Have trouble focusing at work? Are you feeling tired for no obvious reason? Perhaps you're also dealing with hair loss or blurred vision? These are all common signs of nutrient deficiencies.\nIf your diet doesn’t supply enough vitamins and minerals, your health will suffer. Most symptoms are subtle and can go unnoticed for months or even years. However, they can develop into full-blown disorders later down the line.\nIn 2011, nine out of 10 Americans had at least one mineral or vitamin deficiency. This number hasn’t changed too much over the years; on the contrary, the rising popularity of processed foods and crash diets only made things worse.\nLuckily, it's never too late to change your diet and eating habits. Let's see three essential nutrients that you're likely not getting enough of.\nVitamin B12 \nVitamin B12 occurs naturally in animal products, such as meat, fish, and eggs. Some studies indicate that up to 90 percent of vegetarians are deficient in this nutrient. Elderly people are at risk too as the body’s ability to absorb vitamin B12 decreases with age.\nThis vitamin plays a key role in nerve function, red blood cell formation, DNA synthesis, and brain health. Every cell in your body needs it to function optimally.\nIf your diet lacks vitamin B12, you may experience muscle weakness, poor vision, pale skin, shortness of breath, lightheadedness, arrhythmia, and sluggish digestion. In the long run, vitamin B12 deficiency may lead to anemia and mental disorders.\nTo prevent these issues, eat plenty of shellfish, beef liver, dairy, milk, eggs, and meat. Vegan can opt for nutritional yeast, fortified cereals, and vitamin B12 supplements.\nVitamin A \nPremature aging, hair loss, dry skin, eczema, and night blindness are all common signs of vitamin A deficiency. This fat-soluble nutrient promotes healthy skin and hair, keeps your immune system strong, and promotes good vision. It also plays a role in fertility and reproduction.\nIn a clinical trial, the prevalence of dry eyes dropped by 63 percent in children who took vitamin A supplements. Another study has linked vitamin A deficiency to birth defects and reduced fertility.\nSince this nutrient is found in a wide range of foods, you can easily boost your daily intake. Beef liver, for instance, provides over 713 percent of the daily recommended amount of vitamin A per serving. Lamb liver, cod liver oil, salmon, mackerel, and tuna are all excellent sources.\nVitamin D\nA staggering 15 percent of all people worldwide are deficient in vitamin D. This nutrient supports calcium absorption, keeping your teeth and bones strong. It also protects against osteoporosis, regulates cell growth, and maintains immune function.\nYour body can only produce vitamin D when exposed to sunlight. That's why vitamin D deficiency tends to be more common during the winter months and among individuals living in cold climates. Additionally, it's found in a small number of foods, including egg yolks, cheese, beef liver, and cod liver oil.\nVitamin D deficiency is a major contributing factor to bone loss, cognitive decline in older adults, heart disease, joint pain, and muscle weakness. If left unaddressed, it may increase your risk of cancer.\nThe best way to increase your vitamin D intake is to eat foods containing this nutrient or take supplements and spend at least 10-15 minutes outdoors on a daily basis. Nowadays, most stores are offering breakfast cereals, milk, orange juice, eggs, and other foods fortified with vitamin D, so getting more of it in your diet shouldn't be difficult.\nThere are many other nutrients you might be deficient in. Iron, iodine, calcium, and omega-3s are just a few to mention. If you suspect you have mineral or vitamin deficiencies, dietary supplements can help. Ideally, most nutrients should come from real foods, not pills, so tweak your diet and make smarter food choices to enjoy optimal health. \nA good daily multivitamin, like the All-in-One Multivitamins we offer, could greatly aid in supplying the nutrients required for healthy living.