Your mom always said to eat your veggies. Turns out that she may be right! Of course, there are genetic factors involved that influence how your body responds. Some of us may need to eat more veggies than others to get the same effect.
The glutathione S-transferase genes code for enzymes that are involved in the metabolism of a variety of carcinogens and environmental toxins. Two of the genes, GSTM1 and GSTT1, have been extensively studied for the effects of carcinogens and toxins on the fairly common null polymorphisms that involve a deletion on the genes. The deletion is fairly common with 50 – 78% of people, depending on ethnic group, having the null genotype for GSTM1.
Check your genetic data for rs366631 (23andMe v4 only):
- A/A: deletion (null) GSTM1 gene. GSTM1 deletion is associated with 2x increased risk of breast cancer [ref] This is actually the most common genotype in most populations.
- A/G: GSTM1 present
- G/G: GSTM1 present
So What is the GSTM1 enzyme?
GSTM1 – Glutathione S-transferase mu 1 “…functions in the detoxification of electrophilic compounds, including carcinogens, therapeutic drugs, environmental toxins and products of oxidative stress, by conjugation with glutathione. … These genetic variations can change an individual’s susceptibility to carcinogens and toxins as well as affect the toxicity and efficacy of certain drugs. Null mutations of this class mu gene have been linked with an increase in a number of cancers, likely due to an increased susceptibility to environmental toxins and carcinogens. ” [NCBI]
Effects of Fruits and Vegetables in the Diet:
A Korean study looked at the effects of drinking 480 ml (about 16 oz) of grape juice per day for 8 weeks. The study on smokers found that everyone had a decrease in diastolic blood pressure, but that the effect was higher in those with GSTM1-null. Additionally, the GSTM1-null genotype had a greater increase in antioxidant effects with an increase in gamma-tocopherol.[ref]
Another study in 2009 looked at the effect of vegetable intake on bladder cancer. The study found that in general, a higher vegetable intake decreased the risk of bladder cancer. It also found an even more protective effect in those carrying GSTM1 null with an even lower risk of bladder cancer associated with high cruciferous vegetable intake. [ref]
Broccoli has been the focus of several studies in association with GSTM1 null vs. present. Studies have suggested that those having a GSTM1 null genotype would benefit from eating even more servings of broccoli than those with a present gene – at least in terms of prostate cancer. In other words, those with GSTM1 present may benefit from broccoli a few times a week, while those with the null genotype should add in another serving or two.[ref]
Several studies have linked GSTM1 null genotype with lung cancer.[ref] Another excellent reason to stop if you are a smoker.