Eating an orange a day may keep the doctor away

Evolutionary changes may be major epochal productions, planned thousands of years in advance but they exhibit a simple truism that has become a Darwinian dictum: “Use it, or lose it.” Man and primates cannot produce their own vitamin C because, as scientific stories suggest, they started eating fruits containing vitamin C. Hence humans must eat enough vitamin C to satisfy our body’s daily requirement or risk disease as our bodies don’t produce any. Babies in the womb can produce some vitamin C, but lose this ability after birth.

In 1497, Vasco Da Gama, the Portuguese circumnavigator lost 100 out of 160 seamen on his expedition to India due to a mysterious disease. It would take more than two centuries before the cause of this fatal disease, Scurvy, was identified as the lack of vitamin C.

In 1747, James Lind described one of the earliest double-blind trials in medicine, aboard the HMS Salisbury. Lind took twelve men with similar cases of scurvy — as he noted, “… their cases were as similar as I could have them” — and gave half two oranges and one lemon per day; the others, he gave vinegar and seawater. The men that ate the oranges and lemons survived and were able to get back to their duties at sea.

In researching for my book, The Genetics of Health (Simon and Schuster, 2017), I became interested in how individuals metabolize different nutrients differently, and ended up developing a 21-Gene Test to help people “eat for their gene type.” When studying the genetic variations behind vitamin C metabolism, I noted the importance of the GSTT1 gene, that produces proteins for the glutathione S-transferase enzyme family. These enzymes play a key role in the utilization of vitamin C. The GSTT1 gene exists in one of two forms. The insertion (Ins) form is considered functional, while the deletion (Del) form is faulty. People who possess this version (Del) will have lower blood levels of vitamin C even if they eat the same number of oranges and lemons as other people. In other words, these people need to eat more than the usual amount of vitamin C.

In those seafaring days, when so many lives were lost to scurvy, Lind’s study showed the importance of vitamin C, not just for gum health but as a powerful anti-oxidant that can protect the heart, kidney and other major organs. But adding genetic profiles into the mix takes a Lind-like study to the next level of scientific sophistication. Indeed such a study that was done on young Canadian students. These were students in their 20s and 30s and the study looked at the GSTT-1 gene, and the effects having a non-functional gene. Studies showed a raised risk of blood pressure, higher sugar levels and risk of heart disease (and these were young people) demonstrating the risk of having a non-functioning vitamin C gene. Studies were repeated in Asian students with the same results i.e. these good and bad versions of the vitamin C gene exist across different ethnic groups.

People with this Del variant need to take additional amounts of vitamin C in their diets. For such people eating an (extra) organic a day may indeed keep the doctor away! (Peppers are also a good source of vitamin C with some yellow peppers even having more vitamin C than an orange).