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Genetics is a complicated subject, but most of us understand that genes are those parts of the DNA of cells that carry our genetic information in the form of a genetic code. Under normal circumstances the genetic information is transmitted intact every time our cells divide. But sometimes, something can go wrong when our cells divide and the information is no longer transmitted correctly.
According to Prof Sylvia Escott-Stump, president of the Academy of Nutrition & Dietetics in the USA and professor of dietetics at the University of East Carolina, so-called "epigenetic misprogramming" can occur during the development of the foetus and exert a persistent effect on the health of subsequent generations. (Prof Escott-Stumpe recently gave a series of lectures in Sandton, Johannesburg.) Another type of epigenetic transmission problem can occur with so-called "dysregulation" of gene expression. The latter genetic errors in programming usually occur over long periods as we age and tend to be related to chronic health conditions such as the development of tumour as in cancer.
Folate and DNA methylation
From a dietary point of view, Prof Escott-Stump says that one of the first nutrient-related discoveries in the field of human genetics, is that a B vitamin, namely folate (also called folic acid), can change gene expression. An important step in epigenetic programming, is a process called "DNA methylation", which is where folate plays an important role. The following functions are dependent on DNA methylation:
- DNA synthesis and repair
- So-called "silencing" of genes, which stops us from being susceptible to viruses and cancer
- Myelination (growth of the protective layer around the central nervous system) and pruning of synapses (a process that eliminates certain nerve connections or synapses, while allowing other more potent synapses to survive during brain and nerve development)
- Conversion of tryptophan (an amino acid) to serotonin (the feel-good chemical in our brains that prevents depression)
- Conversion of serotonin to melatonin (a neurohormone that regulates our sleep-wake cycle and acts as an antioxidant)
From the above, it is clear that DNA methylation is very important and that any changes or defects in this process can cause many different metabolic and health problems. Genetic research has now identified folate, a B vitamin, as a factor that can help keep our DNA methylation on track.
Examples of folate-related genetic problems
Prof Escott-Stump points out that nearly 40 000 years ago, when the ancestors of modern humans moved out of Africa into Europe, two genetic mutations relating to folate metabolism occurred. Ironically both these mutations give modern humans a selective advantage, but they also make us susceptible to diseases.
The following example serves to illustrate how important folate is to normal development and health.
MTHFR Deficiency
One of these genetic mutations produces a deficiency of an enzyme which is referred to as MTHFR (Methylene Tetra Hydro Folate Reductase), which is important in normal folate metabolism. People with an MTHFR deficiency are vulnerable to the following diseases and conditions:
- Acute leukaemia
- Cleft lip or clef palate
- Delayed development
- Patients do not walk normally, but have a deviant gait
- Gastric cancer
- Infertility or miscarriage
- Mental retardation
- Increased levels of a compound called homocysteine in the urine (rare)
- Paediatric stroke
- Psychiatric problems
- Seizures
(Escott-Stump, 2012)
One variation of the MTHFR mutation (MTHFR C677T (C>T)), causes increased levels of a compound called homocysteine in the blood. These high homocysteine levels are linked to heart disease, increased cholesterol levels, diabetes and insulin resistance. Inflammatory bowel disease and autism, as well as spina bifida are also associated with this genetic mutation. Spina bifida is a genetic defect that has prompted the addition of folate to foods in many countries, including South Africa.
In countries such as America, the incidence of this genetic mutation varies from 21% of people of Latino extraction born in the USA to 8% of German Caucasians. Less than 1% of African Americans are affected by this specific folate-linked error in genetic expression. A number of years ago, researchers in South Africa, also found that high levels of homocysteine were often present in patients with cardiovascular and blood cholesterol problems, particularly in our white population.
As a protective measure against these negative consequences of a folate genetic mutation, it is an excellent idea to ensure that your dietary intake of folate is adequate and that women take folate supplements even before they fall pregnant and for the entire duration of their pregnancy.
Sources of folate in the diet
The following are sources of folate (folic acid) in the diet:
- Liver and lean beef
- Folic acid fortified breakfast cereals or porridges or bread. All maize meal and wheat bread is fortified with folic acid in South Africa. Most other ready-to-eat cereals also contain added folic acid.
- Mushrooms
- Legumes such as dry, cooked or canned lentils and white beans
- Green leafy vegetables - spinach, asparagus, broccoli, cabbage, wild spinach
- Freshly squeezed orange juice, bananas
- Egg yolk
(Mahan, Escott-Stump & Raymond, 2011)
Supplementation?
Prof Escott-Stump suggests that individuals with identified genetic mutations related to folate metabolism may need to take folate supplements. If you have had a genetic test and have been found to have a folate mutation, then it is probably desirable to use a folate supplement that contains L-methylfolate, rather than one of the other forms of folate. During the discussion after Prof Escott-Stump’s presentation, it appeared that most folate supplements available in South Africa at present contain the folic acid form of folate and not the methylfolate form. Hopefully this problem will soon be remedied and products equivalent to American supplements such as Fola-Pro, which contains 800 mcg of L-methylfolate per dose, mentioned by Prof Escott-Stump, will also be available in this country.
In the meanwhile keep eating those green leafy vegetables, legumes and liver to boost your folate intakes and prevent a variety of diseases that may be linked to a genetic inability to metabolise folate properly.
- (Dr IV van Heerden, DietDoc, July 2012)
(DietDoc recently attended the Sylvia Escott-Stump CNE Workshop which took place in Sandton, Johannesburg. Sylvia Escott-Stump is one of the editors of Krause’s Food & the Nutrition Care Process, a highly respected nutrition text with comprehensive and up-to-date information from respected educators and practitioners in the nutrition field.)
References:
(Escott-Stump S, 2012. Nutrition & Genetics: The Missing Link. Lecture presented at the Sylvia Escott-Stump CNE Workshop, Sandton, 19 June 2012. Mahan LK, Escott-Stump S, Raymond, JL (2011). Krause’s Food & the Nutrition Care Process. Ed. 13. Elsevier, USA)
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