait is actually a set of food habits passed down. Here's a look at some of the health conditions that commonly occur in families.

High Cholesterol
We often hear people say, "I have high cholesterol; it runs in my family," assuming that the problem is out of their control. It's true that some cases of high cholesterol—perhaps one in ten—really are genetic. The rest are caused by our food choices: Even small amounts of animal-based food products contain enough fat and cholesterol to push our own cholesterol levels up.

The only way to really know if the problem is genetic is to completely eliminate animal products from your diet while also keeping vegetable oils very low. Then, after about eight weeks, see your doctor. If your cholesterol is still too high, blame your genes. If you do have a genetic tendency toward high cholesterol, continuing with this same plant-based diet will minimize your risk.

There's no question that genes play a major role in what we weigh. Genes even affect where the weight ends up, such as around our waists or on our hips. Some rare genetic disorders cause massive weight gain early in life too. But most weight problems have much more to do with our food habits than our genes. After all, the tremendous increase in obesity in recent decades has occurred while our genes have remained the same. And people who switch to a low-fat, plant-based diet lose, on average, about one pound per week without needing any sort of rearrangement in their genes.

We can draw an important lesson from Japan's history with obesity. A rice-based diet kept obesity rates there under 3 percent until fast food outlets and other Western tastes invaded, causing the rates of weight gain to climb. But shifting away from a meaty, fatty diet can reverse this trend—both here and there.

Alzheimer's Disease
With all four of my grandparents exhibiting signs of dementia late in life, this condition has been at the top of my health-worry list. Although we're still in the dark about many of the contributors to Alzheimer's disease, studies give us hope that a good diet can help counter the threat.

The less saturated fat (the "bad" fat that's particularly plentiful in animal products) you eat, the lower your risk may be, according to a study published in February 2003 in the Archives of Neurology. The researchers found that people who consumed around 13 grams of saturated fat daily had less than half the risk of Alzheimer's as those who ate about 25 grams per day.

Research teams in the United States and Europe are studying whether getting sufficient amounts of vitamins B12, B6 and folic acid can reduce Alzheimer's risk. In theory, these vitamins should help because they help the body eliminate a substance called homo- cysteine, which is associated with Alzheimer's disease (and heart health too). Given the slow nature of Alzheimer's, though, it will likely be many years before it is clear whether these vitamins help.

More than 25 years ago, researchers concluded that cancer was, for the most part, not caused by genes handed down from our parents. Rather, most cases were caused by smoking, exposure to toxic substances, unhealthful diets and risky lifestyles. However, there are exceptions.

For instance, about 5–10 percent of breast cancer cases are clearly genetic. Genes called BRCA1 and BRCA2 normally act to suppress tumors, but abnormalities in these genes actually allow them to potentially cause cancer. Although these abnormalities are rare, affected women have a 50–85 percent risk of developing breast cancer. While diet and lifestyle clearly influence your risk of developing any kind of cancer, so far we don’t know just how powerful they are in reducing that risk.

And diet isn't everything: Even people following healthful diets may develop cancer. Besides, we've all known people who follow abysmal diets and never develop the disease. However, just as quitting smoking lowers your cancer risk, following the healthiest diet possible reduces risk even further. For example, people who avoid animal products cut their risk of colon and prostate cancer. And even after cancer has been diagnosed, diet changes may help. Following a low-fat vegetarian diet for one year slowed—and sometimes even reversed—the progression of prostate cancer, according to the research from the team of Dean Ornish, MD, and published in the September 2005 issue of The Journal of Urology.

Of course, it goes without saying that diet and lifestyle measures should be used in addition to diagnostic and treatment measures, not instead of them. Perhaps the best reason for adopting healthful diet and lifestyle habits is not to counteract our own genetic vulnerabilities. If we can pass these good habits along to our children, we can help them steer clear of any need to battle these diseases at all.