Part 2: Fiber, Starch, and Vitamins
Based on the book "The Science of Nutrition" by Rhiannon Lambert
Soluble fiber is found in the flesh and pulp of many fruits and veggies, grains, seeds, and legumes. This type of fiber dissolves in water to form a gel-like substance that helps make stools soft. This enables them to progress through the gut with ease, preventing constipation. Soluble fiber (in oats, for instance) slows down digestion, which helps with satiety and also with regulating blood sugar levels. Soluble fiber has another great benefit; in the small intestine, its presence reduces the absorption of cholesterol into the bloodstream, which has the positive effect of reducing the levels of LDL cholesterol (the bad type of cholesterol; cholesterol) circulating in the blood. Insoluble fiber is found in the skins and seeds of many fruits and veggies, nuts, seeds, whole grains, rice, and wheat bran. As the name suggests, insoluble fiber does not dissolve in water, so it can be only partially broken down by digestion. It helps to push things along in your digestive tract, preventing digestive problems. Consuming enough insoluble fiber promotes regularity of bowel movements and helps regulate blood sugar levels. Carbohydrates made up of high proportions of beta-glucose monomers, such as cellulose, are referred to as resistant starches because they cannot be broken down by the small intestine. They pass into the large intestine, where they are fermented by gut bacteria. This fermentation process produces short-chain fatty acids (SCFAs), which stimulate the immune system and can impact mental health. Cooked and cooled potatoes and rice contain resistant starch, which is also found in whole grains like barley, oats, and sorghum, green bananas, and beans and legumes. Our bodies cannot make all the micronutrients we need to function, so this requirement is met solely by diet. Most people enjoying a healthy, balanced diet will easily obtain enough vitamins. Vitamins come in two main forms, water-soluble and fat-soluble. Water-soluble vitamins are easily lost through bodily fluids (and in cooking) and must be replaced each day. • B vitamins play an important role in keeping the nervous system healthy and helping our bodies release energy from the foods we eat. Folate (vitamin B9) helps with brain and spinal cord development in unborn babies. Sources of B vitamins are: • B1 Peas, bananas, nuts, whole grains • B2 Milk, eggs, fortified cereals, mushrooms • B3 Meat, fish, wheat flour, eggs • B5 Chicken, beef, eggs, avocado • B6 Pork, soybeans, peanuts, oats, bananas, milk • B7 is needed in trace quantities, and is available from many food sources, so will be present in a varied and balanced diet, B9 Leafy greens, chickpeas, edamame beans, broccoli, liver, foods fortified with folate • B12 is found only in animal products, such as eggs, meat, or fish, or in fortified plant foods, such as some nutritional yeast products. • Vitamin C is often hailed as the cure to colds and flu because it contributes to healing. It also maintains healthy skin, blood vessels, and cartilage, and plays a role in the production of collagen, which maintains our skin’s elasticity and strength. Sources include oranges, peppers, broccoli, and bananas. Fat-soluble vitamins tend to accumulate within the body so are not needed in the diet on a daily basis. Vitamins A and E are powerful antioxidants, helping to protect cells from free radicals and aging. Vitamin A contributes to cell renewal and repair, but note that excesses during pregnancy may harm the baby. Vitamin E reduces the effects of skin aging and the risk of skin cancer. Sources of vitamin A include carrots and sweet potatoes. Sources of vitamin E include almonds and avocados. • Vitamin D is unique because it is a hormone that we can produce in our own bodies with exposure to sunlight. This means we don’t need to get it from diet if there is enough exposure. However, with the use of sunscreen and the lack of sunlight in parts of the US and during winter, we are advised to supplement with vitamin D if our blood levels are low. Dietary sources include egg yolks, oily fish, and fortified foods. • Vitamin K is important for wound healing (we need it for blood clotting), and some evidence links it to bone health. Sources include green leafy vegetables, some cereal grains, and vegetable oil. Unlike vitamins, which are organic compounds (made by plants or animals), minerals are inorganic chemical elements that come from soil, rock, or water. They are absorbed from the environment by plants as they grow, and by animals that eat those plants. There are many minerals, each with benefits. Try to include each type in your diet regularly. You need some minerals in greater quantities, such as calcium, chloride, magnesium, phosphorus, potassium, sodium. Others, like iodine, iron, selenium, and zinc are needed in trace quantities. • Calcium is a vital component of bone and teeth, and a key nutrient for the nervous system, muscles, and heart. Sources include milk, yogurt, spinach. • Iodine deficiency affects nearly one-third of the world’s population. This mineral is essential for normal thyroid function and the production of thyroid hormones, which are involved in many processes in the body such as growth, brain development, and bone maintenance. Thyroid hormones also regulate the metabolic rate. Sources include fish, dairy products, eggs, seaweed. • Iron deficiency is the most common nutritional deficiency in the world and the only one that is prevalent in developed countries. More than 30 percent of the world’s population has anemia. Lack of iron lowers the ability of the blood to carry oxygen. Iron has many benefits, including improved immune and brain function. Sources include shellfish, broccoli, red meat, tofu. • Magnesium plays a role in more than 600 cellular processes, including energy production, nervous system function, and muscle contraction. Sources include avocados, nuts, leafy greens. • Manganese helps make and activate some of the enzymes in the body that carry out chemical reactions such as breaking down food. Sources include bread, nuts, breakfast cereals, and green vegetables. • Potassium is important for blood pressure control, fluid balance, and muscles and nerve function. Sources include bananas, spinach, potatoes, apricots. Phosphorus helps the body build strong bones and also release energy from food. Sources include red meat, dairy, fish, poultry, oats, bread. • Selenium helps the immune system work correctly, prevents damage to cells and tissues, and promotes the health of the reproductive system. Sources include Brazil nuts, eggs, meat, fish. • Zinc supports the immune system, hormone production, and fertility. It can help reduce skin inflammation and support wound healing and protects against UV damage from the sun. Sources include shellfish, red meat, eggs, chickpeas.
