When people say things like “Heart disease runs in my family” and “My parents had cancer, so I’m afraid I will, too,” it confirms our suspicions that DNA is destiny. The truth, however, is that it doesn’t have to be: The DNA we inherited from our parents does not necessarily determine our fate. In fact, we can modify the behavior of our DNA and genes in striking ways.
Certainly, we are all born with a set of genetic strengths and vulnerabilities, but we can bring out the best or worst in our genetic predispositions based on the nutrition, exercise and lifestyle choices we make. The payoff for playing our hand of genetic cards well is better health and, potentially, a longer life. The cost of playing that hand badly, on the other hand, can be high: We may suffer the early symptoms of health problems we would otherwise have staved off until very old age; we may contract diseases we could have avoided altogether.
Genomic research is helping us understand that many of the most common and deadly diseases — including cardiovascular disease, cancer and adult-onset diabetes — are typically the result of interactions between genetic and environmental factors (including diet and lifestyle). Understanding the nature of those interactions can go a long way toward helping us understand why nutrition plays such a central role in determining both our present and future health.
DNA, or deoxyribonucleic acid, is a long strand of molecules that reside in the nucleus of each of our body’s cells and determine how we develop. DNA is associated with heredity, since it is responsible for all inherited traits, and since it is passed on to offspring through both parents. The word “gene” refers to a section of DNA, or a unit of heredity.
Combined, an organism’s thousands of different genes contain all the information and instructions that it requires to function. In the case of human DNA, those instructions include the codes for every protein and enzyme produced by the human body.
We’re accustomed to thinking of our DNA and genes as the reason we have, say, brown hair and green eyes, but we less regularly consider how DNA and genes govern the day-to-day activities of every cell in our bodies. The process is a complex and intricate symphony, with some genes blaring in the foreground and others barely making a peep. But regardless of volume, the symphony is always playing on our body’s sound system.
We all inherit variations in our genes that make us uniquely who we are. Unfortunately, some of these variations hinder our genes’ ability to do their intended jobs. Such hindrances ultimately increase our susceptibility to disease. Furthermore, as we age, our DNA and genes get damaged (mutated), which also leads to a higher risk of disease. We can’t stop the accumulation of genetic damage or the aging process, but we can slow it down and increase our resistance to illness.
Little by little, scientists have gained a clearer idea of how nutrition influences our genes. This has given rise to a new scientific field called nutrigenomics. Over the past 10 years, nutrigenomic experts have made quantum leaps in understanding how nutrients — what we eat or don’t eat — may affect our genes. The research has shown that whether we’ve inherited good genes or bad, nutrition can improve their performance. Poor nutrition and lifestyle habits, meanwhile, can predispose our genes to be on their very worst behavior.
Scientists now know that certain genetic variations can be “switched on or off” by environmental cues. So it’s possible to have a genetic predisposition to a certain trait, but also possible to have that predisposition remain dormant indefinitely — until it is triggered by a specific circumstance (such as a nutritional deficiency or a hormonal imbalance) that throws its precoded instructions into action.
You might have heard the phrase, “All life is based on carbon.” That’s true, and it definitely applies to genetics — specifically, to the synthesis (or replication) of DNA. Before a cell divides to make a new cell (as required for growth or to replace damaged or old cells), it must first make a complete copy of its genes, which become part of the new cell and the basis for its operating instructions. The process begins with an assemblage of single-carbon atoms that contribute to the structure of DNA. These carbon atoms, in turn, are provided by folic acid, a B vitamin. Several other B vitamins, including B3, B6 and B12, play ancillary roles in related biochemical reactions.
This series of related biochemical reactions generates other important molecules that biochemists call “acetyl groups” (related to vinegar) and “methyl groups” (related to some of the compounds in coffee). These acetyl and methyl groups (remember, they’re byproducts of B vitamins) play key roles in turning genes on and off, so that they are either actively “playing” in the symphony or remaining silent. This playing or muting of a particular genetic instruction is referred to as “gene expression” or “gene silencing,” respectively.
Acetyl groups attach to DNA, kind of like a magnet to a refrigerator, and “switch on” selected genes. Conversely, methyl groups attach to selected genes and “switch them off.” This switching activity is crucial — you don’t want genes turning on or off at inappropriate times. For example, you don’t want the genes involved in regulating your heart’s rhythm switching off inopportunely. Conversely, you don’t want obesity- or cancer-promoting genes turned on if you can help it. And with the right nutrition, in many cases, you can help it. Methyl groups, for example, inhibit many of the 1,700 cancer-promoting genes present in each of our body’s 70 trillion cells.
In addition to influencing the on-or-off status of certain genetic variations, key nutrients are also involved in repairing gene damage (the dropping or scrambling of certain strands of DNA code that can occur as the result of age or chemical interference). The repair system isn’t perfect, and it becomes less efficient after about age 27. But working on your behalf are more than a dozen DNA-repair enzymes, which travel up and down DNA strands looking for and fixing damage. These enzymes depend on folic acid, vitamin B3 and the mineral selenium; if you don’t get enough of these nutrients, your DNA-repair enzymes cannot do their job.
The Danger of Deficiencies
So far, we’ve discussed a scant few nutrients, and you can already get a sense of the critical role they play in the function of our body’s basic operating system. Now consider the long list of nutrients known to be essential to human health, and the various and interdependent roles they can all play within that same symphonic system.
Relatively few Americans consume even the very conservative official Dietary Reference Intakes (DRIs) suggested by the U.S. Department of Agriculture. These are the minimal (not necessarily optimal) recommended levels for most vitamins and minerals known to be necessary for proper cell function. Less-than-optimal levels of these nutrients slow the myriad biochemical reactions that depend on them, kind of like how too little yeast will prevent bread from rising. In terms of DNA and genes, low levels of nutrients reduce DNA synthesis (seen in poor healing), diminish repair activities (seen in faster aging) and interfere with cell regulation (seen in cancer).
Playing to Our Weaknesses
Our individual genetic differences — weaknesses, if you will — complicate the situation. A lack of certain essential nutrients amplifies our inherited weaknesses, increasing our risk of disease. Here are three common examples of how that can happen:
Heart Disease. Roughly one-fourth of Americans inherit variations in the gene that produces a crucial enzyme involved in making DNA and regulating gene activity. This gene depends primarily on folic acid and, to a lesser extent, on vitamins B2, B6 and B12.
When this genetic weakness (which programs for an inefficient form of the critical enzyme) is combined with low intake of folic acid (common among people who don’t consume many leafy green vegetables or take appropriate supplements), the enzyme can’t do its job. The result? A greater risk of heart disease, as well as stroke, cancer and birth defects.
The problem can be easily offset, however, by increasing vegetable intake, taking folic acid supplements (400 to 800 mcg daily) or, even better, taking a high-potency multivitamin or B-complex vitamin supplement.
Osteoporosis. Researchers have identified 22 variations in the gene responsible for how our bodies use vitamin D, and one-third of Americans have a particular variation of this gene. These genetic variations interfere with the body’s use of vitamin D, low levels of which can increase the risk of osteoporosis, cancer and susceptibility to infection. The situation is compounded by the fact that there are few available food sources of vitamin D and only limited exposure to sunlight in northern latitudes during the fall, winter and spring.
Again, this genetic variation can be offset by increasing vitamin intake. Unfortunately, it is challenging for many people to get adequate vitamin D through diet alone. But spending just 15 minutes daily in the summer sun (wearing short sleeves and walking shorts, for example) prompts the body’s production of vitamin D, creating an estimated 10,000 IU. (To minimize the risk of sun damage, protect overexposed and sensitive areas, avoid the sun between 10 a.m. and 2 p.m., and don a hat and sunscreen after you’ve gotten your allotted sun time.) Some experts also suggest taking vitamin D supplements in addition, or as an alternative, to spending time in the sun. Walter Willett, MD, professor of epidemiology and nutrition at the Harvard School of Public Health, recommends that everyone take 1,000 IU daily of supplemental vitamin D, and increase it to 2,000 IU if you have a dark complexion or spend most of your time indoors.
Breast Cancer. Women who inherit mutations in the so-called breast- cancer genes (BRCA1 and BRCA2) have a substantially higher risk of developing breast or ovarian cancer. Yet these are not true breast-cancer genes but DNA-repair genes that provide the instructions for making two key proteins involved in DNA repair. Mutations in the genetic instructions for these genes prevent them from doing their intended job.
But proper nutrition can improve how these genes function. A 2005 European study published in Cancer Epidemiology, Biomarkers and Prevention found that women with BRCA1 mutations — who had higher rates of genetic damage — reduced their DNA damage to normal levels in just three months by taking a very high dose of selenium supplements. (Check with your doctor before consuming high amounts of selenium: It can be toxic to some in large doses. But most can benefit from taking 200 to 400 mcg of selenium daily — or eating an ounce of Brazil nuts, the richest food source of the mineral.)
When the repair genes for BRCA1 and BRCA2 fail to do their job, the body does have a backup system. The repair work shifts to another enzyme, and once again, good nutrition plays a role in its proper function. This repair enzyme, known as poly(ADP-ribose) polymerase is built around vitamin B3.
A growing number of researchers, such as Colorado State University’s Loren Cordain, PhD, believe that many of today’s common health problems result from a conflict between our ancient genes and modern foods. Fast foods and convenience foods — loaded with refined sugars, simple carbohydrates and trans fats — don’t supply the nutritional building blocks for our genes.
Worse, because they’re “genetically unfamiliar foods,” they turn on many genes best left alone. For example, sugars turn on the genes that make insulin, high levels of which increase the risk of obesity, diabetes, heart disease and cancer. Reversing such risks involves three key steps:
The first step in eating for your genes is to limit your intake of refined sugars found in soft drinks, desserts, and most conventional packaged or bottled foods. At the same time, reduce your intake of refined carbohydrates found in most breads, cereals, muffins, bagels, pizzas and pastas. The body responds to these refined carbohydrates much the way it does to sugars. Most people are better off opting for more complex, nongrain carbohydrates, such as those in fruits, nuts and sweet veggies, like yams.
The second step is to adopt a modern version of what Cordain calls the Paleo diet. Biologically, we’re designed for lean proteins, fish and lots of vegetables, along with culinary herbs, though there is a certain degree of individual variation. (For example, some people do better than others when it comes to consuming legumes.) Protein provides amino acids, which our genes recombine to make proteins and enzymes needed in normal biochemistry. Fish (specifically, cold-water) provide the healthiest family of dietary fats — omega-3s — which turn off inflammation-promoting genes. Vegetables and culinary herbs are rich sources of antioxidants, which help prevent damage to DNA.
The third step consists of taking nutritional supplements. While ideal supplementation strategies vary by individual, virtually everyone can benefit from taking a daily high-potency multivitamin and multimineral supplement. Such supplements can help compensate for some of the genetic weaknesses all of us inherit, as well as offset absorption problems related to aging or medication use. Look for a high-quality multivitamin supplement that contains at least 25 mg of vitamins B1, B2 and B3.
Consider adding extra amounts of folic acid (about 400 to 800 mcg daily) and vitamin B12 (about 100 mcg daily), both of which are involved in DNA synthesis and repair. If you live north of 35 degrees latitude (Atlanta, Phoenix or Los Angeles, for example), and don’t spend much time outdoors, take 1,000 IU of vitamin D daily throughout the year. If you’re active outdoors most summer days, you can take a vitamin D supplement only during the winter and spring.
While some across-the-board principles have been established for eating to help our genes function properly and help ward off certain diseases such as osteoporosis and heart disease, it’s becoming clear that each of us has our own unique profile of nutritional requirements. Some nutrients appear to be more essential and necessary in greater-than-average quantities to some individuals.
Scientists at Tufts University in Boston, and the University of California, Davis, are focusing their nutrigenomics research primarily on how common genetic variations (sometimes referred to as polymorphisms) can increase the risk of heart disease, cancer, diabetes and other illnesses — and how nutrition might affect the degree of risk. The underlying idea is that eating habits and nutritional supplements could be tailored to a person’s individual genetics, compensating for inherited weaknesses.
It’s very possible that within 10 years you’ll be able to get a comprehensive nutritional genetics workup. At that point, you’ll actually be able to see all of your genetic strengths and weaknesses — and get a clear sense of which foods and supplements will best help you guard against your inherited weaknesses.
The promise of nutrigenomics is an exciting one. In the meantime, this field of study is delivering some important insights that each of us would do well to integrate now. Perhaps the most important and far reaching of these is that while the oft-cited DRIs suggest the minimum levels of nutrients necessary for staving off obvious and immediate nutritional deficiencies in most people, they in no way take into consideration the very stark genetic differences among us. Nor do they consider the ways that a given individual’s genetic expression might be triggered by a chronic low-grade deficiency of a nutrient that plays an important role in his or her personal genetic profile.
The realization that our nutritional status can and does affect our genetic expression — and thus our disease risks and our quality of life — gives us more reason than ever to pay close attention to the way we eat. It is no longer a matter of merely watching our weight, or striving for a particular ratio of carbs, proteins and fats. It’s a matter of supplying the raw materials required for building and maintaining our DNA — the structure and instructions on which our very lives depend.