Six years ago, I sat down with ultra mountain athlete Yuki Ikeda for the first time for an interview about his experience training, competing and recovering in the extreme altitudes of Colorado’s central Rocky Mountains. At the time, Yuki had only recently started competing in running races at over 10,000′ (3048m) since beginning his career as a cyclist in 2003, going pro in 2007.
In 2019, he managed to compete in his first Leadville Race Series, which included 50- and 100-mile MTB and trail run courses starting at above 10,000′ and rising to over 12,000′.
This summer, I had the pleasure of catching up with this extraordinary athlete and his wife Sayako, a dietitian and high-altitude runner herself who inspired Yuki to compete as a runner as well as a cyclist. The pair have been spending summers in the Colorado high country every year to train and compete before returning to their home in Japan to continue competing year-round, and between their experience training and racing and nutritional expertise, they make a formidable team.
Six years ago, we were all three of us in our thirties, and when I asked about what has changed about training and acclimating to the altitude since then, there was certainly a consensus about how it hasn’t gotten easier now that we are all in our forties. A significant part of their strategy for success has always been nutrition, and at this elevation, maximizing the delivery of oxygen throughout the body makes a huge difference. In our last interview, Yuki talked about incorporating foods rich in nitrates, which facilitate your body’s production of nitric oxide, like red bell peppers, arugula and beets, and these are still a big part of their diet.
Something they’ve been paying closer attention to lately is iron, also a critical component of blood. It’s dangerous for iron levels to be too high, but it can be a critical supplement for healthy circulation. In the case of long distance runners, blood vessels can take a considerable beating as feet hit ground over and over again for long periods of time. One food in particular that contains a high level of iron is clams. In Japan and the Pacific, asari, also known as Manila clam or Japanese cockle, is a regular part of cuisine and easy to find. Here in the middle of the Rockies, however, Yuki and Sayako have been buying canned clams to supplement their iron.
Every summer, the couple have come to the Colorado Rockies to train and compete. They’re full-time residence is in Tokyo, Japan, so each time they are traveling from sea-level, a dramatic and quick ascent to a high elevation. The decrease in available oxygen in the air at high altitude prompts a response in the body to create more red blood cells in order to carry more oxygen throughout the body. This requires more iron, which is vital for this process.
Additionally, the two athletes are paying special attention to nutrient absorption. Most of their diet is plant-based, and until recently, Yuki has been eating a completely vegan diet. Organic compounds found in plants called tannins and polyphenols — while beneficial — can inhibit your body’s absorption of nutrients you eat by up to 90%. So consuming something with these compounds along with your meal may dramatically decrease the benefits of nutrition in the food you’re eating. Coffee contains these compounds, so Sayako recommends waiting at least an hour after a meal to have a cup of coffee in order to maximize nutrient uptake. Even better, vitamin C can enable greater absorption, so consuming it (even in other foods such as a citrus) with a meal can be very helpful.
“… iron is also necessary for the hypoxia-inducible-factor (HIF) pathway, cellular energy production, myoglobin function (the muscle oxygen acceptor), and thyroid hormone function,” write DeLoughery and DeLoughery in a recent article for the Wilderness Medical Society. “The HIF pathway is the key regulator of the body’s response to hypoxia. Typically, the HIF-1 and HIF-2 proteins are rapidly degraded, but they are stabilized by hypoxic conditions when prolyl hydroxylase, which tags the HIFp roteins for degradation, is inhibited. When stabilized, the HIF proteins function as transcription factors that coordinate the synthesis of various proteins essential for the body’s response to hypoxia. Prolyl hydroxylase requires iron to function, and with a low iron level, this is less effective, leading to an exaggerated response to hypoxia.”
It is also important to note that, as Yuki and Sayako point out, it can take three to four weeks for anyone to experience noticeable results from any change in diet and nutrition. Keeping this in mind, it is advisable to increase iron intake weeks ahead of a trip to a high altitude environment, although further research may be needed to recommend just how much.
References
DeLoughery, MD, Emma P. Emma P. DeLoughery, MD and Thomas G. DeLoughery, MD, “Women, Iron, and Altitude — Path to the Peak”, Wilderness Medical Society 2025.
