While most pregnancy nutritional advice goes towards women, some fascinating recent research shows that fathers’ diets plays a role in their babies’ health and metabolism. In the beautifully-titled recent Cell article, Paternal Diet Defines Offspring Chromatin State and Intergenerational Obesity, researchers elegantly show that the foods males eat change their DNA and can cause their children to be obese! How does this work?!
In this study, male fruit flies (yes, fruit flies are surprisingly good models for human metabolism) were fed normal or modified diets; researchers carefully scaled up protein and sugar ratios until flies were obese. Notably, flies that ate more protein did not become fat, while those that consumed more sugar (from bananas) stored more triglycerides and had higher body fat percentages. (I’m amazed at the nimble researchers who measured these things!).
Next, male fruit flies (separated into low sugar, normal sugar, or high sugar groups) mated with virgin female fruit flies, and their offspring were analyzed. The body weight of offspring increased with paternal sugar, and triglyceride levels increased for offspring from low- and high-sugar fathers, showing that both extremes can be detrimental. Additionally, high-sugar offspring had more fat (adipose) on their bodies and consumed more food!
To show exactly how fathers’ diets affect babies, sperm was analyzed from low-, normal-, and high-sugar flies before mating. It is important to note that they were looking at epigenetic changes, or the way that DNA is expressed. Throughout your life, your DNA sequence (those helical combinations of A, T, C, G) remains largely the same, but only 1-5% of those sequences are ever expressed as genes. Epigenetics is how your body chooses to express certain genes, and the way you live largely influences how your DNA is expressed. (cool, right?!) Thus, eating a high-sugar diet doesn’t change the sequence of your DNA, but it makes epigenetic changes, ultimately modifying which genes are expressed and which genes are silenced.
High-sugar diets enhanced the expression of genes associated with fat storage, and the specific genes found were consistent with other studies that examined the epigenetics of human adipose tissue. A very recent similar study in which male mice were fed a high fat diet (60% fat) resulted in different RNA signatures in sperm, and their offspring had impaired glucose tolerance and insulin resistance as early as 7 weeks of age. Another high-profile study fed male mice a low protein diet (10% of calories vs 19%), performed extensive analysis of their sperm, and ultimately found that offspring from low-protein fathers had significant genetic up-regulation of a cholesterol biosynthesis enzyme, squalene epoxidase, likely leading to dysregulated triglyceride levels in offspring.
Taken together, these studies show that fathers should not eat an excessively fatty or sugar-laden diet, and they should ensure adequate protein intake before conceiving to put their best swimmers forward. So how long does a father need to maintain a good diet to help make healthy babies? In fruit flies, changing a high-sugar diet to a nutrient-rich, normal-sugar diet as little as 24 hours before conception halted the detrimental effects observed in offspring. But as we’re not fruit flies, let’s convert to human time; 24 hours of fruit fly time translates to a bit over a year of human time. That may seem like awhile, but I’d say that 1 year of becoming your best self to set your children up for their optimal lifetimes is worth it. Furthermore, as another study showed that male mice who fasted for 24 hours once a week for a few weeks produced offspring that had lower blood glucose, there are likely some hacks, like fasting, that can further optimize paternal diets.