Environmental factors, such as diet, smoking, or exposure to certain substances, can influence the epigenome thereby influencing features and traits of people. Our social environment can also affect the epigenome.
The Dutch famine of 1944-1945 (the Hunger winter) during World War II, is a well-known example of the impact of an environmental factor on the epigenome. Malnutrition of women that were in a very early stage of their pregnancy, altered the development of their unborn child.
Malnutrition during the Hunger winter led to changes in the epigenetic regulation of genes related to the growth of the embryo in the womb during a very early stage of pregnancy. This adaptation was apparently necessary for the embryos to survive. Scientists noted that even 60 years later, the epigenetic adaptation is still detectable in the epigenome of adults born during or right after the Hunger winter. The adaptation, which was beneficial for the embryo at the time, appears to have adverse effects later in life, such as an increased risk of obesity, diabetes, and higher blood cholesterol levels.