Individualizing Dietary Guidance—Nutrient-Gene Interactions

Nutrient requirements, drug response, and disease risk are influenced by gene variants (mutations) called SNPs. The term SNP stands for single nucleotide polymorphism. Research on nutrient-gene interactions or nutrigenomics is evolving rapidly. One area of focus relates to SNPs affecting the MTHFR enzyme, which is necessary for the body to convert the vitamin folic acid to its biologically active form (5-methyltetrahydrofolate).

While there are a number of SNPs affecting the MTHFR enzyme, one of the three most common is C677T, which is also known as rs1801133 . On average about 40% of us inherit this SNP from one parent (single mutation), and about 11% of us inherit it from both parents (double mutation), but the rates vary by race/ethnicity. The rate of double mutation is 20% (1 out of every 5) in the Mexican-American population, while it is 12% in the non-Hispanic white and 1% in non-Hispanic black populations.

A single mutation results in about 65% of expected MTHFR enzyme activity, and a double mutation results in about 30% of expected MTHFR enzyme activity. Less enzyme activity means less of the metabolically active form of folate, which adversely affects methylation. Methylation is critically important for a variety of body processes including:

  • DNA repair (helps reduce cancer risk, progression)
  • controlling inflammation
  • controlling homocysteine (to reduce damage to the blood vessel walls)
  • supporting detoxification
  • protecting neurological function (including mental function, mood and behavior).

Those with a double mutation (677TT) affecting the MTHFR enzyme have elevated levels of homocysteine and low levels of folate and vitamin B-12. And because methylation doesn’t work properly when nutrients required for its normal function are inadequate, the risk of neurodegenerative conditions (including peripheral neuropathy associated with diabetes & cognitive decline), reduced ability to eliminate toxins, chemical sensitivities, heart disease, mood disorders (including depression), and cancer is elevated.

Genetic tests for SNPs impacting nutritional status (including those affecting the MTHFR enzyme) generally are available from a number of companies. Your health care provider can help you choose a reliable testing company and can also help you to interpret the results. If you find that you have inherited a mutation (SNP) affecting the MTHFR enzyme, your health care provider will usually recommend that you eat a diet rich in nutrients that support methylation.

Nutrients that support methylation include folate, vitamin B-6 (pyridoxine), vitamin B-12, and choline. The recommended intakes (DRI) and food sources for each of these is listed below.

  • Folate—DRI=400 mcg/d; vegetables (especially dark, green leafy), fruits (especially oranges), whole grains, legumes.
  • B-6—DRI=1.3-1.7 mg/d; dark green leafy vegetables, whole grains, legumes, lean meats.
  • B-12—DRI=2.4 mcg/d; lean meat, fish, poultry, dairy products; those at high risk for inadequate intake = vegans, celiac pts., chronic antacid use, elderly.
  • Choline – DRI=425-550 mg/d; egg yolks, liver, pork, legumes (especially soybeans), wheat germ, seeds (pumpkin, sunflower).

A diet plentiful in vegetables, fruits, whole grains, and legumes (cooked dry peas, beans, lentils) helps to insure adequate nutrients to support methylation. However, a diet of mostly refined & processed food – even when these foods and supplements contain folic acid – will likely result in lower levels of metabolically active folate. This is a particular concern for those who have inherited an MTHFR SNP from both parents, because their ability to convert folic acid to its biologically active form is severely compromised. To overcome this challenge, a supplement with the methylated form of folate is recommended. Methylated folate is available commercially as Metafolin and as Quatrefolic, both of which have the stability required for use as a supplement. Supplements containing folic acid in the methylated form will include the form of folic acid on the Supplement Facts label. For example: folic acid (Metafolin) or folic acid (Quartrefolic).

The nutritional quality, variety, and quantity of foods we eat have a big impact on the metabolic processes that determine our health. Nutrient needs can vary considerably from person to person in part related to genetic differences. Individualized dietary guidance takes these differences into account.

And speaking of the important role of folate in health and of folate-rich leafy greens and legumes, please enjoy Spinach with Garbanzos, Raisins, & Pine Nuts from our Food for Thought—Healing Foods to Savor. This colorful and nourishing quick meal is also rich in fiber and plant protectors. And along with folate, this dish also supplies about 120 mg magnesium per serving!

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