There is mounting evidence that small amounts of essential nutrients like choline and folate have a big impact on human health. However, nutritional studies that attempt to quantify the effects of essential nutrients often produce unclear or contradictory results.
There are several reasons for this, but chief among them is the assumption that all of us process food exactly the same way. This is simply not the case. No one is metabolically identical or even similar to anyone else – not even identical twins. We all require different amounts of specific nutrients and vitamins. Scientists at the UNC Nutrition Research Institute believe this common misconception is responsible for so many contradictory study results.
Our cells are tiny factories full of production lines designed to make everything our bodies need to learn, grow, and fight disease. Efficient genes are able to produce high volumes of quality products, but other genes with variations called single nucleotide polymorphisms (SNPs) – pronounced “snips” – can struggle to meet production quotas and produce sub-standard products. We inherit SNPs from our ancient ancestors, which is why people who share a common ancestry have similar SNPs.
For example, folate (found in leafy green vegetables) plays an important role in DNA production and preventing birth defects. Many people have a SNP in a gene important for folate metabolism, making it harder for them to use the vitamin efficiently. The only way for them to get enough folate is to eat 10% more folate-containing foods, or take a vitamin supplement. The folate SNP is much more common in people in Mexico than it is in people of European descent.
Digestion and metabolism consist of thousands of different biochemical reactions going on simultaneously. Only a small percentage of SNPs affect how we metabolize food, but since each of us carries about 50,000 of them, that small percentage can be important. The sheer number of reactions and the large number of possible SNPs can make nutrition studies incredibly “noisy” if we lump people together and do not recognize that they can differ.
Take choline as an example:
- Fifty-five percent of women of child-bearing age have a gene in their liver that allows them to make choline from estrogen. Making a baby requires a great deal of choline, but these women do not need to get all of their choline from food because they are able to make some of their own.
- Forty-four percent of women of child-bearing age have at least one SNP that prevents them from making choline from estrogen. These women must eat more choline during pregnancy because they cannot make enough of their own.
- Men and postmenopausal women lack enough estrogen to turn the choline producing gene on, so they always must eat choline in their diets. (Foods like liver and eggs are good dietary sources of choline).
If scientists lump these groups together, depending on the mix of people studied, they might report that people need to eat choline, or don’t need to eat choline, or say that they are hopelessly confused. However, by performing simple genetic tests for SNPs, researchers could group people appropriately and clearly identify those who need to eat more choline in their diets. This is what the exciting field of personalized nutrition (perhaps better called “precision nutrition”) is all about.
SNPs are not the only reason people differ metabolically – they are just the easiest to measure. Gut bacteria also play a big role because they can capture essential nutrients for their own use. People have more gut bacteria cells than they have human cells and since no two people have the same mix of bacteria in their digestive tracts, those of us with nutrient-hungry gut bacteria must make do with fewer essential nutrients than those of us whose gut bacteria do not snap up essential nutrients before we can use them.
The future of nutrition research lies in creating screening tools that make it easy to identify metabolic differences. By using those tools to separate study subjects based on specific SNPs and differences in gut bacteria, investigators can precisely group people who have metabolic inefficiencies that make them need more or less of a nutrient. Eventually, physicians and dieticians can stop dispensing one-size-fits-all advice, and start dispensing precise nutritional recommendations based on unique metabolic profiles designed to help each of us achieve and maintain optimal health.